Extend dangerous passed pawn moves (#2089)

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index a9a62dbf8477926c2a53ae2759eee4f4cb4a0f56..7fffae263008e0175cc553844b0adc7137536fd0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -942,6 +942,12 @@ moves_loop: // When in check, search starts from here
       else if (type_of(move) == CASTLING)
           extension = ONE_PLY;
 
+      // Passed pawn extension
+      else if (   move == ss->killers[0]
+               && pos.advanced_pawn_push(move)
+               && pos.pawn_passed(us, to_sq(move)))
+          extension = ONE_PLY;
+
       // Calculate new depth for this move
       newDepth = depth - ONE_PLY + extension;