X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=25570e12a4b54a63f57e194e585caeca02f58368;hp=80db0a41fa31bbfcbc800effee0b2ecd3cb5b544;hb=dcd8ce70941e9b8d5180eb43865bb9819e424c19;hpb=bb751d6c890f5c50c642366d601740366cfae8d0 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 80db0a41..25570e12 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -1,348 +1,180 @@ /* - Glaurung, a UCI chess playing engine. - Copyright (C) 2004-2008 Tord Romstad + Stockfish, a UCI chess playing engine derived from Glaurung 2.1 + Copyright (C) 2004-2008 Tord Romstad (Glaurung author) + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad - Glaurung is free software: you can redistribute it and/or modify + 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. - - Glaurung is distributed in the hope that it will be useful, + + 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 +#include -#include "bitbase.h" #include "bitboard.h" -#include "move.h" -#include "square.h" - - -//// -//// Local definitions -//// - -namespace { - - enum Result { - RESULT_UNKNOWN, - RESULT_INVALID, - RESULT_WIN, - RESULT_LOSS, - RESULT_DRAW - }; - - 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); - -} - - -//// -//// Functions -//// - -void generate_kpk_bitbase(uint8_t bitbase[]) { - // Allocate array and initialize: - Bitbase = new Result[IndexMax]; - initialize(); - - // Iterate until all positions are classified: - while(next_iteration()); - - // 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; -} - +#include "types.h" 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)); + // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7 + const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608 + + // Each uint32_t stores results of 32 positions, one per bit + uint32_t KPKBitbase[MAX_INDEX / 32]; + + // A KPK bitbase index is an integer in [0, IndexMax] range + // + // Information is mapped in a way that minimizes the 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 RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2) + unsigned index(Color us, Square bksq, Square wksq, Square psq) { + return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15); } + enum Result { + INVALID = 0, + UNKNOWN = 1, + DRAW = 2, + WIN = 4 + }; - 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; - } - - - 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; - } - - return false; - } + Result& operator|=(Result& r, Result v) { return r = Result(r | v); } + struct KPKPosition { + KPKPosition() = default; + explicit KPKPosition(unsigned idx); + operator Result() const { return result; } + Result classify(const std::vector& db) + { return us == WHITE ? classify(db) : classify(db); } - 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)); - } - + template Result classify(const std::vector& db); - Bitboard KPKPosition::wk_attacks() const { - return StepAttackBB[WK][whiteKingSquare]; - } + Color us; + Square ksq[COLOR_NB], psq; + Result result; + }; +} // namespace - Bitboard KPKPosition::bk_attacks() const { - return StepAttackBB[BK][blackKingSquare]; - } +bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) { - Bitboard KPKPosition::pawn_attacks() const { - return StepAttackBB[WP][pawnSquare]; - } + assert(file_of(wpsq) <= FILE_D); + unsigned idx = index(us, bksq, wksq, wpsq); + return KPKBitbase[idx / 32] & (1 << (idx & 0x1F)); +} - 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++; - } - } - } +void Bitbases::init() { - bool next_iteration() { - KPKPosition p; - int previousUnknownCount = UnknownCount; - - for(int i = 0; i < IndexMax; i++) - if(Bitbase[i] == RESULT_UNKNOWN) { - p.from_index(i); + std::vector db(MAX_INDEX); + unsigned idx, repeat = 1; - Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p); + // Initialize db with known win / draw positions + for (idx = 0; idx < MAX_INDEX; ++idx) + db[idx] = KPKPosition(idx); - if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS || - Bitbase[i] == RESULT_DRAW) - UnknownCount--; - } + // Iterate through the positions until none of the unknown positions can be + // changed to either wins or draws (15 cycles needed). + while (repeat) + for (repeat = idx = 0; idx < MAX_INDEX; ++idx) + repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN); - return UnknownCount != previousUnknownCount; - } + // Map 32 results into one KPKBitbase[] entry + for (idx = 0; idx < MAX_INDEX; ++idx) + if (db[idx] == WIN) + KPKBitbase[idx / 32] |= 1 << (idx & 0x1F); +} - 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); - } - } +namespace { - // 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; + KPKPosition::KPKPosition(unsigned idx) { + + ksq[WHITE] = Square((idx >> 0) & 0x3F); + ksq[BLACK] = Square((idx >> 6) & 0x3F); + us = Color ((idx >> 12) & 0x01); + psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7)); + + // Check if two pieces are on the same square or if a king can be captured + if ( distance(ksq[WHITE], ksq[BLACK]) <= 1 + || ksq[WHITE] == psq + || ksq[BLACK] == psq + || (us == WHITE && (StepAttacksBB[PAWN][psq] & ksq[BLACK]))) + result = INVALID; + + // Immediate win if a pawn can be promoted without getting captured + else if ( us == WHITE + && rank_of(psq) == RANK_7 + && ksq[us] != psq + DELTA_N + && ( distance(ksq[~us], psq + DELTA_N) > 1 + || (StepAttacksBB[KING][ksq[us]] & (psq + DELTA_N)))) + result = WIN; + + // Immediate draw if it is a stalemate or a king captures undefended pawn + else if ( us == BLACK + && ( !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[PAWN][psq])) + || (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]]))) + result = DRAW; + + // Position will be classified later + else + result = UNKNOWN; } - - 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); - } + template + Result KPKPosition::classify(const std::vector& db) { + + // 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 as DRAW, otherwise the current + // position is classified as UNKNOWN. + // + // 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 as WIN, otherwise the current position is + // classified as UNKNOWN. + + const Color Them = (Us == WHITE ? BLACK : WHITE); + const Result Good = (Us == WHITE ? WIN : DRAW); + const Result Bad = (Us == WHITE ? DRAW : WIN); + + Result r = INVALID; + Bitboard b = StepAttacksBB[KING][ksq[Us]]; + + while (b) + r |= Us == WHITE ? db[index(Them, ksq[Them] , pop_lsb(&b), psq)] + : db[index(Them, pop_lsb(&b), ksq[Them] , psq)]; + + if (Us == WHITE) + { + if (rank_of(psq) < RANK_7) // Single push + r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N)]; + + if ( rank_of(psq) == RANK_2 // Double push + && psq + DELTA_N != ksq[Us] + && psq + DELTA_N != ksq[Them]) + r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N + DELTA_N)]; } - return unknownFound? RESULT_UNKNOWN : RESULT_LOSS; + return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad; } - - 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; - } - -} +} // namespace