+ if (value < singularBeta)
+ {
+ extension = 1;
+
+ // Avoid search explosion by limiting the number of double extensions
+ if ( !PvNode
+ && value < singularBeta - 26
+ && ss->doubleExtensions <= 8)
+ extension = 2;
+ }
+
+ // Multi-cut pruning
+ // Our ttMove is assumed to fail high, and now we failed high also on a reduced
+ // search without the ttMove. So we assume this expected Cut-node is not singular,
+ // that multiple moves fail high, and we can prune the whole subtree by returning
+ // a soft bound.
+ else if (singularBeta >= beta)
+ return singularBeta;
+
+ // If the eval of ttMove is greater than beta, we reduce it (negative extension)
+ else if (ttValue >= beta)
+ extension = -2;
+
+ // If the eval of ttMove is less than alpha and value, we reduce it (negative extension)
+ else if (ttValue <= alpha && ttValue <= value)
+ extension = -1;