Add double bonus for prior countermove fail low

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 77d23ac2f4157a5d3b57ef65d7e9e3a08763b00e..0c8377d01ed6712630efaa665adf4aeb645906c4 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1353,16 +1353,17 @@ moves_loop: // When in check, search starts here
                          quietsSearched, quietCount, capturesSearched, captureCount, depth);
 
     // Bonus for prior countermove that caused the fail low
-    else if (   (depth >= 5 || PvNode)
+    else if (   (depth >= 5 || PvNode || bestValue < alpha - 62 * depth)
              && !priorCapture)
     {
         //Assign extra bonus if current node is PvNode or cutNode
         //or fail low was really bad
         bool extraBonus =    PvNode
-                          || cutNode
-                          || bestValue < alpha - 62 * depth;
+                          || cutNode;
 
-        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus));
+        bool doubleExtraBonus = extraBonus && bestValue < alpha - 85 * depth;
+
+        update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus + doubleExtraBonus));
     }
 
     if (PvNode)