X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=b01a03d4bc8815ea3c20794057dfc1b3cde159c5;hp=d6238395a2cecfa58b9a9402fcd46c0478f18488;hb=a94fd3bbec12722ca5aa09324260ca03d99e54cf;hpb=635be39acf8f1de7686d78fe3fc271c84673d1b8 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index d6238395..b01a03d4 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -25,260 +25,199 @@ namespace { enum Result { - RESULT_UNKNOWN, - RESULT_INVALID, - RESULT_WIN, - RESULT_LOSS, - RESULT_DRAW + INVALID = 0, + UNKNOWN = 1, + DRAW = 2, + WIN = 4 }; + inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); } + struct KPKPosition { - void from_index(int index); - bool is_legal() const; - bool is_immediate_draw() const; - bool is_immediate_win() const; - Bitboard wk_attacks() const { return StepAttacksBB[WK][whiteKingSquare]; } - Bitboard bk_attacks() const { return StepAttacksBB[BK][blackKingSquare]; } - Bitboard pawn_attacks() const { return StepAttacksBB[WP][pawnSquare]; } - - Square whiteKingSquare, blackKingSquare, pawnSquare; - Color sideToMove; + + Result classify_leaf(int idx); + Result classify(int idx, Result db[]); + + private: + 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 + 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]; - Result classify_wtm(const KPKPosition& pos, const Result bb[]); - Result classify_btm(const KPKPosition& pos, const Result bb[]); - 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)); } -void init_kpk_bitbase() { +void kpk_bitbase_init() { - Result bb[IndexMax]; + Result db[IndexMax]; KPKPosition pos; - bool repeat; - - // Initialize table - for (int i = 0; i < IndexMax; i++) - { - pos.from_index(i); - bb[i] = !pos.is_legal() ? RESULT_INVALID - : pos.is_immediate_draw() ? RESULT_DRAW - : pos.is_immediate_win() ? RESULT_WIN : RESULT_UNKNOWN; - } - - // Iterate until all positions are classified (30 cycles needed) - do { - repeat = false; - - for (int i = 0; i < IndexMax; i++) - if (bb[i] == RESULT_UNKNOWN) - { - pos.from_index(i); + int idx, bit, repeat = 1; - bb[i] = (pos.sideToMove == WHITE) ? classify_wtm(pos, bb) - : classify_btm(pos, bb); - if (bb[i] != RESULT_UNKNOWN) - repeat = true; - } + // Initialize table with known win / draw positions + for (idx = 0; idx < IndexMax; idx++) + db[idx] = pos.classify_leaf(idx); - } while (repeat); + // Iterate until all positions are classified (30 cycles needed) + while (repeat) + 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 (int i = 0; i < IndexMax / 32; i++) - for (int j = 0; j < 32; j++) - if (bb[32 * i + j] == RESULT_WIN || bb[32 * i + j] == RESULT_LOSS) - KPKBitbase[i] |= (1 << j); + for (idx = 0; idx < IndexMax / 32; idx++) + for (bit = 0; bit < 32; bit++) + if (db[32 * idx + bit] == WIN) + KPKBitbase[idx] |= 1 << bit; } namespace { - // A KPK bitbase index is an integer in [0, IndexMax] range - // - // Information is mapped in this way - // - // bit 0: side to move (WHITE or BLACK) - // bit 1- 6: black king square (from SQ_A1 to SQ_H8) - // bit 7-12: white king square (from SQ_A1 to SQ_H8) - // 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) { - - assert(square_file(wpsq) <= FILE_D); + // A KPK bitbase index is an integer in [0, IndexMax] range + // + // Information is mapped in this way + // + // bit 0: side to move (WHITE or BLACK) + // bit 1- 6: black king square (from SQ_A1 to SQ_H8) + // bit 7-12: white king square (from SQ_A1 to SQ_H8) + // 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 p = int(square_file(wpsq)) + 4 * int(square_rank(wpsq) - 1); - int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p; + int index(Square w, Square b, Square p, Color c) { - assert(r >= 0 && r < IndexMax); + assert(file_of(p) <= FILE_D); - 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 / 8192) % 24; - - sideToMove = Color(index % 2); - blackKingSquare = Square((index / 2) % 64); - whiteKingSquare = Square((index / 128) % 64); - pawnSquare = make_square(File(s % 4), Rank(s / 4 + 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)); } - bool KPKPosition::is_legal() const { - - if ( whiteKingSquare == pawnSquare - || whiteKingSquare == blackKingSquare - || blackKingSquare == pawnSquare) - return false; - - if (sideToMove == WHITE) - { - if ( bit_is_set(wk_attacks(), blackKingSquare) - || bit_is_set(pawn_attacks(), blackKingSquare)) - return false; - } - else if (bit_is_set(bk_attacks(), whiteKingSquare)) - return false; - - return true; + Result KPKPosition::classify_leaf(int idx) { + + decode_index(idx); + + // 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; + + // 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 ( stm == BLACK + && !(k_attacks() & ~(k_attacks() | p_attacks()))) + return 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 ( bksq == psq + DELTA_N + && rank_of(psq) < RANK_7) + return DRAW; + + // Case 4: White king in front of pawn and black has opposition + 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 ( bksq == SQ_A8 + && file_of(psq) == FILE_A) + return DRAW; + + return UNKNOWN; } - bool KPKPosition::is_immediate_draw() const { + template + Result KPKPosition::classify(const Result db[]) const { - if (sideToMove == BLACK) - { - Bitboard wka = wk_attacks(); - Bitboard bka = bk_attacks(); + // 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. - // Case 1: Stalemate - if ((bka & ~(wka | pawn_attacks())) == EmptyBoardBB) - return true; + Result r = INVALID; + Bitboard b = k_attacks(); - // Case 2: King can capture pawn - if (bit_is_set(bka, pawnSquare) && !bit_is_set(wka, pawnSquare)) - return true; - } - else - { - // Case 1: Stalemate (possible pawn files are only from A to D) - if ( whiteKingSquare == SQ_A8 - && pawnSquare == SQ_A7 - && (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8)) - return true; - } - return false; - } - - bool KPKPosition::is_immediate_win() const { - - // The position is an immediate win if it is white to move and the - // white pawn can be promoted without getting captured. - return sideToMove == WHITE - && square_rank(pawnSquare) == RANK_7 - && whiteKingSquare != pawnSquare + DELTA_N - && ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1 - || bit_is_set(wk_attacks(), pawnSquare + DELTA_N)); - } - - Result classify_wtm(const KPKPosition& pos, const Result bb[]) { - - // If one move leads to a position classified as RESULT_LOSS, 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. - - bool unknownFound = false; - Bitboard b; - Square s; - Result r; - - // King moves - b = pos.wk_attacks(); while (b) { - s = pop_1st_bit(&b); - r = bb[compute_index(s, pos.blackKingSquare, pos.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_LOSS) - 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 (square_rank(pos.pawnSquare) < RANK_7) + if (Us == WHITE && rank_of(psq) < RANK_7) { - s = pos.pawnSquare + DELTA_N; - r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)]; - - if (r == RESULT_LOSS) - return RESULT_WIN; + Square s = psq + DELTA_N; + r |= db[index(wksq, bksq, s, BLACK)]; // Single push - if (r == RESULT_UNKNOWN) - unknownFound = true; + if (rank_of(s) == RANK_3 && s != wksq && s != bksq) + r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push - // Double pawn push - if ( square_rank(s) == RANK_3 - && s != pos.whiteKingSquare - && s != pos.blackKingSquare) - { - s += DELTA_N; - r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)]; - - if (r == RESULT_LOSS) - return RESULT_WIN; - - if (r == RESULT_UNKNOWN) - unknownFound = true; - } + if (r & WIN) + return WIN; } - return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW; - } - - - Result classify_btm(const KPKPosition& pos, const Result bb[]) { - - // 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 current position is classified as - // RESULT_LOSS. Otherwise, the current position is classified as - // RESULT_UNKNOWN. - bool unknownFound = false; - Bitboard b; - Square s; - Result r; - - // King moves - b = pos.bk_attacks(); - while (b) - { - s = pop_1st_bit(&b); - r = bb[compute_index(pos.whiteKingSquare, s, pos.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_LOSS; + decode_index(idx); + return stm == WHITE ? classify(db) : classify(db); } }