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Apply multicut pruning more often

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This patch increases number of nodes where we produce multicut cutoffs.

The idea is that if our ttMove failed to produce a singular extension
but ttValue is greater than beta we can afford to do one more reduced search
near beta excluding ttMove to see if it will produce a fail high -
and if it does so produce muticut by analogy to existing logic.

passed STC
https://tests.stockfishchess.org/tests/view/5e9a162b5b664cdba0ce6e28
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 58238 W: 11192 L: 10917 D: 36129
Ptnml(0-2): 1007, 6704, 13442, 6939, 1027

passed LTC
https://tests.stockfishchess.org/tests/view/5e9a1e845b664cdba0ce7411
LLR: 2.94 (-2.94,2.94) {0.25,1.75}
Total: 137852 W: 17460 L: 16899 D: 103493
Ptnml(0-2): 916, 12610, 41383, 13031, 986

closes https://github.com/official-stockfish/Stockfish/pull/2640

bench 4881443
This commit is contained in:
Vizvezdenec 2020-04-18 03:28:47 +03:00 • committed by Joost VandeVondele
parent bde1506ba5
commit 221893bf67
1 changed files with 12 additions and 0 deletions
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12
src/search.cpp
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@ -1091,6 +1091,18 @@ moves_loop: // When in check, search starts from here
// a soft bound.
else if (singularBeta >= beta)
return singularBeta;
// If the eval of ttMove is greater than beta we try also if there is an other move that
// pushes it over beta, if so also produce a cutoff
else if (ttValue >= beta)
{
ss->excludedMove = move;
value = search<NonPV>(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode);
ss->excludedMove = MOVE_NONE;
if (value >= beta)
return beta;
}
}
// Check extension (~2 Elo)