X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fposition.cpp;h=6f8747635772aa930a604025bd5b0c95a67dbbc2;hp=d2aeb8221209ad391e54480e6442444d91d19749;hb=ddeb01612b122bbeeb59a26ba6f8c6f1e4283199;hpb=e6c9ce635819957bce641a432b0675c5c033631b diff --git a/src/position.cpp b/src/position.cpp index d2aeb822..6f874763 100644 --- a/src/position.cpp +++ b/src/position.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2014 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 @@ -411,24 +411,28 @@ const string Position::pretty(Move move) const { } -/// Position:hidden_checkers() returns a bitboard of all pinned / discovered check -/// pieces, according to the call parameters. Pinned pieces protect our king and -/// discovered check pieces attack the enemy king. +/// Position::check_blockers() returns a bitboard of all the pieces with color +/// 'c' that are blocking check on the king with color 'kingColor'. A piece +/// blocks a check if removing that piece from the board would result in a +/// position where the king is in check. A check blocking piece can be either a +/// pinned or a discovered check piece, according if its color 'c' is the same +/// or the opposite of 'kingColor'. -Bitboard Position::hidden_checkers(Square ksq, Color c, Color toMove) const { +Bitboard Position::check_blockers(Color c, Color kingColor) const { Bitboard b, pinners, result = 0; + Square ksq = king_square(kingColor); // Pinners are sliders that give check when a pinned piece is removed pinners = ( (pieces( ROOK, QUEEN) & PseudoAttacks[ROOK ][ksq]) - | (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq])) & pieces(c); + | (pieces(BISHOP, QUEEN) & PseudoAttacks[BISHOP][ksq])) & pieces(~kingColor); while (pinners) { b = between_bb(ksq, pop_lsb(&pinners)) & pieces(); if (!more_than_one(b)) - result |= b & pieces(toMove); + result |= b & pieces(c); } return result; } @@ -514,7 +518,7 @@ bool Position::pseudo_legal(const Move m) const { if (promotion_type(m) - 2 != NO_PIECE_TYPE) return false; - // If the from square is not occupied by a piece belonging to the side to + // If the 'from' square is not occupied by a piece belonging to the side to // move, the move is obviously not legal. if (pc == NO_PIECE || color_of(pc) != us) return false; @@ -603,8 +607,8 @@ bool Position::pseudo_legal(const Move m) const { if (!((between_bb(lsb(checkers()), king_square(us)) | checkers()) & to)) return false; } - // In case of king moves under check we have to remove king so to catch - // as invalid moves like b1a1 when opposite queen is on c1. + // In case of king moves under check we have to remove king so as to catch + // invalid moves like b1a1 when opposite queen is on c1. else if (attackers_to(to, pieces() ^ from) & pieces(~us)) return false; } @@ -613,7 +617,7 @@ bool Position::pseudo_legal(const Move m) const { } -/// Position::move_gives_check() tests whether a pseudo-legal move gives a check +/// Position::gives_check() tests whether a pseudo-legal move gives a check bool Position::gives_check(Move m, const CheckInfo& ci) const { @@ -625,29 +629,26 @@ bool Position::gives_check(Move m, const CheckInfo& ci) const { Square to = to_sq(m); PieceType pt = type_of(piece_on(from)); - // Is there a direct check ? + // Is there a direct check? if (ci.checkSq[pt] & to) return true; - // Is there a discovered check ? + // Is there a discovered check? if ( unlikely(ci.dcCandidates) && (ci.dcCandidates & from) - && !aligned(from, to, king_square(~sideToMove))) + && !aligned(from, to, ci.ksq)) return true; - // Can we skip the ugly special cases ? + // Can we skip the ugly special cases? if (type_of(m) == NORMAL) return false; - Color us = sideToMove; - Square ksq = king_square(~us); - switch (type_of(m)) { case PROMOTION: - return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & ksq; + return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & ci.ksq; - // En passant capture with check ? We have already handled the case + // En passant capture with check? We have already handled the case // of direct checks and ordinary discovered check, so the only case we // need to handle is the unusual case of a discovered check through // the captured pawn. @@ -656,18 +657,18 @@ bool Position::gives_check(Move m, const CheckInfo& ci) const { Square capsq = file_of(to) | rank_of(from); Bitboard b = (pieces() ^ from ^ capsq) | to; - return (attacks_bb< ROOK>(ksq, b) & pieces(us, QUEEN, ROOK)) - | (attacks_bb(ksq, b) & pieces(us, QUEEN, BISHOP)); + return (attacks_bb< ROOK>(ci.ksq, b) & pieces(sideToMove, QUEEN, ROOK)) + | (attacks_bb(ci.ksq, b) & pieces(sideToMove, QUEEN, BISHOP)); } case CASTLING: { Square kfrom = from; Square rfrom = to; // Castling is encoded as 'King captures the rook' - Square kto = relative_square(us, rfrom > kfrom ? SQ_G1 : SQ_C1); - Square rto = relative_square(us, rfrom > kfrom ? SQ_F1 : SQ_D1); + Square kto = relative_square(sideToMove, rfrom > kfrom ? SQ_G1 : SQ_C1); + Square rto = relative_square(sideToMove, rfrom > kfrom ? SQ_F1 : SQ_D1); - return (PseudoAttacks[ROOK][rto] & ksq) - && (attacks_bb(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & ksq); + return (PseudoAttacks[ROOK][rto] & ci.ksq) + && (attacks_bb(rto, (pieces() ^ kfrom ^ rfrom) | rto | kto) & ci.ksq); } default: assert(false); @@ -694,9 +695,9 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI ++nodes; Key k = st->key; - // Copy some fields of old state to our new StateInfo object except the ones - // which are going to be recalculated from scratch anyway, then switch our state - // pointer to point to the new (ready to be updated) state. + // Copy some fields of the old state to our new StateInfo object except the + // ones which are going to be recalculated from scratch anyway and then switch + // our state pointer to point to the new (ready to be updated) state. std::memcpy(&newSt, st, StateCopySize64 * sizeof(uint64_t)); newSt.previous = st; @@ -705,7 +706,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI // Update side to move k ^= Zobrist::side; - // Increment ply counters.In particular rule50 will be reset to zero later on + // Increment ply counters. In particular, rule50 will be reset to zero later on // in case of a capture or a pawn move. ++gamePly; ++st->rule50; @@ -1010,10 +1011,7 @@ void Position::undo_null_move() { /// Position::see() is a static exchange evaluator: It tries to estimate the -/// material gain or loss resulting from a move. Parameter 'asymmThreshold' takes -/// tempi into account. If the side who initiated the capturing sequence does the -/// last capture, he loses a tempo and if the result is below 'asymmThreshold' -/// the capturing sequence is considered bad. +/// material gain or loss resulting from a move. int Position::see_sign(Move m) const { @@ -1028,7 +1026,7 @@ int Position::see_sign(Move m) const { return see(m); } -int Position::see(Move m, int asymmThreshold) const { +int Position::see(Move m) const { Square from, to; Bitboard occupied, attackers, stmAttackers; @@ -1079,30 +1077,24 @@ int Position::see(Move m, int asymmThreshold) const { // Add the new entry to the swap list swapList[slIndex] = -swapList[slIndex - 1] + PieceValue[MG][captured]; - ++slIndex; // Locate and remove the next least valuable attacker captured = min_attacker(byTypeBB, to, stmAttackers, occupied, attackers); - stm = ~stm; - stmAttackers = attackers & pieces(stm); // Stop before processing a king capture - if (captured == KING && stmAttackers) + if (captured == KING) { - swapList[slIndex++] = QueenValueMg * 16; + if (stmAttackers == attackers) + ++slIndex; + break; } - } while (stmAttackers); + stm = ~stm; + stmAttackers = attackers & pieces(stm); + ++slIndex; - // If we are doing asymmetric SEE evaluation and the same side does the first - // and the last capture, he loses a tempo and gain must be at least worth - // 'asymmThreshold', otherwise we replace the score with a very low value, - // before negamaxing. - if (asymmThreshold) - for (int i = 0; i < slIndex; i += 2) - if (swapList[i] < asymmThreshold) - swapList[i] = - QueenValueMg * 16; + } while (stmAttackers); // Having built the swap list, we negamax through it to find the best // achievable score from the point of view of the side to move. @@ -1192,9 +1184,9 @@ Key Position::compute_material_key() const { } -/// Position::compute_psq_score() computes the incremental scores for the middle -/// game and the endgame. These functions are used to initialize the incremental -/// scores when a new position is set up, and to verify that the scores are correctly +/// Position::compute_psq_score() computes the incremental scores for the middlegame +/// and the endgame. These functions are used to initialize the incremental scores +/// when a new position is set up, and to verify that the scores are correctly /// updated by do_move and undo_move when the program is running in debug mode. Score Position::compute_psq_score() const { @@ -1212,10 +1204,10 @@ Score Position::compute_psq_score() const { } -/// Position::compute_non_pawn_material() computes the total non-pawn middle -/// game material value for the given side. Material values are updated -/// incrementally during the search. This function is only used when -/// initializing a new Position object. +/// Position::compute_non_pawn_material() computes the total non-pawn middlegame +/// material value for the given side. Material values are updated incrementally +/// during the search. This function is only used when initializing a new Position +/// object. Value Position::compute_non_pawn_material(Color c) const { @@ -1228,35 +1220,25 @@ Value Position::compute_non_pawn_material(Color c) const { } -/// Position::is_draw() tests whether the position is drawn by material, -/// repetition, or the 50 moves rule. It does not detect stalemates: this -/// must be done by the search. +/// Position::is_draw() tests whether the position is drawn by material, 50 moves +/// rule or repetition. It does not detect stalemates. + bool Position::is_draw() const { - // Draw by material? if ( !pieces(PAWN) && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg)) return true; - // Draw by the 50 moves rule? if (st->rule50 > 99 && (!checkers() || MoveList(*this).size())) return true; - int i = 4, e = std::min(st->rule50, st->pliesFromNull); - - if (i <= e) + StateInfo* stp = st; + for (int i = 2, e = std::min(st->rule50, st->pliesFromNull); i <= e; i += 2) { - StateInfo* stp = st->previous->previous; - - do { - stp = stp->previous->previous; - - if (stp->key == st->key) - return true; // Draw after first repetition - - i += 2; + stp = stp->previous->previous; - } while (i <= e); + if (stp->key == st->key) + return true; // Draw at first repetition } return false;