Change history reduction in LMR to be a full ply.

uriblass · glinscott · commit d6613b758954 · 2014-09-26T02:22:39.000+08:00
STC: LLR: 2.96 (-2.94,2.94) [-3.00,1.00] Total: 9829 W: 2142 L: 1998 D: 5689 LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00] Total: 27162 W: 4802 L: 4692 D: 17668 Bench: 7284120 Resolves #53
diff --git a/src/search.cpp b/src/search.cpp
@@ -823,12 +823,10 @@ namespace {
       {
           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);
 
