X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=b888d76c780ecc79f17ca5f69bd2f5504c2652e3;hp=726411f46b9bbb1cad49a3213cda632d5e658a00;hb=818a3537a7fecf51f3d24d1c96d653ef29ad1d5a;hpb=a695ed65a8b98c94a928862be76500485b38c414 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 726411f4..b888d76c 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) 2008-2013 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 @@ -18,254 +18,158 @@ */ #include +#include #include "bitboard.h" #include "types.h" namespace { + // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 + const unsigned IndexMax = 2*24*64*64; // stm * psq * wksq * bksq = 196608 + + // Each uint32_t stores results of 32 positions, one per bit + uint32_t KPKBitbase[IndexMax / 32]; + + // A KPK bitbase index is an integer in [0, IndexMax] range + // + // Information is mapped in a way that minimizes number of iterations: + // + // bit 0- 5: white king square (from SQ_A1 to SQ_H8) + // bit 6-11: black king square (from SQ_A1 to SQ_H8) + // bit 12: side to move (WHITE or BLACK) + // bit 13-14: white pawn file (from FILE_A to FILE_D) + // bit 15-17: white pawn 6 - rank (from 6 - RANK_7 to 6 - RANK_2) + unsigned index(Color us, Square bksq, Square wksq, Square psq) { + return wksq + (bksq << 6) + (us << 12) + (file_of(psq) << 13) + ((6 - rank_of(psq)) << 15); + } + 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[]); - 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; - }; + operator Result() const { return res; } + Result classify_leaf(unsigned idx); + Result classify(const std::vector& db) + { return us == WHITE ? classify(db) : classify(db); } - // 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 + private: + template Result classify(const std::vector& db); - // Each uint32_t stores results of 32 positions, one per bit - uint32_t KPKBitbase[IndexMax / 32]; + Color us; + Square bksq, wksq, psq; + Result res; + }; - int compute_index(Square wksq, Square bksq, Square wpsq, Color stm); -} +} // namespace -uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) { +bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color us) { - int index = compute_index(wksq, bksq, wpsq, stm); + assert(file_of(wpsq) <= FILE_D); - return KPKBitbase[index / 32] & (1 << (index & 31)); + unsigned idx = index(us, bksq, wksq, wpsq); + return KPKBitbase[idx / 32] & (1 << (idx & 0x1F)); } -void kpk_bitbase_init() { +void Bitbases::init_kpk() { - Result db[IndexMax]; - KPKPosition pos; - int index, bit, repeat = 1; + unsigned idx, repeat = 1; + std::vector db(IndexMax); - // Initialize table - for (index = 0; index < IndexMax; index++) - db[index] = pos.classify_knowns(index); + // Initialize db with known win / draw positions + for (idx = 0; idx < IndexMax; idx++) + db[idx].classify_leaf(idx); - // Iterate until all positions are classified (30 cycles needed) + // Iterate through the positions until no more of the unknown positions can be + // changed to either wins or draws (15 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].classify(db) != UNKNOWN) repeat = 1; - // Map 32 position results into one KPKBitbase[] entry - for (index = 0; index < IndexMax / 32; index++) - for (bit = 0; bit < 32; bit++) - if (db[32 * index + bit] == RESULT_WIN) - KPKBitbase[index] |= (1 << bit); + // Map 32 results into one KPKBitbase[] entry + for (idx = 0; idx < IndexMax; idx++) + if (db[idx] == WIN) + KPKBitbase[idx / 32] |= 1 << (idx & 0x1F); } 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(file_of(wpsq) <= FILE_D); + Result KPKPosition::classify_leaf(unsigned idx) { - int p = file_of(wpsq) + 4 * (rank_of(wpsq) - 1); - int r = stm + 2 * bksq + 128 * wksq + 8192 * p; + wksq = Square((idx >> 0) & 0x3F); + bksq = Square((idx >> 6) & 0x3F); + us = Color((idx >> 12) & 0x01); + psq = File((idx >> 13) & 3) | Rank(6 - (idx >> 15)); - assert(r >= 0 && r < IndexMax); + // Check if two pieces are on the same square or if a king can be captured + if ( wksq == psq || wksq == bksq || bksq == psq + || (StepAttacksBB[KING][wksq] & bksq) + || (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq))) + return res = INVALID; - return r; - } - - void KPKPosition::from_index(int index) { + if (us == WHITE) + { + // Immediate win if pawn can be promoted without getting captured + if ( rank_of(psq) == RANK_7 + && wksq != psq + DELTA_N + && ( square_distance(bksq, psq + DELTA_N) > 1 + ||(StepAttacksBB[KING][wksq] & (psq + DELTA_N)))) + return res = WIN; + } + // Immediate draw if is stalemate or king captures undefended pawn + else if ( !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq])) + || (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq])) + return res = DRAW; - 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)); + return res = UNKNOWN; } - Result KPKPosition::classify_knowns(int index) { - - from_index(index); - - // Check if two pieces are on the same square - if ( whiteKingSquare == pawnSquare - || whiteKingSquare == blackKingSquare - || blackKingSquare == pawnSquare) - return RESULT_INVALID; - - // Check if a king can be captured - if ( bit_is_set(wk_attacks(), blackKingSquare) - || (bit_is_set(pawn_attacks(), blackKingSquare) && sideToMove == WHITE)) - return RESULT_INVALID; + template + Result KPKPosition::classify(const std::vector& db) { - // 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 - || bit_is_set(wk_attacks(), pawnSquare + DELTA_N))) - return RESULT_WIN; - - // Check for known draw positions + // White to Move: If one move leads to a position classified as WIN, the result + // of the current position is WIN. If all moves lead to positions classified + // as DRAW, the current position is classified DRAW otherwise the current + // position is classified as UNKNOWN. // - // Case 1: Stalemate - if ( sideToMove == BLACK - && !(bk_attacks() & ~(wk_attacks() | pawn_attacks()))) - return RESULT_DRAW; - - // Case 2: King can capture pawn - if ( sideToMove == BLACK - && bit_is_set(bk_attacks(), pawnSquare) && !bit_is_set(wk_attacks(), pawnSquare)) - return RESULT_DRAW; - - // Case 3: Black king in front of white pawn - if ( blackKingSquare == pawnSquare + DELTA_N - && rank_of(pawnSquare) < RANK_7) - return RESULT_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; - - // Case 5: Stalemate with rook pawn - if ( blackKingSquare == SQ_A8 - && file_of(pawnSquare) == FILE_A) - return RESULT_DRAW; - - return RESULT_UNKNOWN; - } - - Result KPKPosition::classify(int index, Result db[]) { + // Black to Move: If one move leads to a position classified as DRAW, the result + // of the current position is DRAW. If all moves lead to positions classified + // as WIN, the position is classified WIN otherwise the current position is + // classified UNKNOWN. - from_index(index); - db[index] = (sideToMove == WHITE ? classify_white(db) : classify_black(db)); - return db[index]; - } - - Result KPKPosition::classify_white(const Result db[]) { + const Color Them = (Us == WHITE ? BLACK : WHITE); - // 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. + Result r = INVALID; + Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq]; - bool unknownFound = false; - Bitboard b; - Square s; - Result r; - - // King moves - b = wk_attacks(); while (b) - { - s = pop_1st_bit(&b); - r = db[compute_index(s, blackKingSquare, pawnSquare, BLACK)]; - - if (r == RESULT_WIN) - return RESULT_WIN; - - if (r == RESULT_UNKNOWN) - unknownFound = true; - } + r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)] + : db[index(Them, pop_lsb(&b), wksq, psq)]; - // 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)]; + Square s = psq + DELTA_N; + r |= db[index(BLACK, bksq, wksq, s)]; // Single push - 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)]; - - if (r == RESULT_WIN) - return RESULT_WIN; - - if (r == RESULT_UNKNOWN) - unknownFound = true; - } + if (rank_of(s) == RANK_3 && s != wksq && s != bksq) + r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push } - 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)]; - - if (r == RESULT_DRAW) - return RESULT_DRAW; - - if (r == RESULT_UNKNOWN) - unknownFound = true; - } - return unknownFound ? RESULT_UNKNOWN : RESULT_WIN; + if (Us == WHITE) + return res = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW; + else + return res = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN; } -} +} // namespace