From a72c55283d132e64cad9101c65e59c1f9406be83 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Tue, 20 Oct 2009 16:14:57 +0100 Subject: [PATCH] Don't prune TT move in qsearch even if SEE < 0 Even if SEE is negative there is always a good possibility that TT move is a cut move anyway. For instance a lot of BXN exchanges that have negative SEE can very easily be good exchanges. A nice side effect is a bit reduced frequency of see_sign() calls. After 643 games at 1+0 Mod vs Orig +174 =327 -142 52.49% 337.5/643 +17 ELO Signed-off-by: Marco Costalba --- src/search.cpp | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/src/search.cpp b/src/search.cpp index ec4272a9..32b37413 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1596,6 +1596,7 @@ namespace { // Don't search captures and checks with negative SEE values if ( !isCheck + && move != ttMove && !move_is_promotion(move) && pos.see_sign(move) < 0) continue; @@ -1622,7 +1623,7 @@ namespace { // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (pos.is_check() && moveCount == 0) // Mate! + if (!moveCount && pos.is_check()) // Mate! return value_mated_in(ply); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); -- 2.39.2