88 lines
2.4 KiB
Go
88 lines
2.4 KiB
Go
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package gago
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import (
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"math/rand"
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)
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// Type specific mutations for slices
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// MutNormalFloat64 modifies a float64 gene if a coin toss is under a defined
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// mutation rate. The new gene value is a random value sampled from a normal
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// distribution centered on the gene's current value and with a standard
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// deviation proportional to the current value. It does so for each gene.
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func MutNormalFloat64(genome []float64, rate float64, rng *rand.Rand) {
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for i := range genome {
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// Flip a coin and decide to mutate or not
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if rng.Float64() < rate {
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genome[i] += rng.NormFloat64() * genome[i]
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}
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}
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}
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// MutUniformString picks a gene at random and replaces it with a random from a
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// provided corpus. It repeats this n times.
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func MutUniformString(genome []string, corpus []string, n int, rng *rand.Rand) {
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for i := 0; i < n; i++ {
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var (
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element = corpus[rng.Intn(len(corpus))]
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pos = rng.Intn(len(genome))
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)
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genome[pos] = element
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}
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}
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// Generic mutations for slices
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// MutPermute permutes two genes at random n times.
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func MutPermute(genome Slice, n int, rng *rand.Rand) {
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// Nothing to permute
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if genome.Len() <= 1 {
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return
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}
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for i := 0; i < n; i++ {
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// Choose two points on the genome
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var points = randomInts(2, 0, genome.Len(), rng)
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genome.Swap(points[0], points[1])
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}
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}
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// MutPermuteInt calls MutPermute on an int slice.
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func MutPermuteInt(s []int, n int, rng *rand.Rand) {
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MutPermute(IntSlice(s), n, rng)
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}
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// MutPermuteFloat64 calls MutPermute on a float64 slice.
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func MutPermuteFloat64(s []float64, n int, rng *rand.Rand) {
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MutPermute(Float64Slice(s), n, rng)
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}
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// MutPermuteString callsMutPermute on a string slice.
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func MutPermuteString(s []string, n int, rng *rand.Rand) {
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MutPermute(StringSlice(s), n, rng)
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}
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// MutSplice splits a genome in 2 and glues the pieces back together in reverse
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// order.
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func MutSplice(genome Slice, rng *rand.Rand) {
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var (
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k = rng.Intn(genome.Len()-1) + 1
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a, b = genome.Split(k)
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)
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genome.Replace(b.Append(a))
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}
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// MutSpliceInt calls MutSplice on an int slice.
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func MutSpliceInt(s []int, rng *rand.Rand) {
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MutSplice(IntSlice(s), rng)
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}
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// MutSpliceFloat64 calls MutSplice on a float64 slice.
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func MutSpliceFloat64(s []float64, rng *rand.Rand) {
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MutSplice(Float64Slice(s), rng)
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}
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// MutSpliceString calls MutSplice on a string slice.
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func MutSpliceString(s []string, rng *rand.Rand) {
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MutSplice(StringSlice(s), rng)
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}
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