Cap evaluation based null move extra reduction to three plies

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 945f5bf25d9c9d88687e9a36e0ad3ff3285fe823..6215b083dd22dc3bc2e408d8fbe09c3a076e0bd0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -567,8 +567,7 @@ namespace {
         // Null move dynamic reduction based on depth and value
         Depth R =  3 * ONE_PLY
                  + depth / 4
-                 + (abs(beta) < VALUE_KNOWN_WIN ? int(eval - beta) / PawnValueMg * ONE_PLY
-                                                : DEPTH_ZERO);
+                 + std::min(int(eval - beta) / PawnValueMg, 3) * ONE_PLY;
 
         pos.do_null_move(st);
         (ss+1)->skipNullMove = true;
@@ -823,12 +822,10 @@ moves_loop: // When in check and at SpNode search starts from here
       {
           ss->reduction = reduction<PvNode>(improving, depth, moveCount);
 
-          if (!PvNode && cutNode)
+          if (   (!PvNode && cutNode)
+              ||  History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
               ss->reduction += ONE_PLY;
 
-          else if (History[pos.piece_on(to_sq(move))][to_sq(move)] < 0)
-              ss->reduction += ONE_PLY / 2;
-
           if (move == countermoves[0] || move == countermoves[1])
               ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);