Reintroduce null move dynamic reduction

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 08e3a997c4d3c63365e24040e1803d298e8b3075..b4e9b14c6c5073c540cb33fc5657c80991a96ba2 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1243,8 +1243,9 @@ namespace {
 
         StateInfo st;
         pos.do_null_move(st);
+        int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
 
-        Value nullValue = -search(pos, ss, -(beta-1), depth-4*OnePly, ply+1, false, threadID);
+        Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
 
         pos.undo_null_move();
 
@@ -1363,7 +1364,7 @@ namespace {
 
       // Try to reduce non-pv search depth by one ply if move seems not problematic,
       // if the move fails high will be re-searched at full depth.
-      if (    depth >= (ss[ply-1].currentMove == MOVE_NULL ? 3 : 2) * OnePly
+      if (    depth >= 3*OnePly
           &&  moveCount >= LMRNonPVMoves
           && !dangerous
           && !moveIsCapture