Increase non-PV IID search depth

bench: 5146380

diff --git a/src/search.cpp b/src/search.cpp
index 7a06dad..8ef2513 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -745,7 +745,7 @@ namespace {
         && ttMove == MOVE_NONE
         && (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta)))
     {
-        Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
+        Depth d = (PvNode ? depth - 2 * ONE_PLY : depth - 4 * ONE_PLY);
 
         ss->skipNullMove = true;
         search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);