Added point mutation

examples/increment_cubed.rb

@@ -25,9 +25,9 @@ def cases(num, value)
   :generations_limit => 500,                    
   :fitness_cases => cases(6, 1),
   :error_function => lambda{|cases| cases.inject{|x, y| x.abs + y.abs } },
-  :elitism_percent => 0.3,
+  :elitism_percent => 0.4,
   :crossover_percent => 0.5,
-  :mutation_percent => 0.0
+  :mutation_percent => 0.1
 })
 
 population.evolve!

examples/polynomial.rb

@@ -25,9 +25,9 @@ def cases(num, value)
   :generations_limit => 500,                    
   :fitness_cases => cases(6, 1),
   :error_function => lambda{|cases| cases.inject{|x, y| x.abs + y.abs } },
-  :elitism_percent => 0.3,
-  :crossover_percent => 0.6,
-  :mutation_percent => 0.0
+  :elitism_percent => 0.4,
+  :crossover_percent => 0.5,
+  :mutation_percent => 0.1
 })
 
 population.evolve!

lib/population.rb

@@ -56,7 +56,7 @@ def evolve_generation!
         elsif number_of_crossovers > 0 && number_of_crossovers -= 1          
           select_program.crossover(select_program)
         elsif number_of_mutations > 0 && number_of_mutations -= 1          
-          select_program.mutate(Program.randomized(rand(size_limit).next, instructions))
+          select_program.mutate(instructions, size_limit)
         elsif number_of_reproductions > 0 && number_of_reproductions -= 1          
           select_program.reproduce
         else

lib/program.rb

@@ -34,10 +34,12 @@ def crossover(mate)
       self.random_subset + mate.random_subset
     end
 
-    def mutate(mutation)
+    def mutate(instructions, size_limit)
       result = self.dup
-      result[rand(result.size)] = mutation
-      result.flatten
+      result.each_with_index do |inst, index| 
+        result[index] = instructions[rand(instructions.size)]  if rand < (1.5 / (size_limit*0.5))
+      end
+      result
     end
 
     def +(program)
@@ -51,13 +53,5 @@ def random_slice
     def random_subset
       self.slice( rand(self.size), rand(self.size) + 1 )
     end
-
-    def slice_left
-      self.slice( 0, rand(self.size).next )
-    end
-
-    def slice_right
-      self.slice( -rand(self.size).next, self.size )
-    end
   end
 end

spec/program/mutate_spec.rb

@@ -5,20 +5,20 @@ module Revolve
 describe Program, "#mutate" do
   before do
     @parent = Program.new(1, 2, 3, 4, 5)
-    @mutation = Program.new("one", "two", "three", "four", "five")
-    @child = @parent.mutate(@mutation)
+    @instructions = [1337]
+    @child = @parent.mutate(@instructions, 20)
   end
 
   it "should produce a new Program" do
     @child.should be_kind_of(Program)
   end
 
-  it "should be of length equal to the sum of the program - 1 and its mutation" do
-    @child.length.should == 9
+  it "should be of length equal to the original program" do
+    @child.length.should == 5
   end
 
   it "should only contain instructions from either program or mutation" do
-    @child.each{|instruction| (@parent + @mutation).should include(instruction) }
+    @child.each{|instruction| (@parent + @instructions).should include(instruction) }
   end
 end