ga_instance.continue() after pygad.load()

[FeBe95]

Suggestion:

I created a GA with pygad where the fitness function needs a lot of time to calculate (several minutes per fitness calculation). When I am manually stopping it by hitting Ctrl+C I let the code continue and save the current state with ga_instance.save("file"). When I start another run I load the last state with ga_instance.load("file") and call ga_instance.run() to continue with the current population. It would be neat to be able to continue the calculations without loosing ga_instance.solutions etc., so when I call plot_fitness() my old data is still there. Currently with ga_instance.run() everything gets reset to [].

Sample Code:

try:
  ga_instance = pygad.load("file")
  ga_instance.continue()
except FileNotFoundError:
  ga_instance = pygad.GA([...])
  ga_instance.run()

ga_instance.save("file")
ga_instance.plot_fitness()

[ahmedfgad]

@FeBe95, thanks for opening the issue.

To get your idea, you mean saving the state when the execution is stopped by force? That is it does not stop by itself but you stop the execution manually, in the middle, by pressing CTRL+C for example?

[FeBe95]

Stopping by force would be one option. Another possible situation is that you have stop_criteria set (reach/saturate) and later want to continue the run with another value for stop_criteria.

ga_instance = pygad.load("file")
ga_instance.stop_criteria = None
ga_instance.continue() # instead of .run() which resets old stats
ga_instance.plot_fitness()

The problem is that calling run() on a loaded ga_instance would reset self.best_solutions, self.best_solutions_fitness, self.solutions and self.solutions_fitness (see line 1262 - 1625 of pygad.py). It just starts a new GA with the loaded parameters and saved population as the initial population, as far as i understood.
To put it simply: I want to be able to continue a loaded ga_instance without loosing the old solution values etc. A final plot_fitness() would show all data, not only the data from the second run.

I hope you understand the issue better now. Feel free to ask again if something is unclear.

[ahmedfgad]

Thanks for the clarification. Note that the following variables are reset to empty values each time the run() method runs.

self.best_solutions = []
self.best_solutions_fitness = []
self.solutions = []
self.solutions_fitness = []

I will consider updating the code to not lose these variables with each call to the run() method.

With the current situation, please note that the plot_fitness() method will recreate the same plot. This is an example.

import pygad
import numpy

function_inputs = [4,-2,3.5,5,-11,-4.7]
desired_output = 44

def fitness_func(solution, solution_idx):
    output = numpy.sum(solution*function_inputs)
    fitness = 1.0 / (numpy.abs(output - desired_output) + 0.000001)
    return fitness

ga_instance = pygad.GA(num_generations=100,
                       num_parents_mating=10,
                       sol_per_pop=20,
                       num_genes=len(function_inputs),
                       fitness_func=fitness_func)

ga_instance.run()

ga_instance.plot_fitness()

filename = 'genetic'
ga_instance.save(filename=filename)

To recreate the same plot, use this code. Note that you have to define all the functions used when loading the file.

import pygad
import numpy

function_inputs = [4,-2,3.5,5,-11,-4.7]
desired_output = 44

def fitness_func(solution, solution_idx):
    output = numpy.sum(solution*function_inputs)
    fitness = 1.0 / (numpy.abs(output - desired_output) + 0.000001)
    return fitness

filename = 'genetic'

loaded_ga_instance = pygad.load(filename=filename)
loaded_ga_instance.plot_fitness()

You can find that the same plot is created.

Please let me know if we can help in anyway.

[FeBe95]

I will consider updating the code to not lose these variables with each call to the run() method.

That's exactly what I thought of. I don't know if anything else needs to be adjusted here in order to be able to continue a calculation. Not losing these values would be a good first improvement.

With the code you provided I am able to recreate the plot. If I call run() right after load() like so

loaded_ga_instance = pygad.load(filename=filename)
loaded_ga_instance.run()
loaded_ga_instance.plot_fitness()

The data is reset. I might be able to improve the fitness further by calling run() again but the resulting plot does not include the loaded old fitness values. Even if you called run() twice in the same file (without saving/loading) the plot is missing the first data (see below). I think you understand what I mean. Sorry if I am being repetitive 😄

Output of plot_fitness() in second script you provided after calling run() again or after calling run() twice in the same script:

Plot

[ahmedfgad]

You are totally right!

So, there are 2 things:

1. When you just plot the fitness without running the code, then it recreates the previous plot exactly.
2. If you called the run() method, then the last plot is discarded and a new plot is created.

These are interesting features to support in a future release of PyGAD. Thanks for opening this issue which yields great stuff to support.

Please let me know if you have something in mind now or later.

[davidmurray]

Hi, this would be useful for me too as my fitness function involves really long transportation network simulations. A way to pause the calculations and restart them later would be really great. Is there any progress on this? Thanks!