Data commit

Task/Evolutionary-algorithm/OCaml/evolutionary-algorithm.ocaml

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+let target = "METHINKS IT IS LIKE A WEASEL"
+let charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
+let tlen = String.length target
+let clen = String.length charset
+let () = Random.self_init()
+
+let parent =
+  let s = String.create tlen in
+  for i = 0 to tlen-1 do
+    s.[i] <- charset.[Random.int clen]
+  done;
+  s
+
+let fitness ~trial =
+  let rec aux i d =
+    if i >= tlen then d else
+      aux (i+1) (if target.[i] = trial.[i] then d+1 else d) in
+  aux 0 0
+
+let mutate parent rate =
+  let s = String.copy parent in
+  for i = 0 to tlen-1 do
+    if Random.float 1.0 > rate then
+      s.[i] <- charset.[Random.int clen]
+  done;
+  s, fitness s
+
+let () =
+  let i = ref 0 in
+  while parent <> target do
+    let pfit = fitness parent in
+    let rate = float pfit /. float tlen in
+    let tries = Array.init 200 (fun _ -> mutate parent rate) in
+    let min_by (a, fa) (b, fb) = if fa > fb then a, fa else b, fb in
+    let best, f = Array.fold_left min_by (parent, pfit) tries in
+    if !i mod 100 = 0 then
+      Printf.printf "%5d - '%s'  (fitness:%2d)\n%!" !i best f;
+    String.blit best 0 parent 0 tlen;
+    incr i
+  done;
+  Printf.printf "%5d - '%s'\n" !i parent