Increase reduction at root

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 56b56733fb2771aa998030887370622a408ff786..66ef5043d28e2280d286509cf2aaee482677e190 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1161,7 +1161,7 @@ moves_loop: // When in check, search starts from here
           if (thisThread->ttHitAverage > 509 * TtHitAverageResolution * TtHitAverageWindow / 1024)
               r--;
 
           if (thisThread->ttHitAverage > 509 * TtHitAverageResolution * TtHitAverageWindow / 1024)
               r--;
 

-          // Reduction if other threads are searching this position
+          // Increase reduction if other threads are searching this position

           if (th.marked())
               r++;
 
           if (th.marked())
               r++;
 


@@ -1169,7 +1169,8 @@ moves_loop: // When in check, search starts from here
           if (ss->ttPv)
               r -= 2;
 
           if (ss->ttPv)
               r -= 2;
 

-          if (!PvNode && depth > 10 && thisThread->bestMoveChanges <= 2)
+          // Increase reduction at root and non-PV nodes when the best move does not change frequently
+          if ((rootNode || !PvNode) && depth > 10 && thisThread->bestMoveChanges <= 2)

               r++;
 
           if (moveCountPruning && !formerPv)
               r++;
 
           if (moveCountPruning && !formerPv)