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https://github.com/sockspls/badfish
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52eac1e535
Also inline defintions of SpaceMask and CenterBindMask. Verified from assembly that compiler computes the values at compile time, so it is also theoretical faster. While there factor out scale factor evaluation. No functional change.
318 lines
12 KiB
C++
318 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) 2008-2015 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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#include <algorithm>
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#include <cassert>
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#include "bitboard.h"
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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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#include "thread.h"
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namespace {
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#define V Value
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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 Doubled[FILE_NB] = {
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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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// Isolated pawn penalty by opposed flag and file
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const Score Isolated[2][FILE_NB] = {
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{ S(37, 45), S(54, 52), S(60, 52), S(60, 52),
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S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
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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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// Backward pawn penalty by opposed flag
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const Score Backward[2] = { S(67, 42), S(49, 24) };
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// Connected pawn bonus by opposed, phalanx, twice supported and rank
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Score Connected[2][2][2][RANK_NB];
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// Levers bonus by rank
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const Score Lever[RANK_NB] = {
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S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
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S(20,20), S(40,40), S(0, 0), S(0, 0) };
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// Unsupported pawn penalty
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const Score UnsupportedPawnPenalty = S(20, 10);
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const Score CenterBind = S(16, 0);
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// Weakness of our pawn shelter in front of the king by [distance from edge][rank]
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const Value ShelterWeakness[][RANK_NB] = {
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{ V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
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{ V(120), V( 0), V(28), V(76), V(88), V(103), V(104) },
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{ V(101), V( 7), V(54), V(78), V(77), V( 92), V(101) },
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{ V( 80), V(11), V(44), V(68), V(87), V( 90), V(119) } };
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// Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
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const Value StormDanger[][4][RANK_NB] = {
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{ { V( 0), V( 67), V( 134), V(38), V(32) },
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{ V( 0), V( 57), V( 139), V(37), V(22) },
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{ V( 0), V( 43), V( 115), V(43), V(27) },
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{ V( 0), V( 68), V( 124), V(57), V(32) } },
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{ { V(20), V( 43), V( 100), V(56), V(20) },
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{ V(23), V( 20), V( 98), V(40), V(15) },
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{ V(23), V( 39), V( 103), V(36), V(18) },
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{ V(28), V( 19), V( 108), V(42), V(26) } },
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{ { V( 0), V( 0), V( 75), V(14), V( 2) },
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{ V( 0), V( 0), V( 150), V(30), V( 4) },
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{ V( 0), V( 0), V( 160), V(22), V( 5) },
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{ V( 0), V( 0), V( 166), V(24), V(13) } },
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{ { V( 0), V(-283), V(-281), V(57), V(31) },
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{ V( 0), V( 58), V( 141), V(39), V(18) },
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{ V( 0), V( 65), V( 142), V(48), V(32) },
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{ V( 0), V( 60), V( 126), V(51), V(19) } } };
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// Max bonus for king safety. Corresponds to start position with all the pawns
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// in front of the king and no enemy pawn on the horizon.
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const Value MaxSafetyBonus = V(258);
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#undef S
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#undef V
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template<Color Us>
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Score evaluate(const Position& pos, Pawns::Entry* e) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
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const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
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const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
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const Bitboard CenterBindMask =
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Us == WHITE ? (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB)
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: (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB);
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Bitboard b, neighbours, doubled, supported, phalanx;
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Square s;
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bool passed, isolated, opposed, backward, lever, connected;
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Score score = SCORE_ZERO;
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const Square* pl = pos.squares<PAWN>(Us);
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const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
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Bitboard ourPawns = pos.pieces(Us , PAWN);
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Bitboard theirPawns = pos.pieces(Them, PAWN);
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e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
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e->kingSquares[Us] = SQ_NONE;
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e->semiopenFiles[Us] = 0xFF;
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e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
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e->pawnsOnSquares[Us][BLACK] = popcount<Max15>(ourPawns & DarkSquares);
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e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
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// Loop through all pawns of the current color and score each pawn
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while ((s = *pl++) != SQ_NONE)
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{
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assert(pos.piece_on(s) == make_piece(Us, PAWN));
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File f = file_of(s);
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e->semiopenFiles[Us] &= ~(1 << f);
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e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
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// Flag the pawn
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neighbours = ourPawns & adjacent_files_bb(f);
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doubled = ourPawns & forward_bb(Us, s);
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opposed = theirPawns & forward_bb(Us, s);
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passed = !(theirPawns & passed_pawn_mask(Us, s));
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lever = theirPawns & pawnAttacksBB[s];
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phalanx = neighbours & rank_bb(s);
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supported = neighbours & rank_bb(s - Up);
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connected = supported | phalanx;
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isolated = !neighbours;
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// Test for backward pawn.
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// If the pawn is passed, isolated, lever or connected it cannot be
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// backward. If there are friendly pawns behind on adjacent files
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// or if it is sufficiently advanced, it cannot be backward either.
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if ( (passed | isolated | lever | connected)
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|| (ourPawns & pawn_attack_span(Them, s))
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|| (relative_rank(Us, s) >= RANK_5))
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backward = false;
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else
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{
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// We now know there are no friendly pawns beside or behind this
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// pawn on adjacent files. We now check whether the pawn is
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// backward by looking in the forward direction on the adjacent
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// files, and picking the closest pawn there.
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b = pawn_attack_span(Us, s) & (ourPawns | theirPawns);
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b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b));
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// If we have an enemy pawn in the same or next rank, the pawn is
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// backward because it cannot advance without being captured.
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backward = (b | shift_bb<Up>(b)) & theirPawns;
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}
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assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
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// Passed pawns will be properly scored in evaluation because we need
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// full attack info to evaluate passed pawns. Only the frontmost passed
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// pawn on each file is considered a true passed pawn.
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if (passed && !doubled)
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e->passedPawns[Us] |= s;
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// Score this pawn
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if (isolated)
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score -= Isolated[opposed][f];
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else if (backward)
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score -= Backward[opposed];
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else if (!supported)
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score -= UnsupportedPawnPenalty;
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if (connected)
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score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
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if (doubled)
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score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
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if (lever)
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score += Lever[relative_rank(Us, s)];
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}
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b = e->semiopenFiles[Us] ^ 0xFF;
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e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
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// Center binds: Two pawns controlling the same central square
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b = shift_bb<Right>(ourPawns) & shift_bb<Left>(ourPawns) & CenterBindMask;
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score += popcount<Max15>(b) * CenterBind;
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return score;
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}
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} // namespace
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namespace Pawns {
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/// Pawns::init() initializes some tables needed by evaluation. Instead of using
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/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
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/// to reduce independent parameters and to allow easier tuning and better insight.
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void init()
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{
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static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
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for (int opposed = 0; opposed <= 1; ++opposed)
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for (int phalanx = 0; phalanx <= 1; ++phalanx)
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for (int apex = 0; apex <= 1; ++apex)
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for (Rank r = RANK_2; r < RANK_8; ++r)
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{
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int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
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v += (apex ? v / 2 : 0);
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Connected[opposed][phalanx][apex][r] = make_score(3 * v / 2, v);
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}
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}
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/// Pawns::probe() looks up the current position's pawns configuration in
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/// the pawns hash table. It returns a pointer to the Entry if the position
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/// is found. Otherwise a new Entry is computed and stored there, so we don't
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/// have to recompute all when the same pawns configuration occurs again.
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Entry* probe(const Position& pos) {
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Key key = pos.pawn_key();
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Entry* e = pos.this_thread()->pawnsTable[key];
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if (e->key == key)
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return e;
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e->key = key;
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e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
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e->asymmetry = popcount<Max15>(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
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return e;
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}
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/// Entry::shelter_storm() calculates shelter and storm penalties for the file
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/// the king is on, as well as the two adjacent files.
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template<Color Us>
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Value Entry::shelter_storm(const Position& pos, Square ksq) {
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
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Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
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Bitboard ourPawns = b & pos.pieces(Us);
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Bitboard theirPawns = b & pos.pieces(Them);
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Value safety = MaxSafetyBonus;
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File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
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for (File f = center - File(1); f <= center + File(1); ++f)
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{
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b = ourPawns & file_bb(f);
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Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
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b = theirPawns & file_bb(f);
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Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
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safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
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+ StormDanger
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[f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
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rkUs == RANK_1 ? NoFriendlyPawn :
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rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
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[std::min(f, FILE_H - f)][rkThem];
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}
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return safety;
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}
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/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
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/// when king square changes, which is about 20% of total king_safety() calls.
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template<Color Us>
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Score Entry::do_king_safety(const Position& pos, Square ksq) {
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kingSquares[Us] = ksq;
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castlingRights[Us] = pos.can_castle(Us);
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int minKingPawnDistance = 0;
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Bitboard pawns = pos.pieces(Us, PAWN);
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if (pawns)
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while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
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if (relative_rank(Us, ksq) > RANK_4)
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return make_score(0, -16 * minKingPawnDistance);
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Value bonus = shelter_storm<Us>(pos, ksq);
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// If we can castle use the bonus after the castling if it is bigger
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if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
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bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
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if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
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bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
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return make_score(bonus, -16 * minKingPawnDistance);
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}
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// Explicit template instantiation
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template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
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template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
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} // namespace Pawns
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