Fix Singular extension condition to handle mate scores

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index acd042c0a8ceb99a5f0fdaca232778c19a722718..8f9a369ae23d86a9a4d62d046a8f35ea4c9f6013 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -700,6 +700,8 @@ moves_loop: // When in check and at SpNode search starts from here
                            &&  depth >= 8 * ONE_PLY
                            &&  abs(beta) < VALUE_KNOWN_WIN
                            &&  ttMove != MOVE_NONE
+                       /*  &&  ttValue != VALUE_NONE Already implicit in the next condition */
+                           &&  abs(ttValue) < VALUE_KNOWN_WIN
                            && !excludedMove // Recursive singular search is not allowed
                            && (tte->bound() & BOUND_LOWER)
                            &&  tte->depth() >= depth - 3 * ONE_PLY;
@@ -766,8 +768,6 @@ moves_loop: // When in check and at SpNode search starts from here
           && !ext
           &&  pos.legal(move, ci.pinned))
       {
-          assert(ttValue != VALUE_NONE);
-
           Value rBeta = ttValue - int(depth);
           ss->excludedMove = move;
           ss->skipNullMove = true;
@@ -979,8 +979,8 @@ moves_loop: // When in check and at SpNode search starts from here
 
       // Step 19. Check for splitting the search
       if (   !SpNode
+          &&  Threads.size() >= 2
           &&  depth >= Threads.minimumSplitDepth
-          &&  Threads.available_slave(thisThread)
           &&  (   !thisThread->activeSplitPoint
                || !thisThread->activeSplitPoint->allSlavesSearching)
           &&  thisThread->splitPointsSize < MAX_SPLITPOINTS_PER_THREAD)