eckity.genetic_operators.mutations.vector_n_point_mutation

  1import random
  2
  3from eckity.genetic_operators.failable_operator import FailableOperator
  4from eckity.genetic_encodings.ga.vector_individual import Vector
  5
  6from typing import List, Tuple, Union
  7
  8
  9class VectorNPointMutation(FailableOperator):
 10    """
 11    Vector N Point Mutation.
 12
 13    Randomly chooses N vector cells and performs a small change in their values.
 14
 15    Parameters
 16    ----------
 17    n : int
 18        Number of mutation points.
 19
 20    probability : float
 21        The probability of the mutation operator to be applied
 22
 23    arity : int
 24        The number of individuals this mutation is applied on
 25
 26    cell_selector: callable
 27        Returns the indices of the cells to mutate
 28
 29    mut_val_getter: callable
 30        Returns a mutated value of a certain cell
 31
 32    success_checker: callable
 33        Checks if a given (mutated) cell value is legal
 34
 35    events: list of strings
 36        Events to publish before/after the mutation operator
 37    """
 38    def __init__(self,
 39                 n=1,
 40                 probability=1.0,
 41                 arity=1,
 42                 cell_selector=None,
 43                 mut_val_getter=None,
 44                 success_checker=None,
 45                 events=None,
 46                 attempts=5):
 47        super().__init__(probability=probability, arity=arity, events=events, attempts=attempts)
 48        self.n = n
 49
 50        if cell_selector is None:
 51            cell_selector = self.default_cell_selector
 52        self.cell_selector = cell_selector
 53
 54        if success_checker is None:
 55            success_checker = self.default_success_checker
 56        self.success_checker = success_checker
 57
 58        if mut_val_getter is None:
 59            mut_val_getter = self.default_mut_val_getter
 60        self.mut_val_getter = mut_val_getter
 61
 62    @staticmethod
 63    def default_mut_val_getter(vec: Vector, idx: int) -> Union[int, float]:
 64        return vec.get_random_number_in_bounds(vec, idx)
 65
 66    @staticmethod
 67    def default_success_checker(old_vec: Vector, new_vec: Vector) -> bool:
 68        return new_vec.check_if_in_bounds()
 69    
 70    def default_cell_selector(self, vec: Vector) -> List[int]:
 71        vector_indices = range(vec.size())
 72        return random.sample(vector_indices, k=self.n)
 73
 74    def attempt_operator(self, individuals: List[Vector], attempt_num) -> Tuple[bool, List[Vector]]:
 75        """
 76        Attempt to perform the mutation operator
 77
 78        Parameters
 79        ----------
 80        individuals : list of vectors
 81            vectors to mutate
 82
 83        attempt_num : int
 84            Current attempt number
 85
 86        Returns
 87        ----------
 88        tuple of (bool, list of vectors)
 89            first return value determines if the the attempt succeeded
 90            second return value is the operator result
 91        """
 92        succeeded = True
 93        for individual in individuals:
 94            old_individual = individual.clone()
 95
 96            # randomly select n points of the vector (without repetitions)
 97            m_points = self.cell_selector(individual)
 98            # obtain the mutated values
 99            mut_vals = [self.mut_val_getter(individual, m_point) for m_point in m_points]
100
101            # update the mutated value in-place
102            for m_point, mut_val in zip(m_points, mut_vals):
103                individual.set_cell_value(m_point, mut_val)
104
105            if not self.success_checker(old_individual, individual):
106                succeeded = False
107                individual.set_vector(old_individual.vector)
108                break
109
110        self.applied_individuals = individuals
111        return succeeded, individuals
112
113    def on_fail(self, payload):
114        """
115        The required fix when the operator fails, does nothing by default and can be overridden by subclasses
116
117        Parameters
118        ----------
119        payload : object
120            relevant data for on_fail (usually the individuals that the mutation was attempted to be applied on)
121        """
122        pass