On Jan 27, 8:21 pm, Scott <sbuck...@gmail.com> wrote:
> wondering if I can please get some advice on how to improve the
> performance of this piece of code
>
> (defn select-n-tournament
> [popu fit-fn n]
> (let [k 7]
> (take n (repeatedly #(first (sort-by fit-fn > (take k (shuffle
> popu))))))
> )
> )
I don't know about using map, but here is a function inspired by one
called 'most' in Paul Graham's On Lisp. You could use (most fit-fn
(take k (shuffle popu))) in place of your (first ...) subexpression
above, and it would avoid sorting elements that you would otherwise
simply be throwing away anyway.
(defn most [fit-fn c]
"Return the element e of collection c that has the largest numerical
value of (fit-fn e)."
(let [c (seq c)]
(when c
(loop [winner (first c)
winner-fitness (fit-fn winner)
c (rest c)]
(if (seq c)
(let [e (first c)
e-fitness (fit-fn e)]
(if (> e-fitness winner-fitness)
(recur e e-fitness (rest c))
(recur winner winner-fitness (rest c))))
winner)))))
Andy
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