+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2016 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/>.
-*/
-
-#include <algorithm>
-#include <cassert>
-
-#include "bitboard.h"
-#include "pawns.h"
-#include "position.h"
-#include "thread.h"
-
-namespace {
-
- #define V Value
- #define S(mg, eg) make_score(mg, eg)
-
- // Isolated pawn penalty by opposed flag
- const Score Isolated[2] = { S(45, 40), S(30, 27) };
-
- // Backward pawn penalty by opposed flag
- const Score Backward[2] = { S(56, 33), S(41, 19) };
-
- // Unsupported pawn penalty for pawns which are neither isolated or backward,
- // by number of pawns it supports [less than 2 / exactly 2].
- const Score Unsupported[2] = { S(17, 8), S(21, 12) };
-
- // 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);
-
- // 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) };
-
- // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
- const Value ShelterWeakness[][RANK_NB] = {
- { V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
- { V(120), V( 0), V(28), V(76), V(88), V(103), V(104) },
- { V(101), V( 7), V(54), V(78), V(77), V( 92), V(101) },
- { V( 80), V(11), V(44), V(68), V(87), V( 90), V(119) } };
-
- // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
- const Value StormDanger[][4][RANK_NB] = {
- { { V( 0), V( 67), V( 134), V(38), V(32) },
- { V( 0), V( 57), V( 139), V(37), V(22) },
- { V( 0), V( 43), V( 115), V(43), V(27) },
- { V( 0), V( 68), V( 124), V(57), V(32) } },
- { { V(20), V( 43), V( 100), V(56), V(20) },
- { V(23), V( 20), V( 98), V(40), V(15) },
- { V(23), V( 39), V( 103), V(36), V(18) },
- { V(28), V( 19), V( 108), V(42), V(26) } },
- { { V( 0), V( 0), V( 75), V(14), V( 2) },
- { V( 0), V( 0), V( 150), V(30), V( 4) },
- { V( 0), V( 0), V( 160), V(22), V( 5) },
- { V( 0), V( 0), V( 166), V(24), V(13) } },
- { { V( 0), V(-283), V(-281), V(57), V(31) },
- { V( 0), V( 58), V( 141), V(39), V(18) },
- { V( 0), V( 65), V( 142), V(48), V(32) },
- { V( 0), V( 60), V( 126), V(51), V(19) } } };
-
- // 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<Color Us>
- Score evaluate(const Position& pos, Pawns::Entry* e) {
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
- const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
- const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
-
- Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
- Square s;
- bool opposed, lever, connected, backward;
- Score score = SCORE_ZERO;
- const Square* pl = pos.squares<PAWN>(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->kingSquares[Us] = SQ_NONE;
- e->semiopenFiles[Us] = 0xFF;
- e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
- e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
- e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(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];
- 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_bb<Up>(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.
- if (!stoppers && !(ourPawns & forward_bb(Us, s)))
- e->passedPawns[Us] |= s;
-
- // Score this pawn
- if (!neighbours)
- score -= Isolated[opposed];
-
- else if (backward)
- score -= Backward[opposed];
-
- else if (!supported)
- score -= Unsupported[more_than_one(neighbours & pawnAttacksBB[s])];
-
- 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)];
- }
-
- b = e->semiopenFiles[Us] ^ 0xFF;
- e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
-
- return score;
- }
-
-} // namespace
-
-namespace Pawns {
-
-/// 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.
-
-void init()
-{
- static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 };
-
- 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)
- {
- 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 * 5 / 8);
- }
-}
-
-
-/// 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.
-
-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<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
- e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
- return e;
-}
-
-
-/// Entry::shelter_storm() calculates shelter and storm penalties for the file
-/// the king is on, as well as the two adjacent files.
-
-template<Color Us>
-Value Entry::shelter_storm(const Position& pos, Square ksq) {
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
-
- enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
-
- 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)));
-
- 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 ? NoFriendlyPawn :
- rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
- [std::min(f, FILE_H - f)][rkThem];
- }
-
- 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.
-
-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 = shelter_storm<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, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
-
- if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
- bonus = std::max(bonus, shelter_storm<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