Initial commit

lib/genetic.ex

@@ -0,0 +1,77 @@
+defmodule Genetic do
+    alias Types.Chromosome
+
+    def initialize(genotype, opts \\ []) do
+        population_size = Keyword.get(opts, :population_size, 100)
+        for _ <- 1..population_size, do: genotype.()
+    end
+
+    def evaluate(population, fitness_function, opts \\ []) do
+        population
+        |> Enum.map(
+            fn chromosome ->
+                fitness = fitness_function.(chromosome)
+                age = chromosome.age + 1
+                %Chromosome{chromosome | fitness: fitness, age: age}
+            end
+        )
+        |> Enum.sort_by(& &1.fitness, &>=/2)
+    end
+
+    def select(population, opts \\ []) do
+        population
+        |> Enum.chunk_every(2)
+        |> Enum.map(&List.to_tuple(&1))
+    end
+
+    def crossover(population, opts \\ []) do
+        population
+        |> Enum.reduce([],
+            fn {p1, p2}, acc ->
+                cx_point = :rand.uniform(length(p1.genes))
+                {{h1,t1},{h2,t2}} =
+                    {Enum.split(p1.genes, cx_point),
+                    Enum.split(p2.genes, cx_point)}
+                {c1,c2} = {%Chromosome{p1 | genes: h1 ++ t2}, %Chromosome{p2 | genes: h2 ++ t1} }
+                [c1,c2 | acc]
+            end
+        )
+    end
+
+    def mutation(population, opts \\ []) do 
+        population
+        |> Enum.map(
+            fn chromosome ->
+                if :rand.uniform() < 0.05 do
+                    %Chromosome{chromosome | genes: Enum.shuffle(chromosome)}
+                else
+                    chromosome
+                end
+            end
+        )
+    end
+
+    def run(problem, opts \\ []) do
+        population = initialize(&problem.genotype/0)
+        population 
+        |> evolve(problem, opts)
+    end
+
+    def evolve(population, problem, opts \\ []) do
+        population = evaluate(population, &problem.fitness_function/1, opts)
+        best = hd(population)
+        IO.write("\rCurrent Best: #{best.fitness}")
+        if problem.terminate?(population) do
+            best
+        else
+            population
+            |> select(opts)
+            |> crossover(opts)
+            |> mutation(opts)
+            |> evolve(problem, opts)
+        end
+
+
+    end
+
+end

lib/types/chromosome.ex

@@ -0,0 +1,12 @@
+defmodule Types.Chromosome do
+    @type t :: %__MODULE__ {
+        genes: Enum.t,
+        size: integer(),
+        fitness: number(),
+        age: integer()
+    }
+
+
+    @enforce_keys :genes
+    defstruct [:genes, size: 0, fitness: 0, age: 0]
+end