🚀 go-pugleaf

In article <C19x7D.DK3@cs.columbia.edu> evs@cs.columbia.edu (Eric Siegel) writes:
>pauld@cs.washington.edu (Paul Barton-Davis) says:
>
>> One really interesting feature that I have observed from my own work
>> with a tierra-like system is the effect of a reproductive burden on
>> the speed of evolution. ...
>
>> So, in normal GA-land, you simply use the "hand of god"
>> approach: you reach in, and *you* do the reproduction, eliminating any
>> selection pressure on this feature. ...
>
>> But wait ! Perhaps, just perhaps, this reproductive feature is just
>> what you want. Its not very difficult to make a tierra-like system
>> evolve its own form of crossover. All kinds of other wierd and
>> wonderful reproductive mechanisms evolve too. It seems possible to me
>> that when evolution is viewed as explorations of a vast state space,
>> particular reproductive methods might be incapable of ever searching
>> some particular areas of that space. Leaving the system free to devise
>> its own reproductive strategies opens up the possibility of exploring
>> areas of the state space that "programmer/user-selected" methods might
>> not. 
>
>Solution: A GA organism does not only represent a "vector" in the 
>solution space of the domain problem, but also has (seperately) 
>encoded a "vector" in _reproduction method space_ (e.g. Weights 
>of crosss-over, mutation; Number of cross-over points, etc.  A big 
>research area?)

Well, not really. This still leaves the programmer to devise an
appropriate set of reproductive methods. The beauty of tierra is that
(1) no fitness function for reproductive fitness is needed, because it
is implicit in the ranking of the genome within the population and (2)
any reproductive method anyone could ever dream up can potentially
evolve within the system, as well as few that no-one ever would.

>Yeah, I was just thinking about evolution a month ago, and said to my
>friend over lunch, "you ever realize that the manner by which evolution
>takes place evolves?"

My precise point. Programmers trying to second-guess what makes it
tick seems like an unnecessary constraint.

>This comparison between tierra-like systems and GAs reminds me: In the
>former, an effective upper-limit on time spent running an organism's 
>program is implicit in the organism's environment.  

Want to explain what you mean ? I don't see such an upper-limit, other
than the one imposed by the realities of the host system (ie. real
world physics).

-- paul

-- 
hybrid rather than pure; compromising rather than clean;    | Militant Agnostic
distorted rather than straightforward; ambiguous rather than| I Don't Know
articulated; both-and rather than either-or; the difficult  |   and You Don't
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