On Fri, Jul 24, 2009 at 5:04 AM, Jan Rychter<j...@rychter.com> wrote: > >> On Jul 21, 5:51 am, Jan Rychter <j...@rychter.com> wrote: >>> Is there a way to get the size of a data structure in Clojure? >>> >>> I've been wondering how much more space-efficient vectors are than >>> lists, but I don't know how to measure it. > > Stuart Sierra <the.stuart.sie...@gmail.com> writes: >> Short answer: no, because Java has no sizeof operator. >> >> You can use Java profiling tools to examine the memory usage of your >> app if needed. >> >> Since all of clojure's data structures are persistent (reusable), they >> won't necessarily meet your expectations for memory usage based on the >> standard definitions of vector/list/etc. A clojure vector is *not* >> just an array. A clojure list is *not* just a linked list. The names >> refer to the performance characteristics (vectors allow random access, >> lists allow linear access) rather than the implementation. In fact, >> most of Clojure's data structures are variants of trees, and they are >> quite efficient. >> >> If you are concerned about memory usage, I recommend you write a >> prototype of your app using Clojure's built-in structures first. If >> that uses too much memory, try refactoring your code to use Java >> arrays or some other Java data structure optimized for your use case. > > I should have described the problem better. In my case, I'm not > considering using native Java data structures. I have stacks implemented > on top of Clojure vectors and Clojure lists. I do not care that much > about random access, but I do care about O(1) count operation (which > both lists and vectors support). I measured the performance in a > real-life scenario and it is nearly identical for vectors and lists > (lists are actually slightly faster). > > What I would like to know is given the same amount of data, which > structure will be more memory-efficient? >
Vectors hold 32 items in a node while lists hold only one item per node, so vectors will be more space efficient. Rich --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
