/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
#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 opposed flag and file
- const Score DoubledPawnPenalty[2][8] = {
- { 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) }};
-
- // Isolated pawn penalty by opposed flag and file
- const Score IsolatedPawnPenalty[2][8] = {
- { 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 BackwardPawnPenalty[2][8] = {
- { 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) }};
-
- // Pawn chain membership bonus by file
- const Score ChainBonus[8] = {
- S(11,-1), S(13,-1), S(13,-1), S(14,-1),
- S(14,-1), S(13,-1), S(13,-1), S(11,-1)
+ // Pawn penalties
+ constexpr Score Backward = S( 6, 23);
+ constexpr Score Doubled = S(13, 53);
+ constexpr Score DoubledEarly = S(20, 10);
+ constexpr Score Isolated = S( 2, 15);
+ constexpr Score WeakLever = S( 5, 57);
+ constexpr Score WeakUnopposed = S(16, 22);
+
+ // Bonus for blocked pawns at 5th or 6th rank
+ constexpr Score BlockedPawn[2] = { S(-15, -3), S(-6, 3) };
+
+ constexpr Score BlockedStorm[RANK_NB] = {
+ S(0, 0), S(0, 0), S(75, 78), S(-8, 16), S(-6, 10), S(-6, 6), S(0, 2)
};
- // Candidate passed pawn bonus by rank
- const Score CandidateBonus[8] = {
- S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0)
+ // Connected pawn bonus
+ constexpr int Connected[RANK_NB] = { 0, 5, 7, 11, 24, 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( -5), V( 82), V( 92), V( 54), V( 36), V( 22), V( 28) },
+ { V(-44), V( 63), V( 33), V(-50), V(-30), V(-12), V( -62) },
+ { V(-11), V( 77), V( 22), V( -6), V( 31), V( 8), V( -45) },
+ { V(-39), V(-12), V(-29), V(-50), V(-43), V(-68), V(-164) }
};
- const Score PawnStructureWeight = S(233, 201);
+ // 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( 87), V(-288), V(-168), V( 96), V( 47), V( 44), V( 46) },
+ { V( 42), V( -25), V( 120), V( 45), V( 34), V( -9), V( 24) },
+ { V( -8), V( 51), V( 167), V( 35), V( -4), V(-16), V(-12) },
+ { V(-17), V( -13), V( 100), V( 4), V( 9), V(-16), V(-31) }
+ };
- #undef S
- inline Score apply_weight(Score v, Score w) {
- return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
- (int(eg_value(v)) * eg_value(w)) / 0x100);
- }
-}
+ // KingOnFile[semi-open Us][semi-open Them] contains bonuses/penalties
+ // for king when the king is on a semi-open or open file.
+ constexpr Score KingOnFile[2][2] = {{ S(-21,10), S(-7, 1) },
+ { S( 0,-3), S( 9,-4) }};
+ #undef S
+ #undef V
+
+
+ /// evaluate() calculates a score for the static pawn structure of the given position.
+ /// We cannot use the location of pieces or king in this function, as the evaluation
+ /// of the pawn structure will be stored in a small cache for speed reasons, and will
+ /// be re-used even when the pieces have moved.
+
+ template<Color Us>
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ constexpr Color Them = ~Us;
+ constexpr Direction Up = pawn_push(Us);
+ constexpr Direction Down = -Up;
+
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
+ Bitboard lever, leverPush, blocked;
+ Square s;
+ bool backward, passed, doubled;
+ Score score = SCORE_ZERO;
+ Bitboard b = pos.pieces(Us, PAWN);
+
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
+
+ e->passedPawns[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
+ e->blockedCount += popcount(shift<Up>(ourPawns) & (theirPawns | doubleAttackThem));
+
+ // Loop through all pawns of the current color and score each pawn
+ while (b) {
+ s = pop_lsb(&b);
+
+ 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 & pawn_attacks_bb(Us, s);
+ leverPush = theirPawns & pawn_attacks_bb(Us, s + Up);
+ doubled = ourPawns & (s - Up);
+ neighbours = ourPawns & adjacent_files_bb(s);
+ phalanx = neighbours & rank_bb(s);
+ support = neighbours & rank_bb(s - Up);
+
+ if (doubled)
+ {
+ // Additional doubled penalty if none of their pawns is fixed
+ if (!(ourPawns & shift<Down>(theirPawns | pawn_attacks_bb<Them>(theirPawns))))
+ score -= DoubledEarly;
+ }
+
+ // 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<Up>(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 (support | phalanx)
+ {
+ int v = Connected[r] * (2 + bool(phalanx) - bool(opposed))
+ + 22 * popcount(support);
+
+ score += make_score(v, v * (r - 2) / 4);
+ }
+
+ else if (!neighbours)
+ {
+ if ( opposed
+ && (ourPawns & forward_file_bb(Them, s))
+ && !(theirPawns & adjacent_files_bb(s)))
+ score -= Doubled;
+ else
+ score -= Isolated
+ + WeakUnopposed * !opposed;
+ }
+
+ else if (backward)
+ score -= Backward
+ + WeakUnopposed * !opposed * bool(~(FileABB | FileHBB) & s);
+
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
+
+ if (blocked && r >= RANK_5)
+ score += BlockedPawn[r - RANK_5];
+ }
+
+ return score;
+ }
-/// 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 an hash table, so we don't have to recompute everything when the same
-/// pawn structure occurs again.
+} // namespace
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
+namespace Pawns {
- Key key = pos.get_pawn_key();
- PawnInfo* pi = probe(key);
- // 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;
+/// 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.
- // Initialize PawnInfo entry
- pi->key = key;
- pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
+Entry* probe(const Position& pos) {
- // Calculate pawn attacks
- Bitboard wPawns = pos.pieces(PAWN, WHITE);
- Bitboard bPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB);
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
- // Evaluate pawns for both colors and weight the result
- pi->value = evaluate_pawns<WHITE>(pos, wPawns, bPawns, pi)
- - evaluate_pawns<BLACK>(pos, bPawns, wPawns, pi);
+ if (e->key == key)
+ return e;
- pi->value = apply_weight(pi->value, PawnStructureWeight);
+ e->key = key;
+ e->blockedCount = 0;
+ e->scores[WHITE] = evaluate<WHITE>(pos, e);
+ e->scores[BLACK] = evaluate<BLACK>(pos, e);
- return pi;
+ return e;
}
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+/// 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<Color Us>
-Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) {
-
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
- const Color Them = (Us == WHITE ? BLACK : WHITE);
-
- Bitboard b;
- Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- Score value = SCORE_ZERO;
- const Square* pl = pos.piece_list(Us, PAWN);
-
- // Loop through all pawns of the current color and score each pawn
- while ((s = *pl++) != SQ_NONE)
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) const {
+
+ constexpr Color Them = ~Us;
+
+ Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
+ Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them];
+ Bitboard theirPawns = b & pos.pieces(Them);
+
+ Score bonus = make_score(5, 5);
+
+ File center = std::clamp(file_of(ksq), FILE_B, FILE_G);
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
- assert(pos.piece_on(s) == make_piece(Us, PAWN));
-
- f = square_file(s);
- r = square_rank(s);
-
- // This file cannot be half open
- pi->halfOpenFiles[Us] &= ~(1 << f);
-
- // Our rank plus previous one. Used for chain detection
- b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
-
- // Flag the pawn as passed, isolated, doubled or member of a pawn
- // chain (but not the backward one).
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- doubled = ourPawns & squares_in_front_of(Us, s);
- opposed = theirPawns & squares_in_front_of(Us, s);
- isolated = !(ourPawns & neighboring_files_bb(f));
- chain = ourPawns & neighboring_files_bb(f) & b;
-
- // Test for backward pawn
- backward = false;
-
- // If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on neighboring files
- // or if can capture an enemy pawn it cannot be backward either.
- if ( !(passed | isolated | chain)
- && !(ourPawns & attack_span_mask(Them, s))
- && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
- {
- // 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.
- b = pos.attacks_from<PAWN>(s, Us);
-
- // Note that we are sure to find something because pawn is not passed
- // nor isolated, so loop is potentially infinite, but it isn't.
- while (!(b & (ourPawns | theirPawns)))
- Us == WHITE ? b <<= 8 : b >>= 8;
-
- // The friendly pawn needs to be at least two ranks closer than the
- // enemy pawn in order to help the potentially backward pawn advance.
- backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
- }
-
- assert(opposed | passed | (attack_span_mask(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 neighboring files is higher or equal than the number of
- // enemy pawns in the forward direction on the neighboring files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
- && count_1s<Max15>(b) >= count_1s<Max15>(attack_span_mask(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)
- set_bit(&(pi->passedPawns[Us]), s);
-
- // Score this pawn
- if (isolated)
- value -= IsolatedPawnPenalty[opposed][f];
-
- if (doubled)
- value -= DoubledPawnPenalty[opposed][f];
-
- if (backward)
- value -= BackwardPawnPenalty[opposed][f];
-
- if (chain)
- value += ChainBonus[f];
-
- if (candidate)
- value += CandidateBonus[relative_rank(Us, s)];
+ b = ourPawns & file_bb(f);
+ 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;
+
+ int d = edge_distance(f);
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
+
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= BlockedStorm[theirRank];
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- return value;
+
+ // King On File
+ bonus -= KingOnFile[pos.is_on_semiopen_file(Us, ksq)][pos.is_on_semiopen_file(Them, ksq)];
+
+ return bonus;
}
-/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total king_shelter() calls.
+/// 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.
+
template<Color Us>
-Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos) {
- const int Shift = (Us == WHITE ? 8 : -8);
+ Square ksq = pos.square<KING>(Us);
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.castling_rights(Us);
+ auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); };
- Bitboard pawns;
- int r, shelter = 0;
+ Score shelter = evaluate_shelter<Us>(pos, ksq);
- if (relative_rank(Us, ksq) <= RANK_4)
- {
- pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
- r = ksq & (7 << 3);
- for (int i = 0; i < 3; i++)
- {
- r += Shift;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] << (6 - i);
- }
- }
- kingSquares[Us] = ksq;
- kingShelters[Us] = make_score(shelter, 0);
- return kingShelters[Us];
+ // If we can castle use the bonus after castling if it is bigger
+
+ if (pos.can_castle(Us & KING_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)), compare);
+
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)), compare);
+
+ // In endgame we like to bring our king near our closest pawn
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = 6;
+
+ if (pawns & attacks_bb<KING>(ksq))
+ minPawnDist = 1;
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
+
+ return shelter - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation
-template Score PawnInfo::updateShelter<WHITE>(const Position& pos, Square ksq);
-template Score PawnInfo::updateShelter<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos);
+template Score Entry::do_king_safety<BLACK>(const Position& pos);
+
+} // namespace Pawns
projects / stockfish / blobdiff