From e0e4bdc9918ac13d8a70058a9813349cb426936a Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Fri, 7 May 2010 09:39:28 +0200 Subject: [PATCH] Retire mate threat detection from evaluation Remove a lot of complex, obscure and useless code. After 999 games at 1+0 Mod vs Orig +162 =673 -164 -1 ELO Signed-off-by: Marco Costalba --- src/evaluate.cpp | 91 ++++++++++-------------------------------------- src/evaluate.h | 3 -- 2 files changed, 18 insertions(+), 76 deletions(-) diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 1036b479..91625782 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -214,12 +214,6 @@ namespace { const int BishopCheckBonus = 1; const int KnightCheckBonus = 1; - // Scan for queen contact mates? - const bool QueenContactMates = true; - - // Bonus for having a mate threat - const int MateThreatBonus = 3; - // InitKingDanger[] contains bonuses based on the position of the defending // king. const int InitKingDanger[64] = { @@ -418,11 +412,7 @@ Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) { } // Interpolate between the middle game and the endgame score - Color stm = pos.side_to_move(); - - Value v = Sign[stm] * scale_by_game_phase(ei.value, phase, factor); - - return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v); + return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor); } } // namespace @@ -695,8 +685,7 @@ namespace { const Color Them = (Us == WHITE ? BLACK : WHITE); - Bitboard undefended, attackedByOthers, escapeSquares, occ, b, b1, b2, safe; - Square from, to; + Bitboard undefended, b, b1, b2, safe; bool sente; int attackUnits, shelter = 0; const Square ksq = pos.king_square(Us); @@ -711,8 +700,8 @@ namespace { // King safety. This is quite complicated, and is almost certainly far // from optimally tuned. if ( pos.piece_count(Them, QUEEN) >= 1 - && ei.kingAttackersCount[Them] >= 2 - && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame + && ei.kingAttackersCount[Them] >= 2 + && pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame && ei.kingAdjacentZoneAttacksCount[Them]) { // Is it the attackers turn to move? @@ -735,60 +724,29 @@ namespace { + InitKingDanger[relative_square(Us, ksq)] - shelter / 32; - // Analyse safe queen contact checks + // Analyse enemy's safe queen contact checks. First find undefended + // squares around the king attacked by enemy queen... b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them); if (b) { - attackedByOthers = ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT) - | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK); - - b &= attackedByOthers; - - // Squares attacked by the queen and supported by another enemy piece and - // not defended by other pieces but our king. + // ...then remove squares not supported by another enemy piece + b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT) + | ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK)); if (b) - { - // The bitboard b now contains the squares available for safe queen - // contact checks. attackUnits += QueenContactCheckBonus * count_1s_max_15(b) * (sente ? 2 : 1); - - // Is there a mate threat? - if (QueenContactMates && !pos.is_check()) - { - escapeSquares = pos.attacks_from(ksq) & ~pos.pieces_of_color(Us) & ~attackedByOthers; - occ = pos.occupied_squares(); - while (b) - { - to = pop_1st_bit(&b); - - // Do we have escape squares from queen contact check attack ? - if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[ksq]))) - { - // We have a mate, unless the queen is pinned or there - // is an X-ray attack through the queen. - for (int i = 0; i < pos.piece_count(Them, QUEEN); i++) - { - from = pos.piece_list(Them, QUEEN, i); - if ( bit_is_set(pos.attacks_from(from), to) - && !bit_is_set(pos.pinned_pieces(Them), from) - && !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(ROOK, QUEEN, Us)) - && !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & pos.pieces(BISHOP, QUEEN, Us))) - - // Set the mate threat move - ei.mateThreat[Them] = make_move(from, to); - } - } - } - } - } } - // Analyse enemy's safe distance checks + // Analyse enemy's safe distance checks for sliders and knights safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us)); b1 = pos.attacks_from(ksq) & safe; b2 = pos.attacks_from(ksq) & safe; + // Enemy queen safe checks + b = (b1 | b2) & ei.attacked_by(Them, QUEEN); + if (b) + attackUnits += QueenCheckBonus * count_1s_max_15(b); + // Enemy rooks safe checks b = b1 & ei.attacked_by(Them, ROOK); if (b) @@ -799,31 +757,18 @@ namespace { if (b) attackUnits += BishopCheckBonus * count_1s_max_15(b); - // Enemy queens safe checks - b = (b1 | b2) & ei.attacked_by(Them, QUEEN); - if (b) - attackUnits += QueenCheckBonus * count_1s_max_15(b); - // Enemy knights safe checks b = pos.attacks_from(ksq) & ei.attacked_by(Them, KNIGHT) & safe; if (b) attackUnits += KnightCheckBonus * count_1s_max_15(b); - // Analyse discovered checks (only for non-pawns right now, consider - // adding pawns later). + // Analyse enemy's discovered checks (only for non-pawns right now, + // consider adding pawns later). b = pos.discovered_check_candidates(Them) & ~pos.pieces(PAWN); if (b) attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente ? 2 : 1); - // Has a mate threat been found? We don't do anything here if the - // side with the mating move is the side to move, because in that - // case the mating side will get a huge bonus at the end of the main - // evaluation function instead. - if (ei.mateThreat[Them] != MOVE_NONE) - attackUnits += MateThreatBonus; - - // Ensure that attackUnits is between 0 and 99, in order to avoid array - // out of bounds errors. + // To index KingDangerTable[] attackUnits must be in [0, 99] range attackUnits = Min(99, Max(0, attackUnits)); // Finally, extract the king danger score from the KingDangerTable[] diff --git a/src/evaluate.h b/src/evaluate.h index ddae4b7e..dcfa74e8 100644 --- a/src/evaluate.h +++ b/src/evaluate.h @@ -89,9 +89,6 @@ struct EvalInfo { // 2 to kingAdjacentZoneAttacksCount[BLACK]. int kingAdjacentZoneAttacksCount[2]; - // mateThreat[color] is a move for the given side which gives a direct mate. - Move mateThreat[2]; - // Middle game and endgame mobility scores Score mobility; -- 2.39.2