Simplify cmh pruning

VoyagerOne · snicolet · commit 6184d2b2ac25 · 2018-07-27T16:23:45.000+02:00
Simplify cmh pruning by removing PvNode exception STC: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 9935 W: 2330 L: 2184 D: 5421 http://tests.stockfishchess.org/tests/view/5b587dc00ebc5902bdb88424 LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 20635 W: 3585 L: 3464 D: 13586 http://tests.stockfishchess.org/tests/view/5b58910a0ebc5902bdb885b9 Closes #1711 Bench: 4905530
diff --git a/src/search.cpp b/src/search.cpp
@@ -935,8 +935,7 @@ namespace {
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
-              if (   lmrDepth < 4
-                  && (lmrDepth < 3 || ((ss - 1)->statScore > 0 && !PvNode))
+              if (   lmrDepth <= ((ss-1)->statScore > 0 ? 3 : 2)
                   && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;
