Error when run parallel_processing "process"

[henryfpassagem]

I am getting an error when I try to run with parallel_processing = ["process", 2] the first example on the PyGad webpage. Could somebody please help me with this?

[ahmedfgad]

This is a working example.

import pygad
import numpy

function_inputs = [4,-2,3.5,5,-11,-4.7] # Function inputs.
desired_output = 44 # Function output.

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

num_generations = 100 # Number of generations.
num_parents_mating = 10 # Number of solutions to be selected as parents in the mating pool.

sol_per_pop = 20 # Number of solutions in the population.
num_genes = len(function_inputs)

last_fitness = 0
def on_generation(ga_instance):
    global last_fitness
    print(f"Generation = {ga_instance.generations_completed}")
    print(f"Fitness    = {ga_instance.best_solution(pop_fitness=ga_instance.last_generation_fitness)[1]}")
    print(f"Change     = {ga_instance.best_solution(pop_fitness=ga_instance.last_generation_fitness)[1] - last_fitness}")
    last_fitness = ga_instance.best_solution(pop_fitness=ga_instance.last_generation_fitness)[1]

if __name__ == '__main__':
    ga_instance = pygad.GA(num_generations=num_generations,
                           num_parents_mating=num_parents_mating,
                           sol_per_pop=sol_per_pop,
                           num_genes=num_genes,
                           suppress_warnings=True,
                           parallel_processing=['process', 2],
                           fitness_func=fitness_func,
                           on_generation=on_generation)
    
    # Running the GA to optimize the parameters of the function.
    ga_instance.run()
    
    ga_instance.plot_fitness()

[steve-allwright]

Good afternoon
Thanks for this example, which I adapt to illustrate a continuation run problem that I encounter.

When I perform the :
ga_instance.run()
command repeatedly, then the continuation run works giving me generations 101-200, 201-300 etc.

However, if I include the keyword
save_best_solutions=True,
then the continuation run fails with the message :-
File ~\miniconda3\Lib\site-packages\pygad\pygad.py:1682 in cal_pop_fitness
elif (self.save_best_solutions) and (len(self.best_solutions) > 0) and (list(sol) in self.best_solutions):
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all

Is this a known problem ?
Best regards
Steve

[ahmedfgad]

In the code, I tried calling the run() method in a loop and it is still working without exceptions.

for i in range(5):
        ga_instance.run()