Revert "Extend full 3 fold detection to PvNodes"

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index 4045a25d96f454182b9de283b593d0b0d48c53c1..310e46e36190704121571efff452399bf53911a9 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1363,31 +1363,36 @@ Value Position::compute_non_pawn_material(Color c) const {
 /// Position::is_draw() tests whether the position is drawn by material,
 /// repetition, or the 50 moves rule. It does not detect stalemates, this
 /// must be done by the search.
-template<bool CheckRepetition, bool CheckThreeFold>
+template<bool SkipRepetition>
 bool Position::is_draw() const {
 
+  // Draw by material?
   if (   !pieces(PAWN)
       && (non_pawn_material(WHITE) + non_pawn_material(BLACK) <= BishopValueMg))
       return true;
 
+  // Draw by the 50 moves rule?
   if (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()))
       return true;
 
-  if (CheckRepetition)
+  // Draw by repetition?
+  if (!SkipRepetition)
   {
-      int i = 4, e = std::min(st->rule50, st->pliesFromNull), cnt;
+      int i = 4, e = std::min(st->rule50, st->pliesFromNull);
 
       if (i <= e)
       {
           StateInfo* stp = st->previous->previous;
 
-          for (cnt = 0; i <= e; i += 2)
-          {
+          do {
               stp = stp->previous->previous;
 
-              if (stp->key == st->key && (!CheckThreeFold || ++cnt >= 2))
+              if (stp->key == st->key)
                   return true;
-          }
+
+              i += 2;
+
+          } while (i <= e);
       }
   }
 
@@ -1395,9 +1400,8 @@ bool Position::is_draw() const {
 }
 
 // Explicit template instantiations
-template bool Position::is_draw<true,  true>() const;
-template bool Position::is_draw<true, false>() const;
-template bool Position::is_draw<false,false>() const;
+template bool Position::is_draw<false>() const;
+template bool Position::is_draw<true>() const;
 
 
 /// Position::flip() flips position with the white and black sides reversed. This