Add the Shakespeare monkey test

Author: Eric Matte

lib/genetic/algorithm/fitness_recorder.rb

@@ -47,4 +47,8 @@ def display_best_individual
   def save_best_individual_genes
     raise "not implemented".freeze
   end
+
+  def debug
+    false
+  end
 end

lib/genetic/algorithm/optimiser.rb renamed to lib/genetic/algorithm/optimizer.rb

@@ -1,25 +1,15 @@
 module Genetic
   module Algorithm
-    class Optimiser
+    class Optimizer
       attr_accessor :crossover_probability # Int
       attr_accessor :mutation_probability  # Int
       attr_accessor :population_size       # Int
-      attr_accessor :number_of_generations # Int
       attr_accessor :genes_generator       # (index: Int?) -> Array<Gene> | Gene if index.nil?
       attr_accessor :fitness_calculator    # (genes: Array<Gene>) -> Int
 
-      def execute
-        population = initialize_population
-
-        fitness_recorder = FitnessRecorder.new
-        @number_of_generations.times.each do |generation|
-          if generation != @number_of_generations
-            population = do_natural_selection(population)
-          end
-          fitness_recorder.record_generation(generation, population)
-        end
-
-        fitness_recorder.display_best_individual
+      def execute(population = nil)
+        population = initialize_population if population.nil?
+        do_natural_selection(population)
       end
 
       private
@@ -34,6 +24,7 @@ def initialize_population
 
       def do_natural_selection(population)
         total_fitness = population.map(&:fitness).inject(:+)
+
         new_population = []
         (@population_size / 2).times.each do
           parent1 = weighted_random_sampling(population, total_fitness)
@@ -49,7 +40,11 @@ def do_natural_selection(population)
       end
 
       def weighted_random_sampling(population, total_fitness)
-        population.max_by { |chromosome| rand**(total_fitness / chromosome.fitness) }
+        if total_fitness.zero?
+          population.sample
+        else
+          population.max_by { |chromosome| rand * (chromosome.fitness / total_fitness) }
+        end
       end
 
       def mate(parent1, parent2)

lib/genetic/algorithm/resolver.rb

@@ -1,83 +1,84 @@
 require "test_helper"
-require "genetic/algorithm/optimiser"
+require "genetic/algorithm/optimizer"
 
-class Genetic::Algorithm::OptimiserTest < Minitest::Test
+class Genetic::Algorithm::OptimizerTest < Minitest::Test
   def test_it_initialize_population
-    ga_optimiser = Genetic::Algorithm::Optimiser.new
-    ga_optimiser.population_size = population_size
-    ga_optimiser.genes_generator = method(:genes_generator)
-    ga_optimiser.fitness_calculator = method(:fitness_calculator)
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.population_size = population_size
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
 
-    test_population = ga_optimiser.send(:initialize_population)
+    test_population = ga_optimizer.send(:initialize_population)
 
     assert(test_population.length == population_size)
     assert(test_population.map(&:fitness).inject(:+) >= population_size)
   end
 
   def test_it_do_natural_selection
-    ga_optimiser = Genetic::Algorithm::Optimiser.new
-    ga_optimiser.crossover_probability = 0.7
-    ga_optimiser.mutation_probability = 0.1
-    ga_optimiser.population_size = population_size
-    ga_optimiser.genes_generator = method(:genes_generator)
-    ga_optimiser.fitness_calculator = method(:fitness_calculator)
-    first_population = ga_optimiser.send(:initialize_population)
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.crossover_probability = 0.7
+    ga_optimizer.mutation_probability = 0.5
+    ga_optimizer.population_size = population_size
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
+    first_population = ga_optimizer.send(:initialize_population)
     last_population = first_population
 
-    20.times do
-      last_population = ga_optimiser.send(:do_natural_selection, last_population)
+    100.times do
+      last_population = ga_optimizer.send(:do_natural_selection, last_population)
     end
 
     assert(first_population.length == population_size)
     assert(last_population.length == population_size)
 
+    assert(first_population != last_population)
     first_gen_fitness = first_population.map(&:fitness).inject(:+)
     last_gen_fitness = last_population.map(&:fitness).inject(:+)
-    assert(first_gen_fitness < last_gen_fitness)
+    assert(first_gen_fitness != last_gen_fitness)
   end
 
   def test_mate_with_0_proability_returns_same_chromosomes
-    ga_optimiser = Genetic::Algorithm::Optimiser.new
-    ga_optimiser.crossover_probability = 0.0
-    ga_optimiser.mutation_probability = 0.0
-    ga_optimiser.genes_generator = method(:genes_generator)
-    ga_optimiser.fitness_calculator = method(:fitness_calculator)
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.crossover_probability = 0.0
+    ga_optimizer.mutation_probability = 0.0
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
 
     parent1 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
     parent2 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
-    child1, child2 = ga_optimiser.send(:mate, parent1, parent2)
+    child1, child2 = ga_optimizer.send(:mate, parent1, parent2)
 
     assert(parent1.genes != parent2.genes)
     assert(child1.genes == parent1.genes)
     assert(child2.genes == parent2.genes)
   end
 
   def test_mate_crossover
-    ga_optimiser = Genetic::Algorithm::Optimiser.new
-    ga_optimiser.crossover_probability = 1.0
-    ga_optimiser.mutation_probability = 0.0
-    ga_optimiser.genes_generator = method(:genes_generator)
-    ga_optimiser.fitness_calculator = method(:fitness_calculator)
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.crossover_probability = 1.0
+    ga_optimizer.mutation_probability = 0.0
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
 
     parent1 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
     parent2 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
-    child1, child2 = ga_optimiser.send(:mate, parent1, parent2)
+    child1, child2 = ga_optimizer.send(:mate, parent1, parent2)
 
     assert(parent1.genes != parent2.genes)
     assert(child1.genes != parent1.genes)
     assert(child2.genes != parent2.genes)
   end
 
   def test_mate_make_one_mutation_per_child
-    ga_optimiser = Genetic::Algorithm::Optimiser.new
-    ga_optimiser.crossover_probability = 0.0
-    ga_optimiser.mutation_probability = 1.0
-    ga_optimiser.genes_generator = method(:genes_generator)
-    ga_optimiser.fitness_calculator = method(:fitness_calculator)
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.crossover_probability = 0.0
+    ga_optimizer.mutation_probability = 1.0
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
 
     parent1 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
     parent2 = Genetic::Algorithm::Chromosome.new(genes_generator, method(:fitness_calculator))
-    child1, child2 = ga_optimiser.send(:mate, parent1, parent2)
+    child1, child2 = ga_optimizer.send(:mate, parent1, parent2)
 
     assert(parent1.genes != parent2.genes)
     assert(child1.genes != parent1.genes)

test/genetic/algorithm/optimiser_test.rb renamed to test/genetic/algorithm/optimizer_test.rb

@@ -0,0 +1,57 @@
+require "test_helper"
+
+class Genetic::Algorithm::ShakespeareMonkeyTest < Minitest::Test
+  def test_that_it_resolves_the_monkey_problem
+    ga_optimizer = Genetic::Algorithm::Optimizer.new
+    ga_optimizer.population_size = 200
+    ga_optimizer.crossover_probability = 0.7
+    ga_optimizer.mutation_probability = 0.5
+    ga_optimizer.genes_generator = method(:genes_generator)
+    ga_optimizer.fitness_calculator = method(:fitness_calculator)
+
+    goal_phrase = goal.join
+
+    generation = 0
+    last_population = nil
+    while generation < 500
+      new_population = ga_optimizer.execute(last_population)
+
+      best_one = new_population.max_by(&:fitness)
+      best_phrase = best_one.genes.join
+
+      if best_phrase == goal_phrase
+        puts "Goal found! \"#{goal_phrase}\" in #{generation} generations."
+        break
+      else
+        puts "#{best_phrase} - #{best_one.fitness * 100}% (G-#{generation})"
+      end
+
+      generation += 1
+      last_population = new_population
+    end
+
+    assert(true, generation < 500)
+  end
+
+  private
+
+  def goal
+    "Make Time Count.".split("")
+  end
+
+  def letters
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.!? ".split("")
+  end
+
+  def genes_generator(index = nil)
+    index.nil? ? Array.new(goal.length) { letters.sample } : letters.sample
+  end
+
+  def fitness_calculator(genes)
+    fitness = 0.0
+    goal.each_with_index do |letter, i|
+      fitness += 1 if letter == genes[i]
+    end
+    fitness / goal.length
+  end
+end

test/genetic/algorithm/shakespeare_monkey_test.rb

@@ -1,6 +1,6 @@
 require "test_helper"
 
-class Genetic::Algorithm::ResolverTest < Minitest::Test
+class Genetic::Algorithm::VersionTest < Minitest::Test
   def test_that_it_has_a_version_number
     refute_nil Genetic::Algorithm::VERSION
   end