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qsearch: do not prune pv nodes with negative SEE

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Also small micro-optimization, take a line out of
the moves loop.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2008-11-11 21:42:36 +01:00
parent bb0da595a7
commit a7227ac26f
1 changed files with 6 additions and 3 deletions
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src/search.cpp
+6 -3
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@@ -1394,6 +1394,8 @@ namespace {
int moveCount = 0; int moveCount = 0;
Bitboard dcCandidates = mp.discovered_check_candidates(); Bitboard dcCandidates = mp.discovered_check_candidates();
bool isCheck = pos.is_check(); bool isCheck = pos.is_check();
bool pvNode = (beta - alpha != 1);
bool enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
// Loop through the moves until no moves remain or a beta cutoff // Loop through the moves until no moves remain or a beta cutoff
// occurs. // occurs.
@@ -1414,8 +1416,8 @@ namespace {
&& !moveIsCheck && !moveIsCheck
&& !move_promotion(move) && !move_promotion(move)
&& !moveIsPassedPawnPush && !moveIsPassedPawnPush
&& beta - alpha == 1 && !pvNode
&& pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame) && enoughMaterial)
{ {
Value futilityValue = staticValue Value futilityValue = staticValue
+ Max(pos.midgame_value_of_piece_on(move_to(move)), + Max(pos.midgame_value_of_piece_on(move_to(move)),
@@ -1431,9 +1433,10 @@ namespace {
} }
} }
// Don't search captures and checks with negative SEE values. // Don't search captures and checks with negative SEE values
if ( !isCheck if ( !isCheck
&& !move_promotion(move) && !move_promotion(move)
&& !pvNode
&& (pos.midgame_value_of_piece_on(move_from(move)) > && (pos.midgame_value_of_piece_on(move_from(move)) >
pos.midgame_value_of_piece_on(move_to(move))) pos.midgame_value_of_piece_on(move_to(move)))
&& pos.see(move) < 0) && pos.see(move) < 0)