EvolutionofHelloWorld.rb

  1 class Population
  2   def initialize(population_size, target)
  3     @target = target
  4 
  5     @population = []
  6     population_size.times do
  7       @population.push Individual.create_random(target, target.length)
  8     end
  9   end
 10 
 11   def next_generation
 12     target_length = @population.length
 13     cull_population
 14     repopulate(target_length).first.score
 15   end
 16 
 17   def cull_population
 18     order_population
 19     @population.each_index do |index|
 20       if should_be_culled?(index)
 21         @population.delete_at(index)
 22       end
 23     end
 24   end
 25  
 26   def repopulate(target_length)
 27     order_population
 28     growth = target_length - @population.length
 29     babies = []
 30     growth.times do
 31       mate_a = find_mate(@population)
 32       mate_b = find_mate_for(mate_a)
 33       babies << mate_a.mate_with(mate_b)
 34     end
 35     @population += babies
 36   end
 37  
 38   def should_be_culled?(index)
 39     rand(@population.length) <= index
 40   end
 41 
 42   def should_mate(index)
 43     rand(@population.length) <= index
 44   end
 45  
 46   def find_mate(population)
 47     while true do
 48       population.each_index do |index|
 49         if should_mate(index)
 50             return population[index]
 51         end
 52       end
 53     end
 54   end
 55  
 56   def find_mate_for(individual)
 57     rest_of_pop = []
 58     @population.each do |ind|
 59       if ind != individual
 60         rest_of_pop << ind
 61       end
 62     end
 63     find_mate(rest_of_pop)
 64   end
 65 
 66   def order_population
 67     @population.sort! do |a,b,|
 68       a.score <=> b.score
 69     end
 70   end
 71 
 72   def log
 73     puts "-----"
 74     @population.each do |individual|
 75       puts individual.to_s
 76     end
 77   end
 78 
 79   def log_best
 80     puts @population.first.to_s
 81   end
 82 end
 83 
 84 class Individual
 85   def initialize(target, reproduction_system)
 86     @target = target
 87     @reproduction_system = reproduction_system
 88   end
 89 
 90   def self.create_random(target, output_length)
 91     Individual.new(target, ReproductionSystem.create_random(output_length))
 92   end
 93 
 94   def score
 95     score = 0
 96     @reproduction_system.genes.each_index do |index|
 97       score += (@target[index] - @reproduction_system.genes[index]).abs
 98     end
 99     score
100   end
101 
102   def mate_with(mate)
103     @reproduction_system.mate_with(mate)
104   end
105 
106   def be_mated_with(genetic_code)
107     Individual.new(@target, @reproduction_system.be_mated_with(genetic_code))
108   end
109 
110   def to_s
111     @reproduction_system.to_s + "  :  " + score.to_s
112   end
113 end
114 
115 class ReproductionSystem
116   attr_reader :genes
117   def initialize(genes)
118     @genes = genes
119   end
120 
121   def self.random_gene_part
122     32 + rand(94)
123   end
124 
125   def self.create_random(output_length)
126     genes = []
127     output_length.times do
128       genes.push(random_gene_part)
129     end
130     ReproductionSystem.new(genes)
131   end
132 
133   def to_s
134     out = ''
135     @genes.each do |part|
136       out += part.chr
137     end
138     out
139   end
140 
141   def mate_with(mate)
142     mate.be_mated_with(@genes)
143   end
144 
145   def be_mated_with(genetic_code)
146     length = @genes.length
147     a_half = genetic_code.slice(0, length/2)
148     b_half = @genes.slice(length/2,length-1)
149     genes = a_half + b_half
150     genes[rand(length)] = ReproductionSystem.random_gene_part
151 
152     ReproductionSystem.new(genes)
153   end
154 end
155 
156 population = Population.new(100, "Hello World")
157 population.order_population
158 population.log
159 i=0
160 while(population.next_generation>0) do
161   puts "generation " + (i+=1).to_s
162   population.log_best
163 end