mirror of
https://github.com/sockspls/badfish
synced 2025-05-01 09:13:08 +00:00
281 lines
9.9 KiB
C++
281 lines
9.9 KiB
C++
/*
|
|
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
|
|
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
|
|
Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, 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 "bitcount.h"
|
|
#include "pawns.h"
|
|
#include "position.h"
|
|
|
|
namespace {
|
|
|
|
#define V Value
|
|
#define S(mg, eg) make_score(mg, eg)
|
|
|
|
// Doubled pawn penalty by opposed flag and file
|
|
const Score Doubled[2][FILE_NB] = {
|
|
{ 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 Isolated[2][FILE_NB] = {
|
|
{ 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 Backward[2][FILE_NB] = {
|
|
{ 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 ChainMember[FILE_NB] = {
|
|
S(11,-1), S(13,-1), S(13,-1), S(14,-1),
|
|
S(14,-1), S(13,-1), S(13,-1), S(11,-1)
|
|
};
|
|
|
|
// Candidate passed pawn bonus by rank
|
|
const Score CandidatePassed[RANK_NB] = {
|
|
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 indexed by [rank]
|
|
const Value ShelterWeakness[RANK_NB] =
|
|
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
|
|
|
|
// Danger of enemy pawns moving toward our king indexed by
|
|
// [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
|
|
const Value StormDanger[3][RANK_NB] = {
|
|
{ V( 0), V(64), V(128), V(51), V(26) },
|
|
{ V(26), V(32), V( 96), V(38), V(20) },
|
|
{ V( 0), V( 0), V( 64), V(25), V(13) }};
|
|
|
|
// Max bonus for king safety. Corresponds to start position with all the pawns
|
|
// in front of the king and no enemy pawn on the horizont.
|
|
const Value MaxSafetyBonus = V(263);
|
|
|
|
#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;
|
|
Square s;
|
|
File f;
|
|
Rank r;
|
|
bool passed, isolated, doubled, opposed, chain, backward, candidate;
|
|
Score value = SCORE_ZERO;
|
|
const Square* pl = pos.list<PAWN>(Us);
|
|
|
|
Bitboard ourPawns = pos.pieces(Us, PAWN);
|
|
Bitboard theirPawns = pos.pieces(Them, PAWN);
|
|
|
|
e->passedPawns[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<Max15>(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));
|
|
|
|
f = file_of(s);
|
|
r = rank_of(s);
|
|
|
|
// This file cannot be semi-open
|
|
e->semiopenFiles[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));
|
|
|
|
// Flag the pawn as passed, isolated, doubled or member of a pawn
|
|
// chain (but not the backward one).
|
|
chain = ourPawns & adjacent_files_bb(f) & b;
|
|
isolated = !(ourPawns & adjacent_files_bb(f));
|
|
doubled = ourPawns & forward_bb(Us, s);
|
|
opposed = theirPawns & forward_bb(Us, s);
|
|
passed = !(theirPawns & passed_pawn_mask(Us, s));
|
|
|
|
// Test for backward pawn
|
|
backward = false;
|
|
|
|
// If the pawn is passed, isolated, or member of a pawn chain it cannot
|
|
// be backward. If there are friendly pawns behind on adjacent files
|
|
// or if can capture an enemy pawn it cannot be backward either.
|
|
if ( !(passed | isolated | chain)
|
|
&& !(ourPawns & pawn_attack_span(Them, s))
|
|
&& !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
|
|
{
|
|
// We now know that there are no friendly pawns beside or behind this
|
|
// pawn on adjacent files. We now check whether the pawn is
|
|
// backward by looking in the forward direction on the adjacent
|
|
// files, and seeing whether we meet a friendly or an enemy pawn first.
|
|
b = pos.attacks_from<PAWN>(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)))
|
|
b = shift_bb<Up>(b);
|
|
|
|
// 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 | shift_bb<Up>(b)) & theirPawns;
|
|
}
|
|
|
|
assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
|
|
|
|
// A not passed pawn is a candidate to become passed if it is free to
|
|
// advance and if the number of friendly pawns beside or behind this
|
|
// pawn on adjacent files is higher or equal than the number of
|
|
// enemy pawns in the forward direction on the adjacent files.
|
|
candidate = !(opposed | passed | backward | isolated)
|
|
&& (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0
|
|
&& popcount<Max15>(b) >= popcount<Max15>(pawn_attack_span(Us, s) & theirPawns);
|
|
|
|
// Passed pawns 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)
|
|
e->passedPawns[Us] |= s;
|
|
|
|
// Score this pawn
|
|
if (isolated)
|
|
value -= Isolated[opposed][f];
|
|
|
|
if (doubled)
|
|
value -= Doubled[opposed][f];
|
|
|
|
if (backward)
|
|
value -= Backward[opposed][f];
|
|
|
|
if (chain)
|
|
value += ChainMember[f];
|
|
|
|
if (candidate)
|
|
value += CandidatePassed[relative_rank(Us, s)];
|
|
}
|
|
|
|
return value;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
namespace Pawns {
|
|
|
|
/// probe() takes a position object as input, computes a Entry 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.
|
|
|
|
Entry* probe(const Position& pos, Table& entries) {
|
|
|
|
Key key = pos.pawn_key();
|
|
Entry* e = entries[key];
|
|
|
|
if (e->key == key)
|
|
return e;
|
|
|
|
e->key = key;
|
|
e->value = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
|
|
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);
|
|
|
|
Value safety = MaxSafetyBonus;
|
|
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);
|
|
Rank rkUs, rkThem;
|
|
File kf = file_of(ksq);
|
|
|
|
kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf;
|
|
|
|
for (int f = kf - 1; f <= kf + 1; f++)
|
|
{
|
|
b = ourPawns & FileBB[f];
|
|
rkUs = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1;
|
|
safety -= ShelterWeakness[rkUs];
|
|
|
|
b = theirPawns & FileBB[f];
|
|
rkThem = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1;
|
|
safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
|
|
}
|
|
|
|
return safety;
|
|
}
|
|
|
|
|
|
/// Entry::update_safety() calculates and caches a bonus for king safety. It is
|
|
/// called only when king square changes, about 20% of total king_safety() calls.
|
|
|
|
template<Color Us>
|
|
Score Entry::update_safety(const Position& pos, Square ksq) {
|
|
|
|
kingSquares[Us] = ksq;
|
|
castleRights[Us] = pos.can_castle(Us);
|
|
minKPdistance[Us] = 0;
|
|
|
|
Bitboard pawns = pos.pieces(Us, PAWN);
|
|
if (pawns)
|
|
while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
|
|
|
|
if (relative_rank(Us, ksq) > RANK_4)
|
|
return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
|
|
|
|
Value bonus = shelter_storm<Us>(pos, ksq);
|
|
|
|
// If we can castle use the bonus after the castle if is bigger
|
|
if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
|
|
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
|
|
|
|
if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
|
|
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
|
|
|
|
return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
|
|
}
|
|
|
|
// Explicit template instantiation
|
|
template Score Entry::update_safety<WHITE>(const Position& pos, Square ksq);
|
|
template Score Entry::update_safety<BLACK>(const Position& pos, Square ksq);
|
|
|
|
} // namespace Pawns
|