Newsgroups: comp.ai.genetic
Path: cantaloupe.srv.cs.cmu.edu!rochester!udel!gatech!howland.reston.ans.net!pipex!uknet!newsfeed.ed.ac.uk!ainews!dave
From: dave@aisb.ed.ac.uk (Dave Corne)
Subject: Re: Help needed with ratio optimisation
Message-ID: <D6zG5x.n15@aisb.ed.ac.uk>
Sender: news@aisb.ed.ac.uk (Network News Administrator)
Organization: Dept AI, Edinburgh University, Scotland
References: <3mdlma$395@sndsu1.sedalia.sinet.slb.com> <1995Apr11.230346.90250@kuhub.cc.ukans.edu>
Date: Thu, 13 Apr 1995 16:51:33 GMT
Lines: 38

 Nick Walton (walton@ukfca1.sinet.slb.com) wrote:
>: I'm currently building GA system which needs to optimise
>: a function of a set of weights. So that chromosmes can be
>: jusdged on a level playing field each set of weights
>: should ideally sum to the same amount.
  [ ...]
>: or something else? I am wary of ending up with a GA that 
>: is weighed down by the need to meet the condition rather
>: than of optimising the actual function.

  This sort of question comes up quite a lot; maybe it 
 should go in the FAQ ? Anyway, all kinds of answers are
 possible. I'd favour simply encoding things so that each weight
 is represented in terms of its proportion (so, encoded by 
 a real gene or binary chunk representing a number between 0 and 1)
 of the total sum. Standard crossover and mutation will be quite
 happy with this.

 Alternatively, (DILLINGER RAY SAMUEL) suggested:
>I would suggest you use an arbitrary unit of weight in your chromosome
>and assign an actual value to the unit depending on how many units 
>there are. 

  ... which is indeed an alternative, but the GA (or anything) will
  probably find it very hard to get a grip on it through all the 
  levels of encoding this would tend to need.

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   _______       __   Dave W. Corne,
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