Add elitism

genetic_selection/gscv.py

@@ -55,8 +55,11 @@ def _eaFunction(population, toolbox, cxpb, mutpb, ngen, ngen_no_change=None, sta
     for ind, fit in zip(invalid_ind, fitnesses):
         ind.fitness.values = fit
 
-    if halloffame is not None:
-        halloffame.update(population)
+    if halloffame is None:
+        raise ValueError("The 'halloffame' parameter should not be None.")
+
+    halloffame.update(population)
+    hof_size = len(halloffame.items) if halloffame.items else 0
 
     record = stats.compile(population) if stats else {}
     logbook.record(gen=0, nevals=len(invalid_ind), **record)
@@ -67,7 +70,7 @@ def _eaFunction(population, toolbox, cxpb, mutpb, ngen, ngen_no_change=None, sta
     wait = 0
     for gen in range(1, ngen + 1):
         # Select the next generation individuals
-        offspring = toolbox.select(population, len(population))
+        offspring = toolbox.select(population, len(population) - hof_size)
 
         # Vary the pool of individuals
         offspring = algorithms.varAnd(offspring, toolbox, cxpb, mutpb)
@@ -78,12 +81,14 @@ def _eaFunction(population, toolbox, cxpb, mutpb, ngen, ngen_no_change=None, sta
         for ind, fit in zip(invalid_ind, fitnesses):
             ind.fitness.values = fit
 
+        # Add the best back to population
+        offspring.extend(halloffame.items)
+
         # Get the previous best individual before updating the hall of fame
         prev_best = halloffame[0]
 
         # Update the hall of fame with the generated individuals
-        if halloffame is not None:
-            halloffame.update(offspring)
+        halloffame.update(offspring)
 
         # Replace the current population by the offspring
         population[:] = offspring