Merge pull request #34 from jromang/repetition

[stockfish] / src / position.cpp

diff --git a/src/position.cpp b/src/position.cpp
index 3f81994611975aaaf31c8f397b1613cf85edb297..feaeee22c606309a474c917bad77bfcc310d9b5d 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1467,7 +1467,7 @@ 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 SkipRepetition>
+template<bool SkipRepetition, bool SkipThreeFoldCheck>
 bool Position::is_draw() const {
 
   // Draw by material?
@@ -1482,7 +1482,7 @@ bool Position::is_draw() const {
   // Draw by repetition?
   if (!SkipRepetition)
   {
-      int i = 4, e = std::min(st->rule50, st->pliesFromNull);
+      int i = 4, e = std::min(st->rule50, st->pliesFromNull), rep_count=0;
 
       if (i <= e)
       {
@@ -1492,7 +1492,10 @@ bool Position::is_draw() const {
               stp = stp->previous->previous;
 
               if (stp->key == st->key)
-                  return true;
+              {
+                if(SkipThreeFoldCheck) return true;
+                else if(++rep_count>=2) return true;
+              }
 
               i +=2;
 
@@ -1504,8 +1507,9 @@ bool Position::is_draw() const {
 }
 
 // Explicit template instantiations
-template bool Position::is_draw<false>() const;
-template bool Position::is_draw<true>() const;
+template bool Position::is_draw<false,true>() const;
+template bool Position::is_draw<true,true>() const;
+template bool Position::is_draw<false,false>() const;
 
 
 /// Position::flip() flips position with the white and black sides reversed. This