Merge pull request #317 from fsmosca/3fold_rep_termination

Fix segfault and end the game by 3-fold repetitions

src/learn/gensfen.cpp

@@ -110,6 +110,8 @@ namespace Learner
                 save_every = std::max(save_every, REPORT_STATS_EVERY);
 
                 num_threads = Options["Threads"];
+
+                random_multi_pv_depth = std::max(search_depth_max, random_multi_pv_depth);
             }
         };
 
@@ -489,8 +491,11 @@ namespace Learner
         // draw at the maximum number of steps to write.
         const int ply = move_hist_scores.size();
 
-        // has it reached the max length or is a draw
-        if (ply >= params.write_maxply || pos.is_draw(ply))
+        // has it reached the max length or is a draw by fifty-move rule
+        // or by 3-fold repetition
+        if (ply >= params.write_maxply 
+            || pos.is_fifty_move_draw() 
+            || pos.is_three_fold_repetition())
         {
             return 0;
         }

src/position.cpp

@@ -1180,6 +1180,22 @@ bool Position::is_draw(int ply) const {
 }
 
 
+/// Position::is_fifty_move_draw() returns true if a game can be claimed
+/// by a fifty-move draw rule.
+
+bool Position::is_fifty_move_draw() const {
+
+  return (st->rule50 > 99 && (!checkers() || MoveList<LEGAL>(*this).size()));
+}
+
+
+/// Position::is_three_fold_repetition() returns true if there is 3-fold repetition.
+bool Position::is_three_fold_repetition() const {
+
+  return st->repetition < 0;
+}
+
+
 // Position::has_repeated() tests whether there has been at least one repetition
 // of positions since the last capture or pawn move.
 

src/position.h

@@ -161,6 +161,8 @@ public:
   bool is_chess960() const;
   Thread* this_thread() const;
   bool is_draw(int ply) const;
+  bool is_fifty_move_draw() const;
+  bool is_three_fold_repetition() const;
   bool has_game_cycle(int ply) const;
   bool has_repeated() const;
   int rule50_count() const;