X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fposition.cpp;h=ad0a621de0b954ce9078aedd0caf860bbcc93473;hb=30c2e3828a5ea143e6190680dcd8e9d93fd17840;hp=4045a25d96f454182b9de283b593d0b0d48c53c1;hpb=483c98a69e8c6836c655d92a150d70fbe780341f;p=stockfish

diff --git a/src/position.cpp b/src/position.cpp
index 4045a25d..ad0a621d 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -802,7 +802,7 @@ void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveI
       // Update piece list, move the last piece at index[capsq] position and
       // shrink the list.
       //
-      // WARNING: This is a not revresible operation. When we will reinsert the
+      // WARNING: This is a not reversible operation. When we will reinsert the
       // captured piece in undo_move() we will put it at the end of the list and
       // not in its original place, it means index[] and pieceList[] are not
       // guaranteed to be invariant to a do_move() + undo_move() sequence.
@@ -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