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Prune negative SEE moves also in PV nodes

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This patch is actually the sum of two contributions that
have been tested independently:

1) Pruning of negative SEE moves in PV

After 10000 games at 20+0.05
ELO: 5.18 +-7 (95%) LOS: 99.2%
Total: 10000 W: 1952 L: 1803 D: 6245

2) Remove of bestValue > VALUE_MATED_IN_MAX_PLY condition

After 23000 games at 20+0.05
ELO: 1.63 +-4 (95%) LOS: 88.1%
Total: 23000 W: 4232 L: 4124 D: 14644

The whole patch as been re-tested at long TC with positive results:

After 10000 games at 60+0.05
ELO: 4.31 +-7 (95%) LOS: 98.3%
Total: 10000 W: 1765 L: 1641 D: 6594
This commit is contained in:
Lucas Braesch 2013-02-21 09:54:06 -05:00 • committed by Marco Costalba
parent 9a1d5f0f1d
commit 335b57b5ef
1 changed files with 5 additions and 6 deletions
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11
src/search.cpp
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@ -857,16 +857,15 @@ split_point_start: // At split points actual search starts from here
newDepth = depth - ONE_PLY + ext;
// Step 13. Futility pruning (is omitted in PV nodes)
if ( !PvNode
&& !captureOrPromotion
if ( !captureOrPromotion
&& !inCheck
&& !dangerous
&& move != ttMove
&& (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE
&& alpha > VALUE_MATED_IN_MAX_PLY)))
&& alpha > VALUE_MATED_IN_MAX_PLY)
{
// Move count based pruning
if ( depth < 16 * ONE_PLY
if ( !PvNode
&& depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[depth]
&& (!threatMove || !refutes(pos, move, threatMove)))
{
@ -883,7 +882,7 @@ split_point_start: // At split points actual search starts from here
futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
+ Gain[pos.piece_moved(move)][to_sq(move)];
if (futilityValue < beta)
if (!PvNode && futilityValue < beta)
{
if (SpNode)
sp->mutex.lock();