Document asymmetric SEE pruning trick

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 1abe022aacefa580d699131310127c8a7910437f..5abbafbcbfcd8b756dbf481efdffff9187e78016 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1225,7 +1225,8 @@ split_point_start: // At split points actual search starts from here
               continue;
           }
 
               continue;
           }
 

-          // Prune moves with negative or equal SEE
+          // Prune moves with negative or equal SEE.
+          // Also prune moves with positive SEE where capturing loses a tempo and SEE < beta - futilityBase.

           if (   futilityBase < beta
               && depth < DEPTH_ZERO
               && pos.see_asymm(move, beta - futilityBase) <= 0)
           if (   futilityBase < beta
               && depth < DEPTH_ZERO
               && pos.see_asymm(move, beta - futilityBase) <= 0)