/*
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) 2015-2018 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 <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
+#include <algorithm>
#include <cassert>
-#include <cstring>
+#include "bitboard.h"
#include "pawns.h"
+#include "position.h"
+#include "thread.h"
+namespace {
-////
-//// Local definitions
-////
+ #define V Value
+ #define S(mg, eg) make_score(mg, eg)
-namespace {
+ // Isolated pawn penalty
+ constexpr Score Isolated = S(13, 16);
- /// Constants and variables
+ // Backward pawn penalty
+ constexpr Score Backward = S(17, 11);
- // 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)
- };
+ // Connected pawn bonus by opposed, phalanx, #support and rank
+ Score Connected[2][2][3][RANK_NB];
- // 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)
- };
+ // Doubled pawn penalty
+ constexpr Score Doubled = S(13, 40);
- // 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)
+ // 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( 7), V(76), V(84), V( 38), V( 7), V( 30), V(-19) },
+ { V(-3), V(93), V(52), V(-17), V(12), V(-22), V(-35) },
+ { V(-6), V(83), V(25), V(-24), V(15), V( 22), V(-39) },
+ { V(11), V(83), V(19), V( 8), V(18), V(-21), V(-30) }
};
- // 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)
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
+ // For the unblocked case, RANK_1 = 0 is used when opponent has no pawn on the
+ // given file, or their pawn is behind our king.
+ constexpr Value StormDanger[][4][RANK_NB] = {
+ { { V(25), V( 79), V(107), V( 51), V( 27) }, // UnBlocked
+ { V(15), V( 45), V(131), V( 8), V( 25) },
+ { V( 0), V( 42), V(118), V( 56), V( 27) },
+ { V( 3), V( 54), V(110), V( 55), V( 26) } },
+ { { V( 0), V( 0), V( 37), V( 5), V(-48) }, // BlockedByPawn
+ { V( 0), V( 0), V( 68), V(-12), V( 13) },
+ { V( 0), V( 0), V(111), V(-25), V( -3) },
+ { V( 0), V( 0), V(108), V( 14), V( 21) } }
};
- // 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)
- };
+ #undef S
+ #undef V
- // 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)
- };
+ template<Color Us>
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
- // 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)
- };
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- // 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 b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard lever, leverPush;
+ Square s;
+ bool opposed, backward;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares<PAWN>(Us);
- // 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)
- };
+ Bitboard ourPawns = pos.pieces( Us, PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
- // 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)
- };
+ 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<Us>(ourPawns);
+ e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
+ e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
- // 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
- };
+ // 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)
+ && !(ourPawns & forward_file_bb(Us, s))
+ && 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<Up>(supported) & ~theirPawns;
+ while (b)
+ if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
+ e->passedPawns[Us] |= s;
+ }
- // Pawn storm open file bonuses by file:
- const int KStormOpenFileBonus[8] = {
- 45, 45, 30, 0, 0, 0, 0, 0
- };
+ // Score this pawn
+ if (supported | phalanx)
+ score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
- const int QStormOpenFileBonus[8] = {
- 0, 0, 0, 0, 0, 30, 45, 30
- };
+ 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;
+ }
+
+} // namespace
-////
-//// Functions
-////
+namespace Pawns {
-/// Constructor
+/// 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.
-PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
+void init() {
- size = numOfEntries;
- entries = new PawnInfo[size];
- if (entries == NULL)
+ static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
+
+ 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)
{
- std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- exit(EXIT_FAILURE);
+ int v = 17 * support;
+ v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+
+ Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
}
- clear();
}
-/// Destructor
+/// 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.
-PawnInfoTable::~PawnInfoTable() {
- delete [] entries;
-}
+Entry* probe(const Position& pos) {
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
-/// PawnInfoTable::clear() clears the pawn hash table by setting all
-/// entries to 0.
+ if (e->key == key)
+ return e;
-void PawnInfoTable::clear() {
- memset(entries, 0, size * sizeof(PawnInfo));
-}
+ e->key = key;
+ e->scores[WHITE] = evaluate<WHITE>(pos, e);
+ e->scores[BLACK] = evaluate<BLACK>(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 e;
+}
-/// 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.
-PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) {
+/// Entry::evaluate_shelter() calculates the shelter bonus and the storm
+/// penalty for a king, looking at the king file and the two closest files.
- assert(pos.is_ok());
+template<Color Us>
+Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
- Key key = pos.get_pawn_key();
- int index = int(key & (size - 1));
- PawnInfo *pi = entries + index;
+ enum { UnBlocked, BlockedByPawn };
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+ constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
+ constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
- // 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;
+ Bitboard b = pos.pieces(PAWN) & (forward_ranks_bb(Us, ksq) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
- // Clear the PawnInfo object, and set the key
- pi->clear();
- pi->key = key;
+ Value safety = (ourPawns & file_bb(ksq)) ? Value(5) : Value(-5);
- Value mgValue[2] = {Value(0), Value(0)};
- Value egValue[2] = {Value(0), Value(0)};
+ if (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq)
+ safety += Value(374);
- // Loop through the pawns for both colors
- for (Color us = WHITE; us <= BLACK; us++)
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ for (File f = File(center - 1); f <= File(center + 1); ++f)
{
- 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
- 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];
- }
+ b = ourPawns & file_bb(f);
+ int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
- // 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);
-
- assert(pos.piece_on(s) == pawn_of_color(us));
-
- // The file containing the pawn is not half open
- pi->halfOpenFiles[us] &= ~(1 << f);
-
- // 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);
-
- // 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
- int KBonus = KStormTable[relative_square(us, s)];
- int QBonus = QStormTable[relative_square(us, s)];
- bool outPostFlag = (KBonus > 0 && (outpost_mask(us, s) & theirPawns));
- bool passedFlag = (QBonus > 0 && (passed_pawn_mask(us, s) & theirPawns));
-
- switch (f) {
-
- case FILE_A:
- QBonus += passedFlag * QBonus / 2;
- break;
-
- case FILE_B:
- QBonus += passedFlag * (QBonus / 2 + QBonus / 4);
- break;
-
- case FILE_C:
- QBonus += passedFlag * QBonus / 2;
- break;
-
- case FILE_F:
- KBonus += outPostFlag * KBonus / 4;
- break;
-
- case FILE_G:
- KBonus += outPostFlag * (KBonus / 2 + KBonus / 4);
- break;
-
- case FILE_H:
- KBonus += outPostFlag * KBonus / 2;
- break;
-
- default:
- break;
- }
- pi->ksStormValue[us] += KBonus;
- pi->qsStormValue[us] += QBonus;
-
- // 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;
- }
- }
+ b = theirPawns & file_bb(f);
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- // 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;
- }
+ int d = std::min(f, ~f);
- // 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)];
- }
+ safety += ShelterStrength[d][ourRank];
+ if (ourRank || theirRank)
+ safety -= StormDanger[ourRank && (ourRank == theirRank - 1) ? BlockedByPawn : UnBlocked][d][theirRank];
+ }
+
+ return safety;
+}
+
+
+/// 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.
- 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)
-
- pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]);
- pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]);
- return pi;
+template<Color Us>
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
+
+ kingSquares[Us] = ksq;
+ castlingRights[Us] = pos.can_castle(Us);
+ int minKingPawnDistance = 0;
+
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
+
+ Value bonus = evaluate_shelter<Us>(pos, ksq);
+
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
+ bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
+ bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
+
+ return make_score(bonus, -16 * minKingPawnDistance);
}
+
+// Explicit template instantiation
+template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
+
+} // namespace Pawns
projects / stockfish / blobdiff