From: Joona Kiiski <joona.kiiski@gmail.com>
Date: Tue, 13 Apr 2010 15:25:50 +0000 (+0300)
Subject: Fix evasion pruning condition
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=9a3fc4d3fb81e5f517ecde5dad8aabf55fb2bd22

Fix evasion pruning condition

Avoid incorrect mate scores in positions like

BK5/1R4b1/2k1Np2/3p3b/2p3pq/p1rB4/n2n1p2/8 w - -

Thanks for Jouni Uski for reporting the problem

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/search.cpp b/src/search.cpp
index efdb287f..fff523c3 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1713,7 +1713,7 @@ namespace {
 
       // Detect blocking evasions that are candidate to be pruned
       evasionPrunable =   isCheck
-                       && bestValue != -VALUE_INFINITE
+                       && bestValue > value_mated_in(PLY_MAX)
                        && !pos.move_is_capture(move)
                        && pos.type_of_piece_on(move_from(move)) != KING
                        && !pos.can_castle(pos.side_to_move());