naive string evolutionary algorithm

1 files changed, 33 insertions, 0 deletions

diff --git a/string_evolution/ev.py b/string_evolution/ev.py
new file mode 100644
index 0000000..4fbf52e
--- /dev/null
+++ b/string_evolution/ev.py
@@ -0,0 +1,33 @@
+### http://www.electricmonk.nl/log/2011/09/28/evolutionary-algorithm-evolving-hello-world/
+
+import random
+from time import sleep
+
+source = "jiKnp4bqpmAbp"
+target = "Hello, World!"
+
+def fitness(source, target):
+    fitval = 0
+    for i in range(0, len(source)):
+        fitval += (ord(target[i]) - ord(source[i])) ** 2
+    return(fitval)
+
+def mutate(source):
+    charpos = random.randint(0, len(source) - 1)
+    parts = list(source)
+    parts[charpos] = chr(ord(parts[charpos]) + random.randint(-1,1))
+    return(''.join(parts))
+
+fitval = fitness(source, target)
+i = 0
+while True:
+    i += 1
+    m = mutate(source)
+    fitval_m = fitness(m, target)
+    if fitval_m < fitval:
+        fitval = fitval_m
+        source = m
+        print "%5i %5i %14s" % (i, fitval_m, m)
+        sleep(0.1)
+    if fitval == 0:
+        break