Makefile: add -Wno-initializer-overrides to clang builds

ADDITIONAL CHANGES

Alpha-Beta search
* Change back to recursive alphabeta with implicit stack
* Add atomic_bool parameter that stops search when set to false
* Update tests accordingly

Evaluation
* Fix bug where black pawns are using white's positional modifier bonus

Makefile
* Add -march=native to clang release builds

.gitignore

@@ -5,3 +5,4 @@ mbb_rook.h
 tests
 *.dSYM
 between_lookup.h
+diagonals.h

Makefile

@@ -3,14 +3,15 @@ BUILD ?= debug
 CC := clang
 
 CFLAGS.gcc := -std=c23 -Wall -Wextra -Wconversion -Wno-unused-function
-CFLAGS.gcc.release := -Ofast
-CFLAGS.gcc.debug := -ggdb -O0 -fsanitize=address
+CFLAGS.gcc.release := -Ofast -march=native -DNDEBUG
+CFLAGS.gcc.debug := -ggdb -O1 -fsanitize=address
 
-CFLAGS.clang := -std=c23 -Wall -Wextra -Wconversion -Wno-unused-function -Wimplicit-int-conversion
-CFLAGS.clang.release := -Ofast
-CFLAGS.clang.debug := -ggdb -O0 -fsanitize=address
+CFLAGS.clang := -std=c23 -g -Wall -Wextra -Wconversion -Wno-unused-function -Wimplicit-int-conversion -Wno-macro-redefined -Wno-initializer-overrides
+CFLAGS.clang.release := -O3 -ffast-math -march=native -DNDEBUG -DNSTATS
+CFLAGS.clang.debug := -g3 -O1 -fsanitize=address,undefined
 CFLAGS.clang.wasm := \
-	--target=wasm32-unknown-unknown -O3 -nostdlib \
+	--target=wasm32-unknown-unknown -nostdlib -g \
+	-DNSTATS \
 	-Wl,--export-all \
 	-Wl,--no-entry
 
@@ -21,9 +22,9 @@ all: tests
 wasm: chess.wasm
 
 codegen: codegen.c
-	$(CC) -o $@ $(CFLAGS) $^
+	$(CC) -D_DEFAULT_SOURCE -o $@ $(CFLAGS) $^
 
-chess.wasm: wasm-compat.c
+chess.wasm: wasm-compat.c mbb_rook.h mbb_bishop.h engine.h
 	$(CC) -DWASM -o $@ wasm-compat.c $(CFLAGS.$(CC)) $(CFLAGS.$(CC).wasm)
 
 mbb_rook.h: codegen
@@ -33,4 +34,4 @@ mbb_bishop.h: codegen
 	./codegen
 
 tests: tests.c mbb_rook.h mbb_bishop.h engine.h
-	$(CC) -o $@ $(CFLAGS) tests.c
+	$(CC) -D_DEFAULT_SOURCE -o $@ $(CFLAGS) tests.c

board_print.h

@@ -1,3 +1,4 @@
+#pragma once
 
 #include <ctype.h>
 #include <locale.h>
@@ -9,15 +10,15 @@
 
 #define INDEX_FMT PRIu8
 
-static void bitboard_print(bitboard b, FILE* out)
+static void bitboard_print(Bb64 b, FILE* out)
 {
     setlocale(LC_ALL, "");
     fprintf(out, "\n");
-    for (index i = 7; i < 8; i--) {
+    for (Index8 i = 7; i < 8; i--) {
         fprintf(out, "\033[0m"); /* reset background color */
         fprintf(out, "%"INDEX_FMT" ", i+1);
-        for (index j = 0; j < 8; ++j) {
-            index const n = INDEX_FROM_RF(i,j);
+        for (Index8 j = 0; j < 8; ++j) {
+            Index8 const n = SQ_FROM_RF(i,j);
             int color;
             if ((b >> n) & 1) {
                 /* 41: red */
@@ -35,68 +36,14 @@ static void bitboard_print(bitboard b, FILE* out)
     fprintf(out, "  A B C D E F G H \n");
 }
 
-static void board_print_threats(const struct pos* pos, FILE* out, struct move* move)
-{
-    enum player const player = pos->player;
-    int buf[8][8] = {0};
-
-    bitboard const threats = all_threats_from_player(pos, player);
-
-    for (enum player player = PLAYER_BEGIN; player < PLAYER_COUNT; ++player) {
-        for (enum piece piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
-            bitboard x = pos->pieces[player][piece];
-
-            for (index i = 7; i < 8; i--) {
-                for (index j = 0; j < 8; ++j) {
-                    if (x & (1ULL<<(i*8+j))) {
-                        buf[i][j] = piece_unicode[player][piece];
-                    }
-                }
-            }
-        }
-    }
-
-    /* see: https://en.wikipedia.org/wiki/ANSI_escape_code#Colors */
-    setlocale(LC_ALL, ""); /* needed for unicode symbols */
-    for (index i = 7; i < 8; i--) {
-        fprintf(out, "\033[0m"); /* reset background color */
-        fprintf(out, "%"INDEX_FMT" ", i+1);
-        for (index j = 0; j < 8; ++j) {
-            index const n = INDEX_FROM_RF(i,j);
-
-            if (move && n == move->from) {
-                fprintf(out, "\033[%d;%dm", 30, 44); /* 44: blue*/
-            } else if (move && n == move->to) {
-                fprintf(out, "\033[%d;%dm", 30, 44); /* 104: bright blue*/
-            }
-            else if ((threats >> n) & 1) {
-                fprintf(out, "\033[%d;%dm", 30, 41); /* 41: red */
-            } else {
-                /* 45: magenta, 47: white */
-                fprintf(out, "\033[%d;%dm", 30, (i+j) % 2 ? 45 : 47);
-            }
-            if (buf[i][j]) {
-                fprintf(out, "%lc ", buf[i][j]);
-            } else {
-                fprintf(out, "  "); /* idk why this hack is needed but "%lc "
-                                       is not working when buf[i][j] = ' ' */
-            }
-        }
-        fprintf(out, "\033[0m"); /* reset background color */
-        fprintf(out, "\n");
-    }
-    fprintf(out, "  A B C D E F G H \n");
-}
-
 static void tt_print_stats(struct tt* tt, FILE* out)
 {
-#ifndef NDEBUG
     double sat = 0;
     for (size_t i = 0; i < TT_ENTRIES; ++i) {
         if (tt->entries[i].init)
             sat += 1.0;
     }
-    double const pct = sat/TT_ENTRIES;
+    double const pct = sat/((double)tt->mask+1.0);
 
     fprintf(out, "---- Stats ---\n");
     fprintf(out, "tt collisions: %"PRIu64"\n", tt->collisions);
@@ -104,23 +51,20 @@ static void tt_print_stats(struct tt* tt, FILE* out)
     fprintf(out, "tt probes:     %"PRIu64"\n", tt->probes);
     fprintf(out, "tt insertions: %"PRIu64"\n", tt->insertions);
     fprintf(out, "saturation:    %.02lf\n", pct);
-#else
-    fprintf(out, "stats not available with NDEBUG\n");
-#endif
 }
 
 static void board_print_fen(struct pos const* pos, FILE* out)
 {
     int buf[8][8] = {0};
 
-    for (enum player player = PLAYER_BEGIN; player < PLAYER_COUNT; ++player) {
-        for (enum piece piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
-            bitboard x = pos->pieces[player][piece];
+    for (Side8 side = SIDE_BEGIN; side < SIDE_COUNT; ++side) {
+        for (Piece8 piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
+                Bb64 x = pos->pieces[side][piece];
 
-            for (index i = 7; i < 8; i--) {
-                for (index j = 0; j < 8; ++j) {
+            for (Index8 i = 7; i < 8; i--) {
+                for (Index8 j = 0; j < 8; ++j) {
                     if (x & (1ULL<<(i*8+j))) {
-                        buf[i][j] = piece_char[player][piece];
+                        buf[i][j] = piece_char[side][piece];
                     }
                 }
             }
@@ -147,22 +91,22 @@ static void board_print_fen(struct pos const* pos, FILE* out)
             fprintf(out, "/");
     }
 
-    fprintf(out, " %c ", pos->player == PLAYER_WHITE ? 'w' : 'b');
+    fprintf(out, " %c ", pos->moving_side == SIDE_WHITE ? 'w' : 'b');
 
     bool any_castle = false;
-    if (!pos->castling_illegal[PLAYER_WHITE][CASTLE_KINGSIDE]) {
+    if (!pos->castling_illegal[SIDE_WHITE][CASTLE_KINGSIDE]) {
         fprintf(out, "K");
         any_castle = true;
     }
-    if (!pos->castling_illegal[PLAYER_WHITE][CASTLE_QUEENSIDE]) {
+    if (!pos->castling_illegal[SIDE_WHITE][CASTLE_QUEENSIDE]) {
         fprintf(out, "Q");
         any_castle = true;
     }
-    if (!pos->castling_illegal[PLAYER_BLACK][CASTLE_KINGSIDE]) {
+    if (!pos->castling_illegal[SIDE_BLACK][CASTLE_KINGSIDE]) {
         fprintf(out, "k");
         any_castle = true;
     }
-    if (!pos->castling_illegal[PLAYER_BLACK][CASTLE_QUEENSIDE]) {
+    if (!pos->castling_illegal[SIDE_BLACK][CASTLE_QUEENSIDE]) {
         fprintf(out, "q");
         any_castle = true;
     }
@@ -172,20 +116,20 @@ static void board_print_fen(struct pos const* pos, FILE* out)
 
     if (pos->ep_targets) {
         /* should be ep target square in algebraic notation */
-		enum square_index const sqi = bitboard_lsb(pos->ep_targets);
+        Sq8 const sqi = bitboard_lsb(pos->ep_targets);
 
-		assert(sqi >= SQ_INDEX_BEGIN && sqi < SQ_INDEX_COUNT);
+        assuming(sqi >= SQ_BEGIN && sqi < SQ_COUNT);
 
-		enum file_index const fi = index_to_file(sqi);
-		enum rank_index const ri = index_to_rank(sqi);
+        enum file_index const fi = sq_to_file(sqi);
+        enum rank_index const ri = sq_to_rank(sqi);
 
-		int const fch = tolower(file_index_char[fi]);
-		int const rch = tolower(rank_index_char[ri]);
+        int const fch = tolower(file_index_char[fi]);
+        int const rch = tolower(rank_index_char[ri]);
 
-		assert(fch >= 'a' && fch <= 'h');
-		assert(rch >= '1' && rch <= '8');
+        assuming(fch >= 'a' && fch <= 'h');
+        assuming(rch >= '1' && rch <= '8');
 
-		fprintf(out, " %c%c", fch, rch);
+        fprintf(out, " %c%c", fch, rch);
     } else {
         fprintf(out, " -");
     }
@@ -196,49 +140,79 @@ static void board_print_fen(struct pos const* pos, FILE* out)
     fprintf(out, "\n");
 }
 
-static void board_print(const struct pos* pos, struct move* move, FILE* out)
+static void board_print(struct pos const* pos, struct move* move, FILE* out, bool print_threats)
 {
     int buf[8][8] = {0};
+    int color[8][8] = {0};
 
-    for (enum player player = PLAYER_BEGIN; player < PLAYER_COUNT; ++player) {
-        for (enum piece piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
-            bitboard x = pos->pieces[player][piece];
+    for (Side8 side = SIDE_BEGIN; side < SIDE_COUNT; ++side) {
+        for (Piece8 piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
+            Bb64 x = pos->pieces[side][piece];
 
-            for (index i = 7; i < 8; i--) {
-                for (index j = 0; j < 8; ++j) {
+            for (Index8 i = 7; i < 8; i--) {
+                for (Index8 j = 0; j < 8; ++j) {
                     if (x & (1ULL<<(i*8+j))) {
-                        buf[i][j] = piece_unicode[player][piece];
+                        buf[i][j] = piece_unicode[SIDE_BLACK][piece];
+                        color[i][j] = (side == SIDE_WHITE)
+                            ? 1
+                            : 2;
                     }
                 }
             }
         }
     }
 
+    Bb64 const threats = all_threats_from_side(pos, pos->moving_side);
+
     /* see: https://en.wikipedia.org/wiki/ANSI_escape_code#Colors */
     setlocale(LC_ALL, "");
-    for (index i = 7; i < 8; i--) {
+    for (Index8 i = 7; i < 8; i--) {
         fprintf(out, "\033[0m"); /* reset background color */
         fprintf(out, "%"INDEX_FMT" ", i+1);
-        for (index j = 0; j < 8; ++j) {
-            index const n = INDEX_FROM_RF(i,j);
-            if (move && n == move->from) {
-                fprintf(out, "\033[%d;%dm", 30, 104); /* 44: blue*/
-            } else if (move && n == move->to) {
-                fprintf(out, "\033[%d;%dm", 30, 44); /* 104: bright blue*/
-            } else {
-                /* 45: magenta, 47: white */
-                fprintf(out, "\033[%d;%dm", 30, (i+j) % 2 ? 45 : 47);
+        for (Index8 j = 0; j < 8; ++j) {
+            Index8 const n = SQ_FROM_RF(i,j);
+
+            int bg, fg;
+
+            /* foreground color */
+            /**/ if (color[i][j] == 1) {
+                fg = 97; /* bright white */
             }
+            else if (color[i][j] == 2) {
+                fg = 30; /* black */
+            }
+            else {
+                fg = 35; /* magenta (should not happen) */
+            }
+
+            /* background color */
+            /**/ if (move && (n == move->to || n == move->from)) {
+                bg = 44; /* bright blue */
+            }
+            else if (print_threats && (threats >> n) & 1) {
+                bg = 41;
+            } else {
+                /* 45: magenta,
+                 * 43: yellow */
+                bg = (i+j) % 2 ? 45 : 43;
+            }
+
+            fprintf(out, "\033[%d;%dm", fg, bg);
+
             if (buf[i][j]) {
                 fprintf(out, "%lc ", buf[i][j]);
             } else {
                 fprintf(out, "  "); /* idk why this hack is needed but "%lc "
-                                       is not working when buf[i][j] = ' ' */
+                                       is not sufficient when buf[i][j] = ' ' */
             }
         }
         fprintf(out, "\033[0m"); /* reset background color */
         fprintf(out, "\n");
     }
     fprintf(out, "  A B C D E F G H \n");
+    fprintf(out, "half moves: %d\n"
+                 "full moves: %d\n",
+                 pos->halfmoves,
+                 pos->fullmoves);
 }
 

chess-worker.js

@@ -1,26 +1,25 @@
 let exports;
 
 async function init() {
-    const resp = await fetch("./chess.wasm");
-    if (!resp.ok) {
-        throw new Error("fetch wasm failed ${resp.status} ${resp.statusText}");
-    }
-
-    const { instance } =
-        await WebAssembly.instantiateStreaming(resp, {});
+    const resp = await fetch("./chess.wasm?rand=" + crypto.randomUUID());
+    if (!resp.ok) throw new Error(`fetch wasm failed ${resp.status} ${resp.statusText}`);
 
+    const { instance } = await WebAssembly.instantiateStreaming(resp, {});
     exports = instance.exports;
 }
+
 await init();
 self.postMessage({ type: "ready" });
 
 self.onmessage = (e) => {
     const { id, method, args = [] } = e.data;
     try {
-        const value = exports[method](...args);
+        let value;
+        value = exports[method](...args);
         self.postMessage({ id, ok: true, value });
     } catch (err) {
-        self.postMessage({ id, ok: false, error: String(err?.message ?? err) });
+        self.postMessage({
+            id, ok: false, error: String(err?.message ?? err)
+        });
     }
 };
-

chess.html

@@ -36,6 +36,7 @@
 </head>
 <body>
     <div id="board"></div>
-    <p id="result"></div>
+    <p id="result"></p>
 </body>
 </html>
+

chess.js

@@ -1,5 +1,7 @@
+/* this code is complete garbage but it's mostly for testing anyways */
 
 const MoveResult = Object.freeze({
+    ILLEGAL:  -1,
     NORMAL:    0,
     CHECK:     1,
     REPEATS:   2,
@@ -15,65 +17,44 @@ const _moveResultName = [
     "Checkmate",
 ];
 
+const moveResultName = (mr) => {
+    if (mr === MoveResult.ILLEGAL) return "Illegal";
+    return _moveResultName[mr] ?? `Unknown(${mr})`;
+};
+
+const isTerminal = (mr) => (mr === MoveResult.STALEMATE || mr === MoveResult.CHECKMATE);
+
 const Player = Object.freeze({
     White: 0,
     Black: 1,
     None:  2,
 });
 
-const _playerName = [
-    "White",
-    "Black",
-    "None",
-];
-
 const Piece = Object.freeze({
-    Pawn:   0,
-    King:   1,
-    Queen:  2,
+	Empty:  0,
+    Pawn:   1,
+    Knight: 2,
     Bishop: 3,
     Rook:   4,
-    Knight: 5,
-    Empty:  6,
+    Queen:  5,
+    King:   6,
 });
 
-const _pieceName = [
-    "Pawn",
-    "King",
-    "Queen",
-    "Bishop",
-    "Rook",
-    "Knight",
-    "Empty",
-];
-
-const _pieceChar = [
-    'P',
-    'K',
-    'Q',
-    'B',
-    'R',
-    'N',
-    ' ',
-];
-
 const _pieceUnicode = [
-    ['♙', '♔', '♕', '♗', '♖', '♘',], // white
-    ['♟', '♚', '♛', '♝', '♜', '♞',], // black
-    ['' , '',  '',  '',  '',  '', ],  // none
+    [' ', '♙', '♘', '♗', '♖', '♕', '♔',], // white
+    [' ', '♟', '♞', '♝', '♜', '♛', '♚',], // black
+    [' ', ' ', ' ', ' ', ' ', ' ', ' ',], // none
 ];
 
 const indexDeserialize = (n) => ({
-    rank: Math.floor(n / 8), // every day we stray further from God
+    rank: Math.floor(n / 8),
     file: (n % 8),
     fileChar() { return ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'][this.file]; },
     rankChar() { return ['1', '2', '3', '4', '5', '6', '7', '8'][this.rank]; },
 });
 
-
-const serializedIndexFromCoord = (rank, file) => (8*rank + file);
-
-const indexSerialize = (index) => (serializedIndexFromCoord(index.rank, index.file));
+const serializedIndexFromCoord = (rank, file) => (8 * rank + file);
+const indexSerialize = (index) => serializedIndexFromCoord(index.rank, index.file);
 
 const moveDeserialize = (n) => ({
     appeal: Number((n >> 24n) & 0xFFn),
@@ -83,80 +64,50 @@ const moveDeserialize = (n) => ({
 });
 
 const moveSerialize = (move) => (
-    (indexSerialize(move.from) & 0xFF) << 8) | ((indexSerialize(move.to) & 0xFF));
+    ((indexSerialize(move.from) & 0xFF) << 8) | (indexSerialize(move.to) & 0xFF)
+);
 
-const squareDeserialize = (n) => ({
-    player: n == -1 ? Player.None : (n >> 8) & 0xFF,
-    piece:  n == -1 ? Piece.Empty : (n & 0xFF),
-    playerName() {
-        if (this.player === Player.None) {
-            return "Empty";
-        } else {
-            return _playerName[this.player];
-        }
-    },
-    pieceName() {
-        if (this.player === Player.None) {
-            return "";
-        } else {
-            return this.playerName() +  _pieceName[this.piece];
-        }
-    },
-    pieceUnicode() {
-        return _pieceUnicode[this.player][this.piece];
-    }
-});
+const squareDeserialize = (n) => {
+	if (n === -1) {
+		return {
+			player: Player.None,
+			piece: Piece.Empty,
+			unicode: ' ',
+		};
+	}
 
-const WasmBoard = async (url) => {
-    /*
-    const res = await fetch(url);
-    if (!res.ok) {
-        throw new Error(`Failed to fetch ${url}: ${res.status} ${res.statusText}`);
-    }
-    const bytes = await res.arrayBuffer();
-    const instantiated = await WebAssembly.instantiate(bytes, {});
-    const instance = instantiated.instance ?? instantiated;
-    const exports = instance.exports;
+	const player  = (n >> 8) & 0xFF;
+	const piece   = n & 0xFF;
+	const unicode = _pieceUnicode[player][piece];
 
-    const wb_init     = exports.wb_init;
-    const wb_move     = exports.wb_move;
-    const wb_search   = exports.wb_search;
-    const wb_board_at = exports.wb_board_at;
-    */
-    const worker = new Worker("./chess-worker.js", { type: "module" });
+	return {
+		player: player,
+		piece:  piece,
+		unicode: unicode,
+	};
+};
+
+const WasmBoard = async () => {
+    const worker = new Worker("./chess-worker.js?rand=" + crypto.randomUUID(), { type: "module" });
 
     await new Promise((resolve, reject) => {
         worker.addEventListener("message", (e) => {
-            if (e.data?.type === "ready") {
-                resolve();
-            }
+            if (e.data?.type === "ready") resolve();
         }, { once: true });
         worker.addEventListener("error", reject, { once: true });
     });
 
     const wasmCall = (method, args = []) => new Promise((resolve, reject) => {
         const id = crypto.randomUUID();
+
         const onMessage = (e) => {
-            if (e.data?.id !== id) {
-                return;
-            }
+            if (e.data?.id !== id) return;
             cleanup();
-            if (e.data.ok) {
-                resolve(e.data.value);
-            } else {
-                reject(new Error(e.data.error));
-            }
-        };
-
-        const onError = (err) => {
-            cleanup();
-            reject(err);
-        };
-
-        const onMessageError = (e) => {
-            cleanup();
-            reject(new Error("Worker message deserialization failed (messageerror)."));
+            if (e.data.ok) resolve(e.data.value);
+            else reject(new Error(e.data.error));
         };
+        const onError = (err) => { cleanup(); reject(err); };
+        const onMessageError = () => { cleanup(); reject(new Error("Worker messageerror")); };
 
         const cleanup = () => {
             worker.removeEventListener("message", onMessage);
@@ -174,96 +125,202 @@ const WasmBoard = async (url) => {
     await wasmCall("wb_init", []);
 
     return {
-        state: MoveResult.Normal,
+        state: MoveResult.NORMAL,
 
-        ongoing: function() /* nil -> bool */ {
-            return (this.state != MoveResult.STALEMATE 
-                 && this.state != MoveResult.CHECKMATE);
+        search: async function(depth, timeout) {
+            return wasmCall("wb_search", [depth]).then(moveDeserialize);
         },
 
-        search: async function(depth) /* Int -> Move */ {
-            return wasmCall("wb_search", [depth])
-                        .then(moveDeserialize);
-        },
-
-        move: async function (move) /* (Move | SerializedMove) -> MoveResult */ {
+        move: async function(move) {
             const m = (typeof move === "number") ? move : moveSerialize(move);
-            return wasmCall("wb_move", [m]);
+            const mr = await wasmCall("wb_move", [m]);
+
+            if (mr === MoveResult.NORMAL || mr === MoveResult.CHECK || mr === MoveResult.REPEATS ||
+                mr === MoveResult.STALEMATE || mr === MoveResult.CHECKMATE) {
+                this.state = mr;
+                return mr;
+            }
+            return MoveResult.ILLEGAL;
         },
 
-        at: async function (index) /* (Index | SerializedIndex) -> Square */ {
+        at: async function(index) {
             const i = (typeof index === "number") ? index : indexSerialize(index);
             return wasmCall("wb_board_at", [i])
-                    .then(squareDeserialize);
+					.then(squareDeserialize);
+        },
+
+        legalMoves: async function() {
+            const n = await wasmCall("wb_all_moves_len", []);
+            const out = new Uint16Array(n);
+            for (let i = 0; i < n; ++i) {
+                out[i] = await wasmCall("wb_all_moves_get", [i]);
+            }
+            return out;
         },
     };
 };
 
-
 const run = async () => {
-    const board = await WasmBoard("./chess-worker.js");
+    const board = await WasmBoard();
 
-    const nextFrame = () => new Promise(requestAnimationFrame);
+    const boardElem = document.getElementById("board");
+    const resultEl = document.getElementById("result");
+    const setStatus = (s) => { resultEl.textContent = s; };
 
-    const createBoardUI = async (board) => {
-        const boardElem = document.getElementById("board");
+    const squares = new Array(64);
+
+    const idxToAlg = (idx) => {
+        const i = indexDeserialize(idx);
+        return `${i.fileChar()}${i.rankChar()}`;
+    };
+
+    const draw = async () => {
+        for (let rank = 7; rank >= 0; --rank) {
+            for (let file = 0; file < 8; ++file) {
+                const idx = 8 * rank + file;
+                const sq = await board.at(idx);
+				console.log(sq);
+				console.log(sq.unicode);
+                squares[idx].textContent = sq.unicode;
+            }
+        }
+    };
+
+    const createBoardUI = () => {
         boardElem.replaceChildren();
-        const filesChars = ["a","b","c","d","e","f","g","h"];
-        const ranksChars = ["8","7","6","5","4","3","2","1"];
-
-        const squares = new Array(64);
-
         for (let rank = 7; rank >= 0; --rank) {
             for (let file = 0; file < 8; ++file) {
+                const idx = 8 * rank + file;
                 const el = document.createElement("div");
-                el.className =
-                    "square " + ((file + rank) % 2 ? "dark" : "light");
-                el.dataset.file = filesChars[file];
-                el.dataset.rank = ranksChars[rank];
-
-                const sq = await board.at(serializedIndexFromCoord(rank, file));
-                el.textContent = sq.pieceUnicode();
-
+                el.className = "square " + (((file + rank) % 2) ? "dark" : "light");
+                el.dataset.idx = String(idx);
                 boardElem.appendChild(el);
-                squares[8*rank+file] = el;
-            }
-        }
-
-        return squares;
-    };
-
-    const draw = async (board, squareElems) => {
-        for (let rank = 7; rank >= 0; --rank) {
-            for (let file = 0; file < 8; ++file) {
-                const sq = await board.at(serializedIndexFromCoord(rank, file));
-                squareElems[8*rank+file].textContent = sq.pieceUnicode();
+                squares[idx] = el;
             }
         }
     };
 
-    const sqElems = await createBoardUI(board);
-    for (let i = 0; i < 200; ++i) {
-        await draw(board, sqElems);
-        await nextFrame();
+    createBoardUI();
+    await draw();
 
-        const move = await board.search(7);
+    let selected = null;     // 0..63 or null
+    let inputEnabled = true;
 
-        const fromSq = await board.at(move.from);
-        const toSq   = await board.at(move.to);
+    const clearSelection = () => {
+        if (selected !== null) squares[selected].classList.remove("blue");
+        selected = null;
+    };
 
-        const mr = board.move(move);
-        if (mr == MoveResult.STALEMATE || mr == MoveResult.CHECKMATE) {
-            const resultEl = document.getElementById("result");
-            resultEl.textContent = _moveResultName[board.state];
-            draw(board, sqElems);
-            await nextFrame();
-            break;
+    const legalHasFrom = (moves, fromIdx) => {
+        for (const mv of moves) {
+            if (((mv >> 8) & 0xFF) === fromIdx) return true;
         }
+        return false;
+    };
+
+    const legalHasMove = (moves, fromIdx, toIdx) => {
+        const key = ((fromIdx & 0xFF) << 8) | (toIdx & 0xFF);
+        for (const mv of moves) {
+            if (mv === key) return true;
+        }
+        return false;
+    };
+
+    const engineReply = async (depth) => {
+        console.log("searching");
+        setStatus("Black thinking...");
+        const m = await board.search(depth, 2000);
+        console.log("found move", m, );
+        let sooner = Date.now();
+        const mr = await board.move(m);
+        await draw();
+        let later = Date.now();
+        let seconds = later - sooner;
+        setStatus(`Black played ${idxToAlg(indexSerialize(m.from))}-${idxToAlg(indexSerialize(m.to))} after ${seconds} seconds\nWhite to move...`);
+        return mr;
+    };
+
+    const onSquareClick = async (idx) => {
+        if (!inputEnabled) return;
+        if (isTerminal(board.state)) return;
+
+        const legalMoves = await board.legalMoves();
+
+        if (selected === null) {
+            const sq = await board.at(idx);
+            if (sq.player !== Player.White) return;
+
+            if (!legalHasFrom(legalMoves, idx)) {
+                clearSelection();
+                setStatus(`No legal moves from ${idxToAlg(idx)}.`);
+                return;
+            }
+
+            selected = idx;
+            squares[selected].classList.add("blue");
+            setStatus(`Selected ${idxToAlg(idx)}.`);
+            return;
+        }
+
+        if (idx === selected) {
+            clearSelection();
+            setStatus("");
+            return;
+        }
+
+        const clickedSq = await board.at(idx);
+
+        // user clicks another white piece: either switch selection (if it has moves) or deselect
+        if (clickedSq.player === Player.White) {
+            clearSelection();
+
+            if (!legalHasFrom(legalMoves, idx)) {
+                setStatus(`No legal moves from ${idxToAlg(idx)}.`);
+                return;
+            }
+
+            selected = idx;
+            squares[selected].classList.add("blue");
+            setStatus(`Selected ${idxToAlg(idx)}.`);
+            return;
+        }
+
+        const from = selected;
+        const to = idx;
+
+        if (!legalHasMove(legalMoves, from, to)) {
+            clearSelection();
+            setStatus(`Illegal: ${idxToAlg(from)}-${idxToAlg(to)}.`);
+            return;
+        }
+
+        clearSelection();
+        inputEnabled = false;
+
+        const mrWhite = await board.move({ from: indexDeserialize(from), to: indexDeserialize(to) });
+        await draw();
+        setStatus(`White played ${idxToAlg(from)}-${idxToAlg(to)}. ${moveResultName(mrWhite)}`);
+
+        if (isTerminal(mrWhite)) {
+            inputEnabled = false;
+            return;
+        }
+
+        const mrBlack = await engineReply(8);
+        if (isTerminal(mrBlack)) {
+            inputEnabled = false;
+            return;
+        }
+
+        inputEnabled = true;
+    };
+
+    for (let i = 0; i < 64; ++i) {
+        squares[i].addEventListener("click", () => { onSquareClick(i).catch(console.error); });
     }
-}
 
-run().catch((err) => {
-    console.error(err);
-});
+    setStatus("White to move.");
+};
 
+run().catch((err) => console.error(err));
 

codegen.c

@@ -5,60 +5,48 @@
 #include <stdlib.h>
 #include <stdio.h>
 
-/* gets the next number with the same bitcount, unless it overflows, in which
- * it returns the first number with popcount+1 */
-uint64_t next_magic(uint64_t seed) {
-
-    uint64_t u = seed & -seed; // rightmost 1-bit
-    uint64_t v = seed + u;     // add it
-    if (v == 0) {
-        if (seed == ~0ULL) {
-            return 0;
-        }
-        return next_magic((1ULL << (popcount(seed)+1)) - 1);
-    }
-    seed = v + (((v ^ seed) / u) >> 2);
-
-    return seed;
-}
-
-
 int main()
 {
-    struct magic rook_magics[SQ_INDEX_COUNT] = {0ULL};
-    bitboard rook_attacks[SQ_INDEX_COUNT][1<<12ULL] = {0};
+    struct magic rook_magics[SQ_COUNT] = {0ULL};
+    Bb64 rook_attacks[SQ_COUNT][1<<12ULL] = {0};
 
-    index rook_relevant_bits[12] = {0};
+    Index8 rook_relevant_bits[12] = {0};
     size_t rook_relevant_bits_count = 0;
 
-    struct magic bishop_magics[SQ_INDEX_COUNT] = {0ULL};
-    bitboard bishop_attacks[SQ_INDEX_COUNT][1<<9ULL] = {0};
+    struct magic bishop_magics[SQ_COUNT] = {0ULL};
+    Bb64 bishop_attacks[SQ_COUNT][1<<9ULL] = {0};
 
-    index bishop_relevant_bits[9] = {0};
+    Index8 bishop_relevant_bits[9] = {0};
     size_t bishop_relevant_bits_count = 0;
 
-    bitboard between_lookup[SQ_INDEX_COUNT][SQ_INDEX_COUNT];
+    Bb64 between_lookup[SQ_COUNT][SQ_COUNT];
 
-    for (enum square_index sq_index = SQ_INDEX_BEGIN; sq_index < SQ_INDEX_COUNT; ++sq_index) {
-        enum file_index file = index_to_file(sq_index);
-        enum rank_index rank = index_to_rank(sq_index);
-        fprintf(stderr, "%s ", square_index_display[sq_index]);
+    Bb64 diagonals[SQ_COUNT];
+
+    for (Sq8 sq = SQ_BEGIN; sq < SQ_COUNT; ++sq) {
+        diagonals[sq] = diagonals_from_index(sq);
+    }
+
+    for (Sq8 sq_index = SQ_BEGIN; sq_index < SQ_COUNT; ++sq_index) {
+        enum file_index file = sq_to_file(sq_index);
+        enum rank_index rank = sq_to_rank(sq_index);
+        fprintf(stderr, "%s ", sq8_display[sq_index]);
 
         /* ROOKS
          * ======================= */
         {
             /* generate attack mask */
-            bitboard atk_mask = 0;
+            Bb64 atk_mask = 0;
             {
                 atk_mask |= FILE_MASK(file) & ~(RANK_MASK_1 | RANK_MASK_8);
                 atk_mask |= RANK_MASK(rank) & ~(FILE_MASK_A | FILE_MASK_H);
-                atk_mask &= ~SQ_MASK_FROM_RF(rank, file);
+                atk_mask &= ~MASK_FROM_RF(rank, file);
 
                 /* populate relevant bits array */
                 rook_relevant_bits_count = 0;
-                bitboard x = atk_mask;
+                Bb64 x = atk_mask;
                 while (x) {
-                    const index lsb = bitboard_pop_lsb(&x);
+                    Sq8 const lsb = bitboard_pop_lsb(&x);
                     rook_relevant_bits[rook_relevant_bits_count++] = lsb;
                 }
             }
@@ -66,12 +54,12 @@ int main()
 
             /* brute force the magic number */
             for (;;) {
-                bitboard magic = my_rand64() & my_rand64() & my_rand64();
+                Bb64 magic = my_rand64() & my_rand64() & my_rand64();
 
-                bitboard atk = 0ULL;
-                for (bitboard test = 0; test < (1ULL<<rook_relevant_bits_count); test++) {
+                Bb64 atk = 0ULL;
+                for (Bb64 test = 0; test < (1ULL<<rook_relevant_bits_count); test++) {
                     /* map test to an occupany set */
-                    bitboard occ = 0ULL;
+                    Bb64 occ = 0ULL;
                     for (size_t i = 0; i < rook_relevant_bits_count; i++) {
                         occ |= ((test >> i) & 1ULL) << rook_relevant_bits[i];
                     }
@@ -102,32 +90,32 @@ int main()
          * ====================== */
         {
             /* generate attack mask */
-            bitboard atk_mask = 0;
+            Bb64 atk_mask = 0;
             {
                 atk_mask |= diagonals_from_index(sq_index);
                 atk_mask &= ~(RANK_MASK_1 | RANK_MASK_8);
                 atk_mask &= ~(FILE_MASK_A | FILE_MASK_H);
-                atk_mask &= ~SQ_MASK_FROM_RF(rank, file);
+                atk_mask &= ~MASK_FROM_RF(rank, file);
 
                 /* populate relevant bits array */
                 bishop_relevant_bits_count = 0;
-                bitboard x = atk_mask;
+                Bb64 x = atk_mask;
                 while (x) {
-                    const index lsb = bitboard_pop_lsb(&x);
+                    Sq8 const lsb = bitboard_pop_lsb(&x);
                     bishop_relevant_bits[bishop_relevant_bits_count++] = lsb;
                 }
             }
             bishop_magics[sq_index].mask = atk_mask;
 
             /* brute force the magic number */
-            bitboard magic = 0ULL;
+            Bb64 magic = 0ULL;
             for (;;) {
                 magic = my_rand64() & my_rand64() & my_rand64();
 
-                bitboard atk = 0ULL;
-                for (bitboard test = 0; test < (1ULL<<bishop_relevant_bits_count); test++) {
+                Bb64 atk = 0ULL;
+                for (Bb64 test = 0; test < (1ULL<<bishop_relevant_bits_count); test++) {
                     /* map test to an occupany set */
-                    bitboard occ = 0ULL;
+                    Bb64 occ = 0ULL;
                     for (size_t i = 0; i < bishop_relevant_bits_count; i++) {
                         occ |= ((test >> i) & 1ULL) << bishop_relevant_bits[i];
                     }
@@ -155,8 +143,8 @@ int main()
         /* BETWEEN TABLE
          * ===================== */
         {
-            for (enum square_index i = SQ_INDEX_BEGIN; i < SQ_INDEX_COUNT; ++i) {
-                for (enum square_index j = SQ_INDEX_BEGIN; j < SQ_INDEX_COUNT; ++j) {
+            for (Sq8 i = SQ_BEGIN; i < SQ_COUNT; ++i) {
+                for (Sq8 j = SQ_BEGIN; j < SQ_COUNT; ++j) {
                     between_lookup[i][j] = between_mask(i, j);
                 }
             }
@@ -167,6 +155,23 @@ int main()
 #define TAB "    "
 #define NL "\n"
 
+    { /* diagonals */
+        FILE* f = fopen("diagonals.h", "w");
+        if (!f) {
+            perror("fopen");
+            exit(EXIT_FAILURE);
+        }
+
+        fprintf(f, "static const Bb64 diagonals[SQ_COUNT] = {\n");
+        for (Sq8 i = SQ_BEGIN; i < SQ_COUNT; ++i) {
+            fprintf(f, "[%s] = 0x%016"BITBOARD_FMT_X",\n",
+                    sq8_str[i],
+                    diagonals[i]);
+        }
+        fprintf(f,"};\n");
+        fclose(f);
+    }
+
     { /* rooks */
         FILE* f = fopen("mbb_rook.h", "w");
         if (!f) {
@@ -175,15 +180,15 @@ int main()
         }
 
         fprintf(f, "#pragma once\n");
-        fprintf(f, "static const struct magic mbb_rook[SQ_INDEX_COUNT] = {\n");
-        for (enum square_index i = SQ_INDEX_BEGIN; i < SQ_INDEX_COUNT; i++) {
+        fprintf(f, "static const struct magic mbb_rook[SQ_COUNT] = {\n");
+        for (Sq8 i = SQ_BEGIN; i < SQ_COUNT; i++) {
             fprintf(f,
                  TAB "[%s] = (struct magic) {"
               NL TAB "    .magic = 0x%016"BITBOARD_FMT_X"ULL,"
               NL TAB "    .mask  = 0x%016"BITBOARD_FMT_X"ULL,"
               NL TAB "},"
               NL,
-              square_index_str[i],
+              sq8_str[i],
               rook_magics[i].magic,
               rook_magics[i].mask);
         }
@@ -191,9 +196,9 @@ int main()
 
         fprintf(f,"\n");
 
-        fprintf(f, "static const bitboard rook_attacks[SQ_INDEX_COUNT][1ULL<<12ULL] = {\n");
-        for (enum square_index sq = SQ_INDEX_BEGIN; sq < SQ_INDEX_COUNT; ++sq) {
-            fprintf(f, "[%s] = {\n", square_index_str[sq]);
+        fprintf(f, "static const Bb64 rook_attacks[SQ_COUNT][1ULL<<12ULL] = {\n");
+        for (Sq8 sq = SQ_BEGIN; sq < SQ_COUNT; ++sq) {
+            fprintf(f, "[%s] = {\n", sq8_str[sq]);
             for (size_t i = 0; i < sizeof rook_attacks[sq] / sizeof *rook_attacks[sq]; i++) {
                 fprintf(f, "0x%016"BITBOARD_FMT_X"ULL, \n", rook_attacks[sq][i]);
             }
@@ -212,15 +217,15 @@ int main()
         }
 
         fprintf(f, "\n");
-        fprintf(f, "static const struct magic mbb_bishop[SQ_INDEX_COUNT] = {\n");
-        for (enum square_index i = SQ_INDEX_BEGIN; i < SQ_INDEX_COUNT; i++) {
+        fprintf(f, "static const struct magic mbb_bishop[SQ_COUNT] = {\n");
+        for (Sq8 i = SQ_BEGIN; i < SQ_COUNT; i++) {
             fprintf(f,
                  TAB "[%s] = (struct magic) {"
               NL TAB "    .magic = 0x%016"BITBOARD_FMT_X"ULL,"
               NL TAB "    .mask  = 0x%016"BITBOARD_FMT_X"ULL,"
               NL TAB "},"
               NL,
-              square_index_str[i],
+              sq8_str[i],
               bishop_magics[i].magic,
               bishop_magics[i].mask);
         }
@@ -228,15 +233,16 @@ int main()
 
         fprintf(f,"\n");
 
-        fprintf(f, "static const bitboard bishop_attacks[SQ_INDEX_COUNT][1ULL<<9ULL] = {\n");
-        for (enum square_index sq = SQ_INDEX_BEGIN; sq < SQ_INDEX_COUNT; ++sq) {
-            fprintf(f, "[%s] = {\n", square_index_str[sq]);
+        fprintf(f, "static const Bb64 bishop_attacks[SQ_COUNT][1ULL<<9ULL] = {\n");
+        for (Sq8 sq = SQ_BEGIN; sq < SQ_COUNT; ++sq) {
+            fprintf(f, "[%s] = {\n", sq8_str[sq]);
             for (size_t i = 0; i < sizeof bishop_attacks[sq] / sizeof *bishop_attacks[sq]; i++) {
                 fprintf(f, "0x%016"BITBOARD_FMT_X"ULL, \n", bishop_attacks[sq][i]);
             }
             fprintf(f, "\n},\n");
         }
         fprintf(f,"};\n");
+        fclose(f);
     }
 
     { /* between table */
@@ -246,15 +252,16 @@ int main()
             exit(EXIT_FAILURE);
         }
 
-        fprintf(f, "static const bitboard between_lookup[SQ_INDEX_COUNT][SQ_INDEX_COUNT] = {\n");
-        for (enum square_index i = SQ_INDEX_BEGIN; i < SQ_INDEX_COUNT; ++i) {
-            fprintf(f, "[%s] = {\n", square_index_str[i]);
-            for (enum square_index j = SQ_INDEX_BEGIN; j < SQ_INDEX_COUNT; ++j) {
+        fprintf(f, "static const Bb64 between_lookup[SQ_COUNT][SQ_COUNT] = {\n");
+        for (Sq8 i = SQ_BEGIN; i < SQ_COUNT; ++i) {
+            fprintf(f, "[%s] = {\n", sq8_str[i]);
+            for (Sq8 j = SQ_BEGIN; j < SQ_COUNT; ++j) {
                 fprintf(f, "0x%016"BITBOARD_FMT_X"ULL, \n", between_lookup[i][j]);
             }
             fprintf(f, "\n},\n");
         }
         fprintf(f,"};\n");
+        fclose(f);
     }
 
 #undef TAB

engine-attack-sets.h

@@ -0,0 +1,610 @@
+#pragma once
+
+#include "engine-types.h"
+#include "engine-board.h"
+
+/* `struct magic` is used by magic bitboard lookups, see
+ * rook_attacks_from_index and bishop_attacks_from_index */
+struct magic {
+    Bb64 mask;
+    Bb64 magic;
+};
+
+static Bb64 cardinals_from_index(Sq8 p)
+{
+    return (FILE_MASK(sq_to_file(p)) | RANK_MASK(sq_to_rank(p)));
+}
+
+static Bb64 cardinals(Bb64 p)
+{
+    Bb64 b = 0ULL;
+    while (p) {
+        Sq8 const lsb = bitboard_pop_lsb(&p);
+        b |= cardinals_from_index(lsb);
+    }
+    return b;
+}
+
+static Bb64 diagonals_from_index(Sq8 sq)
+{
+#ifdef CODEGEN
+    enum rank_index const rank = sq_to_rank(sq);
+    enum file_index const file = sq_to_file(sq);
+
+    Bb64 mask = 0ULL;
+
+    _Static_assert(((enum rank_index)-1) > 0, "rank_index must be unsigned");
+    _Static_assert(((enum file_index)-1) > 0, "file_index must be unsigned");
+
+    enum rank_index r;
+    enum file_index f;
+    for (r = rank+1, f = file+1;
+         r <= RANK_INDEX_8 && f <= FILE_INDEX_H;
+         ++r, ++f)
+    {
+        mask |= MASK_FROM_RF(r, f);
+    }
+
+    for (r = rank+1, f = file-1;
+         r <= RANK_INDEX_8 && f <= FILE_INDEX_H;
+         ++r, --f)
+    {
+        mask |= MASK_FROM_RF(r, f);
+    }
+
+    for (r = rank-1, f = file+1;
+         r <= RANK_INDEX_8 && f <= FILE_INDEX_H;
+         --r, ++f)
+    {
+        mask |= MASK_FROM_RF(r, f);
+    }
+
+    for (r = rank-1, f = file-1;
+         r <= RANK_INDEX_8 && f <= FILE_INDEX_H;
+         --r, --f)
+    {
+        mask |= MASK_FROM_RF(r, f);
+    }
+    return mask;
+
+#else
+    #if ! __has_include("diagonals.h")
+        #error "compile with -DCODEGEN and run once to generate required header files"
+    #endif
+    #include "diagonals.h" /* defines static Bb64 diagonals[SQ_COUNT]; */
+    return diagonals[sq];
+#endif
+}
+
+static Bb64 diagonals(Bb64 p)
+{
+    Bb64 b = 0ULL;
+    while (p) {
+        Sq8 const lsb = bitboard_pop_lsb(&p);
+        b |= diagonals_from_index(lsb);
+    }
+    return b;
+}
+
+
+/* PIECE ATTACKS
+ * ==================
+ *
+ * All piece attack functions rely on the caller masking their own pieces.
+ * e.g. `knight_attacks(knights) & empty`
+ * */
+
+static Bb64 knight_attacks(Bb64 p)
+{
+    Bb64 const l1 = MASK_SHIFT_EAST_1(p /*& ~FILE_MASK_H*/);
+    Bb64 const l2 = MASK_SHIFT_EAST_2(p /*& ~(FILE_MASK_G | FILE_MASK_H)*/);
+    Bb64 const r1 = MASK_SHIFT_WEST_1 (p /*& ~FILE_MASK_A*/);
+    Bb64 const r2 = MASK_SHIFT_WEST_2 (p /*& ~(FILE_MASK_A | FILE_MASK_B)*/);
+    Bb64 const h1 = l1 | r1;
+    Bb64 const h2 = l2 | r2;
+    return MASK_SHIFT_NORTH_2(h1)
+         | MASK_SHIFT_SOUTH_2(h1)
+         | MASK_SHIFT_NORTH_1(h2)
+         | MASK_SHIFT_SOUTH_1(h2);
+}
+
+static Bb64 knight_attacks_from_index(Sq8 sq)
+{
+    return knight_attacks(MASK_FROM_SQ(sq));
+}
+
+static Bb64 rook_attacks_from_index(Sq8 sq, Bb64 occ)
+{
+#ifdef CODEGEN
+    enum rank_index const rank = sq_to_rank(sq);
+    enum file_index const file = sq_to_file(sq);
+
+    Bb64 atk = 0ULL;
+
+    /* following loops assuming rank and file types are unsigned, which relies on C23 enums */
+    _Static_assert(((enum rank_index)-1) > 0, "rank_index must be unsigned");
+    _Static_assert(((enum file_index)-1) > 0, "file_index must be unsigned");
+
+    for (enum rank_index walk_rank = rank+1; walk_rank <= RANK_INDEX_8; ++walk_rank) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (enum rank_index walk_rank = rank-1; walk_rank <= RANK_INDEX_8; --walk_rank) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (enum file_index walk_file = file+1; walk_file <= FILE_INDEX_H; ++walk_file) {
+        Bb64 const sq = MASK_FROM_RF(rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (enum file_index walk_file = file-1; walk_file <= FILE_INDEX_H; --walk_file) {
+        Bb64 const sq = MASK_FROM_RF(rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+
+    return atk;
+
+#else
+    #if ! __has_include("mbb_rook.h")
+        #error "compile with -DCODEGEN and run once to generate required header files"
+    #else
+
+    /* defines
+       - `mbb_rook[SQ_COUNT]`
+       - `Bb64 rook_attacks[SQ_COUNT][1<<12ULL] */
+    #include "mbb_rook.h"
+
+    struct magic const m = mbb_rook[sq];
+    occ &= m.mask;
+    occ *= m.magic;
+    occ >>= (64ULL-12ULL);
+    assuming(rook_attacks[sq][occ] != MASK_FROM_SQ(sq));
+    return rook_attacks[sq][occ];
+
+    #endif
+#endif
+}
+
+static Bb64 rook_attacks(Bb64 p, Bb64 occ)
+{
+    Bb64 b = 0ULL;
+    while (p) {
+        Sq8 const lsb = bitboard_pop_lsb(&p);
+        b |= rook_attacks_from_index(lsb, occ);
+    }
+    return b;
+}
+
+static Bb64 bishop_attacks_from_index(Sq8 sq, Bb64 occ)
+{
+#ifdef CODEGEN
+    enum rank_index const rank = sq_to_rank(sq);
+    enum file_index const file = sq_to_file(sq);
+
+    Bb64 atk = 0ULL;
+
+    /* following loops assuming rank and file types are unsigned, which relies on C23 enums */
+    _Static_assert(((enum rank_index)-1) > 0, "rank_index must be unsigned");
+    _Static_assert(((enum file_index)-1) > 0, "file_index must be unsigned");
+
+    enum rank_index walk_rank;
+    enum file_index walk_file;
+    for (walk_rank = rank+1, walk_file = file+1;
+            walk_rank <= RANK_INDEX_8 && walk_file <= FILE_INDEX_H;
+            ++walk_rank, ++walk_file) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (walk_rank = rank+1, walk_file = file-1;
+            walk_rank <= RANK_INDEX_8 && walk_file <= FILE_INDEX_H;
+            ++walk_rank, --walk_file) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (walk_rank = rank-1, walk_file = file+1;
+            walk_rank <= RANK_INDEX_8 && walk_file <= FILE_INDEX_H;
+            --walk_rank, ++walk_file) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+    for (walk_rank = rank-1, walk_file = file-1;
+            walk_rank <= RANK_INDEX_8 && walk_file <= FILE_INDEX_H;
+            --walk_rank, --walk_file) {
+        Bb64 const sq = MASK_FROM_RF(walk_rank, walk_file);
+        atk |= sq;
+        if (occ & sq) {
+            break;
+        }
+    }
+
+    return atk;
+#else
+    #if ! __has_include("mbb_bishop.h")
+        #error "compile with -DCODEGEN and run once to generate required header files"
+    #else
+
+/* defines
+   - `mbb_bishop[SQ_COUNT]`
+   - `Bb64 bishop_attacks[SQ_COUNT][1<<9ULL] */
+#include "mbb_bishop.h"
+    assuming(sq < SQ_COUNT);
+    struct magic const m = mbb_bishop[sq];
+    occ &= m.mask;
+    occ *= m.magic;
+    occ >>= (64ULL-9ULL);
+    return bishop_attacks[sq][occ];
+    #endif
+#endif
+}
+
+static Bb64 bishop_attacks(Bb64 p, Bb64 occ)
+{
+    Bb64 b = 0ULL;
+    while (p) {
+        Sq8 const lsb = bitboard_pop_lsb(&p);
+        b |= bishop_attacks_from_index(lsb, occ);
+    }
+    return b;
+}
+
+static Bb64 queen_attacks_from_index(Sq8 sq, Bb64 occ)
+{
+    return bishop_attacks_from_index(sq, occ) | rook_attacks_from_index(sq, occ);
+}
+
+static Bb64 queen_attacks(Bb64 p, Bb64 occ)
+{
+    Bb64 b = 0ULL;
+    while (p) {
+        Sq8 const lsb = bitboard_pop_lsb(&p);
+        b |= queen_attacks_from_index(lsb, occ);
+    }
+    return b;
+}
+
+#define DEFINE_PAWN_MOVE_FUNCTIONS(identifier, side_enum, direction, starting_rank, next_rank) \
+static inline Bb64 pawn_moves_##identifier(Bb64 p, Bb64 empty)\
+{\
+    Bb64 const single_push = MASK_SHIFT_##direction##_1(p) & empty;\
+    Bb64 const double_push =\
+        MASK_SHIFT_##direction##_1(single_push & next_rank) & empty;\
+    return (single_push | double_push);\
+}\
+\
+static inline Bb64 pawn_moves_##identifier##_from_index(Sq8 sq, Bb64 empty)\
+{\
+    return pawn_moves_##identifier(MASK_FROM_SQ(sq), empty);\
+}\
+\
+static inline Bb64 pawn_single_push_##identifier(Bb64 p, Bb64 empty)\
+{\
+    return MASK_SHIFT_##direction##_1(p) & empty;\
+}\
+\
+static inline Bb64 pawn_double_push_##identifier(Bb64 p, Bb64 empty)\
+{\
+    Bb64 const once  = MASK_SHIFT_##direction##_1(p) & empty;\
+    Bb64 const twice = MASK_SHIFT_##direction##_1(once) & empty;\
+    return twice;\
+}\
+\
+static inline Bb64 pawn_attacks_right_##identifier(Bb64 p)\
+{\
+    Bb64 const up = MASK_SHIFT_##direction##_1(p);\
+    return MASK_SHIFT_EAST_1(up);\
+}\
+\
+static inline Bb64 pawn_attacks_left_##identifier(Bb64 p)\
+{\
+    Bb64 const up = MASK_SHIFT_##direction##_1(p);\
+    return MASK_SHIFT_WEST_1(up);\
+}\
+\
+static inline Bb64 pawn_attacks_##identifier(Bb64 p)\
+{\
+    Bb64 const up = MASK_SHIFT_##direction##_1(p);\
+    Bb64 const captures_right = MASK_SHIFT_EAST_1(up);\
+    Bb64 const captures_left  = MASK_SHIFT_WEST_1(up);\
+\
+    return (captures_right | captures_left);\
+}\
+\
+static inline Bb64 pawn_attacks_##identifier##_from_index(Sq8 sq)\
+{\
+    return pawn_attacks_##identifier(MASK_FROM_SQ(sq));\
+}
+
+DEFINE_PAWN_MOVE_FUNCTIONS(white, SIDE_WHITE, NORTH, RANK_MASK_2, RANK_MASK_3)
+DEFINE_PAWN_MOVE_FUNCTIONS(black, SIDE_BLACK, SOUTH, RANK_MASK_7, RANK_MASK_6)
+
+/* temporary solution, annoying branch */
+static inline Bb64 pawn_moves_dispatch(Bb64 p, Bb64 empty, Side8 attacker)
+{
+    if (attacker == SIDE_WHITE) {
+        return pawn_moves_white(p, empty);
+    } else {
+        return pawn_moves_black(p, empty);
+    }
+}
+
+/* temporary solution, annoying branch */
+static inline Bb64 pawn_moves_from_index_dispatch(Sq8 sq, Bb64 empty, Side8 attacker)
+{
+    if (attacker == SIDE_WHITE) {
+        return pawn_moves_white_from_index(sq, empty);
+    } else {
+        return pawn_moves_black_from_index(sq, empty);
+    }
+}
+
+/* temporary solution, annoying branch */
+static inline Bb64 pawn_attacks_from_index_dispatch(Sq8 sq, Side8 attacker)
+{
+    if (attacker == SIDE_WHITE) {
+        return pawn_attacks_white_from_index(sq);
+    } else {
+        return pawn_attacks_black_from_index(sq);
+    }
+}
+
+static inline Bb64 pawn_attacks_dispatch(Bb64 b, Side8 attacker)
+{
+    if (attacker == SIDE_WHITE) {
+        return pawn_attacks_white(b);
+    } else {
+        return pawn_attacks_black(b);
+    }
+}
+
+static Bb64 king_attacks(Bb64 sq)
+{
+    /* potential untested improvements:
+     * - lookup table
+     * - union of three files, three ranks and ~sq */
+    Bb64 const n = MASK_SHIFT_NORTH_1(sq);
+    Bb64 const s = MASK_SHIFT_SOUTH_1(sq);
+    Bb64 const w = MASK_SHIFT_WEST_1(sq);
+    Bb64 const e = MASK_SHIFT_EAST_1(sq);
+
+    Bb64 const nw = MASK_SHIFT_WEST_1(n);
+    Bb64 const ne = MASK_SHIFT_EAST_1(n);
+    Bb64 const sw = MASK_SHIFT_WEST_1(s);
+    Bb64 const se = MASK_SHIFT_EAST_1(s);
+
+    return (n | s | w | e | nw | ne | sw | se);
+}
+
+static Bb64 king_attacks_from_index(Sq8 sq)
+{
+    return king_attacks(MASK_FROM_SQ(sq));
+}
+
+static Bb64 non_pawn_piece_attacks(Piece8 piece, Bb64 p, Bb64 occ)
+{
+    assuming(piece != PIECE_PAWN);
+
+    switch (piece) {
+        case PIECE_KNIGHT: {
+            return knight_attacks(p);
+        } break;
+
+        case PIECE_BISHOP: {
+            return bishop_attacks(p, occ);
+        } break;
+
+        case PIECE_ROOK: {
+            return rook_attacks(p, occ);
+        } break;
+
+        case PIECE_QUEEN: {
+            return queen_attacks(p, occ);
+        } break;
+
+        case PIECE_KING: {
+            return king_attacks(p);
+        } break;
+
+        default: {
+            assuming(false);
+        } break;
+    }
+}
+
+static Bb64 non_pawn_piece_attacks_from_index(Piece8 piece, Sq8 sq, Bb64 occ)
+{
+    assuming(piece != PIECE_PAWN);
+
+    switch (piece) {
+        case PIECE_KNIGHT: {
+            return knight_attacks_from_index(sq);
+        } break;
+
+        case PIECE_BISHOP: {
+            return bishop_attacks_from_index(sq, occ);
+        } break;
+
+        case PIECE_ROOK: {
+            return rook_attacks_from_index(sq, occ);
+        } break;
+
+        case PIECE_QUEEN: {
+            return queen_attacks_from_index(sq, occ);
+        } break;
+
+        case PIECE_KING: {
+            return king_attacks_from_index(sq);
+        } break;
+
+        default: {
+            assuming(false);
+        } break;
+    }
+}
+
+static Bb64 between_mask(Sq8 a, Sq8 b)
+{
+#ifdef CODEGEN
+    enum rank_index const ra = sq_to_rank(a);
+    enum file_index const fa = sq_to_file(a);
+    enum rank_index const rb = sq_to_rank(b);
+    enum file_index const fb = sq_to_file(b);
+
+    /* directional differences */
+    int const dr = (int)rb - (int)ra;
+    int const df = (int)fb - (int)fa;
+
+    int step_r = 0;
+    int step_f = 0;
+
+    if (df == 0 && dr != 0) {
+        step_r = (dr > 0) ? 1 : -1;
+        step_f = 0;
+    }
+    else if (dr == 0 && df != 0) {
+        step_r = 0;
+        step_f = (df > 0) ? 1 : -1;
+    }
+    else if (dr != 0 && (dr > 0 ? dr : -dr) == (df > 0 ? df : -df)) {
+        step_r = (dr > 0) ? 1 : -1;
+        step_f = (df > 0) ? 1 : -1;
+    }
+    else {
+        return 0ULL;
+    }
+
+    Bb64 mask = 0ULL;
+
+    enum rank_index r = (enum rank_index)((int)ra + step_r);
+    enum file_index f = (enum file_index)((int)fa + step_f);
+
+    while (r != rb || f != fb) {
+        mask |= MASK_FROM_RF(r, f);
+        r = (enum rank_index)((int)r + step_r);
+        f = (enum file_index)((int)f + step_f);
+    }
+
+    return mask;
+#else
+    #if ! __has_include("between_lookup.h")
+        #error "compile codegen.c and run once to generate required header files"
+    #else
+
+    /* defines static between_lookup[sq8_COUNT][sq8_COUNT] */
+    #include "between_lookup.h"
+    return between_lookup[a][b];
+    #endif
+#endif
+}
+
+static Bb64 attacks_to(struct pos const* pos,
+                       Bb64              targets,
+                       Bb64              pretend_occupied,
+                       Bb64              pretend_empty)
+{
+    Bb64 const occ_orig = ~(pos->pieces[SIDE_WHITE][PIECE_EMPTY] & pos->pieces[SIDE_BLACK][PIECE_EMPTY]);
+    Bb64 const occ = (occ_orig & ~pretend_empty) | pretend_occupied;
+
+    Bb64 const* pw = pos->pieces[SIDE_WHITE];
+    Bb64 const* pb = pos->pieces[SIDE_BLACK];
+
+    Bb64 const wps = pw[PIECE_PAWN];
+
+    Bb64 const bps = pb[PIECE_PAWN];
+
+    Bb64 const ns = (pw[PIECE_KNIGHT]
+                  |  pb[PIECE_KNIGHT])
+                  ;
+    Bb64 const ks = (pw[PIECE_KING]
+                  |  pb[PIECE_KING])
+                  ;
+    Bb64 const qs = (pw[PIECE_QUEEN]
+                  |  pb[PIECE_QUEEN])
+                  ;
+    Bb64 const qrs = (pw[PIECE_ROOK]
+                   |  pb[PIECE_ROOK]
+                   |  qs)
+                   ;
+    Bb64 const qbs = (pw[PIECE_BISHOP]
+                   |  pb[PIECE_BISHOP]
+                   |  qs)
+                   ;
+
+    return ((bps & pawn_attacks_white(targets))
+          | (wps & pawn_attacks_black(targets))
+          | (ns  & knight_attacks(targets))
+          | (qbs & bishop_attacks(targets, occ))
+          | (qrs & rook_attacks(targets, occ))
+          | (ks  & king_attacks(targets)))
+          & ~pretend_occupied;
+}
+
+static
+Bb64 checkers(struct pos const* pos, Side8 us)
+{
+    /* TODO: specialize */
+    return attacks_to(pos, pos->pieces[us][PIECE_KING], 0ULL, 0ULL) & pos->pieces[us][PIECE_EMPTY];
+}
+
+static
+Bb64 pinning_lines_to_target(struct pos const* pos, Side8 us, Sq8 tsq)
+{
+    Side8 const them = other_side(us);
+    Bb64 const our_occ = ~pos->pieces[us][PIECE_EMPTY];
+    Bb64 const their_occ = ~pos->pieces[them][PIECE_EMPTY];
+
+    Bb64 const* p = pos->pieces[them];
+    Bb64 const bqs = p[PIECE_QUEEN] | p[PIECE_BISHOP];
+    Bb64 const rqs = p[PIECE_QUEEN] | p[PIECE_ROOK];
+
+    Bb64 pinners = (bqs & bishop_attacks_from_index(tsq, their_occ))
+                     | (rqs & rook_attacks_from_index(tsq,   their_occ));
+
+    Bb64 pinned = 0;
+    while (pinners) {
+        Sq8 const sq = bitboard_pop_lsb(&pinners);
+        Bb64 const blockers = between_mask(tsq, sq) & our_occ;
+        if (!bitboard_more_than_one(blockers)) {
+            pinned |= blockers;
+        }
+    }
+
+    return pinned;
+}
+
+static
+Bb64 all_threats_from_side(struct pos const * pos, Side8 who)
+{
+    Bb64 const occ = ~(pos->pieces[SIDE_WHITE][PIECE_EMPTY] & pos->pieces[SIDE_BLACK][PIECE_EMPTY]);
+
+    Bb64 const* p = pos->pieces[who];
+    Bb64 t = 0ULL;
+    t |= pawn_attacks_dispatch(p[PIECE_PAWN], who);
+    t |= knight_attacks(p[PIECE_KNIGHT]);
+    t |= bishop_attacks(p[PIECE_BISHOP], occ);
+    t |= rook_attacks(p[PIECE_ROOK], occ);
+    t |= queen_attacks(p[PIECE_QUEEN], occ);
+    t |= king_attacks(p[PIECE_KING]);
+    return t;
+}
+

engine-bitboard.h

@@ -0,0 +1,143 @@
+#pragma once
+
+typedef uint64_t Bb64;
+
+#define BITBOARD(                \
+        a8,b8,c8,d8,e8,f8,g8,h8, \
+        a7,b7,c7,d7,e7,f7,g7,h7, \
+        a6,b6,c6,d6,e6,f6,g6,h6, \
+        a5,b5,c5,d5,e5,f5,g5,h5, \
+        a4,b4,c4,d4,e4,f4,g4,h4, \
+        a3,b3,c3,d3,e3,f3,g3,h3, \
+        a2,b2,c2,d2,e2,f2,g2,h2, \
+        a1,b1,c1,d1,e1,f1,g1,h1) \
+(Bb64)\
+0b##\
+h8##g8##f8##e8##d8##c8##b8##a8##\
+h7##g7##f7##e7##d7##c7##b7##a7##\
+h6##g6##f6##e6##d6##c6##b6##a6##\
+h5##g5##f5##e5##d5##c5##b5##a5##\
+h4##g4##f4##e4##d4##c4##b4##a4##\
+h3##g3##f3##e3##d3##c3##b3##a3##\
+h2##g2##f2##e2##d2##c2##b2##a2##\
+h1##g1##f1##e1##d1##c1##b1##a1##\
+ULL
+
+#define FILE_MASK(n) MASK_SHIFT_EAST((Bb64)0x0101010101010101ULL, n)
+#define RANK_MASK(n) MASK_SHIFT_NORTH((Bb64)0x00000000000000FFULL, n)
+#define MASK_FROM_SQ(idx) (((Bb64)1ULL)<<((Index8)idx))
+#define MASK_FROM_RF(rank, file) (MASK_FROM_SQ(SQ_FROM_RF(rank,file)))
+
+enum : Bb64 {
+    FILE_MASK_A = FILE_MASK(FILE_INDEX_A),
+    FILE_MASK_B = FILE_MASK(FILE_INDEX_B),
+    FILE_MASK_C = FILE_MASK(FILE_INDEX_C),
+    FILE_MASK_D = FILE_MASK(FILE_INDEX_D),
+    FILE_MASK_E = FILE_MASK(FILE_INDEX_E),
+    FILE_MASK_F = FILE_MASK(FILE_INDEX_F),
+    FILE_MASK_G = FILE_MASK(FILE_INDEX_G),
+    FILE_MASK_H = FILE_MASK(FILE_INDEX_H),
+
+    RANK_MASK_1 = RANK_MASK(RANK_INDEX_1),
+    RANK_MASK_2 = RANK_MASK(RANK_INDEX_2),
+    RANK_MASK_3 = RANK_MASK(RANK_INDEX_3),
+    RANK_MASK_4 = RANK_MASK(RANK_INDEX_4),
+    RANK_MASK_5 = RANK_MASK(RANK_INDEX_5),
+    RANK_MASK_6 = RANK_MASK(RANK_INDEX_6),
+    RANK_MASK_7 = RANK_MASK(RANK_INDEX_7),
+    RANK_MASK_8 = RANK_MASK(RANK_INDEX_8),
+
+    MASK_SHIFT_EAST_GUARD_0 = ~0ULL,
+    MASK_SHIFT_EAST_GUARD_1 = ~FILE_MASK_H,
+    MASK_SHIFT_EAST_GUARD_2 = ~(FILE_MASK_G | FILE_MASK_H),
+    MASK_SHIFT_EAST_GUARD_3 = ~(FILE_MASK_F | FILE_MASK_G | FILE_MASK_H),
+    MASK_SHIFT_EAST_GUARD_4 = ~(FILE_MASK_E | FILE_MASK_F | FILE_MASK_G | FILE_MASK_H),
+    MASK_SHIFT_EAST_GUARD_5 = ~(FILE_MASK_D | FILE_MASK_E | FILE_MASK_F | FILE_MASK_G | FILE_MASK_H),
+    MASK_SHIFT_EAST_GUARD_6 = ~(FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F | FILE_MASK_G | FILE_MASK_H),
+    MASK_SHIFT_EAST_GUARD_7 = ~(FILE_MASK_B | FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F | FILE_MASK_G | FILE_MASK_H),
+
+    MASK_SHIFT_WEST_GUARD_0  = ~0ULL,
+    MASK_SHIFT_WEST_GUARD_1  = ~FILE_MASK_A,
+    MASK_SHIFT_WEST_GUARD_2  = ~(FILE_MASK_A | FILE_MASK_B),
+    MASK_SHIFT_WEST_GUARD_3  = ~(FILE_MASK_A | FILE_MASK_B | FILE_MASK_C),
+    MASK_SHIFT_WEST_GUARD_4  = ~(FILE_MASK_A | FILE_MASK_B | FILE_MASK_C | FILE_MASK_D),
+    MASK_SHIFT_WEST_GUARD_5  = ~(FILE_MASK_A | FILE_MASK_B | FILE_MASK_C | FILE_MASK_D | FILE_MASK_E),
+    MASK_SHIFT_WEST_GUARD_6  = ~(FILE_MASK_A | FILE_MASK_B | FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F),
+    MASK_SHIFT_WEST_GUARD_7  = ~(FILE_MASK_A | FILE_MASK_B | FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F | FILE_MASK_G),
+};
+
+#define _MASK_SHIFT_EAST_GUARDED(b, n) \
+    (((Bb64)(b) & MASK_SHIFT_EAST_GUARD_##n) << (Index8)(n))
+
+#define _MASK_SHIFT_WEST_GUARDED(b, n)  \
+    (((Bb64)(b) & MASK_SHIFT_WEST_GUARD_##n) >> (Index8)(n))
+
+/* MASK_SHIFT_EAST_n shifts the bitboard right by n ranks without wrapping */
+#define MASK_SHIFT_EAST_1(b) _MASK_SHIFT_EAST_GUARDED(b, 1)
+#define MASK_SHIFT_EAST_2(b) _MASK_SHIFT_EAST_GUARDED(b, 2)
+#define MASK_SHIFT_EAST_3(b) _MASK_SHIFT_EAST_GUARDED(b, 3)
+#define MASK_SHIFT_EAST_4(b) _MASK_SHIFT_EAST_GUARDED(b, 4)
+#define MASK_SHIFT_EAST_5(b) _MASK_SHIFT_EAST_GUARDED(b, 5)
+#define MASK_SHIFT_EAST_6(b) _MASK_SHIFT_EAST_GUARDED(b, 6)
+#define MASK_SHIFT_EAST_7(b) _MASK_SHIFT_EAST_GUARDED(b, 7)
+#define MASK_SHIFT_EAST_8(b) _MASK_SHIFT_EAST_GUARDED(b, 8)
+
+/* MASK_SHIFT_WEST_n shifts the bitboard left by n ranks without wrapping */
+#define MASK_SHIFT_WEST_1(b) _MASK_SHIFT_WEST_GUARDED(b, 1)
+#define MASK_SHIFT_WEST_2(b) _MASK_SHIFT_WEST_GUARDED(b, 2)
+#define MASK_SHIFT_WEST_3(b) _MASK_SHIFT_WEST_GUARDED(b, 3)
+#define MASK_SHIFT_WEST_4(b) _MASK_SHIFT_WEST_GUARDED(b, 4)
+#define MASK_SHIFT_WEST_5(b) _MASK_SHIFT_WEST_GUARDED(b, 5)
+#define MASK_SHIFT_WEST_6(b) _MASK_SHIFT_WEST_GUARDED(b, 6)
+#define MASK_SHIFT_WEST_7(b) _MASK_SHIFT_WEST_GUARDED(b, 7)
+#define MASK_SHIFT_WEST_8(b) _MASK_SHIFT_WEST_GUARDED(b, 8)
+
+/* MASK_SHIFT_NORTH_n shifts the bitboard towards rank 8 by n ranks without wrapping */
+#define MASK_SHIFT_NORTH_1(b) MASK_SHIFT_NORTH(b, 1)
+#define MASK_SHIFT_NORTH_2(b) MASK_SHIFT_NORTH(b, 2)
+#define MASK_SHIFT_NORTH_3(b) MASK_SHIFT_NORTH(b, 3)
+#define MASK_SHIFT_NORTH_4(b) MASK_SHIFT_NORTH(b, 4)
+#define MASK_SHIFT_NORTH_5(b) MASK_SHIFT_NORTH(b, 5)
+#define MASK_SHIFT_NORTH_6(b) MASK_SHIFT_NORTH(b, 6)
+#define MASK_SHIFT_NORTH_7(b) MASK_SHIFT_NORTH(b, 7)
+#define MASK_SHIFT_NORTH_8(b) MASK_SHIFT_NORTH(b, 8)
+
+/* MASK_SHIFT_SOUTH_n shifts the bitboard towards rank 1 by n ranks without wrapping */
+#define MASK_SHIFT_SOUTH_1(b) MASK_SHIFT_SOUTH(b, 1)
+#define MASK_SHIFT_SOUTH_2(b) MASK_SHIFT_SOUTH(b, 2)
+#define MASK_SHIFT_SOUTH_3(b) MASK_SHIFT_SOUTH(b, 3)
+#define MASK_SHIFT_SOUTH_4(b) MASK_SHIFT_SOUTH(b, 4)
+#define MASK_SHIFT_SOUTH_5(b) MASK_SHIFT_SOUTH(b, 5)
+#define MASK_SHIFT_SOUTH_6(b) MASK_SHIFT_SOUTH(b, 6)
+#define MASK_SHIFT_SOUTH_7(b) MASK_SHIFT_SOUTH(b, 7)
+#define MASK_SHIFT_SOUTH_8(b) MASK_SHIFT_SOUTH(b, 8)
+
+enum {
+    #define X(file, rank) SQMASK_##file##rank = MASK_FROM_RF(RANK_INDEX_##rank, FILE_INDEX_##file),
+    SQUARES_LIST
+    #undef X
+};
+
+static Sq8 bitboard_lsb(Bb64 p)
+{
+    assuming(p != 0);
+    return (Sq8)__builtin_ffsll((int64_t)p) - 1;
+}
+
+static Sq8 bitboard_pop_lsb(Bb64* p)
+{
+    Sq8 const lsb = bitboard_lsb(*p);
+    *p &= ~(1ULL<<(lsb));
+    return lsb;
+}
+
+static inline uint64_t bitboard_popcount(Bb64 b)
+{
+    return (uint64_t)__builtin_popcountll(b);
+}
+
+static inline bool bitboard_more_than_one(Bb64 b)
+{
+    return b & (b - 1);
+}
+

engine-board.h

@@ -0,0 +1,437 @@
+#pragma once
+
+#include "engine-types.h"
+#include "engine-tt.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+struct board {
+    struct pos {
+        Bb64  pieces[SIDE_COUNT][PIECE_COUNT];
+        Side8 moving_side;
+        bool  castling_illegal[SIDE_COUNT][CASTLE_COUNT];
+        Bb64  ep_targets;
+
+        int halfmoves; /* FIXME: this duplicates the hist.length value */
+        int fullmoves;
+        uint64_t hash;
+    } pos;
+
+    struct tt tt;
+
+    /* used for repeated board state detection only */
+    struct history {
+        struct pos items[50];
+        size_t length;
+    } hist;
+
+    /* Used only for square->piece lookups, not central to logic.  Does not
+     * store which side owns the square piece, and checking non-occupied
+     * squares is undefined
+     *
+     * TODO: make mailbox smaller, only 3 bits are needed per piece
+     * */
+    Piece8 mailbox[SQ_COUNT];
+};
+
+/* attack-sets depends on the definition of struct pos, whoops ¯\_(ツ)_/¯ */
+#include "engine-attack-sets.h"
+
+#define BOARD_INIT (struct board) {                       \
+    .pos = {                                              \
+        .fullmoves = 1,                                   \
+        .pieces = {                                       \
+            [SIDE_WHITE] = {                              \
+                [PIECE_EMPTY] = RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6 | RANK_MASK_7 | RANK_MASK_8, \
+                [PIECE_PAWN]   = RANK_MASK_2,             \
+                [PIECE_ROOK]   = SQMASK_A1 | SQMASK_H1,   \
+                [PIECE_KNIGHT] = SQMASK_B1 | SQMASK_G1,   \
+                [PIECE_BISHOP] = SQMASK_C1 | SQMASK_F1,   \
+                [PIECE_QUEEN]  = SQMASK_D1,               \
+                [PIECE_KING]   = SQMASK_E1,               \
+            },                                            \
+            [SIDE_BLACK] = {                              \
+                [PIECE_EMPTY] = RANK_MASK_1 | RANK_MASK_2 | RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6, \
+                [PIECE_PAWN]   = RANK_MASK_7,             \
+                [PIECE_ROOK]   = SQMASK_A8 | SQMASK_H8,   \
+                [PIECE_KNIGHT] = SQMASK_B8 | SQMASK_G8,   \
+                [PIECE_BISHOP] = SQMASK_C8 | SQMASK_F8,   \
+                [PIECE_QUEEN]  = SQMASK_D8,               \
+                [PIECE_KING]   = SQMASK_E8,               \
+            }                                             \
+        },                                                \
+        .hash = ~0ULL,                                    \
+    },                                                    \
+    .mailbox = {                                          \
+        [SQ_A1] = PIECE_ROOK,                             \
+        [SQ_B1] = PIECE_KNIGHT,                           \
+        [SQ_C1] = PIECE_BISHOP,                           \
+        [SQ_D1] = PIECE_QUEEN,                            \
+        [SQ_E1] = PIECE_KING,                             \
+        [SQ_F1] = PIECE_BISHOP,                           \
+        [SQ_G1] = PIECE_KNIGHT,                           \
+        [SQ_H1] = PIECE_ROOK,                             \
+        [SQ_A2] = PIECE_PAWN,                             \
+        [SQ_B2] = PIECE_PAWN,                             \
+        [SQ_C2] = PIECE_PAWN,                             \
+        [SQ_D2] = PIECE_PAWN,                             \
+        [SQ_E2] = PIECE_PAWN,                             \
+        [SQ_F2] = PIECE_PAWN,                             \
+        [SQ_G2] = PIECE_PAWN,                             \
+        [SQ_H2] = PIECE_PAWN,                             \
+        [SQ_A7] = PIECE_PAWN,                             \
+        [SQ_B7] = PIECE_PAWN,                             \
+        [SQ_C7] = PIECE_PAWN,                             \
+        [SQ_D7] = PIECE_PAWN,                             \
+        [SQ_E7] = PIECE_PAWN,                             \
+        [SQ_F7] = PIECE_PAWN,                             \
+        [SQ_G7] = PIECE_PAWN,                             \
+        [SQ_H7] = PIECE_PAWN,                             \
+        [SQ_A8] = PIECE_ROOK,                             \
+        [SQ_B8] = PIECE_KNIGHT,                           \
+        [SQ_C8] = PIECE_BISHOP,                           \
+        [SQ_D8] = PIECE_QUEEN,                            \
+        [SQ_E8] = PIECE_KING,                             \
+        [SQ_F8] = PIECE_BISHOP,                           \
+        [SQ_G8] = PIECE_KNIGHT,                           \
+        [SQ_H8] = PIECE_ROOK,                             \
+    },                                                    \
+    .hist = {0},                                          \
+}
+
+void board_init(struct board* b)
+{
+    if (b->pos.fullmoves == 0 && b->pos.hash == 0) {
+        *b = BOARD_INIT;
+    }
+    if (b->tt.entries == NULL) {
+        size_t const entries = 1<<26;
+        size_t const mask = entries-1;
+        b->tt.entries = sys_mmap_anon_shared(entries * sizeof b->tt.entries[0],
+                                             SYS_PROT_READ | SYS_PROT_WRITE,
+                                             SYS_MADV_RANDOM);
+        b->tt.mask = mask;
+        if (b->tt.entries == NULL) {
+            __builtin_trap();
+        }
+    }
+}
+
+static bool board_load_fen_unsafe(struct board* b, char const* fen_str)
+{
+    /* TODO: this function is not tested for malicious/corrupted inputs */
+    struct {
+        char const* buf;
+        size_t i;
+        size_t len;
+    } fen = {
+        .buf = fen_str,
+        .i = 0,
+        .len = strlen(fen_str),
+    };
+#define BUF_GETCHAR(x) (assuming(x.i < x.len), x.buf[x.i++])
+
+    my_memset(&b->pos, 0, sizeof b->pos);
+    b->pos.hash = ~0ULL;
+
+    for (enum rank_index ri = RANK_INDEX_8; ri < RANK_INDEX_COUNT; --ri) {
+        for (enum file_index fi = FILE_INDEX_BEGIN; fi < FILE_INDEX_COUNT; ++fi) {
+            char const ch = BUF_GETCHAR(fen);
+            if (my_isdigit(ch)) {
+                if (ch == '0') {
+                    __builtin_trap();
+                }
+                fi += ch - '0' - 1;
+            } else {
+                struct piece_side const p = piece_and_side_from_char[(uint8_t)ch];
+                Bb64 const sq_mask = MASK_FROM_RF(ri, fi);
+                b->pos.pieces[p.side][p.piece] |= sq_mask;
+                b->pos.pieces[p.side][PIECE_EMPTY] &= ~sq_mask;
+                b->mailbox[SQ_FROM_RF(ri, fi)] = p.piece;
+            }
+        }
+        (void)BUF_GETCHAR(fen); /* discard '/' or ' ' */
+    }
+
+    b->pos.pieces[SIDE_WHITE][PIECE_EMPTY] = ~0ULL;
+    b->pos.pieces[SIDE_BLACK][PIECE_EMPTY] = ~0ULL;
+    for (Piece8 p = PIECE_BEGIN; p < PIECE_COUNT; ++p) {
+        b->pos.pieces[SIDE_WHITE][PIECE_EMPTY] &= ~b->pos.pieces[SIDE_WHITE][p];
+        b->pos.pieces[SIDE_BLACK][PIECE_EMPTY] &= ~b->pos.pieces[SIDE_BLACK][p];
+    }
+
+    { /* active color */
+        char const ch = BUF_GETCHAR(fen);
+        if (ch == 'w') {
+            b->pos.moving_side = SIDE_WHITE;
+        } else if (ch == 'b') {
+            b->pos.moving_side = SIDE_BLACK;
+        } else {
+            __builtin_trap();
+        }
+    }
+
+    { /* castling */
+        char ch = BUF_GETCHAR(fen);
+        if (ch != ' ') {
+            __builtin_trap();
+        }
+        b->pos.castling_illegal[SIDE_WHITE][CASTLE_KINGSIDE] = true;
+        b->pos.castling_illegal[SIDE_WHITE][CASTLE_QUEENSIDE] = true;
+        b->pos.castling_illegal[SIDE_BLACK][CASTLE_KINGSIDE] = true;
+        b->pos.castling_illegal[SIDE_BLACK][CASTLE_QUEENSIDE] = true;
+        do {
+            ch = BUF_GETCHAR(fen);
+            switch (ch) {
+                case 'K': b->pos.castling_illegal[SIDE_WHITE][CASTLE_KINGSIDE] = false;  break;
+                case 'Q': b->pos.castling_illegal[SIDE_WHITE][CASTLE_QUEENSIDE] = false; break;
+                case 'k': b->pos.castling_illegal[SIDE_BLACK][CASTLE_KINGSIDE] = false;  break;
+                case 'q': b->pos.castling_illegal[SIDE_BLACK][CASTLE_QUEENSIDE] = false; break;
+                case ' ': break;
+                case '-': break;
+                default: {
+                    __builtin_trap();
+                } break;
+            }
+        } while (ch != ' ');
+    }
+
+    { /* en passent */
+        char const ch = BUF_GETCHAR(fen);
+        if (ch != '-') {
+            __builtin_trap();
+        }
+    }
+
+    { /* halfmoves */
+        b->pos.halfmoves = 0;
+        char ch = BUF_GETCHAR(fen);
+        while (ch != ' ') {
+            b->pos.halfmoves *= 10;
+            b->pos.halfmoves += ch-'0';
+            ch = BUF_GETCHAR(fen);
+        }
+    }
+
+    { /* fullmoves */
+        b->pos.fullmoves = 0;
+        char ch = BUF_GETCHAR(fen);
+        while (ch != ' ') {
+            b->pos.fullmoves *= 10;
+            b->pos.fullmoves += ch-'0';
+            ch = BUF_GETCHAR(fen);
+        }
+    }
+#undef BUF_GETCHAR
+
+    return true;
+}
+
+enum move_result {
+    MR_NORMAL,
+    MR_CHECK,
+    MR_REPEATS, /* means this board state has been observed before */
+    MR_STALEMATE,
+    MR_CHECKMATE,
+};
+
+/* does not check validity */
+static enum move_result move_piece(struct pos* restrict     pos,
+                                   Side8                    us,
+                                   struct history* restrict hist,
+                                   Piece8                   mailbox[restrict static SQ_COUNT],
+                                   struct move              move)
+{
+    //Side8 const us   = pos->moving_side;
+    Side8 const them = other_side(us);
+
+    Piece8 const from_piece = mailbox[move.from];
+    Piece8 const to_piece = mailbox[move.to];
+
+    Bb64 const from_mask = MASK_FROM_SQ(move.from);
+    Bb64 const to_mask   = MASK_FROM_SQ(move.to);
+
+    Sq8 const krook       = (us == SIDE_WHITE) ? SQ_H1 : SQ_H8;
+    Sq8 const qrook       = (us == SIDE_WHITE) ? SQ_A1 : SQ_A8;
+    Sq8 const krook_to    = (us == SIDE_WHITE) ? SQ_F1 : SQ_F8;
+    Sq8 const qrook_to    = (us == SIDE_WHITE) ? SQ_D1 : SQ_D8;
+    Sq8 const ksq         = (us == SIDE_WHITE) ? SQ_E1 : SQ_E8;
+    Sq8 const kcast_sq    = (us == SIDE_WHITE) ? SQ_G1 : SQ_G8;
+    Sq8 const qcast_sq    = (us == SIDE_WHITE) ? SQ_C1 : SQ_C8;
+    Sq8 const their_krook = (us != SIDE_WHITE) ? SQ_H1 : SQ_H8;
+    Sq8 const their_qrook = (us != SIDE_WHITE) ? SQ_A1 : SQ_A8;
+
+    #define POS_MOVE(side, piece, from, to) \
+        do { \
+            Bb64 const x = MASK_FROM_SQ(from) | MASK_FROM_SQ(to); \
+            pos->pieces[side][piece] ^= x; \
+            pos->pieces[side][PIECE_EMPTY] ^= x; \
+            pos->hash = tt_hash_update(pos->hash, from, side, piece); \
+            pos->hash = tt_hash_update(pos->hash, to, side, piece); \
+            mailbox[to] = piece; \
+            if (piece == PIECE_PAWN) pos->halfmoves = 0; \
+        } while (0)
+
+    #define POS_REMOVE(owner, piece, at) \
+        do { \
+            Bb64 const x = MASK_FROM_SQ(at); \
+            pos->pieces[owner][piece] &= ~x; \
+            pos->pieces[owner][PIECE_EMPTY] |= x; \
+            pos->hash = tt_hash_update(pos->hash, at, owner, piece); \
+            hist->length = 0; \
+            pos->halfmoves = 0; \
+        } while (0)
+
+    #define POS_ADD(owner, piece, at) \
+        do { \
+            Bb64 const x = MASK_FROM_SQ(at); \
+            pos->pieces[owner][piece] |= x; \
+            pos->pieces[owner][PIECE_EMPTY] &= ~x; \
+            pos->hash = tt_hash_update(pos->hash, at, owner, piece); \
+            mailbox[at] = piece; \
+            pos->halfmoves = 0; \
+            hist->length = 0; \
+        } while (0)
+
+    Bb64 const ep_targets_now = pos->ep_targets;
+    if (ep_targets_now) {
+        pos->hash = tt_hash_update_ep_targets(pos->hash, bitboard_lsb(ep_targets_now));
+    }
+    pos->ep_targets = 0ULL;
+
+    /* castle kingside, legality is checked by the caller */
+    /**/ if (from_piece == PIECE_KING && move.from == ksq && move.to == kcast_sq) {
+        POS_MOVE(us, PIECE_KING, ksq, kcast_sq);
+        POS_MOVE(us, PIECE_ROOK, krook, krook_to);
+    }
+    /* castle queenside, legality is checked by the caller */
+    else if (from_piece == PIECE_KING && move.from == ksq && move.to == qcast_sq) {
+        POS_MOVE(us, PIECE_KING, ksq, qcast_sq);
+        POS_MOVE(us, PIECE_ROOK, qrook, qrook_to);
+    }
+    /* regular move / capture */
+    else {
+        POS_MOVE(us, from_piece, move.from, move.to);
+        /* capture */
+        if (to_mask & ~pos->pieces[them][PIECE_EMPTY]) {
+            POS_REMOVE(them, to_piece, move.to);
+        }
+
+        /* promote / ep */
+        if (from_piece == PIECE_PAWN) {
+            Bb64 const finishline = (us == SIDE_WHITE ? RANK_MASK_8 : RANK_MASK_1);
+
+            /* en passent */
+            /**/ if (to_mask & ep_targets_now) {
+                Sq8 const ti =
+                    (us == SIDE_WHITE)
+                    ? SQ_SHIFT_SOUTH(move.to, 1)
+                    : SQ_SHIFT_NORTH(move.to, 1);
+                POS_REMOVE(them, PIECE_PAWN, ti);
+            }
+            /* pawn double push -> new ep_target */
+            else if (us == SIDE_WHITE && (from_mask & RANK_MASK_2) && (to_mask & RANK_MASK_4)) {
+                pos->ep_targets |= MASK_SHIFT_NORTH_1(from_mask);
+                pos->hash = tt_hash_update_ep_targets(pos->hash, SQ_SHIFT_NORTH(move.from, 1));
+            }
+            else if (us == SIDE_BLACK && (from_mask & RANK_MASK_7) && (to_mask & RANK_MASK_5)) {
+                pos->ep_targets |= MASK_SHIFT_SOUTH_1(from_mask);
+                pos->hash = tt_hash_update_ep_targets(pos->hash, SQ_SHIFT_SOUTH(move.from, 1));
+            }
+            /* promote */
+            else if (to_mask & finishline) {
+                /* already moved to `move.to` */
+                POS_REMOVE(us, PIECE_PAWN, move.to);
+                POS_ADD(us, PIECE_QUEEN, move.to);
+            }
+        }
+    }
+
+    /* castling rights */
+    if (!pos->castling_illegal[us][CASTLE_KINGSIDE]) {
+        if (move.from == ksq || move.from == krook) {
+            pos->castling_illegal[us][CASTLE_KINGSIDE] = true;
+            pos->hash = tt_hash_update_castling_rights(pos->hash, us, CASTLE_KINGSIDE);
+        }
+    }
+    if (!pos->castling_illegal[us][CASTLE_QUEENSIDE]) {
+        if (move.from == ksq || move.from == qrook) {
+            pos->castling_illegal[us][CASTLE_QUEENSIDE] = true;
+            pos->hash = tt_hash_update_castling_rights(pos->hash, us, CASTLE_QUEENSIDE);
+        }
+    }
+
+    if (move.to == their_krook) {
+        if (!pos->castling_illegal[them][CASTLE_KINGSIDE]) {
+            pos->castling_illegal[them][CASTLE_KINGSIDE] = true;
+            pos->hash = tt_hash_update_castling_rights(pos->hash, them, CASTLE_KINGSIDE);
+        }
+    }
+    if (move.to == their_qrook) {
+        if (!pos->castling_illegal[them][CASTLE_QUEENSIDE]) {
+            pos->castling_illegal[them][CASTLE_QUEENSIDE] = true;
+            pos->hash = tt_hash_update_castling_rights(pos->hash, them, CASTLE_QUEENSIDE);
+        }
+    }
+
+    pos->hash = tt_hash_switch_side(pos->hash);
+    pos->moving_side = them;
+    pos->fullmoves += (pos->moving_side == SIDE_BLACK);
+    pos->halfmoves += 1;
+
+    assuming(hist->length < sizeof hist->items / sizeof *hist->items);
+
+    /* check for repeated moves */
+    /* TODO: add move_do and move_undo to create proper repeat checks */
+    assuming(hist->length < 64);
+
+    for (size_t i = 0; i < hist->length; ++i) {
+        _Static_assert(sizeof *pos == sizeof hist->items[i]);
+
+        if (!my_memcmp(&hist->items[i].pieces, &pos->pieces, sizeof pos->pieces)
+         && !my_memcmp(&hist->items[i].castling_illegal, &pos->castling_illegal, sizeof pos->castling_illegal)
+         && hist->items[i].moving_side == pos->moving_side
+         && hist->items[i].ep_targets == pos->ep_targets)
+        {
+            return MR_STALEMATE;
+        }
+    }
+
+    if (pos->halfmoves > 50) {
+        return MR_STALEMATE;
+    }
+    else {
+        return MR_NORMAL;
+    }
+
+#undef POS_MOVE
+#undef POS_ADD
+#undef POS_REMOVE
+}
+
+static enum move_result board_move(struct board* b, struct move move)
+{
+    return move_piece(&b->pos,
+                      b->pos.moving_side,
+                      &b->hist,
+                      b->mailbox,
+                      move);
+}
+
+static bool pos_is_legal(struct pos const* restrict pos)
+{
+    Side8 const mside = pos->moving_side;
+    Side8 const oside = other_side(mside);
+
+    if (pos->pieces[oside][PIECE_KING] & all_threats_from_side(pos, mside)) {
+        return false;
+    }
+
+    return true;
+}
+
+static bool board_is_legal(struct board* b)
+{
+    return pos_is_legal(&b->pos);
+}

engine-evaluations.h

@@ -0,0 +1,473 @@
+/* TODO: candidate for code-generation */
+
+#pragma once
+
+enum game_progress {
+    GP_OPENING,
+    GP_MIDDLE,
+    GP_END,
+    GP_COUNT,
+};
+
+static char const* game_progress_str[GP_COUNT] = {
+    [GP_OPENING] = "GP_OPENING",
+    [GP_MIDDLE]  = "GP_MIDDLE",
+    [GP_END]     = "GP_END",
+};
+
+static enum game_progress endgameness(struct pos const* pos)
+{
+    /* piece_value is already defined similarly elsewhere, but this one should
+     * remain independent of minor tweaks in the global table */
+    static int const piece_value[PIECE_COUNT] = {
+        [PIECE_KING]   = 0,
+        [PIECE_PAWN]   = 1,
+        [PIECE_BISHOP] = 3,
+        [PIECE_KNIGHT] = 3,
+        [PIECE_ROOK]   = 5,
+        [PIECE_QUEEN]  = 9,
+    };
+
+    int npm = 0; /* non-pawn material */
+    for (Side8 pl = SIDE_BEGIN; pl < SIDE_COUNT; ++pl) {
+        npm += piece_value[PIECE_QUEEN]  * bitboard_popcount(pos->pieces[pl][PIECE_QUEEN]);
+        npm += piece_value[PIECE_BISHOP] * bitboard_popcount(pos->pieces[pl][PIECE_BISHOP]);
+        npm += piece_value[PIECE_KNIGHT] * bitboard_popcount(pos->pieces[pl][PIECE_KNIGHT]);
+        npm += piece_value[PIECE_ROOK]   * bitboard_popcount(pos->pieces[pl][PIECE_ROOK]);
+    }
+
+    /**/ if (npm > 24) {
+        return GP_OPENING;
+    }
+    else if (npm > 16) {
+        return GP_MIDDLE;
+    }
+    else {
+        return GP_END;
+    }
+}
+
+#define BITBOARD_WHITE(          \
+        a8,b8,c8,d8,e8,f8,g8,h8, \
+        a7,b7,c7,d7,e7,f7,g7,h7, \
+        a6,b6,c6,d6,e6,f6,g6,h6, \
+        a5,b5,c5,d5,e5,f5,g5,h5, \
+        a4,b4,c4,d4,e4,f4,g4,h4, \
+        a3,b3,c3,d3,e3,f3,g3,h3, \
+        a2,b2,c2,d2,e2,f2,g2,h2, \
+        a1,b1,c1,d1,e1,f1,g1,h1) \
+BITBOARD( \
+        a8,b8,c8,d8,e8,f8,g8,h8, \
+        a7,b7,c7,d7,e7,f7,g7,h7, \
+        a6,b6,c6,d6,e6,f6,g6,h6, \
+        a5,b5,c5,d5,e5,f5,g5,h5, \
+        a4,b4,c4,d4,e4,f4,g4,h4, \
+        a3,b3,c3,d3,e3,f3,g3,h3, \
+        a2,b2,c2,d2,e2,f2,g2,h2, \
+        a1,b1,c1,d1,e1,f1,g1,h1)
+
+#define BITBOARD_BLACK(          \
+        a8,b8,c8,d8,e8,f8,g8,h8, \
+        a7,b7,c7,d7,e7,f7,g7,h7, \
+        a6,b6,c6,d6,e6,f6,g6,h6, \
+        a5,b5,c5,d5,e5,f5,g5,h5, \
+        a4,b4,c4,d4,e4,f4,g4,h4, \
+        a3,b3,c3,d3,e3,f3,g3,h3, \
+        a2,b2,c2,d2,e2,f2,g2,h2, \
+        a1,b1,c1,d1,e1,f1,g1,h1) \
+BITBOARD( \
+        a1,b1,c1,d1,e1,f1,g1,h1, \
+        a2,b2,c2,d2,e2,f2,g2,h2, \
+        a3,b3,c3,d3,e3,f3,g3,h3, \
+        a4,b4,c4,d4,e4,f4,g4,h4, \
+        a5,b5,c5,d5,e5,f5,g5,h5, \
+        a6,b6,c6,d6,e6,f6,g6,h6, \
+        a7,b7,c7,d7,e7,f7,g7,h7, \
+        a8,b8,c8,d8,e8,f8,g8,h8)
+
+#define REL_RANK_1 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1)
+
+#define REL_RANK_2 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_3 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_4 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_5 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_6 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_7 \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_RANK_8 \
+    REL_BITBOARD( \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0)
+
+
+#define DIAGONAL_A1_H8 \
+    BITBOARD( \
+        0,0,0,0,0,0,0,1, \
+        0,0,0,0,0,0,1,0, \
+        0,0,0,0,0,1,0,0, \
+        0,0,0,0,1,0,0,0, \
+        0,0,0,1,0,0,0,0, \
+        0,0,1,0,0,0,0,0, \
+        0,1,0,0,0,0,0,0, \
+        1,0,0,0,0,0,0,0)
+
+#define DIAGONAL_A8_H1 \
+    BITBOARD( \
+        1,0,0,0,0,0,0,0, \
+        0,1,0,0,0,0,0,0, \
+        0,0,1,0,0,0,0,0, \
+        0,0,0,1,0,0,0,0, \
+        0,0,0,0,1,0,0,0, \
+        0,0,0,0,0,1,0,0, \
+        0,0,0,0,0,0,1,0, \
+        0,0,0,0,0,0,0,1)
+
+#define REL_BISHOP_KING_ATTACK \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,1,1, \
+        0,0,0,0,0,1,1,0, \
+        0,0,0,0,1,1,0,0, \
+        0,0,0,1,1,0,0,0, \
+        0,0,1,1,0,0,0,0, \
+        0,1,1,0,0,0,0,0, \
+        1,1,0,0,0,0,0,0, \
+        1,0,0,0,0,0,0,0)
+
+#define REL_BISHOP_QUEEN_ATTACK \
+    REL_BITBOARD( \
+        1,1,0,0,0,0,0,0, \
+        0,1,1,0,0,0,0,0, \
+        0,0,1,1,0,0,0,0, \
+        0,0,0,1,1,0,0,0, \
+        0,0,0,0,1,1,0,0, \
+        0,0,0,0,0,1,1,0, \
+        0,0,0,0,0,0,1,1, \
+        0,0,0,0,0,0,0,1)
+
+#define REL_KING_CASTLE_KINGSIDE \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,1,0)
+
+#define REL_KING_CASTLE_QUEENSIDE \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,1,1,0,0,0,0,0)
+
+#define CORNERS \
+    BITBOARD( \
+        1,0,0,0,0,0,0,1, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,0,0,0,0,0,0,1)
+
+#define REL_EARLY_PAWN_STRUCTURE \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        1,0,0,0,0,0,0,0, \
+        1,1,1,1,1,0,0,0, \
+        1,1,1,1,1,0,0,0, \
+        1,1,1,1,1,0,0,0, \
+        1,1,1,1,1,1,1,1, \
+        0,0,0,0,0,0,0,0)
+
+#define REL_PAWN_KINGSIDE \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,1, \
+        0,0,0,0,0,1,1,0, \
+        0,0,0,0,0,0,0,0)
+
+
+#define REL_UNDEVELOPED_BISHOPS \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,1,0,0,1,0,0)
+
+#define REL_UNDEVELOPED_KNIGHTS \
+    REL_BITBOARD( \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,0,0,0,0,0,0,0, \
+        0,1,0,0,0,0,1,0)
+
+#define BOARD_CENTER_6X6 \
+    ((FILE_MASK_B | FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F | FILE_MASK_G) \
+    & (RANK_MASK_2 | RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6 | RANK_MASK_7))
+
+#define BOARD_CENTER_4X4 \
+    ((FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F) \
+    & (RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6))
+
+#define BOARD_CENTER_2X2 \
+    ((FILE_MASK_D | FILE_MASK_E) \
+    & (RANK_MASK_4 | RANK_MASK_5))
+
+#define POSITIONAL_MODIFIER_COUNT 4
+
+/* ------------------------------ early game ------------------------------- */
+
+#define EARLY_POSITIONAL_BONUS_0 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,       2,  BOARD_CENTER_4X4) \
+    X(PIECE_KNIGHT,     5,  BOARD_CENTER_4X4) \
+    X(PIECE_BISHOP,     5,  BOARD_CENTER_6X6 & (DIAGONAL_A1_H8 | DIAGONAL_A8_H1)) \
+    X(PIECE_KING,      15,  REL_KING_CASTLE_KINGSIDE) \
+    X(PIECE_QUEEN,    -15,  RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6) \
+    X(PIECE_ROOK,      10,  FILE_MASK_D | FILE_MASK_E) \
+    /**/
+
+#define EARLY_POSITIONAL_BONUS_1 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,      2,   BOARD_CENTER_2X2) \
+    X(PIECE_BISHOP,    5,   REL_BISHOP_KING_ATTACK) \
+    /**/
+
+#define EARLY_POSITIONAL_BONUS_2 \
+   /* piece          bonus   area*/ \
+    X(PIECE_PAWN,     -18,  ~REL_EARLY_PAWN_STRUCTURE) \
+    X(PIECE_KNIGHT,   -10,   REL_UNDEVELOPED_KNIGHTS) \
+    X(PIECE_BISHOP,   -10,   REL_UNDEVELOPED_BISHOPS) \
+    /**/
+
+#define EARLY_POSITIONAL_BONUS_3 \
+   /* piece         bonus   area*/ \
+    /**/
+
+
+/* ------------------------------ middle game ------------------------------ */
+/* (almost same as opening for now, but queen is not punished for moving) */
+
+#define MIDDLE_POSITIONAL_BONUS_0 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,       2,  BOARD_CENTER_4X4) \
+    X(PIECE_KNIGHT,     5,  BOARD_CENTER_4X4) \
+    X(PIECE_BISHOP,     5,  BOARD_CENTER_6X6 & (DIAGONAL_A1_H8 | DIAGONAL_A8_H1)) \
+    X(PIECE_KING,      15,  REL_KING_CASTLE_KINGSIDE) \
+    /**/
+
+#define MIDDLE_POSITIONAL_BONUS_1 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,      2,   BOARD_CENTER_2X2) \
+    X(PIECE_BISHOP,    7,   REL_BISHOP_KING_ATTACK) \
+    X(PIECE_QUEEN,     7,   REL_BISHOP_KING_ATTACK) \
+    /**/
+
+#define MIDDLE_POSITIONAL_BONUS_2 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,      2,   REL_PAWN_KINGSIDE) \
+    /**/
+
+#define MIDDLE_POSITIONAL_BONUS_3 \
+   /* piece         bonus   area*/ \
+    X(PIECE_BISHOP,    5,   BOARD_CENTER_6X6) \
+    X(PIECE_KNIGHT,    5,   BOARD_CENTER_6X6) \
+    /**/
+
+/* ------------------------------- end game -------------------------------- */
+
+#define LATE_POSITIONAL_BONUS_0 \
+   /* piece         bonus   area*/ \
+    X(PIECE_PAWN,      30,  REL_RANK_7 | REL_RANK_6 | REL_RANK_5) \
+    X(PIECE_KING,      10,  BOARD_CENTER_6X6) \
+    /**/
+
+#define LATE_POSITIONAL_BONUS_1 \
+   /* piece         bonus    area*/ \
+    X(PIECE_PAWN,      30,   REL_RANK_7 | REL_RANK_6) \
+    X(PIECE_KING,      10,   BOARD_CENTER_4X4) \
+    /**/
+
+#define LATE_POSITIONAL_BONUS_2 \
+   /* piece         bonus    area*/ \
+    X(PIECE_PAWN,      70,   REL_RANK_7) \
+    X(PIECE_KING,      10,   BOARD_CENTER_2X2) \
+    /**/
+
+#define LATE_POSITIONAL_BONUS_3 \
+   /* piece         bonus   area*/ \
+    X(PIECE_KING,     -50,  ~BOARD_CENTER_6X6) \
+    /**/
+
+struct posmod {
+    Bb64 const area;
+    Score16 const val;
+};
+
+static inline struct posmod positional_modifier(Side8 pl, enum game_progress st, size_t layer, Piece8 pz)
+{
+    static struct posmod const
+        lookup[SIDE_COUNT][GP_COUNT][POSITIONAL_MODIFIER_COUNT][PIECE_COUNT] = {
+    #define X(p, b, a) [p] = {.area = (a), .val = b},
+    #define REL_BITBOARD BITBOARD_WHITE
+        [SIDE_WHITE] = {
+            [GP_OPENING] = {
+                {EARLY_POSITIONAL_BONUS_0},
+                {EARLY_POSITIONAL_BONUS_1},
+                {EARLY_POSITIONAL_BONUS_2},
+                {EARLY_POSITIONAL_BONUS_3},
+            },
+            [GP_MIDDLE] = {
+                {MIDDLE_POSITIONAL_BONUS_0},
+                {MIDDLE_POSITIONAL_BONUS_1},
+                {MIDDLE_POSITIONAL_BONUS_2},
+                {MIDDLE_POSITIONAL_BONUS_3},
+            },
+            [GP_END] = {
+                {LATE_POSITIONAL_BONUS_0},
+                {LATE_POSITIONAL_BONUS_1},
+                {LATE_POSITIONAL_BONUS_2},
+                {LATE_POSITIONAL_BONUS_3},
+            },
+        },
+    #undef REL_BITBOARD
+
+    #define REL_BITBOARD BITBOARD_BLACK
+        [SIDE_BLACK] = {
+            [GP_OPENING] = {
+                {EARLY_POSITIONAL_BONUS_0},
+                {EARLY_POSITIONAL_BONUS_1},
+                {EARLY_POSITIONAL_BONUS_2},
+                {EARLY_POSITIONAL_BONUS_3},
+            },
+            [GP_MIDDLE] = {
+                {MIDDLE_POSITIONAL_BONUS_0},
+                {MIDDLE_POSITIONAL_BONUS_1},
+                {MIDDLE_POSITIONAL_BONUS_2},
+                {MIDDLE_POSITIONAL_BONUS_3},
+            },
+            [GP_END] = {
+                {LATE_POSITIONAL_BONUS_0},
+                {LATE_POSITIONAL_BONUS_1},
+                {LATE_POSITIONAL_BONUS_2},
+                {LATE_POSITIONAL_BONUS_3},
+            },
+        }
+    #undef REL_BITBOARD
+    };
+
+    return lookup[pl][st][layer][pz];
+}
+
+/* ------------------------------------------------------------------------- */
+
+#undef POSITIONAL_BONUS_0
+#undef POSITIONAL_BONUS_1
+#undef POSITIONAL_BONUS_2
+#undef POSITIONAL_BONUS_3
+#undef CORNERS
+#undef BOARD_CENTER_4X4
+#undef BOARD_CENTER_2X2
+#undef BITBOARD_WHITE
+#undef BITBOARD_BLACK
+#undef REL_DIAGONAL_A1_H8
+#undef REL_DIAGONAL_A8_H1
+#undef REL_BISHOP_KING_ATTACK
+#undef REL_BISHOP_QUEEN_ATTACK
+#undef REL_KING_CASTLE_KINGSIDE
+#undef REL_KING_CASTLE_QUEENSIDE

engine-macros.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#define STR(x) #x
+
+#if !defined(NDEBUG) && defined(USE_PRINTF)
+#define assuming(expr) \
+            ((expr) ? 0 : (fprintf(stderr, "assumption <" #expr "> failed on line %d\n", __LINE__), __builtin_trap(), 0))
+#elif !defined(NDEBUG)
+#define assuming(expr) \
+            ((expr) ? 0 : (__builtin_trap(), 0))
+#else
+#define assuming(expr) ((expr) ? 0 : (__builtin_unreachable(), 0))
+#endif
+
+#define CACHE_LINE_SIZE 64
+
+#define LIKELY(expr)   __builtin_expect((expr), 1)
+#define UNLIKELY(expr) __builtin_expect((expr), 0)

engine-move-generation.h

@@ -0,0 +1,252 @@
+#pragma once
+
+#define MOVE_MAX 128
+
+#define MOVE_CASTLE_KINGSIDE_WHITE (struct move) \
+    {.from = SQ_E1, .to = SQ_G1}
+
+#define MOVE_CASTLE_QUEENSIDE_WHITE (struct move) \
+    {.from = SQ_E1, .to = SQ_C1}
+
+#define MOVE_CASTLE_KINGSIDE_BLACK (struct move) \
+    {.from = SQ_E8, .to = SQ_G8}
+
+#define MOVE_CASTLE_QUEENSIDE_BLACK (struct move) \
+    {.from = SQ_E8, .to = SQ_C8}
+
+static inline
+struct move move_make(Index8 from, Index8 to)
+{
+    return (struct move){.from = from, .to = to};
+}
+
+enum move_gen_type {
+    MG_ALL,
+    MG_CAPTURES,
+    MG_CHECKS,
+    MG_QUIETS,
+};
+
+static void all_pseudolegal_from_piece(struct pos const* restrict pos,
+                                       enum move_gen_type         type,
+                                       Piece8                     piece,
+                                       Side8                      us,
+                                       Bb64                       piece_mask,
+                                       Bb64                       allowed,
+                                       size_t* restrict           out_count,
+                                       struct move                out[restrict static MOVE_MAX])
+{
+    assuming(piece != PIECE_PAWN);
+
+    Side8 them = other_side(us);
+
+    Bb64 const our_occ = ~pos->pieces[us][PIECE_EMPTY];
+    Bb64 const all_occ = ~(pos->pieces[SIDE_WHITE][PIECE_EMPTY] & pos->pieces[SIDE_BLACK][PIECE_EMPTY]);
+
+    if (type == MG_CHECKS) {
+        allowed &= non_pawn_piece_attacks(piece, pos->pieces[them][PIECE_KING], all_occ);
+    }
+
+    /* pray this gets constprop'ed */
+    while (piece_mask) {
+        Sq8 from = bitboard_pop_lsb(&piece_mask);
+        Bb64 move_mask = non_pawn_piece_attacks_from_index(piece, from, all_occ)
+                       & ~our_occ
+                       & allowed
+                       ;
+        while (move_mask) {
+            Sq8 const to = bitboard_pop_lsb(&move_mask);
+            assuming(*out_count < MOVE_MAX); \
+            out[(*out_count)++] = move_make(from, to);
+        }
+    }
+}
+
+#define DEFINE_ALL_PSEUDOLEGAL_PAWN_MOVES(side, opp_side, side_enum, inverse_direction, pawn_rank) \
+static void all_pseudolegal_pawn_moves_##side(struct pos const* restrict pos,\
+                                              enum move_gen_type         type,\
+                                              Bb64                       piece_mask,\
+                                              Bb64                       allowed,\
+                                              size_t* restrict           out_count,\
+                                              struct move                out[restrict static MOVE_MAX])\
+{\
+    Bb64 const all_occ = ~(pos->pieces[SIDE_WHITE][PIECE_EMPTY] & pos->pieces[SIDE_BLACK][PIECE_EMPTY]);\
+\
+    if (type == MG_CHECKS) {\
+        allowed &= pawn_attacks_##opp_side(pos->pieces[other_side(side_enum)][PIECE_KING]);\
+    }\
+    Bb64 sp = pawn_single_push_##side(piece_mask, ~all_occ)\
+               & allowed\
+               ;\
+    while (sp) {\
+        Sq8 const to = bitboard_pop_lsb(&sp);\
+        Sq8 const from = SQ_SHIFT_##inverse_direction(to, 1);\
+        out[(*out_count)++] = move_make(from, to);\
+    }\
+\
+    Bb64 dp = pawn_double_push_##side(piece_mask & pawn_rank, ~all_occ)\
+               & allowed\
+               ;\
+    while (dp) {\
+        Sq8 const to = bitboard_pop_lsb(&dp);\
+        Sq8 const from = SQ_SHIFT_##inverse_direction(to, 2);\
+        out[(*out_count)++] = move_make(from, to);\
+    }\
+}
+DEFINE_ALL_PSEUDOLEGAL_PAWN_MOVES(white, black, SIDE_WHITE, SOUTH, RANK_MASK_2)
+DEFINE_ALL_PSEUDOLEGAL_PAWN_MOVES(black, white, SIDE_BLACK, NORTH, RANK_MASK_7)
+
+#define DEFINE_ALL_PSEUDOLEGAL_PAWN_ATTACKS(side, opp_side, side_enum, inverse_direction) \
+static void all_pseudolegal_pawn_attacks_##side(struct pos const* restrict pos,\
+                                                enum move_gen_type         type,\
+                                                Bb64                       piece_mask,\
+                                                Bb64                       allowed,\
+                                                size_t* restrict           out_count,\
+                                                struct move                out[restrict static MOVE_MAX])\
+{\
+    Bb64 const their_occ = ~pos->pieces[other_side(side_enum)][PIECE_EMPTY];\
+\
+    if (type == MG_CHECKS) {\
+        allowed &= pawn_attacks_##opp_side(pos->pieces[other_side(side_enum)][PIECE_KING]);\
+    }\
+\
+    Bb64 ratk = pawn_attacks_right_##side(piece_mask)\
+              & (their_occ | pos->ep_targets)\
+              & allowed\
+              ;\
+    while (ratk) {\
+        Sq8 const to = bitboard_pop_lsb(&ratk);\
+        Sq8 const from = SQ_SHIFT_WEST(SQ_SHIFT_##inverse_direction(to, 1), 1);\
+        assuming(*out_count < MOVE_MAX); \
+        out[(*out_count)++] = move_make(from, to);\
+    }\
+\
+    Bb64 latk = pawn_attacks_left_##side(piece_mask)\
+              & (their_occ | pos->ep_targets)\
+              & allowed\
+              ;\
+    while (latk) {\
+        Sq8 const to = bitboard_pop_lsb(&latk);\
+        Sq8 const from = SQ_SHIFT_EAST(SQ_SHIFT_##inverse_direction(to, 1), 1);\
+        assuming(*out_count < MOVE_MAX); \
+        out[(*out_count)++] = move_make(from, to);\
+    }\
+}
+DEFINE_ALL_PSEUDOLEGAL_PAWN_ATTACKS(white, black, SIDE_WHITE, SOUTH)
+DEFINE_ALL_PSEUDOLEGAL_PAWN_ATTACKS(black, white, SIDE_BLACK, NORTH)
+
+static void all_pseudolegal_moves(struct pos const* restrict pos,
+                                  enum move_gen_type         type,
+                                  Side8                      us,
+                                  size_t* restrict           out_count,
+                                  struct move                out[restrict static MOVE_MAX])
+{
+    Side8 const them = other_side(us);
+    if (type == MG_CHECKS && pos->pieces[them][PIECE_KING] == 0ULL) {
+        return;
+    }
+    Bb64 const kmask = pos->pieces[us][PIECE_KING];
+    assuming(kmask);
+    Sq8 const ksq = bitboard_lsb(kmask);
+
+
+    Bb64 const chk = checkers(pos, us);
+
+    Bb64 const their_threats = all_threats_from_side(pos, them);
+
+    Bb64 const their_occ = ~pos->pieces[them][PIECE_EMPTY];
+
+    Bb64 allowed;
+    if (type == MG_CAPTURES) {
+        allowed = their_occ;
+    } else if (type == MG_QUIETS) {
+        allowed = ~their_occ;
+    } else if (type == MG_ALL) {
+        allowed = ~0ULL;
+    } else {
+        allowed = ~0ULL;
+    }
+
+    Bb64 king_allowed = allowed;
+
+    if (chk) {
+        if (bitboard_more_than_one(chk)) {
+            if (type == MG_ALL) {
+                /* no other piece can fix check if the king has two attackers or more */
+                all_pseudolegal_from_piece(pos, type, PIECE_KING, us, pos->pieces[us][PIECE_KING], ~their_threats, out_count, out);
+            }
+            return;
+        }
+
+        Sq8 const asq = bitboard_lsb(chk);
+        Bb64 const blocking_mask = between_mask(ksq, asq);
+        allowed &= blocking_mask | chk;
+    }
+
+    if (type == MG_CAPTURES || type == MG_CHECKS || type == MG_ALL) {
+        Bb64 const x = (type == MG_CHECKS ? pos->ep_targets : 0ULL);
+        if (us == SIDE_WHITE) {
+            all_pseudolegal_pawn_attacks_white(pos, type, pos->pieces[us][PIECE_PAWN], allowed | x, out_count, out);
+        } else {
+            all_pseudolegal_pawn_attacks_black(pos, type, pos->pieces[us][PIECE_PAWN], allowed | x, out_count, out);
+        }
+    }
+
+    if (type == MG_QUIETS || type == MG_CHECKS || type == MG_ALL) {
+        if (us == SIDE_WHITE) {
+            all_pseudolegal_pawn_moves_white(pos, type, pos->pieces[us][PIECE_PAWN], allowed, out_count, out);
+        } else {
+            all_pseudolegal_pawn_moves_black(pos, type, pos->pieces[us][PIECE_PAWN], allowed, out_count, out);
+        }
+    }
+
+    all_pseudolegal_from_piece(pos, type, PIECE_BISHOP, us, pos->pieces[us][PIECE_BISHOP], allowed, out_count, out);
+    all_pseudolegal_from_piece(pos, type, PIECE_KNIGHT, us, pos->pieces[us][PIECE_KNIGHT], allowed, out_count, out);
+    all_pseudolegal_from_piece(pos, type, PIECE_ROOK,   us, pos->pieces[us][PIECE_ROOK],   allowed, out_count, out);
+    all_pseudolegal_from_piece(pos, type, PIECE_QUEEN,  us, pos->pieces[us][PIECE_QUEEN],  allowed, out_count, out);
+
+    all_pseudolegal_from_piece(pos, type, PIECE_KING,   us, pos->pieces[us][PIECE_KING], ~their_threats & king_allowed, out_count, out);
+
+    if (type == MG_CHECKS) {
+        Bb64 discovering = pinning_lines_to_target(pos, us, bitboard_lsb(pos->pieces[them][PIECE_KING]));
+
+        all_pseudolegal_from_piece(pos, MG_ALL, PIECE_BISHOP, us, discovering & pos->pieces[us][PIECE_BISHOP], ~discovering, out_count, out);
+        all_pseudolegal_from_piece(pos, MG_ALL, PIECE_KNIGHT, us, discovering & pos->pieces[us][PIECE_KNIGHT], ~discovering, out_count, out);
+        all_pseudolegal_from_piece(pos, MG_ALL, PIECE_ROOK,   us, discovering & pos->pieces[us][PIECE_ROOK],   ~discovering, out_count, out);
+        all_pseudolegal_from_piece(pos, MG_ALL, PIECE_QUEEN,  us, discovering & pos->pieces[us][PIECE_QUEEN],  ~discovering, out_count, out);
+        all_pseudolegal_from_piece(pos, MG_ALL, PIECE_KING,   us, discovering & pos->pieces[us][PIECE_KING],   ~discovering & ~their_threats, out_count, out);
+    }
+
+    /* castling */
+    if (!chk && type != MG_CAPTURES) {
+        bool can_castle_kingside, can_castle_queenside;
+        Bb64 const blocked = ~(pos->pieces[SIDE_WHITE][PIECE_EMPTY] & pos->pieces[SIDE_BLACK][PIECE_EMPTY]) | their_threats;
+        if (us == SIDE_WHITE) {
+            can_castle_kingside = !(blocked & (SQMASK_F1 | SQMASK_G1))
+                          && (pos->pieces[us][PIECE_ROOK] & SQMASK_H1)
+                          && !pos->castling_illegal[us][CASTLE_KINGSIDE];
+            can_castle_queenside = !(blocked & (SQMASK_C1 | SQMASK_D1))
+                          && (pos->pieces[us][PIECE_ROOK] & SQMASK_A1)
+                          && !pos->castling_illegal[us][CASTLE_QUEENSIDE];
+        } else {
+            can_castle_kingside  = !(blocked & (SQMASK_F8 | SQMASK_G8))
+                          && (pos->pieces[us][PIECE_ROOK] & SQMASK_H8)
+                          && !pos->castling_illegal[us][CASTLE_KINGSIDE];
+            can_castle_queenside = !(blocked & (SQMASK_C8 | SQMASK_D8))
+                          && (pos->pieces[us][PIECE_ROOK] & SQMASK_A8)
+                          && !pos->castling_illegal[us][CASTLE_QUEENSIDE];
+        }
+
+        if (can_castle_kingside) {
+            out[(*out_count)++] = us == SIDE_WHITE
+                                  ? MOVE_CASTLE_KINGSIDE_WHITE
+                                  : MOVE_CASTLE_KINGSIDE_BLACK;
+        }
+
+        if (can_castle_queenside) {
+            out[(*out_count)++] = us == SIDE_WHITE
+                                  ? MOVE_CASTLE_QUEENSIDE_WHITE
+                                  : MOVE_CASTLE_QUEENSIDE_BLACK;
+        }
+    }
+}

engine-tt.h

@@ -0,0 +1,142 @@
+#pragma once
+
+#include "engine-types.h"
+
+struct search_option {
+    uint64_t    hash;
+    Score16     score;
+    struct move move;
+    int         depth : 4;
+    int         init  : 1;
+    enum tt_flag {TT_EXACT, TT_LOWER, TT_UPPER} flag : 3;
+};
+
+#define TT_ADDRESS_BITS 24
+#define TT_ENTRIES (1ULL<<TT_ADDRESS_BITS)
+#define TT_MASK (TT_ENTRIES-1)
+struct tt {
+    struct search_option* entries/*[TT_ENTRIES]*/; /* must be initialized somewhere */
+    size_t mask;
+
+    /* stats */
+    uint64_t collisions;
+    uint64_t hits;
+    uint64_t probes;
+    uint64_t overwritten;
+    uint64_t insertions;
+};
+
+struct zobrist {
+    uint64_t piece_keys[SQ_COUNT][SIDE_COUNT][PIECE_COUNT];
+    uint64_t ep_targets[SQ_COUNT];
+    uint64_t castling_keys[SIDE_COUNT][CASTLE_COUNT];
+    bool init;
+};
+
+static struct zobrist zobrist;
+
+static void init_zobrist()
+{
+    for (Sq8 sq = SQ_BEGIN; sq < SQ_COUNT; ++sq) {
+        for (Side8 pl = SIDE_BEGIN; pl < SIDE_COUNT; ++pl) {
+            for (Piece8 piece = PIECE_BEGIN; piece < PIECE_COUNT; ++piece) {
+                zobrist.piece_keys[sq][pl][piece] = my_rand64();
+            }
+        }
+        zobrist.ep_targets[sq] = my_rand64();
+    }
+    for (Side8 pl = SIDE_BEGIN; pl < SIDE_COUNT; ++pl) {
+        for (enum castle_direction d = CASTLE_BEGIN; d < CASTLE_COUNT; ++d) {
+            zobrist.castling_keys[pl][d] = my_rand64();
+        }
+    }
+    zobrist.init = true;
+}
+
+static inline uint64_t tt_hash_update(uint64_t hash,
+                                      Sq8      sq,
+                                      Side8    us,
+                                      Piece8   piece)
+{
+    if (!zobrist.init) {
+        init_zobrist();
+    }
+    return hash ^ zobrist.piece_keys[sq][us][piece];
+}
+
+static inline uint64_t tt_hash_update_castling_rights(uint64_t              hash,
+                                                      Side8           us,
+                                                      enum castle_direction dir)
+{
+    if (!zobrist.init) {
+        init_zobrist();
+    }
+    return hash ^ zobrist.castling_keys[us][dir];
+}
+
+static inline uint64_t tt_hash_update_ep_targets(uint64_t hash, Sq8 sq)
+{
+    if (!zobrist.init) {
+        init_zobrist();
+    }
+    assuming(sq < SQ_COUNT);
+    return hash ^ zobrist.ep_targets[sq];
+}
+
+static inline uint64_t tt_hash_switch_side(uint64_t hash)
+{
+    if (!zobrist.init) {
+        init_zobrist();
+    }
+    return ~hash;
+}
+
+static inline struct search_option tt_get(struct tt* tt, uint64_t hash)
+{
+    uint64_t const addr = hash & tt->mask;
+    struct search_option tte = tt->entries[addr];
+
+#ifndef NSTATS
+    tt->probes += 1;
+    if (tte.init && tte.hash == hash) {
+        tt->hits += 1;
+    } else if (tte.init && tte.hash != hash) {
+        tt->collisions += 1;
+    }
+#endif
+    return tte;
+}
+
+static inline void tt_insert(struct tt* tt, uint64_t hash, struct search_option so)
+{
+    uint64_t const addr = hash & tt->mask;
+    so.init = true;
+    tt->entries[addr] = so;
+#ifndef NSTATS
+    tt->insertions += 1;
+#endif
+}
+
+/* tt_insert_maybe inserts only if heuristics say it's a good idea. There are
+ * two considerations:
+ * - higher depth saves more work per probe hit
+ * - entries closer to the leaves are more likely to be searched multiple time
+ */
+static inline void tt_insert_maybe(struct tt* tt, uint64_t hash, struct search_option so)
+{
+    uint64_t const addr = hash & tt->mask;
+
+#if 0
+    struct search_option* tte = &tt->entries[addr];
+    if (so.depth < tte->depth) {
+        *tte = so;
+    }
+#endif
+
+    so.init = true;
+    tt->entries[addr] = so;
+#ifndef NSTATS
+    tt->insertions += 1;
+#endif
+}
+

engine-types.h

@@ -0,0 +1,348 @@
+#pragma once
+
+/* --- Score16 (centipawns) ---- */
+
+typedef int16_t Score16;
+
+enum {
+    SCORE_INF       = 9999,
+    SCORE_CHECKMATE = 999,
+};
+
+/* ----------- Index8 ----------- */
+typedef uint8_t Index8;
+
+#define MASK_SHIFT_NORTH(b, n) ((b) << ((Index8)(n)*8U))
+#define MASK_SHIFT_SOUTH(b, n) ((b) >> ((Index8)(n)*8U))
+#define MASK_SHIFT_WEST(b, n)  ((b) >> ((Index8)(n)*1U))
+#define MASK_SHIFT_EAST(b, n) ((b) << ((Index8)(n)*1U))
+
+#define SQ_SHIFT_NORTH(i, n)    ((i) + ((Index8)(n)*8U))
+#define SQ_SHIFT_SOUTH(i, n)  ((i) - ((Index8)(n)*8U))
+#define SQ_SHIFT_WEST(i, n)  ((i) - ((Index8)(n)*1U))
+#define SQ_SHIFT_EAST(i, n) ((i) + ((Index8)(n)*1U))
+
+#define SQ_FROM_RF(rank, file) ((Index8)(8U*(Index8)(rank) + (Index8)(file)))
+
+/* ----------- file_index ----------- */
+enum file_index : Index8 {
+    FILE_INDEX_BEGIN,
+    FILE_INDEX_A = FILE_INDEX_BEGIN,
+    FILE_INDEX_B,
+    FILE_INDEX_C,
+    FILE_INDEX_D,
+    FILE_INDEX_E,
+    FILE_INDEX_F,
+    FILE_INDEX_G,
+    FILE_INDEX_H,
+    FILE_INDEX_COUNT,
+};
+
+char const file_index_char[FILE_INDEX_COUNT] = {
+    [FILE_INDEX_A] = 'A',
+    [FILE_INDEX_B] = 'B',
+    [FILE_INDEX_C] = 'C',
+    [FILE_INDEX_D] = 'D',
+    [FILE_INDEX_E] = 'E',
+    [FILE_INDEX_F] = 'F',
+    [FILE_INDEX_G] = 'G',
+    [FILE_INDEX_H] = 'H',
+};
+
+/* ----------- rank_index ----------- */
+enum rank_index : Index8 {
+    RANK_INDEX_BEGIN,
+    RANK_INDEX_1 = RANK_INDEX_BEGIN,
+    RANK_INDEX_2,
+    RANK_INDEX_3,
+    RANK_INDEX_4,
+    RANK_INDEX_5,
+    RANK_INDEX_6,
+    RANK_INDEX_7,
+    RANK_INDEX_8,
+    RANK_INDEX_COUNT,
+};
+
+char const rank_index_char[RANK_INDEX_COUNT] = {
+    [RANK_INDEX_1] = '1',
+    [RANK_INDEX_2] = '2',
+    [RANK_INDEX_3] = '3',
+    [RANK_INDEX_4] = '4',
+    [RANK_INDEX_5] = '5',
+    [RANK_INDEX_6] = '6',
+    [RANK_INDEX_7] = '7',
+    [RANK_INDEX_8] = '8',
+};
+
+/* ----------- Sq8 ----------- */
+
+#define SQMASK_PREFIX SQMASK_
+#define SQUARES_LIST_BEGIN \
+    X(A, 1)
+#define SQUARES_LIST \
+    X(A, 1) \
+    X(A, 2) \
+    X(A, 3) \
+    X(A, 4) \
+    X(A, 5) \
+    X(A, 6) \
+    X(A, 7) \
+    X(A, 8) \
+    X(B, 1) \
+    X(B, 2) \
+    X(B, 3) \
+    X(B, 4) \
+    X(B, 5) \
+    X(B, 6) \
+    X(B, 7) \
+    X(B, 8) \
+    X(C, 1) \
+    X(C, 2) \
+    X(C, 3) \
+    X(C, 4) \
+    X(C, 5) \
+    X(C, 6) \
+    X(C, 7) \
+    X(C, 8) \
+    X(D, 1) \
+    X(D, 2) \
+    X(D, 3) \
+    X(D, 4) \
+    X(D, 5) \
+    X(D, 6) \
+    X(D, 7) \
+    X(D, 8) \
+    X(E, 1) \
+    X(E, 2) \
+    X(E, 3) \
+    X(E, 4) \
+    X(E, 5) \
+    X(E, 6) \
+    X(E, 7) \
+    X(E, 8) \
+    X(F, 1) \
+    X(F, 2) \
+    X(F, 3) \
+    X(F, 4) \
+    X(F, 5) \
+    X(F, 6) \
+    X(F, 7) \
+    X(F, 8) \
+    X(G, 1) \
+    X(G, 2) \
+    X(G, 3) \
+    X(G, 4) \
+    X(G, 5) \
+    X(G, 6) \
+    X(G, 7) \
+    X(G, 8) \
+    X(H, 1) \
+    X(H, 2) \
+    X(H, 3) \
+    X(H, 4) \
+    X(H, 5) \
+    X(H, 6) \
+    X(H, 7) \
+    X(H, 8)
+
+typedef enum sq8 : uint8_t {
+    #define X(file, rank) SQ_##file##rank = SQ_FROM_RF(RANK_INDEX_##rank, FILE_INDEX_##file),
+    SQUARES_LIST
+    SQ_COUNT,
+    SQ_POISONED,
+    #undef X
+    /* define iterator begin enum */
+    #define X(file, rank) SQ_BEGIN = SQ_##file##rank,
+    SQUARES_LIST_BEGIN
+    #undef X
+} Sq8;
+
+static char* const sq8_display[SQ_COUNT] = {
+    #define X(file, rank) \
+    [SQ_##file##rank] = STR(file##rank),
+    SQUARES_LIST
+    #undef X
+};
+
+static char* const sq8_str[SQ_COUNT] = {
+    #define X(file, rank) \
+    [SQ_##file##rank] = STR(SQ_##file##rank),
+    SQUARES_LIST
+    #undef X
+};
+
+static inline enum file_index sq_to_file(Sq8 p)
+{
+    return p % 8ULL;
+}
+
+static inline enum rank_index sq_to_rank(Sq8 p)
+{
+    return p / 8ULL;
+}
+
+/* ----------- Side8 ----------- */
+typedef enum side : uint8_t {
+    SIDE_WHITE,
+    SIDE_BLACK,
+    SIDE_COUNT,
+    SIDE_BEGIN = SIDE_WHITE,
+} Side8;
+
+static inline Side8 other_side(Side8 p)
+{
+    return (p == SIDE_WHITE ? SIDE_BLACK : SIDE_WHITE);
+}
+
+static char const* side_str[SIDE_COUNT] = {
+    [SIDE_WHITE] = "SIDE_WHITE",
+    [SIDE_BLACK] = "SIDE_BLACK",
+};
+
+/* ----------- Piece8 ----------- */
+
+/* https://en.wikipedia.org/wiki/X_macro */
+/*    enum           value   white char   white unicode   black char    black unicode  */
+#define PIECES \
+    X(PIECE_EMPTY,      0,         ' ',            ' ',         ' ',             ' ') \
+    X(PIECE_PAWN,     100,         'P',         0x2659,         'p',          0x265F) \
+    X(PIECE_KNIGHT,   301,         'N',         0x2658,         'n',          0x265E) \
+    X(PIECE_BISHOP,   302,         'B',         0x2657,         'b',          0x265D) \
+    X(PIECE_ROOK,     500,         'R',         0x2656,         'r',          0x265C) \
+    X(PIECE_QUEEN,    900,         'Q',         0x2655,         'q',          0x265B) \
+    X(PIECE_KING,    1600,         'K',         0x2654,         'k',          0x265A) \
+    /**/
+
+typedef enum piece : uint8_t {
+#define X(e, v, wc, wu, bc, bu) e,
+    PIECES
+    PIECE_COUNT,
+    PIECE_BEGIN = PIECE_PAWN,
+    PIECE_POISONED, /* used as undefined value in debug builds */
+#undef X
+} Piece8;
+
+static Score16 piece_value[PIECE_COUNT] = {
+#define X(e, v, wc, wu, bc, bu) [e] = v,
+    PIECES
+#undef X
+};
+
+static char const* piece_str[PIECE_COUNT] = {
+#define X(e, v, wc, wu, bc, bu) [e] = STR(e),
+    PIECES
+#undef X
+};
+
+struct piece_side {Piece8 piece; Side8 side;} const piece_and_side_from_char[256] = {
+    #define X(e, v, wc, wu, bc, bu) \
+        [(uint8_t)bc] = {.piece = e, .side = SIDE_BLACK}, \
+        [(uint8_t)wc] = {.piece = e, .side = SIDE_WHITE},
+    PIECES
+    #undef X
+};
+
+static char const piece_char[SIDE_COUNT][PIECE_COUNT] = {
+    [SIDE_WHITE] = {
+#define X(e, v, wc, wu, bc, bu) [e] = wc,
+        PIECES
+#undef X
+    },
+    [SIDE_BLACK] = {
+#define X(e, v, wc, wu, bc, bu) [e] = bc,
+        PIECES
+#undef X
+    }
+};
+
+static int const piece_unicode[SIDE_COUNT][PIECE_COUNT] = {
+    [SIDE_WHITE] = {
+#define X(e, v, wc, wu, bc, bu) [e] = wu,
+        PIECES
+#undef X
+    },
+    [SIDE_BLACK] = {
+#define X(e, v, wc, wu, bc, bu) [e] = bu,
+        PIECES
+#undef X
+    }
+};
+
+/* ----------- moves ----------- */
+
+enum {
+    MATTR_PROMOTE = 1<<0,
+    MATTR_POISONED = 1<<1,
+};
+
+struct move {
+    Sq8 from;
+    Sq8 to;
+    uint8_t attr;
+    #define APPEAL_MAX UINT8_MAX
+    uint8_t  appeal;
+};
+
+/*
+ * Move32 layout:
+ * f (from piece):  3 bits
+ * F (from square): 6 bits
+ * t (to piece):    3 bits
+ * T (to square):   6 bits
+ * p (promotion):   ? bits (likely 3)
+ * [x,x,x,x,x,x,x,x,x,x,x,p,p,p,T,T,T,T,T,T,t,t,t,F,F,F,F,F,F,f,f,f]
+ * */
+
+typedef uint32_t Move32;
+
+#define MOVE_FROM_PIECE(m)  (m & 0b000000000000000000111)
+#define MOVE_FROM_SQUARE(m) (m & 0b000000000000111111000)
+#define MOVE_TO_PIECE(m)    (m & 0b000000000111000000000)
+#define MOVE_TO_SQUARE(m)   (m & 0b000111111000000000000)
+#define MOVE_PROMOTION(m)   (m & 0b111000000000000000000)
+
+_Static_assert(sizeof(struct move) == 4,
+        "this static assuming is here to check when sizeof(move) changes");
+
+#define MOVE_NULL (struct move){0}
+
+#define MOVE_POISONED (struct move) {.from = SQ_POISONED, .to = SQ_POISONED, .attr = MATTR_POISONED }
+
+#define IS_MOVE_NULL(m) ((m).from == (m).to)
+
+/* ----------- castle_direction ----------- */
+enum castle_direction {
+    CASTLE_BEGIN,
+    CASTLE_KINGSIDE = CASTLE_BEGIN,
+    CASTLE_QUEENSIDE,
+    CASTLE_COUNT,
+};
+
+
+/* -------------- stop flag --------------- */
+
+/* occupy an entire cache line to avoid invalidation from neighboring writes */
+struct searching_flag {
+    alignas(CACHE_LINE_SIZE) atomic_uint_fast8_t v;
+    uint8_t pad[CACHE_LINE_SIZE - sizeof(atomic_uint_fast8_t)];
+};
+
+static inline void searching_init(struct searching_flag* restrict sf)
+{
+    atomic_init(&sf->v, 0);
+}
+
+static inline bool searching_still(struct searching_flag const* restrict sf)
+{
+    return atomic_load_explicit(&sf->v, memory_order_relaxed);
+}
+
+static inline void searching_start(struct searching_flag* restrict sf)
+{
+    atomic_store_explicit(&sf->v, 1, memory_order_relaxed);
+}
+
+static inline void searching_stop(struct searching_flag* restrict sf)
+{
+    atomic_store_explicit(&sf->v, 0, memory_order_relaxed);
+}

evaluations.h

@@ -1,202 +0,0 @@
-/* TODO: candidate for code-generation */
-
-#pragma once
-
-#define BITBOARD_WHITE(          \
-        a8,b8,c8,d8,e8,f8,g8,h8, \
-        a7,b7,c7,d7,e7,f7,g7,h7, \
-        a6,b6,c6,d6,e6,f6,g6,h6, \
-        a5,b5,c5,d5,e5,f5,g5,h5, \
-        a4,b4,c4,d4,e4,f4,g4,h4, \
-        a3,b3,c3,d3,e3,f3,g3,h3, \
-        a2,b2,c2,d2,e2,f2,g2,h2, \
-        a1,b1,c1,d1,e1,f1,g1,h1) \
-(bitboard)\
-0b##\
-h8##g8##f8##e8##d8##c8##b8##a8##\
-h7##g7##f7##e7##d7##c7##b7##a7##\
-h6##g6##f6##e6##d6##c6##b6##a6##\
-h5##g5##f5##e5##d5##c5##b5##a5##\
-h4##g4##f4##e4##d4##c4##b4##a4##\
-h3##g3##f3##e3##d3##c3##b3##a3##\
-h2##g2##f2##e2##d2##c2##b2##a2##\
-h1##g1##f1##e1##d1##c1##b1##a1##\
-ULL
-
-#define BITBOARD_BLACK(          \
-        a8,b8,c8,d8,e8,f8,g8,h8, \
-        a7,b7,c7,d7,e7,f7,g7,h7, \
-        a6,b6,c6,d6,e6,f6,g6,h6, \
-        a5,b5,c5,d5,e5,f5,g5,h5, \
-        a4,b4,c4,d4,e4,f4,g4,h4, \
-        a3,b3,c3,d3,e3,f3,g3,h3, \
-        a2,b2,c2,d2,e2,f2,g2,h2, \
-        a1,b1,c1,d1,e1,f1,g1,h1) \
-(bitboard)\
-0b##\
-h1##g1##f1##e1##d1##c1##b1##a1##\
-h2##g2##f2##e2##d2##c2##b2##a2##\
-h3##g3##f3##e3##d3##c3##b3##a3##\
-h4##g4##f4##e4##d4##c4##b4##a4##\
-h5##g5##f5##e5##d5##c5##b5##a5##\
-h6##g6##f6##e6##d6##c6##b6##a6##\
-h7##g7##f7##e7##d7##c7##b7##a7##\
-h8##g8##f8##e8##d8##c8##b8##a8##\
-ULL
-
-#define RELATIVE_DIAGONAL_A1_H8 \
-    RELATIVE_BITBOARD( \
-        0,0,0,0,0,0,0,1, \
-        0,0,0,0,0,0,1,0, \
-        0,0,0,0,0,1,0,0, \
-        0,0,0,0,1,0,0,0, \
-        0,0,0,1,0,0,0,0, \
-        0,0,1,0,0,0,0,0, \
-        0,1,0,0,0,0,0,0, \
-        1,0,0,0,0,0,0,0)
-
-#define RELATIVE_DIAGONAL_A8_H1 \
-    RELATIVE_BITBOARD( \
-        1,0,0,0,0,0,0,0, \
-        0,1,0,0,0,0,0,0, \
-        0,0,1,0,0,0,0,0, \
-        0,0,0,1,0,0,0,0, \
-        0,0,0,0,1,0,0,0, \
-        0,0,0,0,0,1,0,0, \
-        0,0,0,0,0,0,1,0, \
-        0,0,0,0,0,0,0,1)
-
-#define RELATIVE_BISHOP_KING_ATTACK \
-    RELATIVE_BITBOARD( \
-        0,0,0,0,0,0,1,1, \
-        0,0,0,0,0,1,1,0, \
-        0,0,0,0,1,1,0,0, \
-        0,0,0,1,1,0,0,0, \
-        0,0,1,1,0,0,0,0, \
-        0,1,1,0,0,0,0,0, \
-        1,1,0,0,0,0,0,0, \
-        1,0,0,0,0,0,0,0)
-
-#define RELATIVE_BISHOP_QUEEN_ATTACK \
-    RELATIVE_BITBOARD( \
-        1,1,0,0,0,0,0,0, \
-        0,1,1,0,0,0,0,0, \
-        0,0,1,1,0,0,0,0, \
-        0,0,0,1,1,0,0,0, \
-        0,0,0,0,1,1,0,0, \
-        0,0,0,0,0,1,1,0, \
-        0,0,0,0,0,0,1,1, \
-        0,0,0,0,0,0,0,1)
-
-#define RELATIVE_KING_CASTLE_KINGSIDE \
-    RELATIVE_BITBOARD( \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,1,0)
-
-#define RELATIVE_KING_CASTLE_QUEENSIDE \
-    RELATIVE_BITBOARD( \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,1,1,0,0,0,0,0)
-
-#define CORNERS \
-    BITBOARD( \
-        1,0,0,0,0,0,0,1, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        1,0,0,0,0,0,0,1)
-
-#define RELATIVE_PAWN_SAFE_ZONE \
-    BITBOARD( \
-        0,0,0,0,0,0,0,0, \
-        0,0,0,0,0,0,0,0, \
-        1,0,0,0,0,0,0,0, \
-        1,0,0,1,1,0,0,0, \
-        1,1,1,1,1,0,0,0, \
-        1,1,1,1,1,0,0,1, \
-        1,1,1,1,1,1,1,1, \
-        0,0,0,0,0,0,0,0)
-
-#define BOARD_CENTER_4X4 \
-    ((FILE_MASK_C | FILE_MASK_D | FILE_MASK_E | FILE_MASK_F) \
-    & (RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6))
-
-#define BOARD_CENTER_2X2 \
-    ((FILE_MASK_D | FILE_MASK_E) \
-    & (RANK_MASK_4 | RANK_MASK_5))
-
-
-#define POSITIONAL_BONUS_0 \
-   /* piece         bonus   area*/ \
-    X(PIECE_PAWN,    0.02,  BOARD_CENTER_4X4) \
-    X(PIECE_KNIGHT,  0.05,  BOARD_CENTER_4X4) \
-    X(PIECE_BISHOP,  0.05,  RELATIVE_DIAGONAL_A1_H8 | RELATIVE_DIAGONAL_A8_H1) \
-    X(PIECE_KING,    0.15,  RELATIVE_KING_CASTLE_KINGSIDE) \
-    X(PIECE_QUEEN,  -0.10,  RANK_MASK_3 | RANK_MASK_4 | RANK_MASK_5 | RANK_MASK_6) \
-    /**/
-
-#define POSITIONAL_BONUS_1 \
-   /* piece         bonus   area*/ \
-    X(PIECE_PAWN,   0.02,   BOARD_CENTER_2X2) \
-    X(PIECE_BISHOP, 0.05,   RELATIVE_BISHOP_KING_ATTACK) \
-    /**/
-
-#define POSITIONAL_BONUS_2 \
-   /* piece         bonus   area*/ \
-    X(PIECE_PAWN,   -0.10,  ~RELATIVE_PAWN_SAFE_ZONE) \
-    X(PIECE_BISHOP,  0.05,   CORNERS) \
-    /**/
-
-#define POSITIONAL_BONUS_3 \
-   /* piece         bonus   area*/ \
-    X(PIECE_BISHOP, 0.02,   RELATIVE_BISHOP_QUEEN_ATTACK)
-
-#define POSITIONAL_MODIFIER_COUNT 4
-static struct {bitboard const area; double const val;} const
-positional_modifier[PLAYER_COUNT][POSITIONAL_MODIFIER_COUNT][PIECE_COUNT] = {
-#define X(p, b, a) [p] = {.area = (a), .val = b},
-#define RELATIVE_BITBOARD BITBOARD_WHITE
-    [PLAYER_WHITE] = {
-            {POSITIONAL_BONUS_0},
-            {POSITIONAL_BONUS_1},
-            {POSITIONAL_BONUS_2},
-            {POSITIONAL_BONUS_3},
-    },
-    [PLAYER_BLACK] = {
-#undef RELATIVE_BITBOARD
-#define RELATIVE_BITBOARD BITBOARD_BLACK
-            {POSITIONAL_BONUS_0},
-            {POSITIONAL_BONUS_1},
-            {POSITIONAL_BONUS_2},
-            {POSITIONAL_BONUS_3},
-    }
-#undef X
-};
-
-
-#undef CORNERS
-#undef BOARD_CENTER_4X4
-#undef BOARD_CENTER_2X2
-#undef BITBOARD_WHITE
-#undef BITBOARD_BLACK
-#undef RELATIVE_DIAGONAL_A1_H8 
-#undef RELATIVE_DIAGONAL_A8_H1 
-#undef RELATIVE_BISHOP_KING_ATTACK 
-#undef RELATIVE_BISHOP_QUEEN_ATTACK 
-#undef RELATIVE_KING_CASTLE_KINGSIDE 
-#undef RELATIVE_KING_CASTLE_QUEENSIDE 

sys.h

@@ -20,8 +20,8 @@ static size_t g_buf_len = 0;
 
 static void* sys_mmap_anon_shared(size_t size, int, int)
 {
-	/* FIXME: this program relies on very few memory allocations, a simple bump
-	 * allocator works for now, but will cause memory leaks in the future */
+    /* FIXME: this program relies on very few memory allocations, a simple bump
+     * allocator works for now, but will cause memory leaks in the future */
     size = (size + 7ULL) & ~7ULL;
 
     if (g_buf_len + size > sizeof g_buf) {

tests.c

@@ -1,6 +1,11 @@
 
+#define FEATURE_STOPPABLE_SEARCH
+#define FEATURE_USE_PRINTF
+#undef NSTATS 
+
 #define _XOPEN_SOURCE 500
 #include <unistd.h> /* usleep */
+#include <pthread.h>
 
 #include "engine.h"
 #include "board_print.h"
@@ -11,10 +16,12 @@
 
 /* Tests are mostly generated by ChatGPT */
 
+#define test_expect(expr) if (!(expr)) { fprintf(stderr, "test failed: expected <" #expr ">\n"); exit(EXIT_FAILURE); }
+
 static void print_rook_test(const char *label,
-                            enum square_index sq,
-                            bitboard all_occ,
-                            bitboard own_occ)
+                            Sq8 sq,
+                            Bb64 all_occ,
+                            Bb64 own_occ)
 {
     printf("\n%s\n", label);
     printf("All occ:\n");
@@ -22,7 +29,7 @@ static void print_rook_test(const char *label,
     printf("Own occ:\n");
     bitboard_print(own_occ, stdout);
 
-    const bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+    const Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
     printf("Rook attacks:\n");
     bitboard_print(attacks, stdout);
 }
@@ -30,84 +37,84 @@ static void print_rook_test(const char *label,
 static void test_rooks()
 {
     {
-        const enum square_index sq = SQ_INDEX_A1;
-        const bitboard rook       = SQ_MASK_A1;
-        const bitboard all_occ    = rook;
-        const bitboard own_occ    = rook;
+        const Sq8 sq = SQ_A1;
+        const Bb64 rook       = SQMASK_A1;
+        const Bb64 all_occ    = rook;
+        const Bb64 own_occ    = rook;
 
         /* Expected: full rank 1 and file A, except A1 */
-        bitboard expected = (FILE_MASK_A | RANK_MASK_1) & ~SQ_MASK_A1;
+        Bb64 expected = (FILE_MASK_A | RANK_MASK_1) & ~SQMASK_A1;
 
         print_rook_test("Test 1: Rook at A1, empty board", sq, all_occ, own_occ);
 
-        const bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     {
-        const enum square_index sq = SQ_INDEX_A1;
-        const bitboard rook        = SQ_MASK_A1;
-        const bitboard own_block   = SQ_MASK_A2 | SQ_MASK_B1;
-        const bitboard all_occ     = rook | own_block;
-        const bitboard own_occ     = all_occ;
+        const Sq8 sq = SQ_A1;
+        const Bb64 rook        = SQMASK_A1;
+        const Bb64 own_block   = SQMASK_A2 | SQMASK_B1;
+        const Bb64 all_occ     = rook | own_block;
+        const Bb64 own_occ     = all_occ;
 
         /* Expected: no legal moves (immediately blocked both directions) */
-        const bitboard expected = 0ULL;
+        const Bb64 expected = 0ULL;
 
         print_rook_test("Test 2: Rook at A1, own blockers A2, B1", sq, all_occ, own_occ);
 
-        const bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     {
-        const enum square_index sq = SQ_INDEX_A1;
-        const bitboard rook        = SQ_MASK_A1;
-        const bitboard enemies     = SQ_MASK_A3 | SQ_MASK_C1;
-        const bitboard all_occ     = rook | enemies;
-        const bitboard own_occ     = rook;
+        const Sq8 sq = SQ_A1;
+        const Bb64 rook        = SQMASK_A1;
+        const Bb64 enemies     = SQMASK_A3 | SQMASK_C1;
+        const Bb64 all_occ     = rook | enemies;
+        const Bb64 own_occ     = rook;
 
         /*
          * Expected:
          *  - Along file A: A2, A3 (enemy at A3 is capturable, stop there)
          *  - Along rank 1: B1, C1 (enemy at C1 capturable, stop there)
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_A2 | SQ_MASK_A3;
-        expected |= SQ_MASK_B1 | SQ_MASK_C1;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_A2 | SQMASK_A3;
+        expected |= SQMASK_B1 | SQMASK_C1;
 
         print_rook_test("Test 3: Rook at A1, enemy blockers A3, C1", sq, all_occ, own_occ);
 
-        const bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
         /* Rook Test 6: center rook on empty board */
     {
-        const enum square_index sq = SQ_INDEX_E5;
-        const bitboard rook        = SQ_MASK_E5;
-        const bitboard all_occ     = rook;
-        const bitboard own_occ     = rook;
+        const Sq8 sq = SQ_E5;
+        const Bb64 rook        = SQMASK_E5;
+        const Bb64 all_occ     = rook;
+        const Bb64 own_occ     = rook;
 
         /* Full rank 5 and file E, except E5 itself */
-        bitboard expected = (FILE_MASK_E | RANK_MASK_5) & ~SQ_MASK_E5;
+        Bb64 expected = (FILE_MASK_E | RANK_MASK_5) & ~SQMASK_E5;
 
         print_rook_test("Rook Test 6: E5, empty board", sq, all_occ, own_occ);
 
-        bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Rook Test 7: center rook, mixed blockers on rays */
     {
-        const enum square_index sq = SQ_INDEX_E5;
-        const bitboard rook        = SQ_MASK_E5;
+        const Sq8 sq = SQ_E5;
+        const Bb64 rook        = SQMASK_E5;
 
         /* Friendly: E7 and C5; Enemy: E3 and H5 */
-        const bitboard friends     = rook | SQ_MASK_E7 | SQ_MASK_C5;
-        const bitboard enemies     = SQ_MASK_E3 | SQ_MASK_H5;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Bb64 friends     = rook | SQMASK_E7 | SQMASK_C5;
+        const Bb64 enemies     = SQMASK_E3 | SQMASK_H5;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /*
          * From E5:
@@ -116,73 +123,73 @@ static void test_rooks()
          *  Left: D5, then friendly C5 (stop before C5)
          *  Right:F5, G5, H5 (enemy, included, then stop)
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_E6;
-        expected |= SQ_MASK_E4 | SQ_MASK_E3;
-        expected |= SQ_MASK_D5;
-        expected |= SQ_MASK_F5 | SQ_MASK_G5 | SQ_MASK_H5;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_E6;
+        expected |= SQMASK_E4 | SQMASK_E3;
+        expected |= SQMASK_D5;
+        expected |= SQMASK_F5 | SQMASK_G5 | SQMASK_H5;
 
         print_rook_test("Rook Test 7: E5, friends E7/C5, enemies E3/H5", sq, all_occ, own_occ);
 
-        bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Rook Test 8: edge rook on empty board (top edge, not corner) */
     {
-        const enum square_index sq = SQ_INDEX_C8;
-        const bitboard rook        = SQ_MASK_C8;
-        const bitboard all_occ     = rook;
-        const bitboard own_occ     = rook;
+        const Sq8 sq = SQ_C8;
+        const Bb64 rook        = SQMASK_C8;
+        const Bb64 all_occ     = rook;
+        const Bb64 own_occ     = rook;
 
         /*
          * From C8:
          *  Down file C: C7..C1
          *  Across rank 8: A8,B8,D8,E8,F8,G8,H8
          */
-        bitboard expected = 0ULL;
-        expected |= (FILE_MASK_C & ~SQ_MASK_C8);
-        expected |= (RANK_MASK_8 & ~SQ_MASK_C8);
+        Bb64 expected = 0ULL;
+        expected |= (FILE_MASK_C & ~SQMASK_C8);
+        expected |= (RANK_MASK_8 & ~SQMASK_C8);
 
         print_rook_test("Rook Test 8: C8, empty board", sq, all_occ, own_occ);
 
-        bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Rook Test 9: rook completely boxed in by friendly orthogonal neighbors */
     {
-        const enum square_index sq = SQ_INDEX_D4;
-        const bitboard rook        = SQ_MASK_D4;
-        const bitboard friends     = rook |
-                                     SQ_MASK_D5 | SQ_MASK_D3 |
-                                     SQ_MASK_C4 | SQ_MASK_E4;
-        const bitboard enemies     = 0ULL;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Sq8 sq = SQ_D4;
+        const Bb64 rook        = SQMASK_D4;
+        const Bb64 friends     = rook |
+                                     SQMASK_D5 | SQMASK_D3 |
+                                     SQMASK_C4 | SQMASK_E4;
+        const Bb64 enemies     = 0ULL;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /* All four rays are immediately blocked by own pieces */
-        const bitboard expected = 0ULL;
+        const Bb64 expected = 0ULL;
 
         print_rook_test("Rook Test 9: D4, boxed by own pieces at D5/D3/C4/E4",
                         sq, all_occ, own_occ);
 
-        bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Rook Test 10: rook on file with non-interfering off-ray pieces */
     {
-        const enum square_index sq = SQ_INDEX_A4;
-        const bitboard rook        = SQ_MASK_A4;
+        const Sq8 sq = SQ_A4;
+        const Bb64 rook        = SQMASK_A4;
 
         /* Pieces placed off the rook's rank/file; they should have no effect */
-        const bitboard off_ray     = SQ_MASK_C1 | SQ_MASK_F6 | SQ_MASK_H8;
+        const Bb64 off_ray     = SQMASK_C1 | SQMASK_F6 | SQMASK_H8;
         (void)off_ray;
-        const bitboard friends     = rook | SQ_MASK_C1;
-        const bitboard enemies     = SQ_MASK_F6 | SQ_MASK_H8;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Bb64 friends     = rook | SQMASK_C1;
+        const Bb64 enemies     = SQMASK_F6 | SQMASK_H8;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /*
          * From A4:
@@ -190,22 +197,21 @@ static void test_rooks()
          *  Rank 4: B4..H4
          * Pieces not on file A or rank 4 must not change attacks.
          */
-        bitboard expected = 0ULL;
-        expected |= (FILE_MASK_A | RANK_MASK_4) & ~SQ_MASK_A4;
+        Bb64 expected = 0ULL;
+        expected |= (FILE_MASK_A | RANK_MASK_4) & ~SQMASK_A4;
 
         print_rook_test("Rook Test 10: A4, random off-ray pieces C1/F6/H8",
                         sq, all_occ, own_occ);
 
-        bitboard attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        Bb64 attacks = rook_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 }
 
-
 static void print_bishop_test(const char *label,
-                              enum square_index sq,
-                              bitboard all_occ,
-                              bitboard own_occ)
+                              Sq8        sq,
+                              Bb64       all_occ,
+                              Bb64       own_occ)
 {
     fprintf(stderr, "\n%s\n", label);
     fprintf(stderr, "All occ:\n");
@@ -213,7 +219,7 @@ static void print_bishop_test(const char *label,
     fprintf(stderr, "Own occ:\n");
     bitboard_print(own_occ, stderr);
 
-    const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+    const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
     fprintf(stderr, "Bishop attacks:\n");
     bitboard_print(attacks, stderr);
 }
@@ -222,10 +228,10 @@ static void test_bishops(void)
 {
     /* Test 1: Bishop at D4 on empty board (only bishop present) */
     {
-        const enum square_index sq = SQ_INDEX_D4;
-        const bitboard bishop      = SQ_MASK_D4;
-        const bitboard all_occ     = bishop;
-        const bitboard own_occ     = bishop;
+        const Sq8 sq = SQ_D4;
+        const Bb64 bishop  = SQMASK_D4;
+        const Bb64 all_occ = bishop;
+        const Bb64 own_occ = bishop;
 
         /*
          * Expected diagonals from D4:
@@ -234,24 +240,24 @@ static void test_bishops(void)
          *  SE: E3, F2, G1
          *  SW: C3, B2, A1
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_E5 | SQ_MASK_F6 | SQ_MASK_G7 | SQ_MASK_H8;
-        expected |= SQ_MASK_C5 | SQ_MASK_B6 | SQ_MASK_A7;
-        expected |= SQ_MASK_E3 | SQ_MASK_F2 | SQ_MASK_G1;
-        expected |= SQ_MASK_C3 | SQ_MASK_B2 | SQ_MASK_A1;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_E5 | SQMASK_F6 | SQMASK_G7 | SQMASK_H8;
+        expected |= SQMASK_C5 | SQMASK_B6 | SQMASK_A7;
+        expected |= SQMASK_E3 | SQMASK_F2 | SQMASK_G1;
+        expected |= SQMASK_C3 | SQMASK_B2 | SQMASK_A1;
 
         print_bishop_test("Bishop Test 1: D4, empty board", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Test 2: Bishop at C1 on empty board (only bishop present) */
     {
-        const enum square_index sq = SQ_INDEX_C1;
-        const bitboard bishop      = SQ_MASK_C1;
-        const bitboard all_occ     = bishop;
-        const bitboard own_occ     = bishop;
+        const Sq8 sq = SQ_C1;
+        const Bb64 bishop      = SQMASK_C1;
+        const Bb64 all_occ     = bishop;
+        const Bb64 own_occ     = bishop;
 
         /*
          * From C1, diagonals:
@@ -259,25 +265,25 @@ static void test_bishops(void)
          *  NW: B2, A3
          *  SE / SW: none (edge of board)
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_D2 | SQ_MASK_E3 | SQ_MASK_F4 |
-                    SQ_MASK_G5 | SQ_MASK_H6;
-        expected |= SQ_MASK_B2 | SQ_MASK_A3;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_D2 | SQMASK_E3 | SQMASK_F4 |
+                    SQMASK_G5 | SQMASK_H6;
+        expected |= SQMASK_B2 | SQMASK_A3;
 
         print_bishop_test("Bishop Test 2: C1, empty board", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Test 3: Bishop at D4, friendly blockers at F6 and B2 (no enemies) */
     {
-        const enum square_index sq = SQ_INDEX_D4;
-        const bitboard bishop      = SQ_MASK_D4;
-        const bitboard friends     = bishop | SQ_MASK_F6 | SQ_MASK_B2;
-        const bitboard enemies     = 0ULL;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Sq8 sq = SQ_D4;
+        const Bb64 bishop      = SQMASK_D4;
+        const Bb64 friends     = bishop | SQMASK_F6 | SQMASK_B2;
+        const Bb64 enemies     = 0ULL;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /*
          * From D4:
@@ -286,26 +292,26 @@ static void test_bishops(void)
          *  NW: C5, B6, A7 (no blockers)
          *  SE: E3, F2, G1 (no blockers)
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_E5;
-        expected |= SQ_MASK_C3;
-        expected |= SQ_MASK_C5 | SQ_MASK_B6 | SQ_MASK_A7;
-        expected |= SQ_MASK_E3 | SQ_MASK_F2 | SQ_MASK_G1;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_E5;
+        expected |= SQMASK_C3;
+        expected |= SQMASK_C5 | SQMASK_B6 | SQMASK_A7;
+        expected |= SQMASK_E3 | SQMASK_F2 | SQMASK_G1;
 
         print_bishop_test("Bishop Test 3: D4, friendly blockers F6, B2", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Test 4: Bishop at D4, enemy blockers at F6 and B2 (no other friends) */
     {
-        const enum square_index sq = SQ_INDEX_D4;
-        const bitboard bishop      = SQ_MASK_D4;
-        const bitboard friends     = bishop;
-        const bitboard enemies     = SQ_MASK_F6 | SQ_MASK_B2;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Sq8 sq = SQ_D4;
+        const Bb64 bishop      = SQMASK_D4;
+        const Bb64 friends     = bishop;
+        const Bb64 enemies     = SQMASK_F6 | SQMASK_B2;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /*
          * From D4:
@@ -314,27 +320,27 @@ static void test_bishops(void)
          *  NW: C5, B6, A7
          *  SE: E3, F2, G1
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_E5 | SQ_MASK_F6;
-        expected |= SQ_MASK_C3 | SQ_MASK_B2;
-        expected |= SQ_MASK_C5 | SQ_MASK_B6 | SQ_MASK_A7;
-        expected |= SQ_MASK_E3 | SQ_MASK_F2 | SQ_MASK_G1;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_E5 | SQMASK_F6;
+        expected |= SQMASK_C3 | SQMASK_B2;
+        expected |= SQMASK_C5 | SQMASK_B6 | SQMASK_A7;
+        expected |= SQMASK_E3 | SQMASK_F2 | SQMASK_G1;
 
         print_bishop_test("Bishop Test 4: D4, enemy blockers F6, B2", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Test 5: Bishop at D4, mixed friend/enemy + another friendly bishop elsewhere */
     {
-        const enum square_index sq = SQ_INDEX_D4;
-        const bitboard bishop1     = SQ_MASK_D4;  /* tested bishop */
-        const bitboard bishop2     = SQ_MASK_F4;  /* another friendly bishop */
-        const bitboard friends     = bishop1 | bishop2 | SQ_MASK_F6;
-        const bitboard enemies     = SQ_MASK_B2;
-        const bitboard all_occ     = friends | enemies;
-        const bitboard own_occ     = friends;
+        const Sq8 sq = SQ_D4;
+        const Bb64 bishop1     = SQMASK_D4;  /* tested bishop */
+        const Bb64 bishop2     = SQMASK_F4;  /* another friendly bishop */
+        const Bb64 friends     = bishop1 | bishop2 | SQMASK_F6;
+        const Bb64 enemies     = SQMASK_B2;
+        const Bb64 all_occ     = friends | enemies;
+        const Bb64 own_occ     = friends;
 
         /*
          * From D4:
@@ -344,24 +350,23 @@ static void test_bishops(void)
          *  SE: E3, F2, G1
          *  Bishop at F4 is irrelevant; it does not sit on a diagonal from D4.
          */
-        bitboard expected = 0ULL;
-        expected |= SQ_MASK_E5;
-        expected |= SQ_MASK_C3 | SQ_MASK_B2;
-        expected |= SQ_MASK_C5 | SQ_MASK_B6 | SQ_MASK_A7;
-        expected |= SQ_MASK_E3 | SQ_MASK_F2 | SQ_MASK_G1;
+        Bb64 expected = 0ULL;
+        expected |= SQMASK_E5;
+        expected |= SQMASK_C3 | SQMASK_B2;
+        expected |= SQMASK_C5 | SQMASK_B6 | SQMASK_A7;
+        expected |= SQMASK_E3 | SQMASK_F2 | SQMASK_G1;
 
         print_bishop_test("Bishop Test 5: D4, mixed friend/enemy + extra bishop F4", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        test_expect(attacks == expected);
     }
 
     /* Test 6: Bishop at H8, no occupancy */
     {
-        const enum square_index sq = SQ_INDEX_H8;
-        const bitboard enemies     = 0ULL;
-        const bitboard all_occ     = 0ULL;
-        const bitboard own_occ     = SQ_MASK_FROM_INDEX(sq);
+        const Sq8 sq = SQ_H8;
+        const Bb64 all_occ     = 0ULL;
+        const Bb64 own_occ     = MASK_FROM_SQ(sq);
 
         /*
          * From D4:
@@ -371,29 +376,46 @@ static void test_bishops(void)
          *  SE: E3, F2, G1
          *  Bishop at F4 is irrelevant; it does not sit on a diagonal from D4.
          */
-        bitboard expected = 0ULL;
-		expected = SQ_MASK_G7 | SQ_MASK_F6 | SQ_MASK_E5 | SQ_MASK_D4 |
-			SQ_MASK_C3 | SQ_MASK_B2 | SQ_MASK_A1;
+        Bb64 expected = 0ULL;
+        expected = SQMASK_G7 | SQMASK_F6 | SQMASK_E5 | SQMASK_D4 |
+            SQMASK_C3 | SQMASK_B2 | SQMASK_A1;
 
         print_bishop_test("Bishop Test 6: H8, no occupancy", sq, all_occ, own_occ);
 
-        const bitboard attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
-		if (attacks != expected) {
-			bitboard_print(attacks, stderr);
-		}
-        assert(attacks == expected);
+        const Bb64 attacks = bishop_attacks_from_index(sq, all_occ) & ~own_occ;
+        if (attacks != expected) {
+            bitboard_print(attacks, stderr);
+        }
+        test_expect(attacks == expected);
     }
 
     printf("\nAll bishop_attacks_from_index tests passed.\n");
 }
 
+struct timeout_params {
+    struct searching_flag* x;
+    uint32_t v;
+    useconds_t us;
+};
+void* set_after_timeout(void* x)
+{
+    struct timeout_params* p = x;
+    usleep(p->us);
+    searching_stop(p->x);
+    return NULL;
+}
+
 int main()
 {
+    bool const print_threats = true;
 
-    printf("sizeof pos:     %zu\n", sizeof (struct pos));
-    printf("sizeof tt:      %zu\n", sizeof (struct tt));
+    printf("sizeof pos:            %zu\n", sizeof (struct pos));
+    printf("sizeof tt:             %zu\n", sizeof (struct tt));
+    printf("sizeof board:          %zu\n", sizeof (struct board));
+    printf("sizeof search_option:  %zu\n", sizeof (struct search_option));
+    printf("sizeof all tt entries: %zu\n", (1<<26) * sizeof (struct search_option));
 
-#if 1
+#if 0
     test_rooks();
     test_bishops();
 #endif
@@ -403,59 +425,81 @@ int main()
     }
     fprintf(stdout, "\033[0m\n"); /* reset background color */
 
-	/* board is too big for the stack */
-	struct board* b = malloc(sizeof *b);
-	if (!b) {
-		abort();
-	}
-	*b = BOARD_INIT;
+    /* board could be too big for the stack */
+    struct board* b = malloc(sizeof *b);
+    if (!b) {
+        abort();
+    }
+    *b = BOARD_INIT;
+    board_init(b);
 
-    //board_load_fen_unsafe(&board, "1n1q1rk1/r1p2P2/1p1pp2p/pB2P3/2P5/PPN5/6b1/3QK1NR b - - 0 1");
-    //board_load_fen_unsafe(&board, "5R2/7k/P7/6pp/3B4/1PPK2bP/4r3/8 b - - 3 57");
-    board_print_fen(&b->pos, stdout);
-    board_print(&b->pos, NULL, stdout);
-
-    struct move moves[MOVE_MAX];
+    //board_load_fen_unsafe(b, "1n1q1rk1/r1p2P2/1p1pp2p/pB2P3/2P5/PPN5/6b1/3QK1NR b - - 0 1");
+    //board_load_fen_unsafe(b, "8/8/2kr4/6R1/4K3/6P1/8/8 b - - 0 1");
+    //board_load_fen_unsafe(b, "8/8/5R2/8/2K3PP/1B2k3/8/8 b - - 1 4");
+    //board_load_fen_unsafe(b, "4r1k1/b1P1B3/P5pK/1p4P1/7q/8/4p3/1R6 w - - 1 54");
+    //board_print_fen(b->pos, stdout);
+    board_print(&b->pos, NULL, stdout, print_threats);
 
     for (int turn = 0; turn < 200; ++turn) {
-        size_t move_count = 0;
-        all_moves(&b->pos, b->pos.player, &move_count, moves);
+        /*
+        move_count = 0;
+        all_pseudolegal_moves(&b->pos, MG_ALL, b->pos.moving_side, &move_count, moves);
 
         if (move_count == 0) {
-            printf("no moves for %s, aborting\n", player_str[b->pos.player]);
-            board_print_threats(&b->pos, stdout, NULL);
-            b->pos.player = opposite_player(b->pos.player);
-            board_print_threats(&b->pos, stdout, NULL);
+            printf("no moves for %s, aborting\n", side_str[b->pos.moving_side]);
+            board_print(&b->pos, NULL, stdout, print_threats);
+            b->pos.moving_side = other_side(b->pos.moving_side);
+            board_print(&b->pos, NULL, stdout, print_threats);
             break;
         }
+        */
 
-        //struct move move = moves[0];
-        struct search_result sr = search(b, b->pos.player, 7);
+        pthread_t timer;
+        struct searching_flag searching;
+        searching_start(&searching);
+        //atomic_init(&searching, 1);
+#if 1
+        struct timeout_params timer_params = {
+            .x = &searching,
+            .v = false,
+            .us = 2*1000*1000,
+        };
+        pthread_create(&timer, NULL, set_after_timeout, &timer_params);
+#endif
 
-		struct move move = sr.move;
-		double const score = sr.score;
+        struct search_result sr = search(b, b->pos.moving_side, 25, &searching);
+
+        struct move move = sr.move;
+        Score16 const score = sr.score;
 
         printf("move %d: {\n"
                "    .from = %s, (%s)\n"
                "    .to = %s,\n"
-               "    .score = %lf,\n"
-               "    .mask = ",
+               "    .score = %d,\n"
+               "    .mask = "
+               "",
                turn,
-               square_index_display[move.from],
+               sq8_display[move.from],
                piece_str[b->mailbox[move.from]],
-               square_index_display[move.to],
-			   score
+               sq8_display[move.to],
+               score
                );
-        if (move.attr & MATTR_CAPTURE) printf("MATTR_CAPTURE ");
-        if (move.attr & MATTR_PROMOTE) printf("MATTR_PROMOTE ");
         printf("\n}\n");
 
-        enum move_result const r = board_move_2(b, move);
+        enum move_result const r = board_move(b, move);
+
+        /* illegal board state from an engine move (i.e. hanging king) means checkmate */
+        if (!board_is_legal(b)) {
+            printf("checkmate!\n");
+            break;
+        }
 
 #if 1
         board_print_fen(&b->pos, stdout);
         tt_print_stats(&b->tt, stdout);
-        board_print(&b->pos, &move, stdout);
+        board_print(&b->pos, &move, stdout, print_threats);
+        fprintf(stderr, "board hist len: %zu\n", b->hist.length);
+        fprintf(stderr, "\n------------------------\n\n\n");
 #endif
 
         if (r == MR_STALEMATE) {
@@ -463,16 +507,15 @@ int main()
             break;
         }
 
-        if (b->pos.pieces[PLAYER_WHITE][PIECE_KING] == 0ULL) {
+        if (b->pos.pieces[SIDE_WHITE][PIECE_KING] == 0ULL) {
             printf("white king gone!!\n");
-            exit(1);
-        }
-        if (b->pos.pieces[PLAYER_BLACK][PIECE_KING] == 0ULL) {
-            printf("black king gone!!\n");
-            exit(1);
+            exit(EXIT_FAILURE);
         }
 
-        //usleep(1000000);
+        if (b->pos.pieces[SIDE_BLACK][PIECE_KING] == 0ULL) {
+            printf("black king gone!!\n");
+            exit(EXIT_FAILURE);
+        }
     }
 
     return EXIT_SUCCESS;

wasm-compat.c

@@ -1,83 +1,116 @@
+/* The purpose of this file is to be a simple wasm helper layer, all state is global */
 
 #include "engine.h"
 
 #include <stdint.h>
+#include <limits.h>
 
 static struct search_option g_tt_buf[TT_ENTRIES];
+static struct board         g_board;
+static uint16_t             g_legal_moves_buf[MOVE_MAX];
+static uint32_t             g_legal_moves_len;
 
-static struct board g_board;
+void wb_init(void)
+{
+    g_board = BOARD_INIT;
+    g_board.tt.entries = g_tt_buf;
+    g_board.tt.mask = TT_MASK;
+    board_init(&g_board);
+}
 
 static inline uint32_t move_serialize(struct move m)
 {
-	_Static_assert(sizeof m.from * CHAR_BIT == 8,
-			"this must be checked if struct move's `from` changes");
-	_Static_assert(sizeof m.to * CHAR_BIT == 8,
-			"this must be checked if struct move's `to` changes");
-	return ((uint32_t)m.appeal << 24ULL)
-		 | ((uint32_t)m.attr << 16ULL)
-		 | ((uint32_t)m.from << 8ULL)
-		 | ((uint32_t)m.to);
+    _Static_assert(sizeof m.from * CHAR_BIT == 8,
+            "this must be checked if struct move's `from` changes");
+    _Static_assert(sizeof m.to * CHAR_BIT == 8,
+            "this must be checked if struct move's `to` changes");
+
+    return ((uint32_t)m.appeal << 24U)
+         | ((uint32_t)m.attr   << 16U)
+         | ((uint32_t)m.from   <<  8U)
+         | ((uint32_t)m.to     <<  0U);
 }
 
-static inline struct move move_deserialize(uint64_t m)
+static inline struct move move_deserialize(uint32_t m)
 {
-	return (struct move) {
-		/* appeal and attributes are ignored regardless */
-		/*
-		.appeal = (m >> 24) & 0xFF,
-		.attr   = (m >> 16) & 0xFF,
-		*/
-		.from   = (m >>  8) & 0xFF,
-		.to     = (m >>  0) & 0xFF,
-	};
+    return (struct move) {
+        /* appeal and attributes are ignored regardless */
+        /*
+        .appeal = (m >> 24) & 0xFF,
+        .attr   = (m >> 16) & 0xFF,
+        */
+        .from   = (m >>  8) & 0xFF,
+        .to     = (m >>  0) & 0xFF,
+    };
 }
 
 uint64_t wb_search(int8_t max_depth)
 {
-	struct search_result const sr = search(&g_board, g_board.pos.player, max_depth);
-	return move_serialize(sr.move);
+    struct search_result const sr = search(&g_board, g_board.pos.moving_side, max_depth);
+    return (uint64_t)move_serialize(sr.move);
 }
 
 int32_t wb_move(uint32_t move)
 {
-	struct move const m = move_deserialize(move);
-	enum move_result const mr = board_move_2(&g_board, m);
+    struct move const m = move_deserialize(move);
+    enum move_result const mr = board_move(&g_board, m);
 
-	/* TODO: this checkmate/stalemate check needs to be abstracted better */
-	if (mr == MR_STALEMATE) {
-		return (int32_t)MR_STALEMATE;
-	}
-	struct move moves[MOVE_MAX];
-	size_t move_count = 0ULL;
-	all_moves(&g_board.pos, opposite_player(g_board.pos.player), &move_count, moves);
-	if (move_count == 0ULL) {
-		return MR_CHECKMATE;
-	}
+    /* TODO: this checkmate/stalemate check needs to be abstracted better */
+    if (mr == MR_STALEMATE) {
+        return (int32_t)MR_STALEMATE;
+    }
+    struct move moves[MOVE_MAX];
+    size_t move_count = 0ULL;
+    all_pseudolegal_moves(&g_board.pos, MG_ALL, other_side(g_board.pos.moving_side), &move_count, moves);
+    if (move_count == 0ULL) {
+        return (int32_t)MR_CHECKMATE;
+    }
 
-	return (int32_t)mr;
+    return (int32_t)mr;
 }
 
-void wb_init()
+
+static int32_t side_piece_serialize(Side8 c, Piece8 pz)
 {
-	g_board = BOARD_INIT;
-	g_board.tt.entries = g_tt_buf;
+    return ((c  & 0xFF) << 8U)
+         |  (pz & 0xFF);
 }
 
-static int32_t player_piece_serialize(enum player c, enum piece pz)
+int32_t wb_board_at(uint8_t at)
 {
-	return ((c  & 0xFF) << 8U)
-		 |  (pz & 0xFF);
-}
-
-int32_t wb_board_at(index at)
-{
-	bitboard const m = SQ_MASK_FROM_INDEX(at);
-	for (enum player pl = PLAYER_BEGIN; pl < PLAYER_COUNT; ++pl) {
-		for (enum piece pz = PIECE_BEGIN; pz < PIECE_COUNT; ++pz) {
-			if (g_board.pos.pieces[pl][pz] & m) {
-				return player_piece_serialize(pl, pz);
-			}
-		}
-	}
+    Bb64 const m = MASK_FROM_SQ((Sq8)at);
+    for (Side8 side = SIDE_BEGIN; side < SIDE_COUNT; ++side) {
+        for (Piece8 pz = PIECE_BEGIN; pz < PIECE_COUNT; ++pz) {
+            if (g_board.pos.pieces[side][pz] & m) {
+                return side_piece_serialize(side, pz);
+            }
+        }
+    }
 	return -1;
 }
+
+uint32_t wb_all_moves_len(void)
+{
+    struct move moves[MOVE_MAX];
+    size_t cnt = 0;
+    all_pseudolegal_moves(&g_board.pos, MG_ALL, g_board.pos.moving_side, &cnt, moves);
+
+    if (cnt > MOVE_MAX) {
+        cnt = MOVE_MAX;
+    }
+
+    g_legal_moves_len = (uint32_t)cnt;
+    for (size_t i = 0; i < cnt; ++i) {
+        g_legal_moves_buf[i] = (uint16_t)(((uint32_t)moves[i].from << 8U)
+                                        |  (uint32_t)moves[i].to);
+    }
+
+    return g_legal_moves_len;
+}
+
+uint32_t wb_all_moves_get(uint32_t i)
+{
+    if (i >= g_legal_moves_len) return 0U;
+    return (uint32_t)g_legal_moves_buf[i];
+}
+