X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=25570e12a4b54a63f57e194e585caeca02f58368;hp=9d2cde030754d48799ab40bed23fc68b7751486e;hb=dcd8ce70941e9b8d5180eb43865bb9819e424c19;hpb=6b5322ce000d6a8a6f845beda2d7e149e1baea0c diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 9d2cde03..25570e12 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -1,7 +1,8 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, 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 @@ -17,13 +18,35 @@ along with this program. If not, see . */ +#include #include +#include +#include #include "bitboard.h" #include "types.h" namespace { + // 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, @@ -31,200 +54,127 @@ namespace { WIN = 4 }; - inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); } + 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); } - Result classify_leaf(int idx); - Result classify(int idx, Result db[]); - - private: - template Result classify(const Result db[]) const; + template Result classify(const std::vector& db); - 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; + Color us; + Square ksq[COLOR_NB], psq; + Result result; }; - // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 - 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]; +} // namespace - int index(Square wksq, Square bksq, Square psq, Color stm); -} +bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) { -uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) { + assert(file_of(wpsq) <= FILE_D); - int idx = index(wksq, bksq, wpsq, stm); - return KPKBitbase[idx / 32] & (1 << (idx & 31)); + unsigned idx = index(us, bksq, wksq, wpsq); + return KPKBitbase[idx / 32] & (1 << (idx & 0x1F)); } -void kpk_bitbase_init() { +void Bitbases::init() { - Result db[IndexMax]; - KPKPosition pos; - int idx, bit, repeat = 1; + std::vector db(MAX_INDEX); + unsigned idx, repeat = 1; - // Initialize table with known win / draw positions - for (idx = 0; idx < IndexMax; idx++) - db[idx] = pos.classify_leaf(idx); + // Initialize db with known win / draw positions + for (idx = 0; idx < MAX_INDEX; ++idx) + db[idx] = KPKPosition(idx); - // Iterate until all positions are classified (30 cycles needed) + // 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 < IndexMax; idx++) - if (db[idx] == UNKNOWN && (db[idx] = pos.classify(idx, db)) != UNKNOWN) - repeat = 1; - - // Map 32 position results into one KPKBitbase[] entry - for (idx = 0; idx < IndexMax / 32; idx++) - for (bit = 0; bit < 32; bit++) - if (db[32 * idx + bit] == WIN) - KPKBitbase[idx] |= 1 << bit; + for (repeat = idx = 0; idx < MAX_INDEX; ++idx) + repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN); + + // Map 32 results into one KPKBitbase[] entry + for (idx = 0; idx < MAX_INDEX; ++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 index(Square w, Square b, Square p, Color c) { - - assert(file_of(p) <= FILE_D); - - return c + (b << 1) + (w << 7) + (file_of(p) << 13) + ((rank_of(p) - 1) << 15); - } - - void KPKPosition::decode_index(int idx) { - - stm = Color(idx & 1); - bksq = Square((idx >> 1) & 63); - wksq = Square((idx >> 7) & 63); - psq = File((idx >> 13) & 3) | Rank((idx >> 15) + 1); - } + KPKPosition::KPKPosition(unsigned idx) { - Result KPKPosition::classify_leaf(int idx) { - - decode_index(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 ( 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; - - // Case 6: White king trapped on the rook file - if ( file_of(wksq) == FILE_A - && file_of(psq) == FILE_A - && rank_of(wksq) > rank_of(psq) - && bksq == wksq + 2) - return DRAW; - - return UNKNOWN; + 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; } template - Result KPKPosition::classify(const Result db[]) const { + Result KPKPosition::classify(const std::vector& db) { - // 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. + // 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 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. + // 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 = k_attacks(); + Bitboard b = StepAttacksBB[KING][ksq[Us]]; while (b) - { - r |= Us == WHITE ? db[index(pop_lsb(&b), bksq, psq, BLACK)] - : db[index(wksq, pop_lsb(&b), psq, WHITE)]; - - if (Us == WHITE && (r & WIN)) - return WIN; - - if (Us == BLACK && (r & DRAW)) - return DRAW; - } + r |= Us == WHITE ? db[index(Them, ksq[Them] , pop_lsb(&b), psq)] + : db[index(Them, pop_lsb(&b), ksq[Them] , psq)]; - if (Us == WHITE && rank_of(psq) < RANK_7) + if (Us == WHITE) { - Square s = psq + DELTA_N; - r |= db[index(wksq, bksq, s, BLACK)]; // Single push + if (rank_of(psq) < RANK_7) // Single push + r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N)]; - if (rank_of(s) == RANK_3 && s != wksq && s != bksq) - r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push - - if (r & WIN) - return WIN; + 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 r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN; + return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad; } - Result KPKPosition::classify(int idx, Result db[]) { - - decode_index(idx); - return stm == WHITE ? classify(db) : classify(db); - } - -} +} // namespace