X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=291d40b6858c8a1e193c42f7debceede349af125;hb=bf6b647a1afd0bfa25ee627622824a3ecb666c5d;hp=df7a0a2d3c507a1215b281b0a2ca6e4e4853c602;hpb=c23cd4d90aa91504a5a3ec3ce896d1e35e34c494;p=stockfish
diff --git a/src/pawns.cpp b/src/pawns.cpp
index df7a0a2d..291d40b6 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) 2008-2010 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
@@ -17,343 +18,232 @@
along with this program. If not, see .
*/
-
-////
-//// Includes
-////
-
+#include
#include
-#include
-#include "bitcount.h"
+#include "bitboard.h"
#include "pawns.h"
#include "position.h"
-
-
-////
-//// Local definitions
-////
+#include "thread.h"
namespace {
- /// Constants and variables
-
+ #define V Value
#define S(mg, eg) make_score(mg, eg)
- // Doubled pawn penalty by file
- const Score DoubledPawnPenalty[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)
+ // Pawn penalties
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+
+ // 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) }
};
- // Isolated pawn penalty by file
- const Score IsolatedPawnPenalty[8] = {
- S(25, 30), S(36, 35), S(40, 35), S(40, 35),
- S(40, 35), S(40, 35), S(36, 35), S(25, 30)
+ // 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) }
};
- // Backward pawn penalty by file
- const Score BackwardPawnPenalty[8] = {
- S(20, 28), S(29, 31), S(33, 31), S(33, 31),
- S(33, 31), S(33, 31), S(29, 31), S(20, 28)
- };
+ #undef S
+ #undef V
+
+ 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, support, 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->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[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));
+
+ File f = file_of(s);
+ Rank r = relative_rank(Us, s);
+
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+
+ // Flag the pawn
+ opposed = theirPawns & forward_file_bb(Us, s);
+ 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(f);
+ phalanx = neighbours & rank_bb(s);
+ support = 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)
+ && (support || !more_than_one(lever))
+ && popcount(phalanx) >= popcount(leverPush))
+ e->passedPawns[Us] |= s;
+
+ else if (stoppers == square_bb(s + Up) && r >= RANK_5)
+ {
+ b = shift(support) & ~theirPawns;
+ while (b)
+ if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+ e->passedPawns[Us] |= s;
+ }
+
+ // Score this pawn
+ if (support | phalanx)
+ {
+ int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1)
+ + 17 * popcount(support);
+
+ score += make_score(v, v * (r - 2) / 4);
+ }
+ else if (!neighbours)
+ score -= Isolated, e->weakUnopposed[Us] += !opposed;
+
+ else if (backward)
+ score -= Backward, e->weakUnopposed[Us] += !opposed;
+
+ if (doubled && !support)
+ score -= Doubled;
+ }
+
+ return score;
+ }
- // 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)
- };
+} // namespace
- // 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)
- };
+namespace Pawns {
- // Pawn storm tables for positions with opposite castling
- const int QStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- -22,-22,-22,-14,-6, 0, 0, 0,
- -6,-10,-10,-10,-6, 0, 0, 0,
- 4, 12, 16, 12, 4, 0, 0, 0,
- 16, 23, 23, 16, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 23, 31, 31, 23, 0, 0, 0, 0,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+/// 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.
- const int KStormTable[64] = {
- 0, 0, 0, 0, 0, 0, 0, 0,
- 0, 0, 0,-10,-19,-28,-33,-33,
- 0, 0, 0,-10,-15,-19,-24,-24,
- 0, 0, 0, 0, 1, 1, 1, 1,
- 0, 0, 0, 0, 1, 10, 19, 19,
- 0, 0, 0, 0, 1, 19, 31, 27,
- 0, 0, 0, 0, 0, 22, 31, 22,
- 0, 0, 0, 0, 0, 0, 0, 0
- };
+Entry* probe(const Position& pos) {
- // Pawn storm open file bonuses by file
- const int16_t KStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 };
- const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 };
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
- // Pawn storm lever bonuses by file
- const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 };
+ if (e->key == key)
+ return e;
-}
+ e->key = key;
+ e->scores[WHITE] = evaluate(pos, e);
+ e->scores[BLACK] = evaluate(pos, e);
+ return e;
+}
-////
-//// Functions
-////
-/// Constructor
+/// Entry::evaluate_shelter() calculates the shelter bonus and the storm
+/// penalty for a king, looking at the king file and the two closest files.
-PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
+template
+void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
- size = numOfEntries;
- entries = new PawnInfo[size];
- if (!entries)
- {
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- Application::exit_with_failure();
- }
-}
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
+ constexpr Bitboard BlockSquares = (Rank1BB | Rank2BB | Rank7BB | Rank8BB)
+ & (FileABB | FileHBB);
+ Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
-/// Destructor
+ Value bonus[] = { (shift(theirPawns) & BlockSquares & ksq) ? Value(374) : Value(5),
+ VALUE_ZERO };
-PawnInfoTable::~PawnInfoTable() {
- delete [] entries;
-}
+ File center = 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 ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+ b = theirPawns & file_bb(f);
+ Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
-/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that
-/// kingSquares[] is initialized to SQ_NONE instead.
+ int d = std::min(f, ~f);
+ bonus[MG] += ShelterStrength[d][ourRank];
-void PawnInfo::clear() {
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus[MG] -= 82 * (theirRank == RANK_3), bonus[EG] -= 82 * (theirRank == RANK_3);
+ else
+ bonus[MG] -= UnblockedStorm[d][theirRank];
+ }
- memset(this, 0, sizeof(PawnInfo));
- kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE;
+ if (bonus[MG] > mg_value(shelter))
+ shelter = make_score(bonus[MG], bonus[EG]);
}
-/// 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.
+/// 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.
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) {
-
- assert(pos.is_ok());
-
- Key key = pos.get_pawn_key();
- int index = int(key & (size - 1));
- PawnInfo* pi = entries + index;
+template
+Score Entry::do_king_safety(const Position& pos) {
- // 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;
+ Square ksq = pos.square(Us);
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.castling_rights(Us);
- // Clear the PawnInfo object, and set the key
- pi->clear();
- pi->key = key;
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = pawns ? 8 : 0;
- // Calculate pawn attacks
- Bitboard whitePawns = pos.pieces(PAWN, WHITE);
- Bitboard blackPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((whitePawns << 9) & ~FileABB) | ((whitePawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((blackPawns >> 7) & ~FileABB) | ((blackPawns >> 9) & ~FileHBB);
+ if (pawns & PseudoAttacks[KING][ksq])
+ minPawnDist = 1;
- // Evaluate pawns for both colors
- pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi)
- - evaluate_pawns(pos, blackPawns, whitePawns, pi);
- return pi;
-}
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
+ Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO);
+ evaluate_shelter(pos, ksq, shelter);
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(Us | KING_SIDE))
+ evaluate_shelter(pos, relative_square(Us, SQ_G1), shelter);
-template
-Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) {
- Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- int bonus;
- Score value = make_score(0, 0);
- const Square* ptr = pos.piece_list_begin(Us, PAWN);
-
- // Initialize pawn storm scores by giving bonuses for open files
- for (f = FILE_A; f <= FILE_H; f++)
- if (!(ourPawns & file_bb(f)))
- {
- pi->ksStormValue[Us] += KStormOpenFileBonus[f];
- pi->qsStormValue[Us] += QStormOpenFileBonus[f];
- pi->halfOpenFiles[Us] |= (1 << f);
- }
-
- // Loop through all pawns of the current color and score each pawn
- while ((s = *ptr++) != SQ_NONE)
- {
- f = square_file(s);
- r = square_rank(s);
-
- assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
-
- // Passed, isolated or doubled pawn?
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- isolated = !(ourPawns & neighboring_files_bb(s));
- doubled = ourPawns & squares_behind(Us, s);
- opposed = theirPawns & squares_in_front_of(Us, s);
-
- // 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[]). Pawns which seem to have good
- // chances of creating an open file by exchanging itself against an
- // enemy pawn on an adjacent file gets an additional bonus.
-
- // Kingside pawn storms
- bonus = KStormTable[relative_square(Us, s)];
- if (f >= FILE_F)
- {
- Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
- while (b)
- {
- // Give a bonus according to the distance of the nearest enemy pawn
- Square s2 = pop_1st_bit(&b);
- int v = StormLeverBonus[f] - 2 * square_distance(s, s2);
-
- // If enemy pawn has no pawn beside itself is particularly vulnerable.
- // Big bonus, especially against a weakness on the rook file
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- v *= (square_file(s2) == FILE_H ? 4 : 2);
-
- bonus += v;
- }
- }
- pi->ksStormValue[Us] += bonus;
-
- // Queenside pawn storms
- bonus = QStormTable[relative_square(Us, s)];
- if (f <= FILE_C)
- {
- Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
- while (b)
- {
- // Give a bonus according to the distance of the nearest enemy pawn
- Square s2 = pop_1st_bit(&b);
- int v = StormLeverBonus[f] - 4 * square_distance(s, s2);
-
- // If enemy pawn has no pawn beside itself is particularly vulnerable.
- // Big bonus, especially against a weakness on the rook file
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- v *= (square_file(s2) == FILE_A ? 4 : 2);
-
- bonus += v;
- }
- }
- pi->qsStormValue[Us] += bonus;
-
- // 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)
- || (ourPawns & behind_bb(Us, r) & neighboring_files_bb(f))
- || (pos.attacks_from(s, Us) & theirPawns))
- 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 = 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;
- }
-
- // Test for candidate passed pawn
- candidate = !passed
- && !opposed
- && ( 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)))
- passed = false;
-
- // Score this pawn
- if (passed)
- set_bit(&(pi->passedPawns), s);
-
- if (isolated)
- {
- value -= IsolatedPawnPenalty[f];
- if (!(theirPawns & file_bb(f)))
- value -= IsolatedPawnPenalty[f] / 2;
- }
- if (doubled)
- value -= DoubledPawnPenalty[f];
-
- if (backward)
- {
- value -= BackwardPawnPenalty[f];
- if (!(theirPawns & file_bb(f)))
- value -= BackwardPawnPenalty[f] / 2;
- }
- if (chain)
- value += ChainBonus[f];
-
- if (candidate)
- value += CandidateBonus[relative_rank(Us, s)];
- }
+ if (pos.can_castle(Us | QUEEN_SIDE))
+ evaluate_shelter(pos, relative_square(Us, SQ_C1), shelter);
- return value;
+ return shelter - make_score(VALUE_ZERO, 16 * minPawnDist);
}
+// Explicit template instantiation
+template Score Entry::do_king_safety(const Position& pos);
+template Score Entry::do_king_safety(const Position& pos);
-/// PawnInfo::updateShelter calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total get_king_shelter() calls.
-int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {
-
- unsigned shelter = 0;
- Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
- unsigned r = ksq & (7 << 3);
- for (int i = 1, k = (c ? -8 : 8); i < 4; i++)
- {
- r += k;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
- }
- kingSquares[c] = ksq;
- kingShelters[c] = shelter;
- return shelter;
-}
+} // namespace Pawns