genetic

commit ba76f5047ee8ec89459d35ff65622e1188a305b0
parent 734900580f9b151a2050eb45433d09ffe10c8ffb
Author: dracuxan <[email protected]>
Date:   Wed,  8 Apr 2026 14:03:56 +0530

new: whole arithmetic crossover and demo of multi parent crossover

Diffstat:
M
genetic/lib/toolbox/crossover.ex
 | 
65
+++++++++++++++++++++++++++++++++++++++++++++++++++--------------

1 file changed, 51 insertions(+), 14 deletions(-)
diff --git a/genetic/lib/toolbox/crossover.ex b/genetic/lib/toolbox/crossover.ex
@@ -24,16 +24,10 @@ defmodule Toolbox.Crossover do
     # create and return
     {c1, c2} = {head1 ++ slice1 ++ tail1, head2 ++ slice2 ++ tail2}
 
-    {%Chromosome{
-       genes: c1,
-       size: p1.size,
-       age: 0
-     },
-     %Chromosome{
-       genes: c2,
-       size: p2.size,
-       age: 0
-     }}
+    {
+      %Chromosome{genes: c1, size: length(c1), age: 0},
+      %Chromosome{genes: c2, size: length(c2), age: 0}
+    }
   end
 
   def single_point(p1, p2, _opts \\ []) do
@@ -45,8 +39,8 @@ defmodule Toolbox.Crossover do
     {c1, c2} = {head1 ++ tail2, head2 ++ tail1}
 
     {
-      %Chromosome{genes: c1, size: p1.size, age: 0},
-      %Chromosome{genes: c2, size: p2.size, age: 0}
+      %Chromosome{genes: c1, size: length(c1), age: 0},
+      %Chromosome{genes: c2, size: length(c2), age: 0}
     }
   end
 
@@ -66,8 +60,51 @@ defmodule Toolbox.Crossover do
       |> Enum.unzip()
 
     {
-      %Chromosome{genes: c1, size: p1.size, age: 0},
-      %Chromosome{genes: c2, size: p2.size, age: 0}
+      %Chromosome{genes: c1, size: length(c1), age: 0},
+      %Chromosome{genes: c2, size: length(c2), age: 0}
+    }
+  end
+
+  def whole_arethmetic(p1, p2, opts \\ []) do
+    alpha = Keyword.get(opts, :alpha, 0.5)
+
+    {c1, c2} =
+      p1.genes
+      |> Enum.zip(p2.genes)
+      |> Enum.map(fn {x, y} ->
+        {
+          x * alpha + y * (1 - alpha),
+          x * (alpha - 1) + y * alpha
+        }
+      end)
+      |> Enum.unzip()
+
+    {
+      %Chromosome{genes: c1, size: length(c1), age: 0},
+      %Chromosome{genes: c2, size: length(c2), age: 0}
     }
   end
+
+  # demo of how crossover can be performed on mulitple parents at once
+  def single_point_multi(parents, opts \\ [])
+  def single_point_multi([], _opts), do: raise("more than one parent needed!")
+  def single_point_multi([p1 | []], _opts), do: p1
+
+  def single_point_multi(parents, _opts) do
+    p1 = hd(parents)
+    cx_point = :rand.uniform(p1.size)
+
+    parents
+    |> Enum.chunk_every(2, 1, [hd(parents)])
+    |> Enum.map(&List.to_tuple(&1))
+    |> Enum.reduce(
+      [],
+      fn {p1, p2}, chd ->
+        {front, _} = Enum.split(p1.genes, cx_point)
+        {_, back} = Enum.split(p2.genes, cx_point)
+        c = %Chromosome{genes: front ++ back, size: length(p1)}
+        [c | chd]
+      end
+    )
+  end
 end