Can't use a method as fitness function

[pedrodardengo]

I need my fitness function to have a state, for that reason I need to use a method instead of a function in the fitness_func parameter.

The problem is, PyGAD won't accept a method as fitness function.
This happens because PyGAD verifies how many arguments a function have and together with "self" argument a method as fitnees function would have 3 arguments. PyGAD won't let any fitness_func with number of arguments different than 2.

Shouldn't this be changed in the lib?
Does someone know a way around this while this feature isn't provided?

[uid89626]

I am having a similar issue. Trying to encapsulate all GA in a Class and global variables are not good design pattern.
e.g.

class MyGA:
def fitness_func(self, solution, sol_idx): ...
def on_generation(self, ga_instance): ...

so then I tried using functools.partial and still no
Traceback (most recent call last): File "C:\python\PyGadCNNADNet.py", line 57, in <module> myga = GadADNN() File "C:\python\PyGadCNNADNet.py", line 37, in __init__ self.ga_instance = GA(num_generations=10, num_parents_mating=2, initial_population=self.population_vectors.copy(), fitness_func=partial(self.fitness_func, self=self), mutation_percent_genes=0.1, parent_selection_type="sss", crossover_type="single_point", mutation_type="random", keep_parents=-1, on_generation=partial(self.on_generation, self=self)) File "C:\Users\foxx0\AppData\Local\Programs\Python\Python310\lib\site-packages\pygad\pygad.py", line 638, in __init__ if (fitness_func.__code__.co_argcount == 2): AttributeError: 'functools.partial' object has no attribute '__code__'. Did you mean: '__call__'?

so then I tried using functools.partialmethod and still no.
Traceback (most recent call last): File "C:\python\PyGadCNNADNet.py", line 57, in <module> myga = GadADNN() File "C:\python\PyGadCNNADNet.py", line 37, in __init__ self.ga_instance = GA(num_generations=10, num_parents_mating=2, initial_population=self.population_vectors.copy(), fitness_func=partialmethod(self.fitness_func, self=self), mutation_percent_genes=0.1, parent_selection_type="sss", crossover_type="single_point", mutation_type="random", keep_parents=-1, on_generation=partialmethod(self.on_generation, self=self)) File "C:\Users\foxx0\AppData\Local\Programs\Python\Python310\lib\site-packages\pygad\pygad.py", line 645, in __init__ raise TypeError("The value assigned to the fitness_func parameter is expected to be of type function but ({fitness_func_type}) found.".format(fitness_func_type=type(fitness_func))) TypeError: The value assigned to the fitness_func parameter is expected to be of type function but (<class 'functools.partialmethod'>) found.

workaround is to remove the argument count checks entirely in pygad.py line 638.

and lines 742

In fact actually there are 2 open PR to address this issue. Can we merge one of them and move forward already?
#99
#92

[borisarloff]

I am facing a similar issue, and posted it as Issue Request #138, with a proposed code patch. It allows for PyGAD GA class constructor to accept my class instance reference as a new parameter, and then delivering it to callback methods within my class. If the reference is set to None, then a function may be assumed, else it should call a method with the provisioned reference. I also like PR #92 proposed solution, either one would work for me. Currently, I am using my own patched code with latest Version 2.18.1.

Another issue I encountered is with on_crossover and on_mutation callbacks not being called if crossover_type or mutation_type are set to None, respectively. I need for my callbacks to be invoked regardless of type being set to None or not. I need to make adjustments for each solution just before the mutation operation, even when no crossover is required. The zip uploaded code monkeypatch solves this problem.

[borisarloff]

I uploaded pull request #143 which fixes both of my issues. Proposed changes are against PyGAD v2.18.1. I have been testing my implementation with these changes and so far it works well with methods as callbacks.

[ahmedfgad]

This is now supported. The fitness or any callback can accept a function or a method.

[borisarloff]

Great!