X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=bbe8e9a7e33bfc7514f2ef122bc78e446969be4b;hp=dbda28e0019cf9e161b826cd4130307f2db6cb97;hb=ce009ea1aaecc577bbdf208cef8e61dd1827a18e;hpb=a646f74e6a62af756b2e51756a81ee983db4ff34 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index dbda28e0..bbe8e9a7 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -1,7 +1,6 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 - Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file) Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -19,17 +18,18 @@ #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 IndexMax = 2*24*64*64; // stm * psq * wksq * bksq = 196608 + // There are 24 possible pawn squares: files A to D and ranks from 2 to 7. + // Positions with the pawn on files E to H will be mirrored before probing. + constexpr 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[IndexMax / 32]; + std::bitset KPKBitbase; // A KPK bitbase index is an integer in [0, IndexMax] range // @@ -40,8 +40,8 @@ namespace { // 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); + unsigned index(Color stm, Square bksq, Square wksq, Square psq) { + return int(wksq) | (bksq << 6) | (stm << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15); } enum Result { @@ -51,55 +51,49 @@ 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(unsigned idx); + KPKPosition() = default; + explicit KPKPosition(unsigned idx); operator Result() const { return result; } - Result classify(const std::vector& db) - { return us == WHITE ? classify(db) : classify(db); } - - private: - template Result classify(const std::vector& db); + Result classify(const std::vector& db); - Color us; - Square bksq, wksq, psq; + Color stm; + Square ksq[COLOR_NB], psq; Result result; }; } // namespace -bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color us) { +bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color stm) { assert(file_of(wpsq) <= FILE_D); - unsigned idx = index(us, bksq, wksq, wpsq); - return KPKBitbase[idx / 32] & (1 << (idx & 0x1F)); + return KPKBitbase[index(stm, bksq, wksq, wpsq)]; } -void Bitbases::init_kpk() { +void Bitbases::init() { + std::vector db(MAX_INDEX); unsigned idx, repeat = 1; - std::vector db; - db.reserve(IndexMax); // Initialize db with known win / draw positions - for (idx = 0; idx < IndexMax; ++idx) - db.push_back(KPKPosition(idx)); + for (idx = 0; idx < MAX_INDEX; ++idx) + db[idx] = KPKPosition(idx); // 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) + 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 < IndexMax; ++idx) + // Fill the bitbase with the decisive results + for (idx = 0; idx < MAX_INDEX; ++idx) if (db[idx] == WIN) - KPKBitbase[idx / 32] |= 1 << (idx & 0x1F); + KPKBitbase.set(idx); } @@ -107,67 +101,70 @@ namespace { KPKPosition::KPKPosition(unsigned idx) { - wksq = Square((idx >> 0) & 0x3F); - bksq = Square((idx >> 6) & 0x3F); - us = Color ((idx >> 12) & 0x01); - psq = File ((idx >> 13) & 0x03) | Rank(RANK_7 - (idx >> 15)); - result = UNKNOWN; + ksq[WHITE] = Square((idx >> 0) & 0x3F); + ksq[BLACK] = Square((idx >> 6) & 0x3F); + stm = Color ((idx >> 12) & 0x01); + psq = make_square(File((idx >> 13) & 0x3), Rank(RANK_7 - ((idx >> 15) & 0x7))); - // Check if two pieces are on the same square or if a king can be captured - if ( square_distance(wksq, bksq) <= 1 || wksq == psq || bksq == psq - || (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq))) + // Invalid 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 + || (stm == WHITE && (pawn_attacks_bb(WHITE, psq) & ksq[BLACK]))) result = INVALID; - else if (us == WHITE) - { - // Immediate win if a 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)))) - result = WIN; - } - // Immediate draw if it is a stalemate or a king captures undefended pawn - else if ( !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq])) - || (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq])) + // Win if the pawn can be promoted without getting captured + else if ( stm == WHITE + && rank_of(psq) == RANK_7 + && ksq[WHITE] != psq + NORTH + && ( distance(ksq[BLACK], psq + NORTH) > 1 + || (distance(ksq[WHITE], psq + NORTH) == 1))) + result = WIN; + + // Draw if it is stalemate or the black king can capture the pawn + else if ( stm == BLACK + && ( !(attacks_bb(ksq[BLACK]) & ~(attacks_bb(ksq[WHITE]) | pawn_attacks_bb(WHITE, psq))) + || (attacks_bb(ksq[BLACK]) & ~attacks_bb(ksq[WHITE]) & psq))) result = DRAW; + + // Position will be classified later + else + result = UNKNOWN; } - template Result KPKPosition::classify(const std::vector& db) { - // White to Move: If one move leads to a position classified as WIN, the result + // 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 + // 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 = (stm == WHITE ? WIN : DRAW); + const Result Bad = (stm == WHITE ? DRAW : WIN); Result r = INVALID; - Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq]; + Bitboard b = attacks_bb(ksq[stm]); while (b) - r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)] - : db[index(Them, pop_lsb(&b), wksq, psq)]; + r |= stm == WHITE ? db[index(BLACK, ksq[BLACK] , pop_lsb(&b), psq)] + : db[index(WHITE, pop_lsb(&b), ksq[WHITE], psq)]; - if (Us == WHITE && rank_of(psq) < RANK_7) + if (stm == WHITE) { - Square s = psq + DELTA_N; - r |= db[index(BLACK, bksq, wksq, s)]; // Single push + if (rank_of(psq) < RANK_7) // Single push + r |= db[index(BLACK, ksq[BLACK], ksq[WHITE], psq + NORTH)]; - if (rank_of(psq) == RANK_2 && s != wksq && s != bksq) - r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push + if ( rank_of(psq) == RANK_2 // Double push + && psq + NORTH != ksq[WHITE] + && psq + NORTH != ksq[BLACK]) + r |= db[index(BLACK, ksq[BLACK], ksq[WHITE], psq + NORTH + NORTH)]; } - if (Us == WHITE) - return result = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW; - else - return result = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN; + return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad; } } // namespace