Handle UCI command "mate in x moves"

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 3ba0dbc905b9f6a75c4da3be45dca9b23a2d17f2..dcd4a5ed71c9a0da313343415a471205509238a0 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -194,7 +194,7 @@ void Search::think() {
       goto finalize;
   }
 
-  if (Options["OwnBook"] && !Limits.infinite)
+  if (Options["OwnBook"] && !Limits.infinite && !Limits.mate)
   {
       Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]);
 
@@ -410,6 +410,12 @@ namespace {
         if (depth > 2 && BestMoveChanges)
             bestMoveNeverChanged = false;
 
+        // Do we have found a "mate in x"?
+        if (   Limits.mate
+            && bestValue >= VALUE_MATE_IN_MAX_PLY
+            && VALUE_MATE - bestValue <= 2 * Limits.mate)
+            Signals.stop = true;
+
         // Do we have time for the next iteration? Can we stop searching now?
         if (Limits.use_time_management() && !Signals.stopOnPonderhit)
         {
@@ -602,6 +608,11 @@ namespace {
                  ss->staticEval, ss->evalMargin);
     }
 
+    // Handling of UCI command 'mate in x moves'. We simply return if after
+    // 'x' moves we still have not checkmated the opponent.
+    if (PvNode && !RootNode && !inCheck && Limits.mate && ss->ply > 2 * Limits.mate)
+        return eval;
+
     // Update gain for the parent non-capture move given the static position
     // evaluation before and after the move.
     if (   (move = (ss-1)->currentMove) != MOVE_NULL