OMOPSO with multi-process failed #159
Description
Hello,
I want run OMOPSO in parallel using multi-process, and the code looks like
problem = ZDT1()
mutation_probability = 1.0 / problem.number_of_variables
max_evaluations = 25000
swarm_size = 100
algorithm = OMOPSO(
problem=problem,
swarm_size=swarm_size,
epsilon=0.0075,
uniform_mutation=UniformMutation(probability=mutation_probability, perturbation=0.5),
non_uniform_mutation=NonUniformMutation(mutation_probability, perturbation=0.5,
max_iterations=int(max_evaluations / swarm_size)),
leaders=CrowdingDistanceArchive(100),
termination_criterion=StoppingByEvaluations(max_evaluations=max_evaluations),
swarm_evaluator = MultiprocessEvaluator(processes=4),
)
and the error:
File ~/opt/miniconda3/lib/python3.9/site-packages/jmetal/core/algorithm.py:84, in Algorithm.run(self)
82 LOGGER.debug('Running main loop until termination criteria is met')
83 while not self.stopping_condition_is_met():
---> 84 self.step()
85 self.update_progress()
87 self.total_computing_time = time.time() - self.start_computing_time
File ~/opt/miniconda3/lib/python3.9/site-packages/jmetal/core/algorithm.py:222, in ParticleSwarmOptimization.step(self)
220 self.update_position(self.solutions)
221 self.perturbation(self.solutions)
--> 222 self.solutions = self.evaluate(self.solutions)
223 self.update_global_best(self.solutions)
224 self.update_particle_best(self.solutions)
File ~/opt/miniconda3/lib/python3.9/site-packages/jmetal/algorithm/multiobjective/omopso.py:93, in OMOPSO.evaluate(self, solution_list)
92 def evaluate(self, solution_list: List[FloatSolution]):
---> 93 return self.swarm_evaluator.evaluate(solution_list, self.problem)
...
769 return self._value
770 else:
--> 771 raise self._value
MaybeEncodingError: Error sending result: '[<jmetal.core.solution.FloatSolution object at 0x7ff59f4abc40>, <jmetal.core.solution.FloatSolution object at 0x7ff5a2248a30>, <jmetal.core.solution.FloatSolution object at 0x7ff5a22d5820>, <jmetal.core.solution.FloatSolution object at 0x7ff5a2303ee0>, <jmetal.core.solution.FloatSolution object at 0x7ff5a20cb8b0>, <jmetal.core.solution.FloatSolution object at 0x7ff5a2012610>, <jmetal.core.solution.FloatSolution object at 0x7ff5a22b6340>]'. Reason: 'RecursionError('maximum recursion depth exceeded while calling a Python object')'
Is it a bug?