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Do more futility pruning for cutNodes that are not in TT. #4700

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Do more futility pruning for cutNodes that are not in TT. #4700

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6 changes: 3 additions & 3 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -63,8 +63,8 @@ namespace {
enum NodeType { NonPV, PV, Root };

// Futility margin
Value futility_margin(Depth d, bool improving) {
return Value(140 * (d - improving));
Value futility_margin(Depth d, bool noTtCutNode, bool improving) {
return Value((140 - 40 * noTtCutNode) * (d - improving));
}

// Reductions lookup table initialized at startup
Expand Down Expand Up @@ -767,7 +767,7 @@ namespace {
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 9
&& eval - futility_margin(depth, improving) - (ss-1)->statScore / 306 >= beta
&& eval - futility_margin(depth, cutNode && !ss->ttHit, improving) - (ss-1)->statScore / 306 >= beta
&& eval >= beta
&& eval < 24923) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval;
Expand Down