+ // Avoid to do an expensive singular extension search on nodes where
+ // such search had already failed in the past.
+ if ( !PvNode
+ && singularExtensionNode
+ && depth < SingularExtensionDepth[PvNode] + 5 * OnePly)
+ {
+ TTEntry* ttx = TT.retrieve(pos.get_exclusion_key());
+ if (ttx && is_lower_bound(ttx->type()))
+ singularExtensionNode = false;
+ }
+