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POEvolutionary Algorithm to guess a string, messed up by replication
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  1. POEvolutionary Algorithm to guess a string, messed up by replication
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    copied!<p>i am working on a python script to test out genetic programming. As an exercise i have made a simple Script that tries to guess a string without the whole population part. </p> <p>My Code is:</p> <pre><code># acts as a gene # it has three operations: # Mutation : One character is changed # Replication: a sequencepart is duplicated # Extinction : A sequencepart is lost # Crossover : the sequence is crossed with another Sequence import random class StringGene: def __init__(self, s): self.sequence = s self.allowedChars = "ABCDEFGHIJKLMOPQRSTUVWXYZ/{}[]*()+-" def __str__(self): return self.sequence def Mutation(self): x = random.randint(0, len(self.sequence)-1) r = random.randint(0, len(self.allowedChars)-1) d = self.sequence self.sequence = d[:x-1]+ self.allowedChars[r] + d[x:] def Replication(self): x1 = random.randint(0, len(self.sequence)-1) x2 = random.randint(0, len(self.sequence)-1) self.sequence =self.sequence[:x1]+ self.sequence[x1:x2] + self.sequence[x2:] self.sequence = self.sequence[:32] def Extinction(self): x1 = random.randint(0, len(self.sequence)-1) x2 = random.randint(0, len(self.sequence)-1) self.sequence = self.sequence[:x1] + self.sequence[x2:] def CrossOver(self, s): x1 = random.randint(0, len(self.sequence)-1) x2 = random.randint(0, len(s)-1) self.sequence = self.sequence[:x1+1]+ s[x2:] #x1 = random.randint(0, len(self.sequence)-1) #self.sequence = s[:x2 ] + self.sequence[x1+1:] if __name__== "__main__": import itertools def hamdist(str1, str2): if (len(str2)&gt;len(str1)): str1, str2 = str2, str1 str2 = str2.ljust(len(str1)) return sum(itertools.imap(str.__ne__, str1, str2)) g = StringGene("Hi there, Hello World !") g.Mutation() print "gm: " + str(g) g.Replication() print "gr: " + str(g) g.Extinction() print "ge: " + str(g) h = StringGene("Hello there, partner") print "h: " + str(h) g.CrossOver(str(h)) print "gc: " + str(g) change = 0 oldres = 100 solutionstring = "Hello Daniel. Nice to meet you." best = StringGene("") res = 100 print solutionstring while (res &gt; 0): g.Mutation() g.Replication() g.Extinction() res = hamdist(str(g), solutionstring) if res&lt;oldres: print "'"+ str(g) + "'" print "'"+ str(best) + "'" best = g oldres = res else : g = best change = change + 1 print "Solution:" + str(g)+ " " + str(hamdist(solutionstring, str(g))) + str (change) </code></pre> <p>I have a crude hamming distance as a measure how far the solution string differs from the current one. However i want to be able to have a varying length in the guessing, so i introduced replication and deletion of parts of the string. </p> <p>Now, however the string grows infinitely and the Solution String is never found. Can you point out, where i went wrong?</p> <p>Can you suggest improvements?</p> <p>cheers</p>
 

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