LMR Tweak: Decrease reduction if cmh>0 && history>0.

VoyagerOne · zamar · commit 7e9f776fcafe · 2015-06-27T09:45:59.000+01:00
STC: LLR: 2.96 (-2.94,2.94) [-1.50,4.50] Total: 9627 W: 1879 L: 1748 D: 6000 LTC: LLR: 2.97 (-2.94,2.94) [0.00,6.00] Total: 21543 W: 3433 L: 3234 D: 14876 Bench: 8646407 Resolves #370 #371
diff --git a/src/search.cpp b/src/search.cpp
@@ -959,7 +959,10 @@ namespace {
                                         [pos.piece_on(to_sq(move))][to_sq(move)] <= VALUE_ZERO))
               ss->reduction += ONE_PLY;
 
-          if (move == countermove)
+          if (    move == countermove
+              || (   History[pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO
+                  && CounterMovesHistory[pos.piece_on(prevMoveSq)][prevMoveSq]
+                                        [pos.piece_on(to_sq(move))][to_sq(move)] > VALUE_ZERO))
               ss->reduction = std::max(DEPTH_ZERO, ss->reduction - ONE_PLY);
 
           // Decrease reduction for moves that escape a capture
