X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=b01a03d4bc8815ea3c20794057dfc1b3cde159c5;hp=c06ca521391fdf466db8b9f68ebe2687a3be1164;hb=a94fd3bbec12722ca5aa09324260ca03d99e54cf;hpb=1a1742ac4f8e0cfe8c1509e40e0631e075e9c1ad;ds=sidebyside diff --git a/src/bitbase.cpp b/src/bitbase.cpp index c06ca521..b01a03d4 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -25,43 +25,47 @@ namespace { enum Result { - RESULT_UNKNOWN, - RESULT_INVALID, - RESULT_WIN, - RESULT_DRAW + INVALID = 0, + UNKNOWN = 1, + DRAW = 2, + WIN = 4 }; + inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); } + struct KPKPosition { - Result classify_knowns(int index); - Result classify(int index, Result db[]); + + Result classify_leaf(int idx); + Result classify(int idx, Result db[]); private: - void from_index(int index); - Result classify_white(const Result db[]); - Result classify_black(const Result db[]); - Bitboard wk_attacks() const { return StepAttacksBB[W_KING][whiteKingSquare]; } - Bitboard bk_attacks() const { return StepAttacksBB[B_KING][blackKingSquare]; } - Bitboard pawn_attacks() const { return StepAttacksBB[W_PAWN][pawnSquare]; } - - Square whiteKingSquare, blackKingSquare, pawnSquare; - Color sideToMove; + template Result classify(const Result db[]) const; + + template Bitboard k_attacks() const { + return Us == WHITE ? StepAttacksBB[W_KING][wksq] : StepAttacksBB[B_KING][bksq]; + } + + Bitboard p_attacks() const { return StepAttacksBB[W_PAWN][psq]; } + void decode_index(int idx); + + Square wksq, bksq, psq; + Color stm; }; // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 - const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq = 196608 + const int IndexMax = 2 * 24 * 64 * 64; // stm * wp_sq * wk_sq * bk_sq = 196608 // Each uint32_t stores results of 32 positions, one per bit uint32_t KPKBitbase[IndexMax / 32]; - int compute_index(Square wksq, Square bksq, Square wpsq, Color stm); + int index(Square wksq, Square bksq, Square psq, Color stm); } uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) { - int index = compute_index(wksq, bksq, wpsq, stm); - - return KPKBitbase[index / 32] & (1 << (index & 31)); + int idx = index(wksq, bksq, wpsq, stm); + return KPKBitbase[idx / 32] & (1 << (idx & 31)); } @@ -69,24 +73,23 @@ void kpk_bitbase_init() { Result db[IndexMax]; KPKPosition pos; - int index, bit, repeat = 1; + int idx, bit, repeat = 1; - // Initialize table - for (index = 0; index < IndexMax; index++) - db[index] = pos.classify_knowns(index); + // Initialize table with known win / draw positions + for (idx = 0; idx < IndexMax; idx++) + db[idx] = pos.classify_leaf(idx); // Iterate until all positions are classified (30 cycles needed) while (repeat) - for (repeat = index = 0; index < IndexMax; index++) - if ( db[index] == RESULT_UNKNOWN - && pos.classify(index, db) != RESULT_UNKNOWN) + for (repeat = idx = 0; idx < IndexMax; idx++) + if (db[idx] == UNKNOWN && (db[idx] = pos.classify(idx, db)) != UNKNOWN) repeat = 1; // Map 32 position results into one KPKBitbase[] entry - for (index = 0; index < IndexMax / 32; index++) + for (idx = 0; idx < IndexMax / 32; idx++) for (bit = 0; bit < 32; bit++) - if (db[32 * index + bit] == RESULT_WIN) - KPKBitbase[index] |= (1 << bit); + if (db[32 * idx + bit] == WIN) + KPKBitbase[idx] |= 1 << bit; } @@ -102,170 +105,119 @@ namespace { // bit 13-14: white pawn file (from FILE_A to FILE_D) // bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1) - int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) { + int index(Square w, Square b, Square p, Color c) { - assert(file_of(wpsq) <= FILE_D); + assert(file_of(p) <= FILE_D); - int p = file_of(wpsq) + 4 * (rank_of(wpsq) - 1); - int r = stm + 2 * bksq + 128 * wksq + 8192 * p; - - assert(r >= 0 && r < IndexMax); - - return r; + return c + (b << 1) + (w << 7) + (file_of(p) << 13) + ((rank_of(p) - 1) << 15); } - void KPKPosition::from_index(int index) { + void KPKPosition::decode_index(int idx) { - int s = index >> 13; - sideToMove = Color(index & 1); - blackKingSquare = Square((index >> 1) & 63); - whiteKingSquare = Square((index >> 7) & 63); - pawnSquare = make_square(File(s & 3), Rank((s >> 2) + 1)); + stm = Color(idx & 1); + bksq = Square((idx >> 1) & 63); + wksq = Square((idx >> 7) & 63); + psq = make_square(File((idx >> 13) & 3), Rank((idx >> 15) + 1)); } - Result KPKPosition::classify_knowns(int index) { + Result KPKPosition::classify_leaf(int idx) { - from_index(index); + decode_index(idx); - // Check if two pieces are on the same square - if ( whiteKingSquare == pawnSquare - || whiteKingSquare == blackKingSquare - || blackKingSquare == pawnSquare) - return RESULT_INVALID; + // Check if two pieces are on the same square or if a king can be captured + if ( wksq == psq || wksq == bksq || bksq == psq + || (k_attacks() & bksq) + || (stm == WHITE && (p_attacks() & bksq))) + return INVALID; - // Check if a king can be captured - if ( (wk_attacks() & blackKingSquare) - || ((pawn_attacks() & blackKingSquare) && sideToMove == WHITE)) - return RESULT_INVALID; - - // The position is an immediate win if it is white to move and the - // white pawn can be promoted without getting captured. - if ( rank_of(pawnSquare) == RANK_7 - && sideToMove == WHITE - && whiteKingSquare != pawnSquare + DELTA_N - && ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1 - || (wk_attacks() & (pawnSquare + DELTA_N)))) - return RESULT_WIN; + // The position is an immediate win if it is white to move and the white + // pawn can be promoted without getting captured. + if ( rank_of(psq) == RANK_7 + && stm == WHITE + && wksq != psq + DELTA_N + && ( square_distance(bksq, psq + DELTA_N) > 1 + ||(k_attacks() & (psq + DELTA_N)))) + return WIN; // Check for known draw positions // // Case 1: Stalemate - if ( sideToMove == BLACK - && !(bk_attacks() & ~(wk_attacks() | pawn_attacks()))) - return RESULT_DRAW; + if ( stm == BLACK + && !(k_attacks() & ~(k_attacks() | p_attacks()))) + return DRAW; - // Case 2: King can capture pawn - if ( sideToMove == BLACK - && (bk_attacks() & pawnSquare) && !(wk_attacks() & pawnSquare)) - return RESULT_DRAW; + // Case 2: King can capture undefended pawn + if ( stm == BLACK + && (k_attacks() & psq & ~k_attacks())) + return DRAW; // Case 3: Black king in front of white pawn - if ( blackKingSquare == pawnSquare + DELTA_N - && rank_of(pawnSquare) < RANK_7) - return RESULT_DRAW; + if ( bksq == psq + DELTA_N + && rank_of(psq) < RANK_7) + return DRAW; // Case 4: White king in front of pawn and black has opposition - if ( whiteKingSquare == pawnSquare + DELTA_N - && blackKingSquare == pawnSquare + DELTA_N + DELTA_N + DELTA_N - && rank_of(pawnSquare) < RANK_5 - && sideToMove == WHITE) - return RESULT_DRAW; + if ( stm == WHITE + && wksq == psq + DELTA_N + && bksq == wksq + DELTA_N + DELTA_N + && rank_of(psq) < RANK_5) + return DRAW; // Case 5: Stalemate with rook pawn - if ( blackKingSquare == SQ_A8 - && file_of(pawnSquare) == FILE_A) - return RESULT_DRAW; + if ( bksq == SQ_A8 + && file_of(psq) == FILE_A) + return DRAW; - return RESULT_UNKNOWN; + return UNKNOWN; } - Result KPKPosition::classify(int index, Result db[]) { + template + Result KPKPosition::classify(const Result db[]) const { - from_index(index); - db[index] = (sideToMove == WHITE ? classify_white(db) : classify_black(db)); - return db[index]; - } - - Result KPKPosition::classify_white(const Result db[]) { - - // If one move leads to a position classified as RESULT_WIN, the result - // of the current position is RESULT_WIN. If all moves lead to positions - // classified as RESULT_DRAW, the current position is classified RESULT_DRAW - // otherwise the current position is classified as RESULT_UNKNOWN. + // White to Move: If one move leads to a position classified as RESULT_WIN, + // the result of the current position is RESULT_WIN. If all moves lead to + // positions classified as RESULT_DRAW, the current position is classified + // RESULT_DRAW otherwise the current position is classified as RESULT_UNKNOWN. + // + // Black to Move: If one move leads to a position classified as RESULT_DRAW, + // the result of the current position is RESULT_DRAW. If all moves lead to + // positions classified as RESULT_WIN, the position is classified RESULT_WIN. + // Otherwise, the current position is classified as RESULT_UNKNOWN. - bool unknownFound = false; - Bitboard b; - Square s; - Result r; + Result r = INVALID; + Bitboard b = k_attacks(); - // King moves - b = wk_attacks(); while (b) { - s = pop_1st_bit(&b); - r = db[compute_index(s, blackKingSquare, pawnSquare, BLACK)]; + r |= Us == WHITE ? db[index(pop_1st_bit(&b), bksq, psq, BLACK)] + : db[index(wksq, pop_1st_bit(&b), psq, WHITE)]; - if (r == RESULT_WIN) - return RESULT_WIN; + if (Us == WHITE && (r & WIN)) + return WIN; - if (r == RESULT_UNKNOWN) - unknownFound = true; + if (Us == BLACK && (r & DRAW)) + return DRAW; } - // Pawn moves - if (rank_of(pawnSquare) < RANK_7) + if (Us == WHITE && rank_of(psq) < RANK_7) { - s = pawnSquare + DELTA_N; - r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)]; - - if (r == RESULT_WIN) - return RESULT_WIN; - - if (r == RESULT_UNKNOWN) - unknownFound = true; - - // Double pawn push - if (rank_of(s) == RANK_3 && r != RESULT_INVALID) - { - s += DELTA_N; - r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)]; + Square s = psq + DELTA_N; + r |= db[index(wksq, bksq, s, BLACK)]; // Single push - if (r == RESULT_WIN) - return RESULT_WIN; + if (rank_of(s) == RANK_3 && s != wksq && s != bksq) + r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push - if (r == RESULT_UNKNOWN) - unknownFound = true; - } + if (r & WIN) + return WIN; } - return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW; - } - - Result KPKPosition::classify_black(const Result db[]) { - // If one move leads to a position classified as RESULT_DRAW, the result - // of the current position is RESULT_DRAW. If all moves lead to positions - // classified as RESULT_WIN, the position is classified as RESULT_WIN. - // Otherwise, the current position is classified as RESULT_UNKNOWN. - - bool unknownFound = false; - Bitboard b; - Square s; - Result r; - - // King moves - b = bk_attacks(); - while (b) - { - s = pop_1st_bit(&b); - r = db[compute_index(whiteKingSquare, s, pawnSquare, WHITE)]; + return r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN; + } - if (r == RESULT_DRAW) - return RESULT_DRAW; + Result KPKPosition::classify(int idx, Result db[]) { - if (r == RESULT_UNKNOWN) - unknownFound = true; - } - return unknownFound ? RESULT_UNKNOWN : RESULT_WIN; + decode_index(idx); + return stm == WHITE ? classify(db) : classify(db); } }