X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=7d39a4a08bde360f2299f3cc231817e0d749ac07;hb=340e9ea5096fb1c8e4a0914827f1af1d30075039;hp=6897969cb08398414470f902b839a9e67faec84b;hpb=f59323b56a0920676c2589a36356a44fc42c8f40;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
index 6897969c..7d39a4a0 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) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2019 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
@@ -17,265 +18,246 @@
along with this program. If not, see .
*/
+#include
#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 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( 9, 24);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+
+ // Connected pawn bonus by opposed, phalanx, #support and rank
+ Score Connected[2][2][3][RANK_NB];
+
+ // 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) }
};
- // 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)
+ // 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.
+ constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
+ { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) },
+ { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) },
+ { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) },
+ { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) }
};
- const Score PawnStructureWeight = S(233, 201);
-
- // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank]
- const Value ShelterWeakness[2][8] =
- { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) },
- { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } };
-
- // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank]
- const Value StormDanger[2][8] =
- { { V(26), V(0), V(128), V(51), V(26) },
- { V(13), 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.
- const Value MaxSafetyBonus = V(263);
-
#undef S
#undef V
-}
-
-
-/// PawnTable::probe() takes a position object as input, computes a PawnEntry
-/// 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.
-PawnEntry* PawnTable::probe(const Position& pos) {
+ template
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
+
+ Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard lever, leverPush;
+ Square s;
+ bool opposed, backward;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares(Us);
+
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
+ e->semiopenFiles[Us] = 0xFF;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
+ e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK];
+
+ // 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));
+
+ File f = file_of(s);
+
+ e->semiopenFiles[Us] &= ~(1 << f);
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+
+ // Flag the pawn
+ opposed = theirPawns & forward_file_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_mask(Us, s);
+ lever = theirPawns & PawnAttacks[Us][s];
+ leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ doubled = ourPawns & (s - Up);
+ neighbours = ourPawns & adjacent_files_bb(f);
+ phalanx = neighbours & rank_bb(s);
+ supported = neighbours & rank_bb(s - Up);
+
+ // A pawn is backward when it is behind all pawns of the same color
+ // on the adjacent files and cannot be safely advanced.
+ backward = !(ourPawns & pawn_attack_span(Them, s + Up))
+ && (stoppers & (leverPush | (s + Up)));
+
+ // Passed pawns will be properly scored in evaluation because we need
+ // full attack info to evaluate them. Include also not passed pawns
+ // which could become passed after one or two pawn pushes when are
+ // not attacked more times than defended.
+ if ( !(stoppers ^ lever ^ leverPush)
+ && popcount(supported) >= popcount(lever) - 1
+ && popcount(phalanx) >= popcount(leverPush))
+ e->passedPawns[Us] |= s;
+
+ else if ( stoppers == SquareBB[s + Up]
+ && relative_rank(Us, s) >= RANK_5)
+ {
+ b = shift(supported) & ~theirPawns;
+ while (b)
+ if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+ e->passedPawns[Us] |= s;
+ }
+
+ // Score this pawn
+ if (supported | phalanx)
+ score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
+
+ else if (!neighbours)
+ score -= Isolated, e->weakUnopposed[Us] += !opposed;
+
+ else if (backward)
+ score -= Backward, e->weakUnopposed[Us] += !opposed;
+
+ if (doubled && !supported)
+ score -= Doubled;
+ }
+
+ return score;
+ }
- Key key = pos.pawn_key();
- PawnEntry* e = entries[key];
+} // namespace
- // If e->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 (e->key == key)
- return e;
+namespace Pawns {
- e->key = key;
- e->passedPawns[WHITE] = e->passedPawns[BLACK] = 0;
- e->kingSquares[WHITE] = e->kingSquares[BLACK] = SQ_NONE;
- e->halfOpenFiles[WHITE] = e->halfOpenFiles[BLACK] = 0xFF;
+/// Pawns::init() initializes some tables needed by evaluation. Instead of using
+/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
+/// to reduce independent parameters and to allow easier tuning and better insight.
- Bitboard wPawns = pos.pieces(PAWN, WHITE);
- Bitboard bPawns = pos.pieces(PAWN, BLACK);
- e->pawnAttacks[WHITE] = ((wPawns & ~FileHBB) << 9) | ((wPawns & ~FileABB) << 7);
- e->pawnAttacks[BLACK] = ((bPawns & ~FileHBB) >> 7) | ((bPawns & ~FileABB) >> 9);
+void init() {
- e->value = evaluate_pawns(pos, wPawns, bPawns, e)
- - evaluate_pawns(pos, bPawns, wPawns, e);
+ static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
- e->value = apply_weight(e->value, PawnStructureWeight);
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (int support = 0; support <= 2; ++support)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int v = 17 * support;
+ v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
- return e;
+ Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
+ }
}
-/// PawnTable::evaluate_pawns() evaluates each pawn of the given color
+/// 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.
-template
-Score PawnTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnEntry* e) {
+Entry* probe(const Position& pos) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
- 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);
+ if (e->key == key)
+ return e;
- // 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);
- r = rank_of(s);
-
- // This file cannot be half open
- e->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).
- 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));
-
- // 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 adjacent 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(s, Us) & theirPawns))
- {
- // 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 seeing whether we meet a friendly or an enemy pawn first.
- b = pos.attacks_from(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 adjacent files is higher or equal than the number of
- // enemy pawns in the forward direction on the adjacent files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
- && popcount(b) >= popcount(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)
- e->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)];
- }
+ e->key = key;
+ e->scores[WHITE] = evaluate(pos, e);
+ e->scores[BLACK] = evaluate(pos, e);
+ e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
+ e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK])
+ | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]));
- return value;
+ return e;
}
-/// PawnEntry::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 PawnEntry::shelter_storm(const Position& pos, Square ksq) {
+Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
+ constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
- Value safety = MaxSafetyBonus;
- Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | rank_bb(ksq));
- Bitboard ourPawns = b & pos.pieces(Us) & ~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);
- Rank rkUs, rkThem;
- File kf = file_of(ksq);
- kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf;
+ Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
+ Value(374) : Value(5);
- for (int f = kf - 1; f <= kf + 1; f++)
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
- // Shelter penalty is higher for the pawn in front of the king
- b = ourPawns & FileBB[f];
- rkUs = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
- safety -= ShelterWeakness[f != kf][rkUs];
-
- // Storm danger is smaller if enemy pawn is blocked
- b = theirPawns & FileBB[f];
- rkThem = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
- safety -= StormDanger[rkThem == rkUs + 1][rkThem];
+ b = ourPawns & file_bb(f);
+ int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
+
+ b = theirPawns & file_bb(f);
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
+
+ int d = std::min(f, ~f);
+ safety += ShelterStrength[d][ourRank];
+ safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3)
+ : UnblockedStorm[d][theirRank];
}
return safety;
}
-/// PawnEntry::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::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
-Score PawnEntry::update_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);
+ int minKingPawnDistance = 0;
- if (relative_rank(Us, ksq) > RANK_4)
- return kingSafety[Us] = SCORE_ZERO;
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
- Value bonus = shelter_storm(pos, ksq);
+ Value bonus = evaluate_shelter(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)))
- bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1)));
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(Us | KING_SIDE))
+ bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
- bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1)));
+ if (pos.can_castle(Us | QUEEN_SIDE))
+ bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_C1)));
- return kingSafety[Us] = make_score(bonus, 0);
+ return make_score(bonus, -16 * minKingPawnDistance);
}
// Explicit template instantiation
-template Score PawnEntry::update_safety(const Position& pos, Square ksq);
-template Score PawnEntry::update_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