40 lines
942 B
Ruby
40 lines
942 B
Ruby
@target = "METHINKS IT IS LIKE A WEASEL"
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Charset = [" ", *"A".."Z"]
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COPIES = 100
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def random_char; Charset.sample end
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def fitness(candidate)
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sum = 0
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candidate.chars.zip(@target.chars) {|x,y| sum += (x[0].ord - y[0].ord).abs}
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100.0 * Math.exp(Float(sum) / -10.0)
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end
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def mutation_rate(candidate)
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1.0 - Math.exp( -(100.0 - fitness(candidate)) / 400.0)
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end
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def mutate(parent, rate)
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parent.each_char.collect {|ch| rand <= rate ? random_char : ch}.join
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end
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def log(iteration, rate, parent)
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puts "%4d %.2f %5.1f %s" % [iteration, rate, fitness(parent), parent]
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end
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iteration = 0
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parent = Array.new(@target.length) {random_char}.join
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prev = ""
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while parent != @target
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iteration += 1
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rate = mutation_rate(parent)
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if prev != parent
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log(iteration, rate, parent)
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prev = parent
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end
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copies = [parent] + Array.new(COPIES) {mutate(parent, rate)}
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parent = copies.max_by {|c| fitness(c)}
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end
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log(iteration, rate, parent)
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