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Penalize TTEs whose inexact value mismatches the current window

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Credit shared with @xu-shawn, who has done much of the work to instrument the search and investigate search explosions and endgame paralysis: https://github.com/official-stockfish/Stockfish/issues/6742#issuecomment-4386174472

This patch is a natural result of that commentary. It can also be seen as a refinement of more generalized secondary aging.

Passed STC: https://tests.stockfishchess.org/tests/view/69fb18e8c91f9625ce325427
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 434784 W: 111417 L: 110528 D: 212839
Ptnml(0-2): 1089, 50675, 112949, 51616, 1063

Passed LTC: https://tests.stockfishchess.org/tests/view/6a0379588d9bd4cd7cd68edf
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 81018 W: 20558 L: 20154 D: 40306
Ptnml(0-2): 35, 8554, 22939, 8934, 47

VVLTC *reversion*: https://tests.stockfishchess.org/tests/view/6a0622538d9bd4cd7cd69340
Ptnml(0-2): 2, 5159, 18107, 5050, 0
LLR: -2.94 <0.50,2.50>
LLR: -2.47 <0.00,2.00>
LLR: -2.24 <-0.25,1.75>

closes https://github.com/official-stockfish/Stockfish/pull/6819

Bench: 2676789
This commit is contained in:
Dubslow
2026-05-19 18:38:07 +02:00
committed by Joost VandeVondele
parent b82f5b59f7
commit 319d61effd
4 changed files with 14 additions and 0 deletions
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src/search.cpp
+6
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@@ -853,6 +853,12 @@ Value Search::Worker::search(
else
return ttData.value;
}
} // No cutoff, but why? Does the stored inexact value mismatch our aspiration window?
else if (!PvNode && !excludedMove && ttData.depth > depth - (ttData.value <= beta)
&& is_valid(ttData.value) && ttData.bound != BOUND_EXACT
&& ttData.bound & (ttData.value >= beta ? BOUND_UPPER : BOUND_LOWER) && depth > 5)
{ // If a window-bound mismatch is the only reason cutoff failed, penalize the now-useless tte
ttWriter.penalize(1);
}
// Step 6. Tablebases probe