Simplified shuffle extension version (#2121)

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index f9fdc261b16c9185520fa79d7a0d02e0eccdf2a6..44347f79f8b85ec1aee88b579c65c6f9d9b48908 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -927,6 +927,13 @@ moves_loop: // When in check, search starts from here
       else if (type_of(move) == CASTLING)
           extension = ONE_PLY;
 
+      // Shuffle extension
+      else if (   PvNode
+               && pos.rule50_count() > 18
+               && depth < 3 * ONE_PLY
+               && ss->ply < 3 * thisThread->rootDepth / ONE_PLY) // To avoid too deep searches
+          extension = ONE_PLY;
+
       // Passed pawn extension
       else if (   move == ss->killers[0]
                && pos.advanced_pawn_push(move)