Increase null reduction at high depths

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1668a74a40a3bfcf87b2e45300ca6a4706a4537a..5fc9be3679aa1d265b71285ab82b69e4460936eb 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1376,7 +1376,7 @@ namespace {
         pos.do_null_move(st);
 
         // Null move dynamic reduction based on depth
-        int R = (depth >= 5 * OnePly ? 4 : 3);
+        int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0);
 
         // Null move dynamic reduction based on value
         if (approximateEval - beta > PawnValueMidgame)