eckity.genetic_operators.crossovers.vector_k_point_crossover

 1from random import sample
 2
 3from eckity.genetic_operators.genetic_operator import GeneticOperator
 4from eckity.genetic_encodings.ga.vector_individual import Vector
 5
 6
 7class VectorKPointsCrossover(GeneticOperator):
 8    def __init__(self, probability=1, arity=2, k=1, events=None):
 9        """
10            Vector N Point Mutation.
11
12            Randomly chooses N vector cells and performs a small change in their values.
13
14            Parameters
15            ----------
16            probability : float
17                The probability of the mutation operator to be applied
18
19            arity : int
20                The number of individuals this mutation is applied on
21
22            k : int
23                Number of points to cut the vector for the crossover.
24
25            events: list of strings
26                Events to publish before/after the mutation operator
27        """
28        self.individuals = None
29        self.applied_individuals = None
30        self.k = k
31        self.points = None
32        super().__init__(probability=probability, arity=arity, events=events)
33
34    def apply(self, individuals):
35        """
36        Attempt to perform the mutation operator
37
38        Parameters
39        ----------
40        individuals : list of individuals
41            individuals to perform crossover on
42
43        Returns
44        ----------
45        list of individuals
46            individuals after the crossover
47        """
48        self.individuals = individuals
49        self.points = sorted(sample(range(1, individuals[0].size()), self.k))
50        
51        start_index = 0
52        for i in range(0, len(self.points), 2):
53            end_point = self.points[i]
54            replaced_part = individuals[0].get_vector_part(start_index, end_point)
55            replaced_part = individuals[1].replace_vector_part(replaced_part, start_index)
56            individuals[0].replace_vector_part(replaced_part, start_index)
57            start_index = end_point
58
59        # replace the last part (from last point to end)
60        replaced_part = individuals[0].get_vector_part(self.points[-1], individuals[0].size())
61        replaced_part = individuals[1].replace_vector_part(replaced_part, self.points[-1])
62        individuals[0].replace_vector_part(replaced_part, self.points[-1])
63
64        self.applied_individuals = individuals
65        return individuals