Source code for jmetal.algorithm.singleobjective.local_search

import copy
import random
import threading
import time
from typing import TypeVar, List

from jmetal.config import store
from jmetal.core.algorithm import Algorithm
from jmetal.core.operator import Mutation
from jmetal.core.problem import Problem
from jmetal.core.solution import Solution
from jmetal.util.comparator import Comparator
from jmetal.util.termination_criterion import TerminationCriterion

S = TypeVar('S')
R = TypeVar('R')

"""
.. module:: local_search
   :platform: Unix, Windows
   :synopsis: Implementation of Local search.

.. moduleauthor:: Antonio J. Nebro <antonio@lcc.uma.es>, Antonio Benítez-Hidalgo <antonio.b@uma.es>
"""


[docs]class LocalSearch(Algorithm[S, R], threading.Thread):

    def __init__(self,
                 problem: Problem[S],
                 mutation: Mutation,
                 termination_criterion: TerminationCriterion = store.default_termination_criteria,
                 comparator: Comparator = store.default_comparator):
        super(LocalSearch, self).__init__()
        self.comparator = comparator
        self.problem = problem
        self.mutation = mutation
        self.termination_criterion = termination_criterion
        self.observable.register(termination_criterion)

[docs]    def create_initial_solutions(self) -> List[S]:
        self.solutions.append(self.problem.create_solution())
        return self.solutions

[docs]    def evaluate(self, solutions: List[S]) -> List[S]:
        return [self.problem.evaluate(solutions[0])]

[docs]    def stopping_condition_is_met(self) -> bool:
        return self.termination_criterion.is_met

[docs]    def init_progress(self) -> None:
        self.evaluations = 0

[docs]    def step(self) -> None:
        mutated_solution = copy.deepcopy(self.solutions[0])
        mutated_solution: Solution = self.mutation.execute(mutated_solution)
        mutated_solution = self.evaluate([mutated_solution])[0]

        result = self.comparator.compare(mutated_solution, self.solutions[0])
        if result == -1:
            self.solutions[0] = mutated_solution
        elif result == 1:
            pass
        else:
            if random.random() < 0.5:
                self.solutions[0] = mutated_solution

[docs]    def update_progress(self) -> None:
        self.evaluations += 1

        observable_data = self.get_observable_data()
        self.observable.notify_all(**observable_data)

[docs]    def get_observable_data(self) -> dict:
        ctime = time.time() - self.start_computing_time
        return {'PROBLEM': self.problem, 'EVALUATIONS': self.evaluations, 'SOLUTIONS': self.get_result(),
                'COMPUTING_TIME': ctime}

[docs]    def get_result(self) -> R:
        return self.solutions[0]

[docs]    def get_name(self) -> str:
        return 'LS'
Table Of Contents

Source code for jmetal.algorithm.singleobjective.local_search
