genetic_algorithm.sf

#!/usr/bin/ruby

#
## A simple genetic algorithm in Sidef
## Inspired by Daniel Shiffman
## https://www.youtube.com/watch?v=DIXtg5VVz2E
#

var target = 'sidef lang'.chars
var parts = [('a'..'z')..., ' '].shuffle

var population_num = 150
var mutation_rate = 0.01

var population = population_num.of {
    target.len.of { parts.rand }
}

func fitness(item) {
    item ~Z== target -> count_by { _ }
}

func crossover(a, b) {
    a ~Z b -> map { |g|
        1.rand < mutation_rate ? parts.rand : g.rand
    }
}

loop {
    var matingpool = population.map { |item|
        ([item] * fitness(item))...
    }

    var fitness_score = 0
    var target_found = false

    population.map! {
        var child = crossover(matingpool.pick(2)...)
        fitness_score += fitness(child)
        target_found = true if child==target
        child
    }

    printf("Average fitness score: %.2f%%\n",
        fitness_score/population_num / target.len * 100)

    if (target_found) {
        say "** Target found!"
        break
    }
}