Changeset 1289 for framspy/evolalg/structures

Timestamp:

01/15/24 05:43:37 (12 months ago)

Author:

Maciej Komosinski

Message:

fitness_set_negative_to_zero boolean (a.k.a. "only positive fitness", needed for novelty and niching diversity control) becomes a command-line flag instead of a hardcoded value

File:

• framspy/evolalg/structures/individual.py (modified) (2 diffs)

framspy/evolalg/structures/individual.py

@@ -3 +3 @@
 
 class Individual:
-    only_positive_fitness = True # Note: when using diversification techniques (e.g. niching), setting this to False and allowing negative fitness values requires verifying/improving diversification formulas. Dividing fitness by similarity (or multiplying by diversity) may have undesired consequences when fitness can be both positive and negative (e.g. low similarity may make positive fitness values higher and negative fitness values lower, while the intention would be to improve fitness for low similarity).
+    fitness_set_negative_to_zero = False # "static" field. Note: when using diversification techniques (e.g. niching or novelty), leaving this as False and allowing negative fitness values requires verifying/improving diversification formulas. Dividing fitness by similarity (or multiplying by diversity) may have undesired consequences when fitness can be both positive and negative (e.g. low similarity may make positive fitness values higher and negative fitness values lower, while the intention would be to improve fitness for low similarity).
 
     def __init__(self):
@@ -29 +29 @@
         fitness = evaluate(genotype)
         if fitness is not BAD_FITNESS:  # BAD_FITNESS indicates that the genotype was not valid or some other problem occurred during evaluation
-            if self.only_positive_fitness:
-                if fitness < 0:
-                    fitness = 0
+            if Individual.fitness_set_negative_to_zero and fitness < 0:
+                fitness = 0
         self.fitness = self.rawfitness = fitness