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Remove a superfluous subtrahend

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The '- 1' subtrahend was introduced for guarding against null move
search at root, which would be nonsense. But this is actually already
guaranteed by the !PvNode condition. This followed from the discussion
in pull request 1609: https://github.com/official-stockfish/Stockfish/pull/1609

No functional change
This commit is contained in:
Guenther Demetz
2018-06-04 09:10:30 +02:00
committed by Stéphane Nicolet
parent 6b5d671cdc
commit b939788f9d
1 changed files with 2 additions and 2 deletions
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4
src/search.cpp
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@@ -751,7 +751,7 @@ namespace {
&& ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply > thisThread->nmpMinPly || us != thisThread->nmpColor))
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
{
assert(eval - beta >= 0);
@@ -780,7 +780,7 @@ namespace {
// Do verification search at high depths, with null move pruning disabled
// for us, until ply exceeds nmpMinPly.
thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4 - 1;
thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4;
thisThread->nmpColor = us;
Value v = search<NonPV>(pos, ss, beta-1, beta, depth-R, false);