1
0
Fork 0
mirror of https://github.com/sockspls/badfish synced 2025-04-29 16:23:09 +00:00
BadFish/src/movepick.cpp
Stéphane Nicolet af802da65b Clean up comments for movepicker
Remove references to checks in MovePicker comments. Follow-up for
https://github.com/official-stockfish/Stockfish/pull/5498

closes https://github.com/official-stockfish/Stockfish/pull/5516

No functional change
2024-07-28 22:21:03 +02:00

318 lines
9.9 KiB
C++

/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2024 The Stockfish developers (see AUTHORS file)
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 "movepick.h"
#include <algorithm>
#include <cassert>
#include <utility>
#include "bitboard.h"
#include "position.h"
namespace Stockfish {
namespace {
enum Stages {
// generate main search moves
MAIN_TT,
CAPTURE_INIT,
GOOD_CAPTURE,
QUIET_INIT,
GOOD_QUIET,
BAD_CAPTURE,
BAD_QUIET,
// generate evasion moves
EVASION_TT,
EVASION_INIT,
EVASION,
// generate probcut moves
PROBCUT_TT,
PROBCUT_INIT,
PROBCUT,
// generate qsearch moves
QSEARCH_TT,
QCAPTURE_INIT,
QCAPTURE
};
// Sort moves in descending order up to and including a given limit.
// The order of moves smaller than the limit is left unspecified.
void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
for (ExtMove *sortedEnd = begin, *p = begin + 1; p < end; ++p)
if (p->value >= limit)
{
ExtMove tmp = *p, *q;
*p = *++sortedEnd;
for (q = sortedEnd; q != begin && *(q - 1) < tmp; --q)
*q = *(q - 1);
*q = tmp;
}
}
} // namespace
// Constructors of the MovePicker class. As arguments, we pass information
// to decide which class of moves to emit, to help sorting the (presumably)
// good moves first, and how important move ordering is at the current node.
// MovePicker constructor for the main search and for the quiescence search
MovePicker::MovePicker(const Position& p,
Move ttm,
Depth d,
const ButterflyHistory* mh,
const CapturePieceToHistory* cph,
const PieceToHistory** ch,
const PawnHistory* ph) :
pos(p),
mainHistory(mh),
captureHistory(cph),
continuationHistory(ch),
pawnHistory(ph),
ttMove(ttm),
depth(d) {
if (pos.checkers())
stage = EVASION_TT + !(ttm && pos.pseudo_legal(ttm));
else
stage = (depth > 0 ? MAIN_TT : QSEARCH_TT) + !(ttm && pos.pseudo_legal(ttm));
}
// MovePicker constructor for ProbCut: we generate captures with Static Exchange
// Evaluation (SEE) greater than or equal to the given threshold.
MovePicker::MovePicker(const Position& p, Move ttm, int th, const CapturePieceToHistory* cph) :
pos(p),
captureHistory(cph),
ttMove(ttm),
threshold(th) {
assert(!pos.checkers());
stage = PROBCUT_TT
+ !(ttm && pos.capture_stage(ttm) && pos.pseudo_legal(ttm) && pos.see_ge(ttm, threshold));
}
// Assigns a numerical value to each move in a list, used for sorting.
// Captures are ordered by Most Valuable Victim (MVV), preferring captures
// with a good history. Quiets moves are ordered using the history tables.
template<GenType Type>
void MovePicker::score() {
static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
[[maybe_unused]] Bitboard threatenedByPawn, threatenedByMinor, threatenedByRook,
threatenedPieces;
if constexpr (Type == QUIETS)
{
Color us = pos.side_to_move();
threatenedByPawn = pos.attacks_by<PAWN>(~us);
threatenedByMinor =
pos.attacks_by<KNIGHT>(~us) | pos.attacks_by<BISHOP>(~us) | threatenedByPawn;
threatenedByRook = pos.attacks_by<ROOK>(~us) | threatenedByMinor;
// Pieces threatened by pieces of lesser material value
threatenedPieces = (pos.pieces(us, QUEEN) & threatenedByRook)
| (pos.pieces(us, ROOK) & threatenedByMinor)
| (pos.pieces(us, KNIGHT, BISHOP) & threatenedByPawn);
}
for (auto& m : *this)
if constexpr (Type == CAPTURES)
m.value =
7 * int(PieceValue[pos.piece_on(m.to_sq())])
+ (*captureHistory)[pos.moved_piece(m)][m.to_sq()][type_of(pos.piece_on(m.to_sq()))];
else if constexpr (Type == QUIETS)
{
Piece pc = pos.moved_piece(m);
PieceType pt = type_of(pc);
Square from = m.from_sq();
Square to = m.to_sq();
// histories
m.value = (*mainHistory)[pos.side_to_move()][m.from_to()];
m.value += 2 * (*pawnHistory)[pawn_structure_index(pos)][pc][to];
m.value += 2 * (*continuationHistory[0])[pc][to];
m.value += (*continuationHistory[1])[pc][to];
m.value += (*continuationHistory[2])[pc][to] / 3;
m.value += (*continuationHistory[3])[pc][to];
m.value += (*continuationHistory[5])[pc][to];
// bonus for checks
m.value += bool(pos.check_squares(pt) & to) * 16384;
// bonus for escaping from capture
m.value += threatenedPieces & from ? (pt == QUEEN && !(to & threatenedByRook) ? 51700
: pt == ROOK && !(to & threatenedByMinor) ? 25600
: !(to & threatenedByPawn) ? 14450
: 0)
: 0;
// malus for putting piece en prise
m.value -= (pt == QUEEN ? bool(to & threatenedByRook) * 49000
: pt == ROOK ? bool(to & threatenedByMinor) * 24335
: bool(to & threatenedByPawn) * 14900);
}
else // Type == EVASIONS
{
if (pos.capture_stage(m))
m.value =
PieceValue[pos.piece_on(m.to_sq())] - type_of(pos.moved_piece(m)) + (1 << 28);
else
m.value = (*mainHistory)[pos.side_to_move()][m.from_to()]
+ (*continuationHistory[0])[pos.moved_piece(m)][m.to_sq()]
+ (*pawnHistory)[pawn_structure_index(pos)][pos.moved_piece(m)][m.to_sq()];
}
}
// Returns the next move satisfying a predicate function.
// This never returns the TT move, as it was emitted before.
template<MovePicker::PickType T, typename Pred>
Move MovePicker::select(Pred filter) {
while (cur < endMoves)
{
if constexpr (T == Best)
std::swap(*cur, *std::max_element(cur, endMoves));
if (*cur != ttMove && filter())
return *cur++;
cur++;
}
return Move::none();
}
// This is the most important method of the MovePicker class. We emit one
// new pseudo-legal move on every call until there are no more moves left,
// picking the move with the highest score from a list of generated moves.
Move MovePicker::next_move(bool skipQuiets) {
auto quiet_threshold = [](Depth d) { return -3560 * d; };
top:
switch (stage)
{
case MAIN_TT :
case EVASION_TT :
case QSEARCH_TT :
case PROBCUT_TT :
++stage;
return ttMove;
case CAPTURE_INIT :
case PROBCUT_INIT :
case QCAPTURE_INIT :
cur = endBadCaptures = moves;
endMoves = generate<CAPTURES>(pos, cur);
score<CAPTURES>();
partial_insertion_sort(cur, endMoves, std::numeric_limits<int>::min());
++stage;
goto top;
case GOOD_CAPTURE :
if (select<Next>([&]() {
// Move losing capture to endBadCaptures to be tried later
return pos.see_ge(*cur, -cur->value / 18) ? true
: (*endBadCaptures++ = *cur, false);
}))
return *(cur - 1);
++stage;
[[fallthrough]];
case QUIET_INIT :
if (!skipQuiets)
{
cur = endBadCaptures;
endMoves = beginBadQuiets = endBadQuiets = generate<QUIETS>(pos, cur);
score<QUIETS>();
partial_insertion_sort(cur, endMoves, quiet_threshold(depth));
}
++stage;
[[fallthrough]];
case GOOD_QUIET :
if (!skipQuiets && select<Next>([]() { return true; }))
{
if ((cur - 1)->value > -7998 || (cur - 1)->value <= quiet_threshold(depth))
return *(cur - 1);
// Remaining quiets are bad
beginBadQuiets = cur - 1;
}
// Prepare the pointers to loop over the bad captures
cur = moves;
endMoves = endBadCaptures;
++stage;
[[fallthrough]];
case BAD_CAPTURE :
if (select<Next>([]() { return true; }))
return *(cur - 1);
// Prepare the pointers to loop over the bad quiets
cur = beginBadQuiets;
endMoves = endBadQuiets;
++stage;
[[fallthrough]];
case BAD_QUIET :
if (!skipQuiets)
return select<Next>([]() { return true; });
return Move::none();
case EVASION_INIT :
cur = moves;
endMoves = generate<EVASIONS>(pos, cur);
score<EVASIONS>();
++stage;
[[fallthrough]];
case EVASION :
return select<Best>([]() { return true; });
case PROBCUT :
return select<Next>([&]() { return pos.see_ge(*cur, threshold); });
case QCAPTURE :
return select<Next>([]() { return true; });
}
assert(false);
return Move::none(); // Silence warning
}
} // namespace Stockfish