one example added

dream/simulation/Examples/ParallelServers4.py

+from dream.simulation.imports import Machine, Source, Exit, Part, Queue, Globals, Failure, G 
+from dream.simulation.Globals import runSimulation
+
+#the custom queue
+class SelectiveQueue(Queue):
+    #override so that it first chooses M1 and then M2
+    def selectReceiver(self,possibleReceivers=[]):
+        # sort the receivers according to their priority
+        possibleReceivers.sort(key=lambda x: x.priority, reverse=True)
+        if possibleReceivers[0].canAccept():
+            return possibleReceivers[0]
+        elif possibleReceivers[1].canAccept():
+            return possibleReceivers[1]
+        return None
+
+#the custom machine
+class Milling(Machine):
+    def getEntity(self):
+        activeEntity=Machine.getEntity(self)        #call the parent method to get the entity
+        part=self.getActiveObjectQueue()[0]         #retrieve the obtained part
+        part.machineId=self.id                      #create an attribute to the obtained part and give it the value of the object's id
+        return activeEntity                         #return the entity obtained
+
+#the custom exit
+class CountingExit(Exit):
+    def getEntity(self):
+        activeEntity=Exit.getEntity(self)                        #call the parent method to get the entity
+        #check the attribute and update the counters accordingly
+        if activeEntity.machineId=='M1':         
+            G.NumM1+=1
+        elif activeEntity.machineId=='M2':
+            G.NumM2+=1
+        return activeEntity             #return the entity obtained
+        
+#define the objects of the model
+S=Source('S','Source', interarrivalTime={'distributionType':'Fixed','mean':0.5}, entity='Dream.Part')
+Q=SelectiveQueue('Q','Queue', capacity=float("inf"))
+M1=Milling('M1','Milling1', processingTime={'distributionType':'Fixed','mean':0.25})
+M2=Milling('M2','Milling2', processingTime={'distributionType':'Fixed','mean':0.25})
+E=CountingExit('E1','Exit')  
+F=Failure(victim=M1, distribution={'distributionType':'Fixed','MTTF':60,'MTTR':5})
+
+#create the global counter variables
+G.NumM1=0
+G.NumM2=0
+
+#create priority attribute in the Machines
+M1.priority=10
+M2.priority=0
+
+
+#define predecessors and successors for the objects    
+S.defineRouting([Q])
+Q.defineRouting([S],[M1,M2])
+M1.defineRouting([Q],[E])
+M2.defineRouting([Q],[E])
+E.defineRouting([M1,M2])
+
+def main():
+
+    # add all the objects in a list
+    objectList=[S,Q,M1,M2,E,F]  
+    # set the length of the experiment  
+    maxSimTime=1440.0
+    # call the runSimulation giving the objects and the length of the experiment
+    runSimulation(objectList, maxSimTime)
+    
+    #print the results
+    print "the system produced", E.numOfExits, "parts"
+    working_ratio_M1=(M1.totalWorkingTime/maxSimTime)*100
+    working_ratio_M2=(M2.totalWorkingTime/maxSimTime)*100
+    print "the working ratio of", M1.objName,  "is", working_ratio_M1, "%"
+    print "the working ratio of", M2.objName,  "is", working_ratio_M2, "%"
+    print M1.objName, "produced", G.NumM1, "parts"
+    print M2.objName, "produced", G.NumM2, "parts"
+    return {"parts": E.numOfExits,
+          "working_ratio_M1": working_ratio_M1,
+          "working_ratio_M2": working_ratio_M2,
+          "NumM1":G.NumM1,
+          "NumM2":G.NumM2}
+
+if __name__ == '__main__':
+    main()