From ac3690837d392e5972233cf13b4e37551ac38175 Mon Sep 17 00:00:00 2001
From: Lee Spector <lspector@hampshire.edu>
Date: Wed, 1 Nov 2023 18:28:37 -0400
Subject: [PATCH] Add autoconstructive-crossover

---
 src/propeller/problems/boolean/mul3.cljc |  2 +-
 src/propeller/variation.cljc             | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/propeller/problems/boolean/mul3.cljc b/src/propeller/problems/boolean/mul3.cljc
index d204d34..db56c0c 100644
--- a/src/propeller/problems/boolean/mul3.cljc
+++ b/src/propeller/problems/boolean/mul3.cljc
@@ -314,7 +314,7 @@
      ;:parent-selection         :motley-batch-lexicase
      ;:max-batch-size           [1 2 4 8 16 32 64 128 256]
      ;:tournament-size          5
-     ;:umad-rate                0.09
+     :umad-rate                0.09
      ;:ah-umad-min              0.01
      ;:ah-umad-max              0.5
      ;:ah-umad-mean             0.05
diff --git a/src/propeller/variation.cljc b/src/propeller/variation.cljc
index 0a142a9..0e65e93 100644
--- a/src/propeller/variation.cljc
+++ b/src/propeller/variation.cljc
@@ -279,6 +279,22 @@ The function `new-individual` returns a new individual produced by selection and
                       plushy
                       (ah-rates plushy ah-min ah-max ah-mean)))))
 
+(defn autoconstructive-crossover
+  "Crosses over two individuals using autoconstructive crossover, one Push instruction at a time.
+   Pads shorter one from the end of the list of instructions."
+  [plushy-a plushy-b]
+  (let [a-genes (partition-by #(= % :gene) plushy-a)
+        b-genes (partition-by #(= % :gene) plushy-b)
+        shorter (min-key count a-genes b-genes)
+        longer (if (= shorter a-genes)
+                 b-genes
+                 a-genes)
+        length-diff (- (count longer) (count shorter))
+        shorter-padded (concat shorter (repeat length-diff ()))]
+    (flatten (mapv #(if (< (rand) 0.5) %1 %2)
+                   shorter-padded
+                   longer))))
+
 (defn new-individual
   "Returns a new individual produced by selection and variation of
   individuals in the population."
@@ -306,6 +322,11 @@ The function `new-individual` returns a new individual produced by selection and
          (tail-aligned-crossover
           (:plushy (selection/select-parent pop argmap))
           (:plushy (selection/select-parent pop argmap)))
+       ;
+         :autoconstructive-crossover
+         (autoconstructive-crossover
+          (:plushy (selection/select-parent pop argmap))
+          (:plushy (selection/select-parent pop argmap)))
        ;
          :umad
          (let [rate (utils/onenum (:umad-rate argmap))]