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Refine deeper post-lmr searches

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This patch improves logic conditions for performing deeper searches after passed LMR.

Instead of exceeding alpha by some margin now it requires to exceed the
current best value - which may be lower than alpha (but never bigger since we
update alpha with bestvalue if it exceeds alpha).

Passed STC:
https://tests.stockfishchess.org/tests/view/6455f78008858de8313775b6
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 209344 W: 55993 L: 55448 D: 97903
Ptnml(0-2): 507, 22798, 57526, 23325, 516

Passed LTC:
https://tests.stockfishchess.org/tests/view/64572d46eb75932ccfebff97
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 66288 W: 17867 L: 17514 D: 30907
Ptnml(0-2): 21, 6240, 20269, 6593, 21

closes https://github.com/official-stockfish/Stockfish/pull/4559

bench 3808503
This commit is contained in:
Michael Chaly 2023-05-07 23:33:04 +03:00 • committed by Joost VandeVondele
parent 464ebdf127
commit 65e2150501
1 changed files with 1 additions and 1 deletions
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2
src/search.cpp
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@ -1201,7 +1201,7 @@ moves_loop: // When in check, search starts here
{ {
// Adjust full depth search based on LMR results - if result // Adjust full depth search based on LMR results - if result
// was good enough search deeper, if it was bad enough search shallower // was good enough search deeper, if it was bad enough search shallower
const bool doDeeperSearch = value > (alpha + 58 + 12 * (newDepth - d)); const bool doDeeperSearch = value > (bestValue + 68 + 12 * (newDepth - d));
const bool doEvenDeeperSearch = value > alpha + 588 && ss->doubleExtensions <= 5; const bool doEvenDeeperSearch = value > alpha + 588 && ss->doubleExtensions <= 5;
const bool doShallowerSearch = value < bestValue + newDepth; const bool doShallowerSearch = value < bestValue + newDepth;