On Jan 23, 2009, at 14:04, Rich Hickey wrote: >> Then why not make a pipeline using lazy sequences right from the >> start? I don't see anything that I could do better with streams than >> with lazy sequences. >> > > There are a couple of advantages. First, streams are faster, at least > 2x faster. Since a lazy sequence must allocate per stage, a multi- > stage pipeline would incur multiple allocations per step. A stream > could be built that has no allocation other than the results. If your > calculations per step are significant, they'll dominate the time. but > when they are not, this allocation time matters. > > Second, streams are fully lazy. Seqs could be made fully lazy, but > currently are not. > > Third, stream iters currently provide transparent MT access. Doing the > same for a seq means wrapping it in a ref.
Thanks for those explanations, that makes a lot of sense. I just wonder about the performance aspect. If I have a pipeline stage with very little computational cost, say adding 1 to every element, the I would expect the overhead of the iter layer and the thread-safeness to dominate CPU time anyway. Does an allocation really add that much on top of that that it makes a difference? Konrad. --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
