number of best ants to keep in the next generation to be defined different...

number of best ants to keep in the next generation to be defined different than the number of solutions to be outputted

dream/plugins/ACO.py

@@ -55,7 +55,10 @@ class ACO(plugin.ExecutionPlugin):
     assert collated 
 
     max_results = int(data['general'].get('numberOfSolutions',0))
+    numberOfAntsForNextGeneration=int(data['general'].get('numberOfAntsForNextGeneration',1))
     assert max_results >= 1
+    assert numberOfAntsForNextGeneration>=1 \
+                and numberOfAntsForNextGeneration<=int(data["general"]["numberOfAntsPerGenerations"])
 
     ants = [] #list of ants for keeping track of their performance
 
@@ -149,8 +152,13 @@ class ACO(plugin.ExecutionPlugin):
         # best (max_results) are selected
         ants = sorted(ants_without_duplicates.values(),
           key=operator.itemgetter('score'))[:max_results]
+          
+        # The ants in this generation are ranked based on their scores and the
+        # best (numberOfAntsForNextGeneration) are selected to carry their pheromones to next generation
+        antsForNextGeneration = sorted(ants_without_duplicates.values(),
+          key=operator.itemgetter('score'))[:numberOfAntsForNextGeneration]
 
-        for l in ants:
+        for l in antsForNextGeneration:
             # update the options list to ensure that good performing queue-rule
             # combinations have increased representation and good chance of
             # being selected in the next generation