radiate-alters 1.2.22

Alters - mutations and crossovers for the Radiate genetic algorithm library.
Documentation 
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use radiate_core::{AlterContext, AlterResult, Chromosome, Mutate, Rate, random_provider};

/// The [SwapMutator] is a simple mutator that swaps random genes in the [Chromosome].
#[derive(Debug, Clone)]
pub struct SwapMutator {
    rate: Rate,
}

impl SwapMutator {
    pub fn new(rate: impl Into<Rate>) -> Self {
        let rate = rate.into();
        SwapMutator { rate }
    }
}

impl<C: Chromosome> Mutate<C> for SwapMutator {
    fn rate(&self) -> Rate {
        self.rate.clone()
    }

    #[inline]
    fn mutate_chromosome(&self, chromosome: &mut C, ctx: &mut AlterContext) -> AlterResult {
        let mut mutations = 0;

        random_provider::with_rng(|rand| {
            for i in 0..chromosome.len() {
                if rand.bool(ctx.rate()) {
                    let swap_index = rand.range(0..chromosome.len());
                    if swap_index == i {
                        continue;
                    }

                    chromosome.as_mut_slice().swap(i, swap_index);
                    mutations += 1;
                }
            }
        });

        AlterResult::from(mutations)
    }
}