X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=6d90f6b5858f9fb314a8f2bf61092a7ef7142a23;hp=91da8a7b0858cf748e7ba57231aabfa93b6f238a;hb=45973245726d8ba62969891a15cf61fe46cc1f31;hpb=e8f9447b11efd80a01733175c5076db988c45aa9 diff --git a/src/pawns.cpp b/src/pawns.cpp index 91da8a7b..6d90f6b5 100644 --- a/src/pawns.cpp +++ b/src/pawns.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 @@ -30,35 +30,38 @@ namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by opposed flag and file - const Score Doubled[2][FILE_NB] = { - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }, - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }}; + // Doubled pawn penalty by file + const Score Doubled[FILE_NB] = { + S(13, 43), S(20, 48), S(23, 48), S(23, 48), + S(23, 48), S(23, 48), S(20, 48), S(13, 43) }; // Isolated pawn penalty by opposed flag and file const Score Isolated[2][FILE_NB] = { { S(37, 45), S(54, 52), S(60, 52), S(60, 52), S(60, 52), S(60, 52), S(54, 52), S(37, 45) }, { S(25, 30), S(36, 35), S(40, 35), S(40, 35), - S(40, 35), S(40, 35), S(36, 35), S(25, 30) }}; + S(40, 35), S(40, 35), S(36, 35), S(25, 30) } }; // Backward pawn penalty by opposed flag and file const Score Backward[2][FILE_NB] = { { S(30, 42), S(43, 46), S(49, 46), S(49, 46), S(49, 46), S(49, 46), S(43, 46), S(30, 42) }, { S(20, 28), S(29, 31), S(33, 31), S(33, 31), - S(33, 31), S(33, 31), S(29, 31), S(20, 28) }}; + S(33, 31), S(33, 31), S(29, 31), S(20, 28) } }; - // Pawn chain membership bonus by file and rank (initialized by formula) - Score ChainMember[FILE_NB][RANK_NB]; + // Connected pawn bonus by file and rank (initialized by formula) + Score Connected[FILE_NB][RANK_NB]; // Candidate passed pawn bonus by rank const Score CandidatePassed[RANK_NB] = { S( 0, 0), S( 6, 13), S(6,13), S(14,29), - S(34,68), S(83,166), S(0, 0), S( 0, 0) - }; + S(34,68), S(83,166), S(0, 0), S( 0, 0) }; + + // Bonus for file distance of the two outermost pawns + const Score PawnsFileSpan = S(0, 15); + + // Unsupported pawn penalty + const Score UnsupportedPawnPenalty = S(20, 10); // Weakness of our pawn shelter in front of the king indexed by [rank] const Value ShelterWeakness[RANK_NB] = @@ -69,10 +72,10 @@ namespace { const Value StormDanger[3][RANK_NB] = { { V( 0), V(64), V(128), V(51), V(26) }, { V(26), V(32), V( 96), V(38), V(20) }, - { V( 0), V( 0), V( 64), V(25), V(13) }}; + { V( 0), V( 0), V( 64), V(25), V(13) } }; // Max bonus for king safety. Corresponds to start position with all the pawns - // in front of the king and no enemy pawn on the horizont. + // in front of the king and no enemy pawn on the horizon. const Value MaxSafetyBonus = V(263); #undef S @@ -86,10 +89,10 @@ namespace { const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); - Bitboard b; + Bitboard b, p, doubled; Square s; File f; - bool passed, isolated, doubled, opposed, chain, backward, candidate; + bool passed, isolated, opposed, connected, backward, candidate, unsupported; Score value = SCORE_ZERO; const Square* pl = pos.list(Us); @@ -113,22 +116,26 @@ namespace { // This file cannot be semi-open e->semiopenFiles[Us] &= ~(1 << f); - // Our rank plus previous one. Used for chain detection - b = rank_bb(s) | rank_bb(s - pawn_push(Us)); + // Previous rank + p = rank_bb(s - pawn_push(Us)); - // Flag the pawn as passed, isolated, doubled or member of a pawn - // chain (but not the backward one). - chain = ourPawns & adjacent_files_bb(f) & b; - isolated = !(ourPawns & adjacent_files_bb(f)); - doubled = ourPawns & forward_bb(Us, s); - opposed = theirPawns & forward_bb(Us, s); - passed = !(theirPawns & passed_pawn_mask(Us, s)); + // Our rank plus previous one + b = rank_bb(s) | p; + + // Flag the pawn as passed, isolated, doubled, + // unsupported or connected (but not the backward one). + connected = ourPawns & adjacent_files_bb(f) & b; + unsupported = !(ourPawns & adjacent_files_bb(f) & p); + isolated = !(ourPawns & adjacent_files_bb(f)); + doubled = ourPawns & forward_bb(Us, s); + opposed = theirPawns & forward_bb(Us, s); + passed = !(theirPawns & passed_pawn_mask(Us, s)); // Test for backward pawn. - // If the pawn is passed, isolated, or member of a pawn chain it cannot - // be backward. If there are friendly pawns behind on adjacent files - // or if can capture an enemy pawn it cannot be backward either. - if ( (passed | isolated | chain) + // If the pawn is passed, isolated, or connected it cannot be + // backward. If there are friendly pawns behind on adjacent files + // or if it can capture an enemy pawn it cannot be backward either. + if ( (passed | isolated | connected) || (ourPawns & pawn_attack_span(Them, s)) || (pos.attacks_from(s, Us) & theirPawns)) backward = false; @@ -148,9 +155,9 @@ namespace { assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns)); - // A not passed pawn is a candidate to become passed if it is free to + // A not-passed pawn is a candidate to become passed, if it is free to // advance and if the number of friendly pawns beside or behind this - // pawn on adjacent files is higher or equal than the number of + // pawn on adjacent files is higher than or equal to the number of // enemy pawns in the forward direction on the adjacent files. candidate = !(opposed | passed | backward | isolated) && (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0 @@ -166,14 +173,17 @@ namespace { if (isolated) value -= Isolated[opposed][f]; + if (unsupported && !isolated) + value -= UnsupportedPawnPenalty; + if (doubled) - value -= Doubled[opposed][f]; + value -= Doubled[f] / rank_distance(s, lsb(doubled)); if (backward) value -= Backward[opposed][f]; - if (chain) - value += ChainMember[f][relative_rank(Us, s)]; + if (connected) + value += Connected[f][relative_rank(Us, s)]; if (candidate) { @@ -184,6 +194,14 @@ namespace { } } + // In endgame it's better to have pawns on both wings. So give a bonus according + // to file distance between left and right outermost pawns. + if (pos.count(Us) > 1) + { + b = e->semiopenFiles[Us] ^ 0xFF; + value += PawnsFileSpan * int(msb(b) - lsb(b)); + } + return value; } @@ -191,18 +209,18 @@ namespace { namespace Pawns { -/// init() initializes some tables by formula instead of hard-code their values +/// init() initializes some tables by formula instead of hard-coding their values void init() { - const int chainByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 }; + const int bonusesByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 }; int bonus; for (Rank r = RANK_1; r < RANK_8; ++r) for (File f = FILE_A; f <= FILE_H; ++f) { - bonus = r * (r-1) * (r-2) + chainByFile[f] * (r/2 + 1); - ChainMember[f][r] = make_score(bonus, bonus); + bonus = r * (r-1) * (r-2) + bonusesByFile[f] * (r/2 + 1); + Connected[f][r] = make_score(bonus, bonus); } } @@ -232,6 +250,7 @@ template Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); + static const Bitboard MiddleEdges = (FileABB | FileHBB) & (Rank2BB | Rank3BB); Value safety = MaxSafetyBonus; Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); @@ -244,25 +263,32 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { { b = ourPawns & file_bb(f); rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; - safety -= ShelterWeakness[rkUs]; b = theirPawns & file_bb(f); rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; - safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; + + if ( (MiddleEdges & make_square(f, rkThem)) + && file_of(ksq) == f + && relative_rank(Us, ksq) == rkThem - 1) + safety += Value(200); + else + safety -= ShelterWeakness[rkUs] + + StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; } return safety; } -/// Entry::update_safety() calculates and caches a bonus for king safety. It is -/// called only when king square changes, about 20% of total king_safety() calls. +/// Entry::update_safety() calculates and caches a bonus for king safety. +/// It is called only when king square changes, which is about 20% of total +/// king_safety() calls. template Score Entry::update_safety(const Position& pos, Square ksq) { kingSquares[Us] = ksq; - castleRights[Us] = pos.can_castle(Us); + castlingRights[Us] = pos.can_castle(Us); minKPdistance[Us] = 0; Bitboard pawns = pos.pieces(Us, PAWN); @@ -274,11 +300,11 @@ Score Entry::update_safety(const Position& pos, Square ksq) { Value bonus = shelter_storm(pos, ksq); - // If we can castle use the bonus after the castle if is bigger - if (pos.can_castle(make_castle_right(Us, KING_SIDE))) + // If we can castle use the bonus after the castling if it is bigger + if (pos.can_castle(MakeCastling::right)) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); - if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) + if (pos.can_castle(MakeCastling::right)) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);