X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=c6d390b32efb0ea9e9a22276605a0c688485a0ae;hb=353e20674b2019094059caaa3567e9a44abe9cd1;hp=3a8f88bb1f1a646d1a71fdf750f22a4a8d1cfc93;hpb=389dc0e83bd0a205952432fc9e866dbe32bd54e1;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index 3a8f88bb..7b266e77 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,391 +1,261 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008 Marco Costalba + 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 the Free Software Foundation, either version 3 of the License, or (at your option) any later version. - + Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. - + You should have received a copy of the GNU General Public License along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include +#include "bitboard.h" #include "pawns.h" - - -//// -//// Local definitions -//// +#include "position.h" +#include "thread.h" namespace { - /// Constants and variables - - // Doubled pawn penalty by file, middle game. - const Value DoubledPawnMidgamePenalty[8] = { - Value(20), Value(30), Value(34), Value(34), - Value(34), Value(34), Value(30), Value(20) + #define V Value + #define S(mg, eg) make_score(mg, eg) + + // 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) } }; - // Doubled pawn penalty by file, endgame. - const Value DoubledPawnEndgamePenalty[8] = { - Value(35), Value(40), Value(40), Value(40), - Value(40), Value(40), Value(40), Value(35) + // 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) } }; - // Isolated pawn penalty by file, middle game. - const Value IsolatedPawnMidgamePenalty[8] = { - Value(20), Value(30), Value(34), Value(34), - Value(34), Value(34), Value(30), Value(20) - }; + #undef S + #undef V - // Isolated pawn penalty by file, endgame. - const Value IsolatedPawnEndgamePenalty[8] = { - Value(35), Value(40), Value(40), Value(40), - Value(40), Value(40), Value(40), Value(35) - }; + template + Score evaluate(const Position& pos, Pawns::Entry* e) { - // Backward pawn penalty by file, middle game. - const Value BackwardPawnMidgamePenalty[8] = { - Value(16), Value(24), Value(27), Value(27), - Value(27), Value(27), Value(24), Value(16) - }; + constexpr Color Them = ~Us; + constexpr Direction Up = pawn_push(Us); - // Backward pawn penalty by file, endgame. - const Value BackwardPawnEndgamePenalty[8] = { - Value(28), Value(32), Value(32), Value(32), - Value(32), Value(32), Value(32), Value(28) - }; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; + Square s; + bool backward, passed, doubled; + Score score = SCORE_ZERO; + const Square* pl = pos.squares(Us); - // Pawn chain membership bonus by file, middle game. - const Value ChainMidgameBonus[8] = { - Value(14), Value(16), Value(17), Value(18), - Value(18), Value(17), Value(16), Value(14) - }; + Bitboard ourPawns = pos.pieces( Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); - // Pawn chain membership bonus by file, endgame. - const Value ChainEndgameBonus[8] = { - Value(16), Value(16), Value(16), Value(16), - Value(16), Value(16), Value(16), Value(16) - }; + Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); - // Candidate passed pawn bonus by rank, middle game. - const Value CandidateMidgameBonus[8] = { - Value( 0), Value(12), Value(12), Value(20), - Value(40), Value(90), Value( 0), Value( 0) - }; + e->passedPawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns); - // Candidate passed pawn bonus by rank, endgame. - const Value CandidateEndgameBonus[8] = { - Value( 0), Value(24), Value(24), Value(40), - Value(80), Value(180), Value(0), Value( 0) - }; + // 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)); + + 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; - // Evaluate pawn storms? - const bool EvaluatePawnStorms = true; - - // Pawn storm tables for positions with opposite castling: - const int QStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - -22,-22,-22,-13,-4, 0, 0, 0, - -4, -9, -9, -9,-4, 0, 0, 0, - 9, 18, 22, 18, 9, 0, 0, 0, - 22, 31, 31, 22, 0, 0, 0, 0, - 31, 40, 40, 31, 0, 0, 0, 0, - 31, 40, 40, 31, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0 - }; - - const int KStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0,-4,-13,-22,-27,-27, - 0, 0, 0,-4, -9,-13,-18,-18, - 0, 0, 0, 0, 9, 9, 9, 9, - 0, 0, 0, 0, 9, 18, 27, 27, - 0, 0, 0, 0, 9, 27, 40, 36, - 0, 0, 0, 0, 0, 31, 40, 31, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + // Score this pawn + if (support | phalanx) + { + int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2 + + 21 * popcount(support); - // Pawn storm open file bonuses by file: - const int KStormOpenFileBonus[8] = { - 45, 45, 30, 0, 0, 0, 0, 0 - }; + score += make_score(v, v * (r - 2) / 4); + } - const int QStormOpenFileBonus[8] = { - 0, 0, 0, 0, 0, 30, 45, 30 - }; + else if (!neighbours) + score -= Isolated + + WeakUnopposed * !opposed; -} + else if (backward) + score -= Backward + + WeakUnopposed * !opposed; + if (!support) + score -= Doubled * doubled + + WeakLever * more_than_one(lever); + } -//// -//// Functions -//// + return score; + } -/// Constructor +} // namespace -PawnInfoTable::PawnInfoTable(unsigned numOfEntries) { +namespace Pawns { - size = numOfEntries; - entries = new PawnInfo[size]; - if (entries == NULL) - { - std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - exit(EXIT_FAILURE); - } - clear(); -} +/// 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) { -/// Destructor + Key key = pos.pawn_key(); + Entry* e = pos.this_thread()->pawnsTable[key]; -PawnInfoTable::~PawnInfoTable() { - delete [] entries; + if (e->key == key) + return e; + + e->key = key; + e->blockedCount = 0; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + + return e; } -/// PawnInfoTable::clear() clears the pawn hash table by setting all -/// entries to 0. +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. -void PawnInfoTable::clear() { - memset(entries, 0, size * sizeof(PawnInfo)); -} +template +Score Entry::evaluate_shelter(const Position& pos, Square ksq) { + constexpr Color Them = ~Us; -/// PawnInfoTable::get_pawn_info() takes a position object as input, computes -/// a PawnInfo 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. + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); -PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) { + Score bonus = make_score(5, 5); - assert(pos.is_ok()); + 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); + int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - Key key = pos.get_pawn_key(); - int index = int(key & (size - 1)); - PawnInfo *pi = entries + index; + b = theirPawns & file_bb(f); + int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - // If pi->key matches the position's pawn hash key, it means that we - // have analysed this pawn structure before, and we can simply return the - // information we found the last time instead of recomputing it - if (pi->key == key) - return pi; + File d = File(edge_distance(f)); + bonus += make_score(ShelterStrength[d][ourRank], 0); - // Clear the PawnInfo object, and set the key - pi->clear(); - pi->key = key; + if (ourRank && (ourRank == theirRank - 1)) + bonus -= BlockedStorm * int(theirRank == RANK_3); + else + bonus -= make_score(UnblockedStorm[d][theirRank], 0); + } - Value mgValue[2] = {Value(0), Value(0)}; - Value egValue[2] = {Value(0), Value(0)}; + return bonus; +} - // Loop through the pawns for both colors - for (Color us = WHITE; us <= BLACK; us++) - { - Color them = opposite_color(us); - Bitboard ourPawns = pos.pawns(us); - Bitboard theirPawns = pos.pawns(them); - Bitboard pawns = ourPawns; - - // Initialize pawn storm scores by giving bonuses for open files - if (EvaluatePawnStorms) - for(File f = FILE_A; f <= FILE_H; f++) - if(pos.file_is_half_open(us, f)) - { - pi->ksStormValue[us] += KStormOpenFileBonus[f]; - pi->qsStormValue[us] += QStormOpenFileBonus[f]; - } - // Loop through all pawns of the current color and score each pawn - while (pawns) - { - bool passed, doubled, isolated, backward, chain, candidate; - Square s = pop_1st_bit(&pawns); - File f = square_file(s); - Rank r = square_rank(s); +/// Entry::do_king_safety() calculates a bonus for king safety. It is called only +/// when king square changes, which is about 20% of total king_safety() calls. - assert(pos.piece_on(s) == pawn_of_color(us)); +template +Score Entry::do_king_safety(const Position& pos) { - // The file containing the pawn is not half open - pi->halfOpenFiles[us] &= ~(1 << f); + Square ksq = pos.square(Us); + kingSquares[Us] = ksq; + castlingRights[Us] = pos.castling_rights(Us); + auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); }; - // Passed, isolated or doubled pawn? - passed = pos.pawn_is_passed(us, s); - isolated = pos.pawn_is_isolated(us, s); - doubled = pos.pawn_is_doubled(us, s); + Score shelter = evaluate_shelter(pos, ksq); - if (EvaluatePawnStorms) - { - // We calculate kingside and queenside pawn storm scores - // for both colors. These are used when evaluating middle - // game positions with opposite side castling. - // - // Each pawn is given a base score given by a piece square table - // (KStormTable[] or QStormTable[]). This score is increased if - // there are enemy pawns on adjacent files in front of the pawn. - // This is because we want to be able to open files against the - // enemy king, and to avoid blocking the pawn structure (e.g. white - // pawns on h6, g5, black pawns on h7, g6, f7). - - // Kingside and queenside pawn storms - bool outPost = (outpost_mask(us, s) & theirPawns); - bool passed = (passed_pawn_mask(us, s) & theirPawns); - int KBonus = KStormTable[relative_square(us, s)]; - int QBonus = QStormTable[relative_square(us, s)]; - - switch (f) { - - case FILE_A: - QBonus += passed * QBonus / 4; - break; - - case FILE_B: - QBonus += passed * (QBonus / 2 + QBonus / 4); - break; - - case FILE_C: - QBonus += passed * QBonus / 2; - break; - - case FILE_F: - KBonus += outPost * KBonus / 4; - break; - - case FILE_G: - KBonus += outPost * (KBonus / 2 + KBonus / 4); - break; - - case FILE_H: - KBonus += outPost * KBonus / 2; - break; - - default: - break; - } - pi->ksStormValue[us] += KBonus; - pi->qsStormValue[us] += QBonus; - } + // If we can castle use the bonus after castling if it is bigger - // Member of a pawn chain (but not the backward one)? We could speed up - // the test a little by introducing an array of masks indexed by color - // and square for doing the test, but because everything is hashed, - // it probably won't make any noticable difference. - chain = ourPawns - & neighboring_files_bb(f) - & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1))); - - // Test for backward pawn - // - // If the pawn is passed, isolated, or member of a pawn chain - // it cannot be backward. If can capture an enemy pawn or if - // there are friendly pawns behind on neighboring files it cannot - // be backward either. - if ( passed - || isolated - || chain - || (pos.pawn_attacks(us, s) & theirPawns) - || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f))) - backward = false; - else - { - // We now know that there are no friendly pawns beside or behind this - // pawn on neighboring files. We now check whether the pawn is - // backward by looking in the forward direction on the neighboring - // files, and seeing whether we meet a friendly or an enemy pawn first. - Bitboard b; - if (us == WHITE) - { - for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b <<= 8); - backward = (b | (b << 8)) & theirPawns; - } - else - { - for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b >>= 8); - backward = (b | (b >> 8)) & theirPawns; - } - } + if (pos.can_castle(Us & KING_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); - // Test for candidate passed pawn - candidate = !passed - && pos.file_is_half_open(them, f) - && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns) - - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r) & theirPawns) - >= 0); - - // In order to prevent doubled passed pawns from receiving a too big - // bonus, only the frontmost passed pawn on each file is considered as - // a true passed pawn. - if (passed && (ourPawns & squares_in_front_of(us, s))) - { - // candidate = true; - passed = false; - } + if (pos.can_castle(Us & QUEEN_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare); - // Score this pawn - Value mv = Value(0), ev = Value(0); - if (isolated) - { - mv -= IsolatedPawnMidgamePenalty[f]; - ev -= IsolatedPawnEndgamePenalty[f]; - if (pos.file_is_half_open(them, f)) - { - mv -= IsolatedPawnMidgamePenalty[f] / 2; - ev -= IsolatedPawnEndgamePenalty[f] / 2; - } - } - if (doubled) - { - mv -= DoubledPawnMidgamePenalty[f]; - ev -= DoubledPawnEndgamePenalty[f]; - } - if (backward) - { - mv -= BackwardPawnMidgamePenalty[f]; - ev -= BackwardPawnEndgamePenalty[f]; - if (pos.file_is_half_open(them, f)) - { - mv -= BackwardPawnMidgamePenalty[f] / 2; - ev -= BackwardPawnEndgamePenalty[f] / 2; - } - } - if (chain) - { - mv += ChainMidgameBonus[f]; - ev += ChainEndgameBonus[f]; - } - if (candidate) - { - mv += CandidateMidgameBonus[relative_rank(us, s)]; - ev += CandidateEndgameBonus[relative_rank(us, s)]; - } + // In endgame we like to bring our king near our closest pawn + Bitboard pawns = pos.pieces(Us, PAWN); + int minPawnDist = 6; - mgValue[us] += mv; - egValue[us] += ev; - - // If the pawn is passed, set the square of the pawn in the passedPawns - // bitboard - if (passed) - set_bit(&(pi->passedPawns), s); - } // while(pawns) - } // for(colors) + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]); - pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]); - return pi; + return shelter - make_score(0, 16 * minPawnDist); } + +// Explicit template instantiation +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); + +} // namespace Pawns