Full three fold repetition detection only at root node

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 4ac944029fa8d1b02bf2086b545560e8b79808e2..9980dcf95b1aeb347986ce6cab2e6ac2000fe00f 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -524,7 +524,7 @@ namespace {
     if (!RootNode)
     {
         // Step 2. Check for aborted search and immediate draw
-        if (Signals.stop || pos.is_draw<false>() || ss->ply > MAX_PLY)
+        if (Signals.stop || pos.is_draw<false,true>() || ss->ply > MAX_PLY)
             return DrawValue[pos.side_to_move()];
 
         // Step 3. Mate distance pruning. Even if we mate at the next move our score
@@ -538,6 +538,10 @@ namespace {
         if (alpha >= beta)
             return alpha;
     }
+       else 
+       {
+               if(pos.is_draw<false,false>()) return DrawValue[pos.side_to_move()];
+       }
 
     // Step 4. Transposition table lookup
     // We don't want the score of a partial search to overwrite a previous full search
@@ -1103,7 +1107,7 @@ split_point_start: // At split points actual search starts from here
     ss->ply = (ss-1)->ply + 1;
 
     // Check for an instant draw or maximum ply reached
-    if (pos.is_draw<true>() || ss->ply > MAX_PLY)
+    if (pos.is_draw<true,true>() || ss->ply > MAX_PLY)
         return DrawValue[pos.side_to_move()];
 
     // Transposition table lookup. At PV nodes, we don't use the TT for
@@ -1552,7 +1556,7 @@ void RootMove::extract_pv_from_tt(Position& pos) {
          && pos.is_pseudo_legal(m)
          && pos.pl_move_is_legal(m, pos.pinned_pieces())
          && ply < MAX_PLY
-         && (!pos.is_draw<false>() || ply < 2))
+         && (!pos.is_draw<false,true>() || ply < 2))
   {
       pv.push_back(m);
       pos.do_move(m, *st++);