X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=c8c2e6d8c243db77d67b30afd109dfd2ea1fff4f;hp=e3201081635be80e9aaa5a3520b13ff90cf3d21e;hb=471f7a1b5c4da03a712da2ce079034de45b4c35b;hpb=efeb37c33f15a903dbe5706529a7a26511e9ca58
diff --git a/src/pawns.cpp b/src/pawns.cpp
index e3201081..fb91afcb 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) 2015-2017 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
@@ -17,222 +18,284 @@
along with this program. If not, see .
*/
-
-////
-//// Includes
-////
-
+#include
#include
-#include
-#include "bitcount.h"
+#include "bitboard.h"
#include "pawns.h"
#include "position.h"
+#include "thread.h"
+
+namespace {
+ #define V Value
+ #define S(mg, eg) make_score(mg, eg)
-////
-//// Local definitions
-////
+ // Isolated pawn penalty by opposed flag
+ const Score Isolated[2] = { S(45, 40), S(30, 27) };
-namespace {
+ // Backward pawn penalty by opposed flag
+ const Score Backward[2] = { S(56, 33), S(41, 19) };
- /// Constants and variables
+ // Unsupported pawn penalty for pawns which are neither isolated or backward
+ const Score Unsupported = S(17, 8);
- #define S(mg, eg) make_score(mg, eg)
+ // Connected pawn bonus by opposed, phalanx, twice supported and rank
+ Score Connected[2][2][2][RANK_NB];
+
+ // Doubled pawn penalty
+ const Score Doubled = S(18, 38);
- // 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)
+ // Lever bonus by rank
+ const Score Lever[RANK_NB] = {
+ S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
+ S(17, 16), S(33, 32), S(0, 0), S(0, 0)
};
- // 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)
+ // Weakness of our pawn shelter in front of the king by [distance from edge][rank].
+ // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
+ const Value ShelterWeakness[][RANK_NB] = {
+ { V(100), V(20), V(10), V(46), V(82), V( 86), V( 98) },
+ { V(116), V( 4), V(28), V(87), V(94), V(108), V(104) },
+ { V(109), V( 1), V(59), V(87), V(62), V( 91), V(116) },
+ { V( 75), V(12), V(43), V(59), V(90), V( 84), V(112) }
};
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
+ // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has no pawn
+ // on the given file, or their pawn is behind our king.
+ const Value StormDanger[][4][RANK_NB] = {
+ { { V( 0), V(-290), V(-274), V(57), V(41) }, //BlockedByKing
+ { V( 0), V( 60), V( 144), V(39), V(13) },
+ { V( 0), V( 65), V( 141), V(41), V(34) },
+ { V( 0), V( 53), V( 127), V(56), V(14) } },
+ { { V( 4), V( 73), V( 132), V(46), V(31) }, //Unopposed
+ { V( 1), V( 64), V( 143), V(26), V(13) },
+ { V( 1), V( 47), V( 110), V(44), V(24) },
+ { V( 0), V( 72), V( 127), V(50), V(31) } },
+ { { V( 0), V( 0), V( 79), V(23), V( 1) }, //BlockedByPawn
+ { V( 0), V( 0), V( 148), V(27), V( 2) },
+ { V( 0), V( 0), V( 161), V(16), V( 1) },
+ { V( 0), V( 0), V( 171), V(22), V(15) } },
+ { { V(22), V( 45), V( 104), V(62), V( 6) }, //Unblocked
+ { V(31), V( 30), V( 99), V(39), V(19) },
+ { V(23), V( 29), V( 96), V(41), V(15) },
+ { V(21), V( 23), V( 116), V(41), V(15) } }
+ };
+
+ // Max bonus for king safety. Corresponds to start position with all the pawns
+ // in front of the king and no enemy pawn on the horizon.
+ const Value MaxSafetyBonus = V(258);
+
#undef S
-}
+ #undef V
+
+ template
+ Score evaluate(const Position& pos, Pawns::Entry* e) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? NORTH : SOUTH);
+ const Square Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
+ const Square Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
+
+ Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+ Bitboard lever, leverPush, connected;
+ Square s;
+ bool opposed, backward;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares(Us);
+ const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
+
+ Bitboard ourPawns = pos.pieces(Us , PAWN);
+ Bitboard theirPawns = pos.pieces(Them, PAWN);
+
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
+ e->semiopenFiles[Us] = 0xFF;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = shift(ourPawns) | shift(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_bb(Us, s);
+ stoppers = theirPawns & passed_pawn_mask(Us, s);
+ lever = theirPawns & pawnAttacksBB[s];
+ leverPush = theirPawns & pawnAttacksBB[s + Up];
+ doubled = ourPawns & (s + Up);
+ neighbours = ourPawns & adjacent_files_bb(f);
+ phalanx = neighbours & rank_bb(s);
+ supported = neighbours & rank_bb(s - Up);
+ connected = supported | phalanx;
+
+ // A pawn is backward when it is behind all pawns of the same color on the
+ // adjacent files and cannot be safely advanced.
+ if (!neighbours || lever || relative_rank(Us, s) >= RANK_5)
+ backward = false;
+ else
+ {
+ // Find the backmost rank with neighbours or stoppers
+ b = rank_bb(backmost_sq(Us, neighbours | stoppers));
+
+ // The pawn is backward when it cannot safely progress to that rank:
+ // either there is a stopper in the way on this rank, or there is a
+ // stopper on adjacent file which controls the way to that rank.
+ backward = (b | shift(b & adjacent_files_bb(f))) & stoppers;
+
+ assert(!backward || !(pawn_attack_span(Them, s + Up) & neighbours));
+ }
+
+ // 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_bb(Us, s))
+ && popcount(supported) >= popcount(lever)
+ && popcount(phalanx) >= popcount(leverPush))
+ e->passedPawns[Us] |= s;
+
+ // Score this pawn
+ if (!neighbours)
+ score -= Isolated[opposed];
+
+ else if (backward)
+ score -= Backward[opposed];
+
+ else if (!supported)
+ score -= Unsupported;
+
+ if (connected)
+ score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
+
+ if (doubled)
+ score -= Doubled;
+
+ if (lever)
+ score += Lever[relative_rank(Us, s)];
+ }
+
+ return score;
+ }
+} // namespace
-////
-//// Functions
-////
+namespace Pawns {
-/// PawnInfoTable c'tor and d'tor instantiated one each thread
+/// 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() {
+void init() {
- entries = new PawnInfo[PawnTableSize];
+ static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 };
- if (!entries)
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (int apex = 0; apex <= 1; ++apex)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
{
- std::cerr << "Failed to allocate " << (PawnTableSize * sizeof(PawnInfo))
- << " bytes for pawn hash table." << std::endl;
- exit(EXIT_FAILURE);
+ int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+ v += (apex ? v / 2 : 0);
+ Connected[opposed][phalanx][apex][r] = make_score(v, v * (r-2) / 4);
}
- memset(entries, 0, PawnTableSize * sizeof(PawnInfo));
}
-PawnInfoTable::~PawnInfoTable() {
+/// 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.
- delete [] entries;
-}
+Entry* probe(const Position& pos) {
+
+ Key key = pos.pawn_key();
+ Entry* e = pos.this_thread()->pawnsTable[key];
+ if (e->key == key)
+ return e;
+
+ e->key = key;
+ e->score = evaluate(pos, e) - evaluate(pos, e);
+ e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+ e->openFiles = popcount(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) const {
+/// Entry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two closest files.
- assert(pos.is_ok());
+template
+Value Entry::shelter_storm(const Position& pos, Square ksq) {
- Key key = pos.get_pawn_key();
- unsigned index = unsigned(key & (PawnTableSize - 1));
- PawnInfo* pi = entries + index;
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
- // 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;
+ enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked };
- // Clear the PawnInfo object, and set the key
- memset(pi, 0, sizeof(PawnInfo));
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
- pi->key = key;
+ Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Value safety = MaxSafetyBonus;
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- // 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);
+ for (File f = center - File(1); f <= center + File(1); ++f)
+ {
+ b = ourPawns & file_bb(f);
+ Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+
+ b = theirPawns & file_bb(f);
+ Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+
+ safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+ + StormDanger
+ [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
+ rkUs == RANK_1 ? Unopposed :
+ rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
+ [std::min(f, FILE_H - f)][rkThem];
+ }
- // Evaluate pawns for both colors
- pi->value = evaluate_pawns(pos, wPawns, bPawns, pi)
- - evaluate_pawns(pos, bPawns, wPawns, pi);
- return pi;
+ return safety;
}
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+/// 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 PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
- Bitboard theirPawns, PawnInfo* pi) const {
- Bitboard b;
- Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- Score value = SCORE_ZERO;
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
- const Square* ptr = pos.piece_list_begin(Us, PAWN);
-
- // Loop through all pawns of the current color and score each pawn
- while ((s = *ptr++) != SQ_NONE)
- {
- assert(pos.piece_on(s) == piece_of_color_and_type(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));
-
- // 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 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 & attack_span_mask(opposite_color(Us), s))
- && !(pos.attacks_from(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(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(passed | opposed | (attack_span_mask(Us, s) & theirPawns));
-
- // Test for candidate passed pawn
- candidate = !(opposed | passed)
- && (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
- && count_1s(b) >= count_1s(attack_span_mask(Us, s) & theirPawns);
-
- // Mark the pawn as passed. Pawn 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)];
- }
- return value;
+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 = shelter_storm(pos, ksq);
+
+ // If we can castle use the bonus after the castling if it is bigger
+ if (pos.can_castle(MakeCastling::right))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(MakeCastling::right))
+ bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1)));
+
+ return make_score(bonus, -16 * minKingPawnDistance);
}
+
+// Explicit template instantiation
+template Score Entry::do_king_safety(const Position& pos, Square ksq);
+template Score Entry::do_king_safety(const Position& pos, Square ksq);
+
+} // namespace Pawns