alogos.systems.whge.mutation

Mutation functions for WHGE.

Functions

bit_flip_by_probability(grammar, genotype, parameters=None)

Mutate a genotype by random bit flips with a certain probability.

bit_flip_by_count(grammar, genotype, parameters=None)

Mutate a genotype by n random bit flips.

Detailed object descriptions

alogos.systems.whge.mutation.bit_flip_by_probability(grammar, genotype, parameters=None)[source]

Mutate a genotype by random bit flips with a certain probability.

The probability for a bit flip is considered independently for each position in the genotype, regardless of the genotype length.

Caution: Mutation is performed in-place for performance reasons, which means that the provided genotype is modified. If this is not desired, a copy needs to be made beforehand.

Parameters:

  • grammar (Grammar)

  • genotype (Genotype)

  • parameters (dict or ParameterCollection, optional) – Following keyword-value pairs are considered by this function:

    • mutation_bit_flip_probability (int) : Probability of changing a bit.

References

  • Medvet in 2017: Hierarchical Grammatical Evolution

    • p. 250: “we performed 30 independent executions of the evolutionary search […] with the following evolution parameters: […] bit flip mutation with p_mut = 0.01 and 0.2 rate”

  • Bartoli, Castelli, Medvet in 2018: Weighted Hierarchical Grammatical Evolution

      1. 7, Table 1: “Mutation op. bit flip w. p_mut = 0.01”

  • Reference implementation in Java: evolved-ge

    • ProbabilisticMutation.java

      • The algorithm loops over each bit of the genotype, in each run generating a random number between 0.0 and 1.0 and if it is smaller than p_mut the current bit is flipped.

    • Folder with example scripts

      • Using ProbabilisticMutation with p_mut 0.01 and rate 0.2: DeepExperimenter.java, DeepDistributedExperimenter.java, GOM.java, MapperGenerationExperimenter.java, MapperGenerationDistributedExperimenter.java

alogos.systems.whge.mutation.bit_flip_by_count(grammar, genotype, parameters=None)[source]

Mutate a genotype by n random bit flips.