diff --git a/src/main/java/avatartranslator/AvatarActionAssignment.java b/src/main/java/avatartranslator/AvatarActionAssignment.java
index 8a558a16bb35a92a92d64cf184b25e6c8eeaec43..40d0c911d5892dbcc116cb1c75b654110ed71eef 100644
--- a/src/main/java/avatartranslator/AvatarActionAssignment.java
+++ b/src/main/java/avatartranslator/AvatarActionAssignment.java
@@ -42,6 +42,8 @@ import myutil.TraceManager;
 
 import java.util.Map;
 
+import avatartranslator.modelchecker.SpecificationBlock;
+
 /**
    * Class AvatarActionAssignment
    * Creation: 16/09/2015
@@ -51,10 +53,14 @@ import java.util.Map;
 public class AvatarActionAssignment implements AvatarAction {
     AvatarLeftHand leftHand;
     AvatarTerm rightHand;
+    AvatarExpressionSolver actionSolver;
+    private AvatarExpressionAttribute leftAttribute;
 
     public AvatarActionAssignment (AvatarLeftHand _leftHand, AvatarTerm _rightHand) {
         this.leftHand = _leftHand;
         this.rightHand = _rightHand;
+        this.actionSolver = null;
+        this.leftAttribute = null;
     }
 
     public boolean isAVariableSetting () {
@@ -72,6 +78,10 @@ public class AvatarActionAssignment implements AvatarAction {
     public AvatarTerm getRightHand () {
         return this.rightHand;
     }
+    
+    public AvatarExpressionSolver getActionSolver() {
+        return actionSolver;
+    }
 
     public boolean isABasicVariableSetting () {
         return  (this.leftHand instanceof AvatarAttribute || this.leftHand instanceof AvatarTuple) &&
@@ -85,6 +95,19 @@ public class AvatarActionAssignment implements AvatarAction {
     public String toString () {
         return this.leftHand.getName() + " = " + this.rightHand.getName();
     }
+    
+    public boolean buildActionSolver(AvatarBlock block) {
+        boolean res;
+        actionSolver = new AvatarExpressionSolver(rightHand.getName());
+        res = actionSolver.buildExpression((AvatarBlock) block);
+        leftAttribute = new AvatarExpressionAttribute(block, leftHand.getName());
+        res &= !leftAttribute.hasError();
+        return res;
+    }
+    
+    public void executeActionSolver(SpecificationBlock sb) {
+        leftAttribute.setValue(sb, actionSolver.getResult(sb));
+    }
 
     @Override
     public boolean containsAMethodCall () {
diff --git a/src/main/java/avatartranslator/AvatarExpressionAttribute.java b/src/main/java/avatartranslator/AvatarExpressionAttribute.java
index 264eef134bcdbf1805e5568c6e870334d9c11b4e..5f8ccad448546216a70744bd00f51b9a661b3334 100644
--- a/src/main/java/avatartranslator/AvatarExpressionAttribute.java
+++ b/src/main/java/avatartranslator/AvatarExpressionAttribute.java
@@ -190,6 +190,30 @@ public class AvatarExpressionAttribute {
         return value;
     }
     
+    public void setValue(SpecificationState ss, int value) {
+        int v = value;
+        
+        if (isNot) {
+            v = (value == 0) ? 1 : 0;
+        } else if (isNegated) {
+            v = -value;
+        }
+        
+        ss.blocks[blockIndex].values[accessIndex] = v;
+    }
+    
+    public void setValue(SpecificationBlock sb, int value) {
+        int v = value;
+        
+        if (isNot) {
+            v = (value == 0) ? 1 : 0;
+        } else if (isNegated) {
+            v = -value;
+        }
+        
+        sb.values[accessIndex] = v;
+    }
+    
     public String toString() {
         String res = "";
         if (isNot) {
diff --git a/src/main/java/avatartranslator/modelchecker/AvatarModelChecker.java b/src/main/java/avatartranslator/modelchecker/AvatarModelChecker.java
index b90ea40fbada911b2b7980c6e66174b1953dc1aa..ca5d24b9e9e46f574329152b12a00a2b2ae85278 100644
--- a/src/main/java/avatartranslator/modelchecker/AvatarModelChecker.java
+++ b/src/main/java/avatartranslator/modelchecker/AvatarModelChecker.java
@@ -159,20 +159,6 @@ public class AvatarModelChecker implements Runnable, myutil.Graph {
     public AvatarSpecification getReworkedAvatarSpecification() {
         return spec;
     }
-    
-    private void initExpressionSolvers() {
-        for (AvatarBlock block : spec.getListOfBlocks()) {
-            AvatarStateMachine asm = block.getStateMachine();
-
-            for (AvatarStateMachineElement elt : asm.getListOfElements()) {
-                if (elt instanceof AvatarTransition) {
-                    if (((AvatarTransition) elt).isGuarded()) {
-                        ((AvatarTransition) elt).buildGuardSolver();
-                    }
-                }
-            }
-        }
-    }
 
     public int getNbOfStates() {
         if (states == null) {
@@ -448,6 +434,7 @@ public class AvatarModelChecker implements Runnable, myutil.Graph {
 
 
         nbOfThreads = Runtime.getRuntime().availableProcessors();
+        nbOfThreads = 1;
         TraceManager.addDev("Starting the model checking with " + nbOfThreads + " threads");
         TraceManager.addDev("Ignore internal state:" + ignoreInternalStates);
         startModelChecking(nbOfThreads);
@@ -680,6 +667,28 @@ public class AvatarModelChecker implements Runnable, myutil.Graph {
         }
         nbOfCurrentComputations = 0;
     }
+    
+    private void initExpressionSolvers() {
+        AvatarTransition at;
+        
+        for (AvatarBlock block : spec.getListOfBlocks()) {
+            AvatarStateMachine asm = block.getStateMachine();
+
+            for (AvatarStateMachineElement elt : asm.getListOfElements()) {
+                if (elt instanceof AvatarTransition) {
+                    at = (AvatarTransition) elt;
+                    if (at.isGuarded()) {
+                        at.buildGuardSolver();
+                    }
+                    for (AvatarAction aa : at.getActions()) {
+                        if (aa instanceof AvatarActionAssignment) {
+                            ((AvatarActionAssignment) aa).buildActionSolver(block);
+                        }
+                    }
+                }
+            }
+        }
+    }
 
     private void prepareTransitionsOfState(SpecificationState _ss) {
 
@@ -1419,23 +1428,25 @@ public class AvatarModelChecker implements Runnable, myutil.Graph {
                 if (retAction == null) {
                     retAction = nameOfVar + "=" + act;
                 }
-
-                int indexVar = block.getIndexOfAvatarAttributeWithName(nameOfVar);
-                AvatarType type = block.getAttribute(indexVar).getType();
-                if (indexVar != -1) {
-                    if (type == AvatarType.INTEGER) {
-                        //TraceManager.addDev("Evaluating int expr=" + act);
-                        int result = evaluateIntExpression(act, _st.blocks[0], _newState.blocks[_st.blocksInt[0]]);
-                        _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = result;
-                    } else if (type == AvatarType.BOOLEAN) {
-                        boolean bool = evaluateBoolExpression(act, _st.blocks[0], _newState.blocks[_st.blocksInt[0]]);
-                        if (bool) {
-                            _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = 1;
-                        } else {
-                            _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = 0;
-                        }
-                    }
-                }
+                
+                ((AvatarActionAssignment) aAction).executeActionSolver(_newState.blocks[_st.blocksInt[0]]);
+
+//                int indexVar = block.getIndexOfAvatarAttributeWithName(nameOfVar);
+//                AvatarType type = block.getAttribute(indexVar).getType();
+//                if (indexVar != -1) {
+//                    if (type == AvatarType.INTEGER) {
+//                        //TraceManager.addDev("Evaluating int expr=" + act);
+//                        int result = evaluateIntExpression(act, _st.blocks[0], _newState.blocks[_st.blocksInt[0]]);
+//                        _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = result;
+//                    } else if (type == AvatarType.BOOLEAN) {
+//                        boolean bool = evaluateBoolExpression(act, _st.blocks[0], _newState.blocks[_st.blocksInt[0]]);
+//                        if (bool) {
+//                            _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = 1;
+//                        } else {
+//                            _newState.blocks[_st.blocksInt[0]].values[SpecificationBlock.ATTR_INDEX + indexVar] = 0;
+//                        }
+//                    }
+//                }
             }
         }