Data commit

Task/Evolutionary-algorithm/Wren/evolutionary-algorithm.wren

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+import "random" for Random
+
+var target = "METHINKS IT IS LIKE A WEASEL"
+var set = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
+var rand = Random.new()
+
+// fitness:  0 is perfect fit.  greater numbers indicate worse fit.
+var fitness = Fn.new { |a| (0...target.count).count { |i| a[i] != target[i] } }
+
+// set m to mutation of p, with each character of p mutated with probability r
+var mutate = Fn.new { |p, m, r|
+    var i = 0
+    for (ch in p) {
+        if (rand.float(1) < r) {
+            m[i] = set[rand.int(set.count)]
+        } else {
+            m[i] = ch
+        }
+        i = i + 1
+    }
+}
+
+var parent = List.filled(target.count, "")
+(0...parent.count).each { |i| parent[i] = set[rand.int(set.count)] }
+var c = 20 // number of times to copy and mutate parent
+var copies = List.filled(c, null)
+for (i in 0...c) copies[i] = List.filled(parent.count, 0)
+System.print(parent.join())
+var best = fitness.call(parent)
+while (best > 0) {
+    for (cp in copies) mutate.call(parent, cp, 0.05)
+    for (cp in copies) {
+        var fm = fitness.call(cp)
+        if (fm < best) {
+            best = fm
+            parent = cp.toList
+            System.print(parent.join())
+        }
+    }
+}