Adjust singular extension depth restriction

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f3a96ae29fe441bb13fc1899dcc94f804a63bd32..cded8614ad9d6c77851b5b71db034ec96baa0e38 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1089,7 +1089,7 @@ moves_loop: // When in check, search starts here
       // a reduced search on all the other moves but the ttMove and if the
       // result is lower than ttValue minus a margin, then we will extend the ttMove.
       if (   !rootNode
-          &&  depth >= 7
+          &&  depth >= 6 + 2 * (PvNode && tte->is_pv())
           &&  move == ttMove
           && !excludedMove // Avoid recursive singular search
        /* &&  ttValue != VALUE_NONE Already implicit in the next condition */