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https://github.com/sockspls/badfish
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2ed3358faf
In this form it is even more evident we have some issue there to be fixed sooner then later.... No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
358 lines
12 KiB
C++
358 lines
12 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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////
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//// Includes
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////
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#include <cassert>
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#include <cstring>
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#include "bitcount.h"
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#include "pawns.h"
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#include "position.h"
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////
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//// Local definitions
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////
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namespace {
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/// Constants and variables
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#define S(mg, eg) make_score(mg, eg)
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// Doubled pawn penalty by file
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const Score DoubledPawnPenalty[8] = {
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S(13, 43), S(20, 48), S(23, 48), S(23, 48),
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S(23, 48), S(23, 48), S(20, 48), S(13, 43)
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};
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// Isolated pawn penalty by file
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const Score IsolatedPawnPenalty[8] = {
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S(25, 30), S(36, 35), S(40, 35), S(40, 35),
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S(40, 35), S(40, 35), S(36, 35), S(25, 30)
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};
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// Backward pawn penalty by file
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const Score BackwardPawnPenalty[8] = {
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S(20, 28), S(29, 31), S(33, 31), S(33, 31),
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S(33, 31), S(33, 31), S(29, 31), S(20, 28)
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};
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// Pawn chain membership bonus by file
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const Score ChainBonus[8] = {
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S(11,-1), S(13,-1), S(13,-1), S(14,-1),
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S(14,-1), S(13,-1), S(13,-1), S(11,-1)
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};
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// Candidate passed pawn bonus by rank
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const Score CandidateBonus[8] = {
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S( 0, 0), S( 6, 13), S(6,13), S(14,29),
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S(34,68), S(83,166), S(0, 0), S( 0, 0)
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};
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// Pawn storm tables for positions with opposite castling
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const int QStormTable[64] = {
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0, 0, 0, 0, 0, 0, 0, 0,
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-22,-22,-22,-14,-6, 0, 0, 0,
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-6,-10,-10,-10,-6, 0, 0, 0,
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4, 12, 16, 12, 4, 0, 0, 0,
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16, 23, 23, 16, 0, 0, 0, 0,
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23, 31, 31, 23, 0, 0, 0, 0,
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23, 31, 31, 23, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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const int KStormTable[64] = {
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0,-10,-19,-28,-33,-33,
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0, 0, 0,-10,-15,-19,-24,-24,
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0, 0, 0, 0, 1, 1, 1, 1,
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0, 0, 0, 0, 1, 10, 19, 19,
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0, 0, 0, 0, 1, 19, 31, 27,
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0, 0, 0, 0, 0, 22, 31, 22,
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0, 0, 0, 0, 0, 0, 0, 0
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};
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// Pawn storm open file bonuses by file
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const int16_t KStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 };
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const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 };
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// Pawn storm lever bonuses by file
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const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 };
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}
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////
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//// Functions
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////
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/// Constructor
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PawnInfoTable::PawnInfoTable(unsigned numOfEntries) {
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size = numOfEntries;
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entries = new PawnInfo[size];
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if (!entries)
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{
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std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo))
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<< " bytes for pawn hash table." << std::endl;
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Application::exit_with_failure();
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}
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}
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/// Destructor
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PawnInfoTable::~PawnInfoTable() {
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delete [] entries;
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}
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/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that
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/// kingSquares[] is initialized to SQ_NONE instead.
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void PawnInfo::clear() {
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memset(this, 0, sizeof(PawnInfo));
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kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE;
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}
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/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
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/// a PawnInfo object, and returns a pointer to it. The result is also
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/// stored in a hash table, so we don't have to recompute everything when
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/// the same pawn structure occurs again.
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PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) {
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assert(pos.is_ok());
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Key key = pos.get_pawn_key();
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int index = int(key & (size - 1));
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PawnInfo* pi = entries + index;
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// If pi->key matches the position's pawn hash key, it means that we
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// have analysed this pawn structure before, and we can simply return
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// the information we found the last time instead of recomputing it.
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if (pi->key == key)
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return pi;
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// Clear the PawnInfo object, and set the key
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pi->clear();
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pi->key = key;
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// Calculate pawn attacks
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Bitboard whitePawns = pos.pieces(PAWN, WHITE);
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Bitboard blackPawns = pos.pieces(PAWN, BLACK);
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pi->pawnAttacks[WHITE] = ((whitePawns << 9) & ~FileABB) | ((whitePawns << 7) & ~FileHBB);
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pi->pawnAttacks[BLACK] = ((blackPawns >> 7) & ~FileABB) | ((blackPawns >> 9) & ~FileHBB);
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// Evaluate pawns for both colors
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pi->value = evaluate_pawns<WHITE>(pos, whitePawns, blackPawns, pi)
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- evaluate_pawns<BLACK>(pos, blackPawns, whitePawns, pi);
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return pi;
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}
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/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
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template<Color Us>
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Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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Bitboard theirPawns, PawnInfo* pi) {
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Square s;
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File f;
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Rank r;
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bool passed, isolated, doubled, chain, backward, candidate;
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int bonus;
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Score value = make_score(0, 0);
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const Square* ptr = pos.piece_list_begin(Us, PAWN);
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// Initialize pawn storm scores by giving bonuses for open files
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for (f = FILE_A; f <= FILE_H; f++)
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if (!(ourPawns & file_bb(f)))
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{
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pi->ksStormValue[Us] += KStormOpenFileBonus[f];
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pi->qsStormValue[Us] += QStormOpenFileBonus[f];
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pi->halfOpenFiles[Us] |= (1 << f);
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}
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// Loop through all pawns of the current color and score each pawn
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while ((s = *ptr++) != SQ_NONE)
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{
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f = square_file(s);
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r = square_rank(s);
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assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
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// Passed, isolated or doubled pawn?
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passed = Position::pawn_is_passed(theirPawns, Us, s);
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isolated = Position::pawn_is_isolated(ourPawns, s);
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doubled = Position::pawn_is_doubled(ourPawns, Us, s);
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// We calculate kingside and queenside pawn storm
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// scores for both colors. These are used when evaluating
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// middle game positions with opposite side castling.
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//
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// Each pawn is given a base score given by a piece square table
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// (KStormTable[] or QStormTable[]). Pawns which seem to have good
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// chances of creating an open file by exchanging itself against an
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// enemy pawn on an adjacent file gets an additional bonus.
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// Kingside pawn storms
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bonus = KStormTable[relative_square(Us, s)];
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if (f >= FILE_F)
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{
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Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
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while (b)
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{
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// Give a bonus according to the distance of the nearest enemy pawn
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Square s2 = pop_1st_bit(&b);
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int v = StormLeverBonus[f] - 2 * square_distance(s, s2);
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// If enemy pawn has no pawn beside itself is particularly vulnerable.
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// Big bonus, especially against a weakness on the rook file
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if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
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v *= (square_file(s2) == FILE_H ? 4 : 2);
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bonus += v;
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}
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}
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pi->ksStormValue[Us] += bonus;
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// Queenside pawn storms
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bonus = QStormTable[relative_square(Us, s)];
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if (f <= FILE_C)
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{
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Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
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while (b)
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{
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// Give a bonus according to the distance of the nearest enemy pawn
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Square s2 = pop_1st_bit(&b);
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int v = StormLeverBonus[f] - 4 * square_distance(s, s2);
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// If enemy pawn has no pawn beside itself is particularly vulnerable.
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// Big bonus, especially against a weakness on the rook file
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if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
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v *= (square_file(s2) == FILE_A ? 4 : 2);
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bonus += v;
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}
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}
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pi->qsStormValue[Us] += bonus;
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// Member of a pawn chain (but not the backward one)? We could speed up
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// the test a little by introducing an array of masks indexed by color
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// and square for doing the test, but because everything is hashed,
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// it probably won't make any noticable difference.
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chain = ourPawns
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& neighboring_files_bb(f)
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& (rank_bb(r) | rank_bb(r - (Us == WHITE ? 1 : -1)));
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// Test for backward pawn
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//
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// If the pawn is passed, isolated, or member of a pawn chain
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// it cannot be backward. If can capture an enemy pawn or if
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// there are friendly pawns behind on neighboring files it cannot
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// be backward either.
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if ( (passed | isolated | chain)
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|| (ourPawns & behind_bb(Us, r) & neighboring_files_bb(f))
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|| (pos.attacks_from<PAWN>(s, Us) & theirPawns))
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backward = false;
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else
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{
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// We now know that there are no friendly pawns beside or behind this
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// pawn on neighboring files. We now check whether the pawn is
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// backward by looking in the forward direction on the neighboring
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// files, and seeing whether we meet a friendly or an enemy pawn first.
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Bitboard b = pos.attacks_from<PAWN>(s, Us);
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// Note that we are sure to find something because pawn is not passed
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// nor isolated, so loop is potentially infinite, but it isn't.
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while (!(b & (ourPawns | theirPawns)))
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Us == WHITE ? b <<= 8 : b >>= 8;
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// The friendly pawn needs to be at least two ranks closer than the enemy
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// pawn in order to help the potentially backward pawn advance.
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backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
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}
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// Test for candidate passed pawn
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candidate = !passed
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&& !(theirPawns & file_bb(f))
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&& ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(Us, r) | rank_bb(r)) & ourPawns)
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- count_1s_max_15(neighboring_files_bb(f) & in_front_bb(Us, r) & theirPawns)
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>= 0);
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// In order to prevent doubled passed pawns from receiving a too big
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// bonus, only the frontmost passed pawn on each file is considered as
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// a true passed pawn.
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if (passed && (ourPawns & squares_in_front_of(Us, s)))
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passed = false;
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// Score this pawn
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if (passed)
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set_bit(&(pi->passedPawns), s);
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if (isolated)
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{
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value -= IsolatedPawnPenalty[f];
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if (!(theirPawns & file_bb(f)))
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value -= IsolatedPawnPenalty[f] / 2;
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}
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if (doubled)
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value -= DoubledPawnPenalty[f];
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if (backward)
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{
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value -= BackwardPawnPenalty[f];
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if (!(theirPawns & file_bb(f)))
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value -= BackwardPawnPenalty[f] / 2;
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}
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if (chain)
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value += ChainBonus[f];
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if (candidate)
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value += CandidateBonus[relative_rank(Us, s)];
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}
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return value;
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}
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/// PawnInfo::updateShelter calculates and caches king shelter. It is called
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/// only when king square changes, about 20% of total get_king_shelter() calls.
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int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {
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unsigned shelter = 0;
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Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
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unsigned r = ksq & (7 << 3);
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for (int i = 1, k = (c ? -8 : 8); i < 4; i++)
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{
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r += k;
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shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
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}
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kingSquares[c] = ksq;
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kingShelters[c] = shelter;
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return shelter;
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}
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