mattm · September 26, 2018 06:56 · Aug 18, 2013 · Aug 18, 2013 · Aug 18, 2013
diff --git a/gistfile1.rb b/gistfile1.rb
@@ -135,7 +135,7 @@ def select
     end
   end
 
-  puts "Generation #{generation} - Average: #{population.average_fitness.round} - Max: #{population.max_fitness}"
+  puts "Generation #{generation} - Average: #{population.average_fitness.round(2)} - Max: #{population.max_fitness}"
 
   population = offspring
 end

diff --git a/gistfile1.rb b/gistfile1.rb
@@ -1,8 +1,6 @@
 POPULATION_SIZE = 24
 NUM_BITS = 64
-
 NUM_GENERATIONS = 1000
-
 CROSSOVER_RATE = 0.7
 MUTATION_RATE = 0.001
 

diff --git a/gistfile1.rb b/gistfile1.rb
@@ -0,0 +1,145 @@
+POPULATION_SIZE = 24
+NUM_BITS = 64
+
+NUM_GENERATIONS = 1000
+
+CROSSOVER_RATE = 0.7
+MUTATION_RATE = 0.001
+
+class Chromosome
+
+  attr_accessor :genes
+
+  def initialize(genes = "")
+    if genes == ""
+      self.genes = (1..NUM_BITS).map{ rand(2) }.join
+    else
+      self.genes = genes
+    end
+  end
+
+  def to_s
+    genes.to_s
+  end
+
+  def count
+    genes.count
+  end
+
+  def fitness
+    genes.count("1")
+  end
+
+  def mutate!
+    mutated = ""
+    0.upto(genes.length - 1).each do |i|
+      allele = genes[i, 1]
+      if rand <= MUTATION_RATE
+        mutated += (allele == "0") ? "1" : "0"
+      else
+        mutated += allele
+      end
+    end
+
+    self.genes = mutated    
+  end
+
+  def &(other)
+    locus = rand(genes.length) + 1
+
+    child1 = genes[0, locus] + other.genes[locus, other.genes.length]
+    child2 = other.genes[0, locus] + genes[locus, other.genes.length]
+
+    return [
+      Chromosome.new(child1),
+      Chromosome.new(child2),
+    ]
+  end
+end
+
+class Population
+
+  attr_accessor :chromosomes
+
+  def initialize
+    self.chromosomes = Array.new
+  end
+
+  def inspect
+    chromosomes.join(" ")
+  end
+
+  def seed!
+    chromosomes = Array.new
+    1.upto(POPULATION_SIZE).each do
+      chromosomes << Chromosome.new
+    end
+
+    self.chromosomes = chromosomes    
+  end
+
+  def count
+    chromosomes.count
+  end
+
+  def fitness_values
+    chromosomes.collect(&:fitness)
+  end
+
+  def total_fitness
+    fitness_values.inject{|total, value| total + value }
+  end
+
+  def max_fitness
+    fitness_values.max
+  end
+
+  def average_fitness
+    total_fitness.to_f / chromosomes.length.to_f
+  end
+
+  def select
+    rand_selection = rand(total_fitness)
+
+    total = 0
+    chromosomes.each_with_index do |chromosome, index|
+      total += chromosome.fitness
+      return chromosome if total > rand_selection || index == chromosomes.count - 1
+    end
+  end
+end
+
+population = Population.new
+population.seed!
+
+1.upto(NUM_GENERATIONS).each do |generation|
+
+  offspring = Population.new
+
+  while offspring.count < population.count
+    parent1 = population.select
+    parent2 = population.select
+
+    if rand <= CROSSOVER_RATE
+      child1, child2 = parent1 & parent2
+    else
+      child1 = parent1
+      child2 = parent2
+    end
+
+    child1.mutate!
+    child2.mutate!
+
+    if POPULATION_SIZE.even?
+      offspring.chromosomes << child1 << child2
+    else
+      offspring.chromosomes << [child1, child2].sample
+    end
+  end
+
+  puts "Generation #{generation} - Average: #{population.average_fitness.round} - Max: #{population.max_fitness}"
+
+  population = offspring
+end
+
+puts "Final population: " + population.inspect