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Adjust return bonus from tt cutoffs at fail highs

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This is reintroduction of the recently simplified logic - if positive tt cutoff
occurs return not a tt value but smth between it and beta.  Difference is that
instead of static linear combination there we use basically the same formula as
we do in the main search - with the only difference being using tt depth
instead of depth, which makes a lot of sense.

Passed STC:
https://tests.stockfishchess.org/tests/view/665b3a34f4a1fd0c208ea870
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 54944 W: 14239 L: 13896 D: 26809
Ptnml(0-2): 151, 6407, 14008, 6760, 146

Passed LTC:
https://tests.stockfishchess.org/tests/view/665b520011645bd3d3fac341
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 90540 W: 23070 L: 22640 D: 44830
Ptnml(0-2): 39, 9903, 24965, 10315, 48

closes https://github.com/official-stockfish/Stockfish/pull/5336

bench 1381237
This commit is contained in:
Michael Chaly 2024-06-01 20:44:06 +03:00 • committed by Joost VandeVondele
parent cb4a623119
commit 783dfc2eb2
1 changed files with 5 additions and 0 deletions
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5
src/search.cpp
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@ -640,7 +640,12 @@ Value Search::Worker::search(
// Partial workaround for the graph history interaction problem
// For high rule50 counts don't produce transposition table cutoffs.
if (pos.rule50_count() < 90)
{
if (ttValue >= beta && std::abs(ttValue) < VALUE_TB_WIN_IN_MAX_PLY
&& std::abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
ttValue = (ttValue * tte->depth() + beta) / (tte->depth() + 1);
return ttValue;
}
}
// Step 5. Tablebases probe