add generation-based termination

Author: spencerolson

lib/genetic.ex

@@ -55,22 +55,26 @@ defmodule Genetic do
 
   def run(problem, opts \\ []) do
     population = initialize(&problem.genotype/0)
+    first_generation = 0
+
     population
-    |> evolve(problem, opts)
+    |> evolve(problem, first_generation, opts)
   end
 
-  def evolve(population, problem, opts \\ []) do
+  def evolve(population, problem, generation, opts \\ []) do
     population = evaluate(population, &problem.fitness_function/1, opts)
     best = hd(population)
     IO.write("\rCurrent Best: #{problem.fitness_function(best)}")
-    if problem.terminate?(population) do
+    if problem.terminate?(population, generation) do
       best
     else
+      generation = generation + 1
+
       population
       |> select(opts)
       |> crossover(opts)
       |> mutation(opts)
-      |> evolve(problem, opts)
+      |> evolve(problem, generation, opts)
     end
   end
 end

lib/problem.ex

@@ -3,5 +3,5 @@ defmodule Problem do
 
   @callback genotype :: Chromosome.t
   @callback fitness_function(Chromosome.t) :: number()
-  @callback terminate?(Enum.t) :: boolean()
+  @callback terminate?(Enum.t(), integer()) :: boolean()
 end

scripts/cargo.exs

@@ -0,0 +1,48 @@
+defmodule Cargo do
+  @behaviour Problem
+  alias Types.Chromosome
+
+  @impl true
+  def genotype do
+    genes = for _ <- 1..10, do: Enum.random(0..1)
+    %Chromosome{genes: genes, size: length(genes)}
+  end
+
+  @impl true
+  def fitness_function(chromosome) do
+    profits = [6, 5, 8, 9, 6, 7, 3, 1, 2, 6]
+    weights = [10, 6, 8, 7, 10, 9, 7, 11, 6, 8]
+    weight_limit = 40
+
+    potential_profits =
+      profits
+      |> Enum.zip(chromosome.genes)
+      |> Enum.map(fn {profit, on_off} -> profit * on_off end)
+      |> Enum.sum()
+
+    over_limit? =
+      weights
+      |> Enum.zip(chromosome.genes)
+      |> Enum.map(fn {weight, on_off} -> weight * on_off end)
+      |> Enum.sum()
+      |> Kernel.>(weight_limit)
+
+    profits = if over_limit?, do: 0, else: potential_profits
+    profits
+  end
+
+  @impl true
+  def terminate?(_population, generation), do: generation == 100
+end
+
+solution = Genetic.run(Cargo, population_size: 50)
+IO.write("\n")
+IO.inspect(solution)
+
+weight =
+solution.genes
+|> Enum.zip([10, 6, 8, 7, 10, 9, 7, 11, 6, 8])
+|> Enum.map(fn {on_off, weight} -> weight * on_off end)
+|> Enum.sum()
+
+IO.write("\nWeight is: #{weight}\n")

scripts/one_max.exs

@@ -12,7 +12,7 @@ defmodule OneMax do
   def fitness_function(chromosome), do: Enum.sum(chromosome.genes)
 
   @impl true
-  def terminate?([best | _]), do: best.fitness == 42
+  def terminate?(_population, generation), do: generation == 100
 end
 
 solution = Genetic.run(OneMax)

scripts/speller.ex renamed to scripts/speller.exs

@@ -18,7 +18,7 @@ defmodule Speller do
   end
 
   @impl true
-  def terminate?([best | _]), do: best.fitness == 1
+  def terminate?(_population, generation), do: generation == 100
 end
 
 solution = Genetic.run(Speller)