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Qsearch pruning: follow-up

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This is a follow-up of the recent qsearch pruning patch in
a260c9a8a2

We now use the same guard condition (testing that we already have a defense with
a score better  score than a TB loss) for all pruning heuristics in qsearch().
This allows some pruning when in check, but  in a controlled way to ensure that
no wrong mate scores appear.

Tested with Elo-gaining bounds:

STC:
LLR: 2.97 (-2.94,2.94) {-0.25,1.25}
Total: 22632 W: 2433 L: 2264 D: 17935
Ptnml(0-2): 98, 1744, 7487, 1865, 122
https://tests.stockfishchess.org/tests/view/5fa59405936c54e11ec99515

LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 105432 W: 4965 L: 4648 D: 95819
Ptnml(0-2): 85, 4110, 44011, 4423, 87
https://tests.stockfishchess.org/tests/view/5fa5b609936c54e11ec9952a

closes https://github.com/official-stockfish/Stockfish/pull/3221

Bench: 3578092
This commit is contained in:
Stéphane Nicolet 2020-11-06 19:20:27 +01:00
parent 32edb1d009
commit 392b529c3f
1 changed files with 2 additions and 2 deletions
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4
src/search.cpp
View file

@ -1525,7 +1525,7 @@ moves_loop: // When in check, search starts from here
moveCount++;
// Futility pruning
if ( !ss->inCheck
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !givesCheck
&& futilityBase > -VALUE_KNOWN_WIN
&& !pos.advanced_pawn_push(move))
@ -1552,7 +1552,7 @@ moves_loop: // When in check, search starts from here
}
// Do not search moves with negative SEE values
if ( !ss->inCheck
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !(givesCheck && pos.is_discovery_check_on_king(~pos.side_to_move(), move))
&& !pos.see_ge(move))
continue;