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Fix a minor bug in search

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As Joona says: "The problem is that when doing full
window search (-VALUE_INFINITE, VALUE_INFINITE), and
pruning all the moves will return fail low which is
mate score, because only clause touching alpha is
"mate distance pruning". So we are returning mate score
although we are just pruning all the moves. In reality
there probably is no mate in sight.

Bug spotted and fixed by Joona.
This commit is contained in:
Marco Costalba
2012-10-11 21:11:11 +02:00
parent 7f9ebf8e86
commit aba152ea3a
1 changed files with 2 additions and 1 deletions
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3
src/search.cpp
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@@ -826,7 +826,8 @@ split_point_start: // At split points actual search starts from here
&& !inCheck && !inCheck
&& !dangerous && !dangerous
&& move != ttMove && move != ttMove
&& (bestValue > VALUE_MATED_IN_MAX_PLY || bestValue == -VALUE_INFINITE)) && (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE
&& alpha > VALUE_MATED_IN_MAX_PLY)))
{ {
// Move count based pruning // Move count based pruning
if ( depth < 16 * ONE_PLY if ( depth < 16 * ONE_PLY