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Don't copy around DirtyThreats

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The contents of DirtyThreats gets memcpyed twice for each call to do_move.
(Return value optimization doesn't apply to the do_move function itself because
it constructs a std::pair, so it gets copied; and the calls to reset also
require a copy.) This patch inserts the dirty info in place.

Sometimes the caller of do_move ignores the DirtyThreats info, so we pass in
scratch objects. I found that stack-allocating these scratch objects was bad on
Fishtest, so I begrudgingly put them in the Position struct. Both templating
the do_move function on whether dirty threats are needed and putting a
null-check branch for each use of dirty threats were slowdowns locally. Of
course, nothing prevents a future attempt at cleaning this up.

passed STC
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 68448 W: 17770 L: 17418 D: 33260
Ptnml(0-2): 198, 7425, 18630, 7769, 202
https://tests.stockfishchess.org/tests/view/6914c01a7ca87818523318ba

closes https://github.com/official-stockfish/Stockfish/pull/6414

No functional change
This commit is contained in:
Timothy Herchen
2025-11-13 22:17:03 +01:00
committed by Joost VandeVondele
parent 3ae7684714
commit fa4f05d3ef
5 changed files with 55 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/position.h
+23 -14
View File
@@ -24,6 +24,7 @@
#include <deque>
#include <iosfwd>
#include <memory>
#include <new>
#include <string>
#include "bitboard.h"
@@ -133,11 +134,16 @@ class Position {
Piece captured_piece() const;
// Doing and undoing moves
void do_move(Move m, StateInfo& newSt, const TranspositionTable* tt);
DirtyBoardData do_move(Move m, StateInfo& newSt, bool givesCheck, const TranspositionTable* tt);
void undo_move(Move m);
void do_null_move(StateInfo& newSt, const TranspositionTable& tt);
void undo_null_move();
void do_move(Move m, StateInfo& newSt, const TranspositionTable* tt);
void do_move(Move m,
StateInfo& newSt,
bool givesCheck,
DirtyPiece& dp,
DirtyThreats& dts,
const TranspositionTable* tt);
void undo_move(Move m);
void do_null_move(StateInfo& newSt, const TranspositionTable& tt);
void undo_null_move();
// Static Exchange Evaluation
bool see_ge(Move m, int threshold = 0) const;
@@ -196,14 +202,16 @@ class Position {
std::array<Bitboard, PIECE_TYPE_NB> byTypeBB;
std::array<Bitboard, COLOR_NB> byColorBB;
int pieceCount[PIECE_NB];
int castlingRightsMask[SQUARE_NB];
Square castlingRookSquare[CASTLING_RIGHT_NB];
Bitboard castlingPath[CASTLING_RIGHT_NB];
StateInfo* st;
int gamePly;
Color sideToMove;
bool chess960;
int pieceCount[PIECE_NB];
int castlingRightsMask[SQUARE_NB];
Square castlingRookSquare[CASTLING_RIGHT_NB];
Bitboard castlingPath[CASTLING_RIGHT_NB];
StateInfo* st;
int gamePly;
Color sideToMove;
bool chess960;
DirtyPiece scratch_dp;
DirtyThreats scratch_dts;
};
std::ostream& operator<<(std::ostream& os, const Position& pos);
@@ -389,7 +397,8 @@ inline void Position::swap_piece(Square s, Piece pc, DirtyThreats* const dts) {
}
inline void Position::do_move(Move m, StateInfo& newSt, const TranspositionTable* tt = nullptr) {
do_move(m, newSt, gives_check(m), tt);
new (&scratch_dts) DirtyThreats;
do_move(m, newSt, gives_check(m), scratch_dp, scratch_dts, tt);
}
inline StateInfo* Position::state() const { return st; }