Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/BreathFirstMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/BreathFirstMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/BreathFirstMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,4 +17,6 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
 #endregion
Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/DepthFirstMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/DepthFirstMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/DepthFirstMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,5 +17,8 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
+
 #endregion
 
Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/GenotypeToPhenotypeMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/GenotypeToPhenotypeMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/GenotypeToPhenotypeMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,4 +17,6 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
 #endregion
@@ -32,5 +34,5 @@
 namespace HeuristicLab.Problems.GrammaticalEvolution {
   /// <summary>
-  /// GenotypeToPhenotypeMapper
+  /// Abstract base class for GenotypeToPhenotypeMappers
   /// </summary>
   public abstract class GenotypeToPhenotypeMapper : IntegerVectorOperator, IGenotypeToPhenotypeMapper {
@@ -64,5 +66,5 @@
 
       // no terminal node exists for the given parent node
-      if (possibleSymbolsList.Count() < 1) return null;
+      if (!possibleSymbolsList.Any()) return null;
 
       var newNode = possibleSymbolsList.SelectRandom(random).CreateTreeNode();
Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/IGenotypeToPhenotypeMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/IGenotypeToPhenotypeMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/IGenotypeToPhenotypeMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,4 +17,6 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
 #endregion
Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/PIGEMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/PIGEMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/PIGEMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,4 +17,6 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
 #endregion
@@ -69,4 +71,5 @@
   public class PIGEMapper : GenotypeToPhenotypeMapper {
 
+    private object nontVectorLocker = new object();
     private IntegerVector nontVector;
 
@@ -76,5 +79,5 @@
     }
 
-    private IntegerVector GetNontVector(IRandom random, IntMatrix bounds, int length) {
+    private static IntegerVector GetNontVector(IRandom random, IntMatrix bounds, int length) {
       IntegerVector v = new IntegerVector(length);
       v.Randomize(random, bounds);
@@ -112,6 +115,9 @@
       tree.Root = rootNode;
 
-      if (NontVector == null) {
-        NontVector = GetNontVector(random, bounds, length);
+      // Map can be called simultaniously on multiple threads
+      lock (nontVectorLocker) {
+        if (NontVector == null) {
+          NontVector = GetNontVector(random, bounds, length);
+        }
       }
 
Index: trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/RandomMapper.cs
===================================================================
--- branches/GrammaticalEvolution/HeuristicLab.Problems.GrammaticalEvolution/Mappers/RandomMapper.cs	(revision 10328)
+++ trunk/sources/HeuristicLab.Problems.GrammaticalEvolution/Mappers/RandomMapper.cs	(revision 10975)
@@ -1,5 +1,5 @@
 ﻿#region License Information
 /* HeuristicLab
- * Copyright (C) 2002-2013 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
+ * Copyright (C) 2002-2014 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
  *
  * This file is part of HeuristicLab.
@@ -17,4 +17,6 @@
  * You should have received a copy of the GNU General Public License
  * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
+ * 
+ * Author: Sabine Winkler
  */
 #endregion
