X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=700eea9892aa04819a4c27fd490bba36cd74d0a8;hp=19cf3f7901f7eae4fc205bb065b426adf8368624;hb=10d29add187fbc7ce20535a2beddc76e4a8ad0c2;hpb=d3600c39a745179ed6b094b305d0645e83a1ee86 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 19cf3f79..700eea98 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -1,349 +1,217 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008 Marco Costalba + 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 the Free Software Foundation, either version 3 of the License, or (at your option) any later version. - + Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. - + You should have received a copy of the GNU General Public License along with this program. If not, see . */ - -//// -//// Includes -//// - #include +#include -#include "bitbase.h" #include "bitboard.h" -#include "move.h" -#include "square.h" - - -//// -//// Local definitions -//// +#include "types.h" namespace { + // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 + const unsigned IndexMax = 24*64*64*2; // wp_sq * wk_sq * bk_sq * stm = 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 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 6 - rank (from 6 - RANK_7 to 6 - RANK_2) + unsigned index(Color stm, Square bksq, Square wksq, Square psq) { + return stm + (bksq << 1) + (wksq << 7) + (file_of(psq) << 13) + ((6 - rank_of(psq)) << 15); + } + 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); - int to_index() const; - bool is_legal() const; - bool is_immediate_draw() const; - bool is_immediate_win() const; - Bitboard wk_attacks() const; - Bitboard bk_attacks() const; - Bitboard pawn_attacks() const; - - Square whiteKingSquare, blackKingSquare, pawnSquare; - Color sideToMove; - }; - - - Result *Bitbase; - const int IndexMax = 2*24*64*64; - int UnknownCount = 0; - - void initialize(); - bool next_iteration(); - Result classify_wtm(const KPKPosition &p); - Result classify_btm(const KPKPosition &p); - int compute_index(Square wksq, Square bksq, Square psq, Color stm); - int compress_result(Result r); - -} + void classify_leaf(unsigned idx); -//// -//// Functions -//// + Result classify(const std::vector& db) + { return stm == WHITE ? classify(db) : classify(db); } -void generate_kpk_bitbase(uint8_t bitbase[]) { - // Allocate array and initialize: - Bitbase = new Result[IndexMax]; - initialize(); + operator Result() const { return res; } - // Iterate until all positions are classified: - while(next_iteration()); + private: + template Bitboard k_attacks() const + { return StepAttacksBB[KING][Us == WHITE ? wksq : bksq]; } - // Compress bitbase into the supplied parameter: - int i, j, b; - for(i = 0; i < 24576; i++) { - for(b = 0, j = 0; j < 8; b |= (compress_result(Bitbase[8*i+j]) << j), j++); - bitbase[i] = b; - } - - // Release allocated memory: - delete [] Bitbase; -} + template Result classify(const std::vector& db); + Color stm; + Square bksq, wksq, psq; + Result res; + }; -namespace { +} // namespace - void KPKPosition::from_index(int index) { - int s; - sideToMove = Color(index % 2); - blackKingSquare = Square((index / 2) % 64); - whiteKingSquare = Square((index / 128) % 64); - s = (index / 8192) % 24; - pawnSquare = make_square(File(s % 4), Rank(s / 4 + 1)); - } +bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { - int KPKPosition::to_index() const { - return compute_index(whiteKingSquare, blackKingSquare, pawnSquare, - sideToMove); - } - - - bool KPKPosition::is_legal() const { - if(whiteKingSquare == pawnSquare || whiteKingSquare == blackKingSquare || - pawnSquare == blackKingSquare) - return false; - if(sideToMove == WHITE) { - if(bit_is_set(this->wk_attacks(), blackKingSquare)) - return false; - if(bit_is_set(this->pawn_attacks(), blackKingSquare)) - return false; - } - else { - if(bit_is_set(this->bk_attacks(), whiteKingSquare)) - return false; - } - return true; - } + assert(file_of(wpsq) <= FILE_D); + unsigned idx = index(stm, bksq, wksq, wpsq); + return KPKBitbase[idx / 32] & (1 << (idx & 31)); +} - bool KPKPosition::is_immediate_draw() const { - if(sideToMove == BLACK) { - Bitboard wka = this->wk_attacks(); - Bitboard bka = this->bk_attacks(); - - // Case 1: Stalemate - if((bka & ~(wka | this->pawn_attacks())) == EmptyBoardBB) - return true; - // Case 2: King can capture pawn - if(bit_is_set(bka, pawnSquare) && !bit_is_set(wka, pawnSquare)) - return true; - } - else { - // Case 1: Stalemate - if(whiteKingSquare == SQ_A8 && pawnSquare == SQ_A7 && - (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8)) - return true; - } +void Bitbases::init_kpk() { - return false; - } + unsigned idx, repeat = 1; + std::vector db(IndexMax); + // Initialize db with known win / draw positions + for (idx = 0; idx < IndexMax; idx++) + db[idx].classify_leaf(idx); - 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 && - (square_distance(blackKingSquare, pawnSquare+DELTA_N) > 1 || - bit_is_set(this->wk_attacks(), pawnSquare+DELTA_N)); - } - + // Iterate until all positions are classified (26 cycles needed) + while (repeat) + for (repeat = idx = 0; idx < IndexMax; idx++) + if (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN) + repeat = 1; - Bitboard KPKPosition::wk_attacks() const { - return StepAttackBB[WK][whiteKingSquare]; - } + // Map 32 results into one KPKBitbase[] entry + for (idx = 0; idx < IndexMax; idx++) + if (db[idx] == WIN) + KPKBitbase[idx / 32] |= 1 << (idx & 31); +} - Bitboard KPKPosition::bk_attacks() const { - return StepAttackBB[BK][blackKingSquare]; - } +namespace { + void KPKPosition::classify_leaf(unsigned idx) { - Bitboard KPKPosition::pawn_attacks() const { - return StepAttackBB[WP][pawnSquare]; - } + stm = Color(idx & 1); + bksq = Square((idx >> 1) & 0x3F); + wksq = Square((idx >> 7) & 0x3F); + psq = File((idx >> 13) & 3) | Rank(6 - (idx >> 15)); + // 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 && (StepAttacksBB[PAWN][psq] & bksq))) + res = INVALID; - void initialize() { - KPKPosition p; - for(int i = 0; i < IndexMax; i++) { - p.from_index(i); - if(!p.is_legal()) - Bitbase[i] = RESULT_INVALID; - else if(p.is_immediate_draw()) - Bitbase[i] = RESULT_DRAW; - else if(p.is_immediate_win()) - Bitbase[i] = RESULT_WIN; - else { - Bitbase[i] = RESULT_UNKNOWN; - UnknownCount++; - } - } + // The position is an immediate win if it is white to move and the white + // pawn can be promoted without getting captured. + else if ( rank_of(psq) == RANK_7 + && stm == WHITE + && wksq != psq + DELTA_N + && ( square_distance(bksq, psq + DELTA_N) > 1 + ||(k_attacks() & (psq + DELTA_N)))) + res = WIN; + + // Check for known draw positions + // + // Case 1: Stalemate + else if ( stm == BLACK + && !(k_attacks() & ~(k_attacks() | StepAttacksBB[PAWN][psq]))) + res = DRAW; + + // Case 2: King can capture undefended pawn + else if ( stm == BLACK + && (k_attacks() & psq & ~k_attacks())) + res = DRAW; + + // Case 3: Black king in front of white pawn + else if ( bksq == psq + DELTA_N + && rank_of(psq) < RANK_7) + res = DRAW; + + // Case 4: White king in front of pawn and black has opposition + else if ( stm == WHITE + && wksq == psq + DELTA_N + && bksq == wksq + DELTA_N + DELTA_N + && rank_of(psq) < RANK_5) + res = DRAW; + + // Case 5: Stalemate with rook pawn + else if ( bksq == SQ_A8 + && file_of(psq) == FILE_A) + res = DRAW; + + // Case 6: White king trapped on the rook file + else if ( file_of(wksq) == FILE_A + && file_of(psq) == FILE_A + && rank_of(wksq) > rank_of(psq) + && bksq == wksq + 2) + res = DRAW; + + else + res = UNKNOWN; } + template + Result KPKPosition::classify(const std::vector& db) { - bool next_iteration() { - KPKPosition p; - int previousUnknownCount = UnknownCount; - - for(int i = 0; i < IndexMax; i++) - if(Bitbase[i] == RESULT_UNKNOWN) { - p.from_index(i); - - Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p); + // 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. - if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS || - Bitbase[i] == RESULT_DRAW) - UnknownCount--; - } + Result r = INVALID; + Bitboard b = k_attacks(); - return UnknownCount != previousUnknownCount; - } + while (b) + { + r |= Us == WHITE ? db[index(BLACK, bksq, pop_lsb(&b), psq)] + : db[index(WHITE, pop_lsb(&b), wksq, psq)]; + if (Us == WHITE && (r & WIN)) + return res = WIN; - Result classify_wtm(const KPKPosition &p) { - - // 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 as - // RESULT_DRAW. Otherwise, the current position is classified as - // RESULT_UNKNOWN. - - bool unknownFound = false; - Bitboard b; - Square s; - - // King moves - b = p.wk_attacks(); - while(b) { - s = pop_1st_bit(&b); - switch(Bitbase[compute_index(s, p.blackKingSquare, p.pawnSquare, - BLACK)]) { - case RESULT_LOSS: - return RESULT_WIN; - - case RESULT_UNKNOWN: - unknownFound = true; - break; - - case RESULT_DRAW: case RESULT_INVALID: - break; - - default: - assert(false); - } + if (Us == BLACK && (r & DRAW)) + return res = DRAW; } - // Pawn moves - if(square_rank(p.pawnSquare) < RANK_7) { - s = p.pawnSquare + DELTA_N; - switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s, - BLACK)]) { - case RESULT_LOSS: - return RESULT_WIN; - - case RESULT_UNKNOWN: - unknownFound = true; - break; - - case RESULT_DRAW: case RESULT_INVALID: - break; - - default: - assert(false); - } - - if(square_rank(s) == RANK_3 && - s != p.whiteKingSquare && s != p.blackKingSquare) { - s += DELTA_N; - switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s, - BLACK)]) { - case RESULT_LOSS: - return RESULT_WIN; - - case RESULT_UNKNOWN: - unknownFound = true; - break; - - case RESULT_DRAW: case RESULT_INVALID: - break; - - default: - assert(false); - } - } - } - - return unknownFound? RESULT_UNKNOWN : RESULT_DRAW; - } + if (Us == WHITE && rank_of(psq) < RANK_7) + { + Square s = psq + DELTA_N; + r |= db[index(BLACK, bksq, wksq, s)]; // Single push + if (rank_of(s) == RANK_3 && s != wksq && s != bksq) + r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push - Result classify_btm(const KPKPosition &p) { - - // 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; - - // King moves - b = p.bk_attacks(); - while(b) { - s = pop_1st_bit(&b); - switch(Bitbase[compute_index(p.whiteKingSquare, s, p.pawnSquare, - WHITE)]) { - case RESULT_DRAW: - return RESULT_DRAW; - - case RESULT_UNKNOWN: - unknownFound = true; - break; - - case RESULT_WIN: case RESULT_INVALID: - break; - - default: - assert(false); - } + if (r & WIN) + return res = WIN; } - return unknownFound? RESULT_UNKNOWN : RESULT_LOSS; + return res = r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN; } - - int compute_index(Square wksq, Square bksq, Square psq, Color stm) { - int p = int(square_file(psq)) + (int(square_rank(psq)) - 1) * 4; - int result = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*p; - assert(result >= 0 && result < IndexMax); - return result; - } - - - int compress_result(Result r) { - return (r == RESULT_WIN || r == RESULT_LOSS)? 1 : 0; - } - -} +}