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Prune evasions with negative SEE in qsearch

Browse source 
Only pure blocking evasions are candidate
for pruning.

After 998 games at 1+0

Mod vs Orig +215 =596 -187  +10 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-01-20 11:40:33 +01:00
parent d844a75d2c
commit 81cfd81366
1 changed files with 10 additions and 3 deletions
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13
src/search.cpp
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@ -1643,7 +1643,7 @@ namespace {
StateInfo st; StateInfo st;
Move ttMove, move; Move ttMove, move;
Value staticValue, bestValue, value, futilityBase, futilityValue; Value staticValue, bestValue, value, futilityBase, futilityValue;
bool isCheck, enoughMaterial, moveIsCheck; bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
const TTEntry* tte = NULL; const TTEntry* tte = NULL;
int moveCount = 0; int moveCount = 0;
bool pvNode = (beta - alpha != 1); bool pvNode = (beta - alpha != 1);
@ -1744,8 +1744,15 @@ namespace {
} }
} }
// Don't search captures and checks with negative SEE values // Detect blocking evasions that are candidate to be pruned
if ( !isCheck evasionPrunable = isCheck
&& bestValue != -VALUE_INFINITE
&& !pos.move_is_capture(move)
&& pos.type_of_piece_on(move_from(move)) != KING
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
if ( (!isCheck || evasionPrunable)
&& move != ttMove && move != ttMove
&& !move_is_promotion(move) && !move_is_promotion(move)
&& pos.see_sign(move) < 0) && pos.see_sign(move) < 0)