eckity.genetic_operators.failable_operator

 1from eckity.genetic_operators.genetic_operator import GeneticOperator
 2from abc import abstractmethod
 3
 4
 5class FailableOperator(GeneticOperator):
 6    """
 7    Genetic operator that has a chance of failing.
 8
 9    For example, adding a gaussian noise to a FloatVector cell might exceed the legal bounds of the vector.
10    In that case, the Gauss Mutation fails.
11
12    Parameters
13    -------
14    probability: float
15        the probability of the operator to be applied
16
17    arity: int
18        number of individuals to be applied on
19
20    events: list of strings
21        events to be published before, after and during the operator
22
23    attempts: int
24        number of attempts to be made during the operator execution
25    """
26    def __init__(self, probability=0.05, arity=0, events=None, attempts=1):
27        super().__init__(probability, arity, events)
28        if attempts <= 1:
29            raise ValueError("Number of attempts must be at least 1")
30        self.attempts = attempts
31
32    # TODO add event of on fail or on fail all retries
33    def apply(self, payload):
34        """
35        Apply the operator, with a chance of failing.
36
37        Attempt to apply the operator `attempts` times, finish by succeeding in one of the attempts or by failing
38        all attempts and executing `on_fail` method.
39
40        Parameters
41        -------
42        payload: object
43            relevant data for the applied operator (usually a list of individuals)
44        """
45        for i in range(self.attempts):
46            # attempt to execute the operator
47            succeeded, result = self.attempt_operator(payload, i)
48
49            # return if succeeded
50            if succeeded:
51                return result
52        # after all attempts failed, execute the `on_fail` mechanism
53        return self.on_fail(payload)
54
55    @abstractmethod
56    def attempt_operator(self, payload, attempt_num):
57        """
58        A single attempt of the operator
59
60        Parameters
61        -------
62        payload: object
63            relevant data for the applied operator (usually a list of individuals)
64
65        attempt_num: int
66            current attempt number
67
68        Returns
69        -------
70        (bool, object)
71            tuple of (succeeded or not, result value)
72        """
73        pass
74
75    @abstractmethod
76    def on_fail(self, payload):
77        """
78        What to do when all operator attempts failed
79
80        This method is called once all operator attempts have failed
81
82        Parameters
83        -------
84        payload: object
85            relevant data for the failure handling mechanism (usually a list of individuals)
86
87        Returns
88        -------
89        object
90            result value
91        """
92        pass