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Research at intermediate depth if LMR is very high

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After a fail high in LMR, if reduction is very high do
a research at lower depth before teh full depth one.
Chances are that the re-search will fail low and the
full depth one is skipped.

Passed both short TC:
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 11363 W: 2204 L: 2069 D: 7090

And long TC:
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 7292 W: 1195 L: 1061 D: 5036

bench: 7869223
This commit is contained in:
Ralph Stößer 2013-12-09 08:02:49 +01:00 • committed by Marco Costalba
parent 4630ab5743
commit 8e9d4081ee
1 changed files with 7 additions and 0 deletions
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7
src/search.cpp
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@ -933,6 +933,13 @@ moves_loop: // When in check and at SpNode search starts from here
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
// Research at intermediate depth if reduction is very high
if (value > alpha && ss->reduction >= 4 * ONE_PLY)
{
Depth d2 = std::max(newDepth - 2 * ONE_PLY, ONE_PLY);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d2, true);
}
doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
ss->reduction = DEPTH_ZERO;
}