On Friday, February 22, 2013 8:23:38 PM UTC+1, David Nolen wrote: > > > >> I'll give you one specific item that I keep tripping upon: the lack of >> reassignable, stack-based locals. Without them I can't efficiently get more >> than one value out of a loop. Another item is that I can get zero primitive >> values out of a loop. How do you cope with those? >> > > Some ideas for the first point: > > * atoms >
These are thread-safe and nowhere near as efficient as stack-based locals. > * implement efficient tuple type which uses mutation for multiple value > return > Basically, this is the ^:unsynchronized-mutable that we just mentioned :) This is much better, but still it's not stack-based, so incurs the cost of allocation and GC. > I suspect the second option will be pretty fast. Annoying, but that's a > tradeoff with Clojure's mostly functional design. > Annoying *and* slower than Java's locals, unfortunately. Most of the time it won't make a huge dent in the performance, but I just happen to have an inner loop that iterates between zero and three times only, zero being by far the most common case, and is entered many times from the surrounding loop. The performance drop is considerable. > Second point, I think 1.5.0 addresses that to some degree thanks to > Christophe. > As far as I got it, it only prevents loop-recur from destroying the primitive-returning semantics of functions. Loops used within function bodies stay the same. > Heh, I always point out test.benchmark - > http://github.com/clojure/test.benchmark. There's some horrifying stuff > in there ;) > I remember you mentioning that on StackOverflow, maybe it's time for me to check it out more seriously. -- -- 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
