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Tweak stand pat usage in qsearch. #4922

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Tweak stand pat usage in qsearch. #4922

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15 changes: 10 additions & 5 deletions src/search.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1468,14 +1468,19 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
ss->staticEval = bestValue =
(ss - 1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss - 1)->staticEval;

// Stand pat. Return immediately if static value is at least beta
// Stand pat. Return immediately if bestValue is at least beta at non-Pv nodes.
// At PvNodes set bestValue between alpha and beta instead
if (bestValue >= beta)
{
if (!ss->ttHit)
tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, DEPTH_NONE,
MOVE_NONE, ss->staticEval);
if (!PvNode || abs(bestValue) >= VALUE_TB_WIN_IN_MAX_PLY)
{
if (!ss->ttHit)
tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, DEPTH_NONE,
MOVE_NONE, ss->staticEval);

return bestValue;
return bestValue;
}
bestValue = std::min((alpha + beta) / 2, beta - 1);
}

if (bestValue > alpha)
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