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Avoid high rule50 count zeroing cutoffs

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If the depth is low enough, don't TT cut if the rule50 count is high and the TT move is zeroing.

Passed STC:
https://tests.stockfishchess.org/tests/view/68a8fdd8b6fb3300203bcb92
LLR: 3.05 (-2.94,2.94) <0.00,2.00>
Total: 110304 W: 28805 L: 28402 D: 53097
Ptnml(0-2): 275, 11174, 31875, 11529, 299

Passed LTC:
https://tests.stockfishchess.org/tests/view/68aa200f75da51a345a5a809
LLR: 3.00 (-2.94,2.94) <0.50,2.50>
Total: 187956 W: 48489 L: 47928 D: 91539
Ptnml(0-2): 59, 16118, 61075, 16655, 71

closes https://github.com/official-stockfish/Stockfish/pull/6271

bench: 2641840
This commit is contained in:
Nonlinear2
2025-08-30 15:05:11 +02:00
committed by Joost VandeVondele
parent 69de394439
commit 75f07da912
1 changed files with 4 additions and 1 deletions
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src/search.cpp
+4 -1
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@@ -679,7 +679,10 @@ Value Search::Worker::search(
if (!PvNode && !excludedMove && ttData.depth > depth - (ttData.value <= beta)
&& is_valid(ttData.value) // Can happen when !ttHit or when access race in probe()
&& (ttData.bound & (ttData.value >= beta ? BOUND_LOWER : BOUND_UPPER))
&& (cutNode == (ttData.value >= beta) || depth > 5))
&& (cutNode == (ttData.value >= beta) || depth > 5)
// avoid a TT cutoff if the rule50 count is high and the TT move is zeroing
&& (depth > 8 || ttData.move == Move::none() || pos.rule50_count() < 80
|| (!ttCapture && type_of(pos.moved_piece(ttData.move)) != PAWN)))
{
// If ttMove is quiet, update move sorting heuristics on TT hit
if (ttData.move && ttData.value >= beta)