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Simplify Zobrist keys for captures

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The Zobrist keys for NO_PIECE are 0 so no need to special case captures.
Also the TranspositionTable reference passed to do_null_move() can be
const.

STC Simplification:
https://tests.stockfishchess.org/tests/view/6764a79a86d5ee47d9544005
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 114240 W: 29654 L: 29523 D: 55063
Ptnml(0-2): 329, 12360, 31620, 12473, 338

closes https://github.com/official-stockfish/Stockfish/pull/5731

No functional change
This commit is contained in:
mstembera
2024-12-19 15:08:16 -08:00
committed by Disservin
parent 79261bec59
commit f656fdfa9a
2 changed files with 3 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/position.cpp
+2 -5
View File
@@ -1012,7 +1012,7 @@ void Position::do_castling(Color us, Square from, Square& to, Square& rfrom, Squ
// Used to do a "null move": it flips // Used to do a "null move": it flips
// the side to move without executing any move on the board. // the side to move without executing any move on the board.
void Position::do_null_move(StateInfo& newSt, TranspositionTable& tt) { void Position::do_null_move(StateInfo& newSt, const TranspositionTable& tt) {
assert(!checkers()); assert(!checkers());
assert(&newSt != st); assert(&newSt != st);
@@ -1071,10 +1071,7 @@ Key Position::key_after(Move m) const {
Piece captured = piece_on(to); Piece captured = piece_on(to);
Key k = st->key ^ Zobrist::side; Key k = st->key ^ Zobrist::side;
if (captured) k ^= Zobrist::psq[captured][to] ^ Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from];
k ^= Zobrist::psq[captured][to];
k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[pc][from];
return (captured || type_of(pc) == PAWN) ? k : adjust_key50<true>(k); return (captured || type_of(pc) == PAWN) ? k : adjust_key50<true>(k);
} }
src/position.h
+1 -1
View File
@@ -143,7 +143,7 @@ class Position {
void do_move(Move m, StateInfo& newSt); void do_move(Move m, StateInfo& newSt);
void do_move(Move m, StateInfo& newSt, bool givesCheck); void do_move(Move m, StateInfo& newSt, bool givesCheck);
void undo_move(Move m); void undo_move(Move m);
void do_null_move(StateInfo& newSt, TranspositionTable& tt); void do_null_move(StateInfo& newSt, const TranspositionTable& tt);
void undo_null_move(); void undo_null_move();
// Static Exchange Evaluation // Static Exchange Evaluation