X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=915cd0ce22771aab12bf45e2a43e35bbcb8a4743;hp=2f7bb5a6c20ab1904681c15dd31a809c769935f7;hb=353e20674b2019094059caaa3567e9a44abe9cd1;hpb=6c9f4cf36f54a2437c843ebe0184a3356da9d82a diff --git a/src/pawns.cpp b/src/pawns.cpp index 2f7bb5a6..7b266e77 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,8 @@ /* 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) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2020 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 @@ -21,67 +22,45 @@ #include #include "bitboard.h" -#include "bitcount.h" #include "pawns.h" #include "position.h" +#include "thread.h" namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // 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) } }; - - // 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) } }; - - // 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) }; - - // Levers bonus by rank - const Score Lever[RANK_NB] = { - S( 0, 0), S( 0, 0), S(0, 0), S(0, 0), - S(20,20), S(40,40), 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] = - { V(100), V(0), V(27), V(73), V(92), V(101), V(101) }; - - // Danger of enemy pawns moving toward our king indexed by - // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn] - const Value StormDanger[][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(160), 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 horizon. - const Value MaxSafetyBonus = V(263); + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score BlockedStorm = S(82, 82); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); + constexpr Score WeakLever = S( 0, 56); + constexpr Score WeakUnopposed = S(13, 27); + + // Connected pawn bonus + constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 }; + + // Strength of pawn shelter for our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king. + constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = { + { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) }, + { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) }, + { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) }, + { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) } + }; + + // Danger of enemy pawns moving toward our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn + // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn + // on edge, likely blocked by our king. + constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { + { V( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) }, + { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) }, + { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) }, + { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) } + }; #undef S #undef V @@ -89,202 +68,156 @@ namespace { template Score evaluate(const Position& pos, Pawns::Entry* e) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const Square Up = (Us == WHITE ? DELTA_N : DELTA_S); - const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); - const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); + constexpr Color Them = ~Us; + constexpr Direction Up = pawn_push(Us); - Bitboard b, p, doubled; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; Square s; - File f; - bool passed, isolated, opposed, connected, backward, candidate, unsupported, lever; - Score value = SCORE_ZERO; - const Square* pl = pos.list(Us); - const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + bool backward, passed, doubled; + Score score = SCORE_ZERO; + const Square* pl = pos.squares(Us); - Bitboard ourPawns = pos.pieces(Us, PAWN); + Bitboard ourPawns = pos.pieces( Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); - e->passedPawns[Us] = e->candidatePawns[Us] = 0; + Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); + + e->passedPawns[Us] = 0; e->kingSquares[Us] = SQ_NONE; - e->semiopenFiles[Us] = 0xFF; - e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(ourPawns); - e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); - e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; + e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns); // Loop through all pawns of the current color and score each pawn while ((s = *pl++) != SQ_NONE) { assert(pos.piece_on(s) == make_piece(Us, PAWN)); - f = file_of(s); - - // This file cannot be semi-open - e->semiopenFiles[Us] &= ~(1 << f); - - // Previous rank - p = rank_bb(s - pawn_push(Us)); - - // 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)); - lever = theirPawns & pawnAttacksBB[s]; - - // Test for backward pawn. - // 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; - else - { - // We now know that there are no friendly pawns beside or behind this - // pawn on adjacent files. We now check whether the pawn is - // backward by looking in the forward direction on the adjacent - // files, and picking the closest pawn there. - b = pawn_attack_span(Us, s) & (ourPawns | theirPawns); - b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b)); - - // If we have an enemy pawn in the same or next rank, the pawn is - // backward because it cannot advance without being captured. - backward = (b | shift_bb(b)) & theirPawns; - } - - assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns)); - - // 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 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 - && popcount(b) >= popcount(pawn_attack_span(Us, s) & theirPawns); - - // Passed pawns will be properly scored in evaluation because we need - // full attack info to evaluate passed pawns. Only the frontmost passed - // pawn on each file is considered a true passed pawn. - if (passed && !doubled) + Rank r = relative_rank(Us, s); + + // Flag the pawn + opposed = theirPawns & forward_file_bb(Us, s); + blocked = theirPawns & (s + Up); + stoppers = theirPawns & passed_pawn_span(Us, s); + lever = theirPawns & PawnAttacks[Us][s]; + leverPush = theirPawns & PawnAttacks[Us][s + Up]; + doubled = ourPawns & (s - Up); + neighbours = ourPawns & adjacent_files_bb(s); + phalanx = neighbours & rank_bb(s); + support = neighbours & rank_bb(s - Up); + + e->blockedCount += blocked || more_than_one(leverPush); + + // A pawn is backward when it is behind all pawns of the same color on + // the adjacent files and cannot safely advance. + backward = !(neighbours & forward_ranks_bb(Them, s + Up)) + && (leverPush | blocked); + + // Compute additional span if pawn is not backward nor blocked + if (!backward && !blocked) + e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); + + // A pawn is passed if one of the three following conditions is true: + // (a) there is no stoppers except some levers + // (b) the only stoppers are the leverPush, but we outnumber them + // (c) there is only one front stopper which can be levered. + // (Refined in Evaluation::passed) + passed = !(stoppers ^ lever) + || ( !(stoppers ^ leverPush) + && popcount(phalanx) >= popcount(leverPush)) + || ( stoppers == blocked && r >= RANK_5 + && (shift(support) & ~(theirPawns | doubleAttackThem))); + + passed &= !(forward_file_bb(Us, s) & ourPawns); + + // Passed pawns will be properly scored later in evaluation when we have + // full attack info. + if (passed) e->passedPawns[Us] |= s; // Score this pawn - if (isolated) - value -= Isolated[opposed][f]; - - if (unsupported && !isolated) - value -= UnsupportedPawnPenalty; - - if (doubled) - value -= Doubled[f] / rank_distance(s, lsb(doubled)); - - if (backward) - value -= Backward[opposed][f]; - - if (connected) - value += Connected[f][relative_rank(Us, s)]; - - if (lever) - value += Lever[relative_rank(Us, s)]; - - if (candidate) + if (support | phalanx) { - value += CandidatePassed[relative_rank(Us, s)]; + int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2 + + 21 * popcount(support); - if (!doubled) - e->candidatePawns[Us] |= s; + score += make_score(v, v * (r - 2) / 4); } - } - b = e->semiopenFiles[Us] ^ 0xFF; - e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; + else if (!neighbours) + score -= Isolated + + WeakUnopposed * !opposed; - // 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. - value += PawnsFileSpan * e->pawnSpan[Us]; + else if (backward) + score -= Backward + + WeakUnopposed * !opposed; - return value; + if (!support) + score -= Doubled * doubled + + WeakLever * more_than_one(lever); + } + + return score; } } // namespace namespace Pawns { -/// init() initializes some tables by formula instead of hard-coding their values - -void init() { - - const int bonusByFile[] = { 1, 3, 3, 4, 4, 3, 3, 1 }; - - for (Rank r = RANK_1; r < RANK_8; ++r) - for (File f = FILE_A; f <= FILE_H; ++f) - { - int bonus = r * (r - 1) * (r - 2) + bonusByFile[f] * (r / 2 + 1); - Connected[f][r] = make_score(bonus, bonus); - } -} - - -/// probe() takes a position as input, computes a Entry object, and returns a -/// pointer to it. The result is also stored in a hash table, so we don't have -/// to recompute everything when the same pawn structure occurs again. +/// Pawns::probe() looks up the current position's pawns configuration in +/// the pawns hash table. It returns a pointer to the Entry if the position +/// is found. Otherwise a new Entry is computed and stored there, so we don't +/// have to recompute all when the same pawns configuration occurs again. -Entry* probe(const Position& pos, Table& entries) { +Entry* probe(const Position& pos) { Key key = pos.pawn_key(); - Entry* e = entries[key]; + Entry* e = pos.this_thread()->pawnsTable[key]; if (e->key == key) return e; e->key = key; - e->value = evaluate(pos, e) - evaluate(pos, e); + e->blockedCount = 0; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + return e; } -/// Entry::shelter_storm() calculates shelter and storm penalties for the file -/// the king is on, as well as the two adjacent files. +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. template -Value Entry::shelter_storm(const Position& pos, Square ksq) { +Score Entry::evaluate_shelter(const Position& pos, Square ksq) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB); + constexpr Color Them = ~Us; - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); Bitboard ourPawns = b & pos.pieces(Us); Bitboard theirPawns = b & pos.pieces(Them); - Value safety = MaxSafetyBonus; - File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - for (File f = kf - File(1); f <= kf + File(1); ++f) + Score bonus = make_score(5, 5); + + File center = Utility::clamp(file_of(ksq), FILE_B, FILE_G); + for (File f = File(center - 1); f <= File(center + 1); ++f) { b = ourPawns & file_bb(f); - Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; + + b = theirPawns & file_bb(f); + int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - b = theirPawns & file_bb(f); - Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + File d = File(edge_distance(f)); + bonus += make_score(ShelterStrength[d][ourRank], 0); - if ( (Edges & make_square(f, rkThem)) - && file_of(ksq) == f - && relative_rank(Us, ksq) == rkThem - 1) - safety += 200; + if (ourRank && (ourRank == theirRank - 1)) + bonus -= BlockedStorm * int(theirRank == RANK_3); else - safety -= ShelterWeakness[rkUs] - + StormDanger[rkUs == RANK_1 ? 0 : - rkThem != rkUs + 1 ? 1 : 2][rkThem]; + bonus -= make_score(UnblockedStorm[d][theirRank], 0); } - return safety; + return bonus; } @@ -292,33 +225,37 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { /// when king square changes, which is about 20% of total king_safety() calls. template -Score Entry::do_king_safety(const Position& pos, Square ksq) { +Score Entry::do_king_safety(const Position& pos) { + Square ksq = pos.square(Us); kingSquares[Us] = ksq; - castlingRights[Us] = pos.can_castle(Us); - minKPdistance[Us] = 0; + castlingRights[Us] = pos.castling_rights(Us); + auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); }; - Bitboard pawns = pos.pieces(Us, PAWN); - if (pawns) - while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} + Score shelter = evaluate_shelter(pos, ksq); + + // If we can castle use the bonus after castling if it is bigger - if (relative_rank(Us, ksq) > RANK_4) - return make_score(0, -16 * minKPdistance[Us]); + if (pos.can_castle(Us & KING_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); - Value bonus = shelter_storm(pos, ksq); + if (pos.can_castle(Us & QUEEN_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare); - // 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))); + // In endgame we like to bring our king near our closest pawn + Bitboard pawns = pos.pieces(Us, PAWN); + int minPawnDist = 6; - if (pos.can_castle(MakeCastling::right)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - return make_score(bonus, -16 * minKPdistance[Us]); + return shelter - make_score(0, 16 * minPawnDist); } // Explicit template instantiation -template Score Entry::do_king_safety(const Position& pos, Square ksq); -template Score Entry::do_king_safety(const Position& pos, Square ksq); +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); } // namespace Pawns