X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=4170952b5607fd5625ecf34e6bfc4991ff109900;hp=8d3b37c040a1a6f56f38fa1b897501d49b730b9c;hb=e0504ab876a997321102f040ab88203cb893db12;hpb=18375e3bfbd03b0851969bda5427d5b22cb4fea1 diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 8d3b37c0..4170952b 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -2,6 +2,7 @@ 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 Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -53,20 +54,19 @@ 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; - KPKPosition(unsigned idx); + explicit KPKPosition(unsigned idx); operator Result() const { return result; } Result classify(const std::vector& db) { return us == WHITE ? classify(db) : classify(db); } template Result classify(const std::vector& db); - unsigned id; Color us; - Square bksq, wksq, psq; + Square ksq[COLOR_NB], psq; Result result; }; @@ -85,19 +85,22 @@ bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) { void Bitbases::init() { std::vector db(MAX_INDEX); + unsigned idx, repeat = 1; // Initialize db with known win / draw positions - std::generate(db.begin(), db.end(), [](){ static unsigned id; return KPKPosition(id++); }); + 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 (std::accumulate(db.begin(), db.end(), false, [&](bool repeat, KPKPosition& pos) - { return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; })); + while (repeat) + 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 (auto& pos : db) - if (pos == WIN) - KPKBitbase[pos.id / 32] |= 1 << (pos.id & 0x1F); + for (idx = 0; idx < MAX_INDEX; ++idx) + if (db[idx] == WIN) + KPKBitbase[idx / 32] |= 1 << (idx & 0x1F); } @@ -105,44 +108,46 @@ namespace { KPKPosition::KPKPosition(unsigned idx) { - id = idx; - wksq = Square((idx >> 0) & 0x3F); - bksq = Square((idx >> 6) & 0x3F); - us = Color ((idx >> 12) & 0x01); - psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7)); - result = UNKNOWN; + 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(wksq, bksq) <= 1 - || wksq == psq - || bksq == psq - || (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq))) + if ( distance(ksq[WHITE], ksq[BLACK]) <= 1 + || ksq[WHITE] == psq + || ksq[BLACK] == psq + || (us == WHITE && (StepAttacksBB[PAWN][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 - && ( distance(bksq, psq + DELTA_N) > 1 - ||(StepAttacksBB[KING][wksq] & (psq + DELTA_N)))) - result = WIN; - } + // Immediate win if a pawn can be promoted without getting captured + else if ( us == WHITE + && rank_of(psq) == RANK_7 + && ksq[us] != psq + NORTH + && ( distance(ksq[~us], psq + NORTH) > 1 + || (StepAttacksBB[KING][ksq[us]] & (psq + NORTH)))) + 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])) + 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 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. @@ -152,19 +157,21 @@ namespace { const Result Bad = (Us == WHITE ? DRAW : WIN); Result r = INVALID; - Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq]; + Bitboard b = StepAttacksBB[KING][ksq[Us]]; while (b) - r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)] - : db[index(Them, pop_lsb(&b), wksq, psq)]; + 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(BLACK, bksq, wksq, s)]; // Single push + if (rank_of(psq) < RANK_7) // Single push + r |= db[index(Them, ksq[Them], ksq[Us], 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[Us] + && psq + NORTH != ksq[Them]) + r |= db[index(Them, ksq[Them], ksq[Us], psq + NORTH + NORTH)]; } return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad;