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Don't prune discovered checks

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Don't prune and eventually extend check moves of type
DISCO_CHECK (pun intended, Lucas will understand :-) ).

Patch from Lucas Braesch that has also tested it:

Result: 879-661-2137, score=52.96%, LOS=100.00% (time 10"+0.1")

I have started a verification test right now.

bench: 6004966
This commit is contained in:
Marco Costalba
2012-11-07 18:20:39 +01:00
parent 3b87314331
commit 96d3b1c92b
4 changed files with 22 additions and 12 deletions
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src/search.cpp
+7 -3
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@@ -483,7 +483,8 @@ namespace {
Depth ext, newDepth;
Value bestValue, value, ttValue;
Value eval, nullValue, futilityValue;
bool inCheck, givesCheck, pvMove, singularExtensionNode;
CheckType givesCheck;
bool inCheck, pvMove, singularExtensionNode;
bool captureOrPromotion, dangerous, doFullDepthSearch;
int moveCount, playedMoveCount;
@@ -815,7 +816,7 @@ split_point_start: // At split points actual search starts from here
if (PvNode && dangerous)
ext = ONE_PLY;
else if (givesCheck && pos.see_sign(move) >= 0)
else if (givesCheck && (givesCheck == DISCO_CHECK || pos.see_sign(move) >= 0))
ext = ONE_PLY / 2;
// Singular extension search. If all moves but one fail low on a search of
@@ -882,6 +883,7 @@ split_point_start: // At split points actual search starts from here
// Prune moves with negative SEE at low depths
if ( predictedDepth < 2 * ONE_PLY
&& givesCheck != DISCO_CHECK
&& pos.see_sign(move) < 0)
{
if (SpNode)
@@ -1102,7 +1104,8 @@ split_point_start: // At split points actual search starts from here
Key posKey;
Move ttMove, move, bestMove;
Value bestValue, value, ttValue, futilityValue, futilityBase;
bool givesCheck, enoughMaterial, evasionPrunable, fromNull;
CheckType givesCheck;
bool enoughMaterial, evasionPrunable, fromNull;
Depth ttDepth;
ss->currentMove = bestMove = MOVE_NONE;
@@ -1234,6 +1237,7 @@ split_point_start: // At split points actual search starts from here
if ( !PvNode
&& (!InCheck || evasionPrunable)
&& move != ttMove
&& givesCheck != DISCO_CHECK
&& type_of(move) != PROMOTION
&& pos.see_sign(move) < 0)
continue;