9-add-perft (#17)

Reviewed-on: #17
Co-authored-by: Josh <josh@joshuaschuett.com>
Co-committed-by: Josh <josh@joshuaschuett.com>

engine/src/bitboard.c

@@ -604,8 +604,8 @@ void rebuild_occ(struct Board *board) {
     uint64_t white=0;
     uint64_t black=0;
 
-    for (int p = P; p <= K; ++p) white |= board->pieces[p];
+    for (int i = P; i <= K; ++i) white |= board->pieces[i];
-    for (int p = p; p <= k; ++p) black |= board->pieces[p];
+    for (int i = p; i <= k; ++i) black |= board->pieces[i];
 
     board->occ[WHITE] = white;
     board->occ[BLACK] = black;
@@ -785,6 +785,26 @@ int get_legal_moves(struct Board *board, struct Move *out) {
     return count;
 }
 
+uint64_t perft(struct Board *board, int depth) {
+    if (depth == 0) return 1;
+
+    struct Move moves[256];
+    int n = get_legal_moves(board, moves);
+
+    if (depth == 1) return (uint64_t) n;
+    
+    uint64_t nodes = 0;
+    for (int i = 0; i < n; ++i) {
+        struct Board after;
+        if (!apply_move_on_copy(board, &after, moves[i])) {
+            // Shouldn't happen with legal moves, but be defensive
+            continue;
+        }
+        nodes += perft(&after, depth - 1);
+    }
+    return nodes;
+}
+
 void print_board(const struct Board *board) {
     const char PIECE_CH[12] = {
         'P','N','B','R','Q','K',

test/chess_ffi.py

@@ -98,6 +98,8 @@ in_check = _bind_opt("in_check", INCHECK_ARGS, C.c_bool)
 attackers_to = _bind_opt("attackers_to", ATTACKERS_TO, C.c_uint64)
 get_legal_moves = _bind_opt("get_legal_moves", GEN_LEGAL_MOVES, C.c_int)
 
+PERFT_SIG = (C.POINTER(Board), C.c_int)
+perft = _bind_opt("perft", PERFT_SIG, C.c_uint64)
 
 # Attack cache tables.
 KnightArr = (C.c_uint64 * 64)

test/test_perft.py

@@ -0,0 +1,90 @@
+from test.base import ChessLibTestBase
+from test.chess_ffi import Board
+from test.chess_ffi import perft
+
+
+class TestPerftQuick(ChessLibTestBase):
+    def test_perft_1(self):
+        b = Board()
+        self.load_fen("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1", board=b)
+        node_count = {
+            1: 20,
+            2: 400,
+            3: 8902,
+            4: 197281,
+            5: 4865609,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")
+
+
+    def test_perft_2(self):
+        b = Board()
+        self.load_fen("r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1", board=b)
+        node_count = {
+            1: 48,
+            2: 2039,
+            3: 97862,
+            4: 4085603,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")
+
+
+    def test_perft_3(self):
+        b = Board()
+        self.load_fen("8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - - 0 1", board=b)
+        node_count = {
+            1: 14,
+            2: 191,
+            3: 2812,
+            4: 43238,
+            5: 674624,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")
+
+
+    def test_perft_4(self):
+        b = Board()
+        self.load_fen("r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 1", board=b)
+        node_count = {
+            1: 6,
+            2: 264,
+            3: 9467,
+            4: 422333,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")
+
+
+    def test_perft_5(self):
+        b = Board()
+        self.load_fen("rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 8  ", board=b)
+        node_count = {
+            1: 44,
+            2: 1486,
+            3: 62379,
+            4: 2103487,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")
+
+
+    def test_perft_6(self):
+        b = Board()
+        self.load_fen("r4rk1/1pp1qppp/p1np1n2/2b1p1B1/2B1P1b1/P1NP1N2/1PP1QPPP/R4RK1 w - - 0 10 ", board=b)
+        node_count = {
+            1: 46,
+            2: 2079,
+            3: 89890,
+            4: 3894594,
+        }
+        for node, count  in node_count.items():
+            actual = int(perft(b, node))
+            self.assertEqual(count, actual, f"perft({node}) start pos")