Disable use of aspiration window in known win positions

When we are hunting for mate, transposition table is filled in
with mate scores. Current implemenatation of aspiration search
can't cope with this very well.

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

diff --git a/src/search.cpp b/src/search.cpp
index 3382e09c745183130458ca1db03506fa3345b71e..7e501fc41fa1278b143222641ffe414085a690b5 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -657,7 +657,7 @@ namespace {
         // Calculate dynamic search window based on previous iterations
         Value alpha, beta;
 
         // Calculate dynamic search window based on previous iterations
         Value alpha, beta;
 

-        if (MultiPV == 1 && Iteration >= 6)
+        if (MultiPV == 1 && Iteration >= 6 && abs(IterationInfo[Iteration - 1].value) < VALUE_KNOWN_WIN)

         {
             int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
             int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
         {
             int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
             int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;