Small tweaks to recent code changes

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 0619db3a12a2420a2ef85864ab84e709c614a158..b4096ebad3559edc4dad28a99091e1365bad910e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -82,7 +82,7 @@ namespace {
   // History and stats update bonus, based on depth
   int stat_bonus(Depth depth) {
     int d = depth / ONE_PLY;
-    return d > 17 ? 0 : 32 * d * d + 64 * d - 64;
+    return d > 17 ? 0 : 33 * d * d + 66 * d - 66;
   }
 
   // Skill structure is used to implement strength limit
@@ -935,7 +935,7 @@ moves_loop: // When in check, search starts from here
               int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;
 
               // Countermoves based pruning (~20 Elo)
-              if (   lmrDepth < 3
+              if (   lmrDepth < 3 + ((ss-1)->statScore > 0)
                   && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold
                   && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
                   continue;
@@ -985,11 +985,9 @@ moves_loop: // When in check, search starts from here
 
           if (captureOrPromotion) // (~5 Elo)
           {
-              // Increase reduction by comparing opponent's stat score
-              if ((ss-1)->statScore >= 0)
-                  r += ONE_PLY;
-
-              r -= r ? ONE_PLY : DEPTH_ZERO;
+              // Decrease reduction by comparing opponent's stat score
+              if ((ss-1)->statScore < 0)
+                  r -= ONE_PLY;
           }
           else
           {
@@ -1030,10 +1028,10 @@ moves_loop: // When in check, search starts from here
                   r += ONE_PLY;
 
               // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
-              r = std::max(DEPTH_ZERO, (r / ONE_PLY - ss->statScore / 20000) * ONE_PLY);
+              r -= ss->statScore / 20000 * ONE_PLY;
           }
 
-          Depth d = std::max(newDepth - r, ONE_PLY);
+          Depth d = std::max(newDepth - std::max(r, DEPTH_ZERO), ONE_PLY);
 
           value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);