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simplify stalemate further

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Non-regression STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 155200 W: 40650 L: 40562 D: 73988
Ptnml(0-2): 533, 17588, 41258, 17700, 521
https://tests.stockfishchess.org/tests/view/68abe11375da51a345a5adec

Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 82824 W: 21442 L: 21287 D: 40095
Ptnml(0-2): 51, 8738, 23675, 8901, 47
https://tests.stockfishchess.org/tests/view/68b205606217b8721dca9c8e

10k Stalemate:
Elo: 1.46 ± 1.2 (95%) LOS: 99.0%
Total: 10000 W: 4640 L: 4598 D: 762
Ptnml(0-2): 0, 140, 4678, 182, 0
https://tests.stockfishchess.org/tests/view/68b2059b6217b8721dca9c90

closes https://github.com/official-stockfish/Stockfish/pull/6283

Bench: 2431727
This commit is contained in:
Shawn Xu
2025-09-02 20:39:02 +02:00
committed by Joost VandeVondele
parent da63060ea3
commit 75ac6c7a06
1 changed files with 4 additions and 9 deletions
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src/search.cpp
+3 -8
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@@ -1049,17 +1049,12 @@ moves_loop: // When in check, search starts here
} }
// SEE based pruning for captures and checks // SEE based pruning for captures and checks
// Avoid pruning sacrifices of our last piece for stalemate
int margin = std::max(157 * depth + captHist / 29, 0); int margin = std::max(157 * depth + captHist / 29, 0);
if (!pos.see_ge(move, -margin)) if ((alpha >= VALUE_DRAW || pos.non_pawn_material(us) != PieceValue[movedPiece])
{ && !pos.see_ge(move, -margin))
bool mayStalemateTrap =
depth > 2 && alpha < 0 && pos.non_pawn_material(us) == PieceValue[movedPiece];
// avoid pruning sacrifices of our last piece for stalemate
if (!mayStalemateTrap)
continue; continue;
} }
}
else else
{ {
int history = (*contHist[0])[movedPiece][move.to_sq()] int history = (*contHist[0])[movedPiece][move.to_sq()]