[racket] simple genetic algorithm

Yes, thank you!


On Sun, Nov 10, 2013 at 2:39 PM, Matthias Felleisen <matthias at ccs.neu.edu>wrote:

>
> I think this is the program you want:
>
> #lang racket
>
> (module+ test
>   (require rackunit))
>
> ;; [List-of Real] -> [List-of Real]
>
> (module+ test
>   (check-equal? (roulette-wheel-ratio '(1 2 3)) '(1/6 2/6 3/6)))
>
> (define (roulette-wheel-ratio generation-fitness)
>   (define total-population-fitness (foldl + 0 generation-fitness))
>   (map (lambda (fitness) (/ fitness total-population-fitness))
> generation-fitness))
>
>
>
>
> On Nov 10, 2013, at 2:28 PM, Rian Shams wrote:
>
> > Hello All,
> >
> > As part of the design for a simple genetic algorithm I have this
> function:
> >
> > (define (roulette-wheel-ratio generation-fitness )
> >   (cond [(empty? generation-fitness) empty]
> >            [else (cons (/ (first generation-fitness)
> >                                (total-population-fitness
> generation-fitness))
> >                     (roulette-wheel-ratio (rest generation-fitness)))]))
> >
> > where generation-fitness is a list of values that correspond to the
> fitness of each individual in a population. For example, in a generation
> with population size 12, generation fitness may look like:
> >
> > '(7.8807275269175125
> >   6.78896220864992
> >   6.52572681075793
> >   3.208263473483078
> >   9.970710802683316
> >   10.400703374724888
> >   7.434703353949041
> >   6.009574612909729
> >   2.9503066173989634
> >   6.07124467626777
> >   2.1893449585751754
> >   1.0741024515301607)
> >
> > Here is how I have defined the auxiliary function,
> total-population-fitness:
> >
> > (define (total-population-fitness generation-fitness)
> >   (foldl + 0 generation-fitness))
> >
> > I was wondering how can I modify the above function,
> roulette-wheel-ratio so that when it evaluates the helper function,
> total-population-fitness it only does so for the initial list of
> generation-fitness. Otherwise the total population fitness decreases for
> each recursive call which is what I don't want, it should remain constant
> throughout the entire function call.
> >
> > Basically, is it possible to modify this function so that the auxiliary
> function call (total-population-fitness generation-fitness) remains
> unaffected by the natural recursion imposed by roulette-wheel-ratio?
> >
> > Any help would be appreciated as I am still learning the Racket basics.
> >
> > Kind Regards,
> > --
> > Rian Shams
> > ____________________
> >  Racket Users list:
> >  http://lists.racket-lang.org/users
>
>
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