On Fri, Mar 19, 2010 at 06:56, Greg Fodor <gfo...@gmail.com> wrote:
> I would like to memoize bar such that the memory used for memoization
> is GC'ed at the end of the call to foo, and additionally the cache
> used for memoization is thread local (so no need for heavyweight
> synchronization tools like atoms, etc.) In Ruby, I would implement
> this as a simple local hash with the ||= operator through each
> iteration of a loop inside foo that calls bar.
;; the "trick" I found is to explicitly deref the var binding the
;; function to be memoized. This way fib's recursive calls will use
;; the memoized binding established in
;; use-fib-memoized-thread-locally.
(defn fib [n]
(if (> 2 n) n
(+ (@#'fib (dec n))
(@#'fib (dec (dec n))))))
(defn use-fib-memoized-thread-locally [n]
(binding [fib (memoize fib)]
(fib n)))
;; user> (time (fib 32))
;; "Elapsed time: 1755.796366 msecs" ;; SLOW
;; 2178309
;;
;; user> (time (use-fib-memoized-thread-locally 32))
;; "Elapsed time: 1.514927 msecs" ;; FAST
;; 2178309
;;
;; user> (time (fib 32))
;; "Elapsed time: 2024.836838 msecs" ;; SLOW, again
;; 2178309
// Ben
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
To unsubscribe from this group, send email to
clojure+unsubscribegooglegroups.com or reply to this email with the words
"REMOVE ME" as the subject.
