Re: How to loop over several sequences in parallel for side-effects?
First: Thanks all for your thoughts. Second: I have the same question as Allen (why would the doseq variant be faster in this case?) Finally: so I guess that what I did was also OK then? Jm On Jan 20, 9:57 pm, Alan Malloy a...@malloys.org wrote: But I don't see any reason why this would be faster than (dorun (map side-effect-fn s1 s2 s3)). You're creating and then dismantling a three-element vector at every iteration to no purpose. On Jan 20, 12:40 pm, Meikel Brandmeyer m...@kotka.de wrote: Hi, to add to Lars answer: (doseq [[a b c] (map vector s1 s2 s3)] (side-effect-fn a b c)) This should do the trick. Sincerely Meikel -- 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
Re: How to loop over several sequences in parallel for side-effects?
Well, you can always use the (time) macro and pick what runs faster: (dorun (map some-fn-with-side-effects sequence-1 sequence-2)) (doseq [x (map some-fn-with-side-effects sequence-1 sequence-2))]) (doseq) could be faster in some cases because its implementation uses chunked sequences. Now, (doseq) can take multiple sequences, but that may not be what you want: user= (doseq [x '(1 2) y '(3 4)] (println x y)) 1 3 1 4 2 3 2 4 On Jan 23, 3:51 am, joachim joachim.de.be...@gmail.com wrote: First: Thanks all for your thoughts. Second: I have the same question as Allen (why would the doseq variant be faster in this case?) Finally: so I guess that what I did was also OK then? Jm On Jan 20, 9:57 pm, Alan Malloy a...@malloys.org wrote: But I don't see any reason why this would be faster than (dorun (map side-effect-fn s1 s2 s3)). You're creating and then dismantling a three-element vector at every iteration to no purpose. On Jan 20, 12:40 pm, Meikel Brandmeyer m...@kotka.de wrote: Hi, to add to Lars answer: (doseq [[a b c] (map vector s1 s2 s3)] (side-effect-fn a b c)) This should do the trick. Sincerely Meikel -- 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
Re: How to loop over several sequences in parallel for side-effects?
And (dorun (map )) is creating a cons with a random value (most likely nil) and traverses it and throws it away at every sequence step. YMMV. -- 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
Re: How to loop over several sequences in parallel for side-effects?
Can you point to where that's happening? I can only see an iteration of next over the sequence returned by map. On Jan 23, 6:43 am, Meikel Brandmeyer (kotarak) m...@kotka.de wrote: And (dorun (map )) is creating a cons with a random value (most likely nil) and traverses it and throws it away at every sequence step. YMMV. -- 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
Re: How to loop over several sequences in parallel for side-effects?
Shameless plug: If you want to do this type of iteration efficiently, try my
library at https://github.com/jpalmucci/clj-iterate
user (iter {for x in '(1 2 3)}
{for y in '(a b c)}
(println x y))
1 a
2 b
3 c
nil
user
Expands into a fast loop/recur form. No intermediate data structures
On Jan 20, 2012, at 8:18 AM, joachim wrote:
Hi All,
Here is a simple problem for which I nevertheless can't seem to find
the right solution: How to run over several sequences in parallel for
side-effects? Here is one way:
(dorun (map some-fn-with-side-effects sequence-1 sequence-2))
However, I was told that the form (dorun (map ... )) indicates that
doseq should be used instead because it is faster, and I can use
speed. I think that this is not possible however because doseq only
allows to loop over a single sequence at a time? I was wondering what
is the idiomatic clojure way in this case?
Thanks! Jm.
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Re: How to loop over several sequences in parallel for side-effects?
Hi, Am 23.01.2012 um 17:40 schrieb Armando Blancas: Can you point to where that's happening? I can only see an iteration of next over the sequence returned by map. Exactly. And what does (map f xs) return? (cons (f (first xs)) (map f (rest xs))). Each such a cons is created for one step of the input sequence(s). The fact that you don't use the first part of the cons, does not mean it's not created. Sincerely Meikel -- 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
Re: How to loop over several sequences in parallel for side-effects?
Ah. Nevermind. -- 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
Re: How to loop over several sequences in parallel for side-effects?
(dorun (map f xs ys zs)) creates and discards a cons for each iteration, no argument there. But its first element is very cheap: just the result of f, which you had to compute anyway. (doseq [[x y z] (map vector xs ys zs)] (f x y z)) similarly creates a cons for each iteration. But its value, rather than being the result of f, is a vector constructed simply for bookkeeping purposes. Then before you can call f you must tear apart that vector to get at the pieces. If performance (either amount of garbage or number of operations) were the only factor, I can't see any way that this could be better than the dorun/map approach. On Jan 23, 6:43 am, Meikel Brandmeyer (kotarak) m...@kotka.de wrote: And (dorun (map )) is creating a cons with a random value (most likely nil) and traverses it and throws it away at every sequence step. YMMV. -- 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
Re: How to loop over several sequences in parallel for side-effects?
On Fri, Jan 20, 2012 at 8:18 AM, joachim joachim.de.be...@gmail.com wrote: Hi All, Here is a simple problem for which I nevertheless can't seem to find the right solution: How to run over several sequences in parallel for side-effects? Here is one way: (dorun (map some-fn-with-side-effects sequence-1 sequence-2)) However, I was told that the form (dorun (map ... )) indicates that doseq should be used instead because it is faster, and I can use speed. I think that this is not possible however because doseq only allows to loop over a single sequence at a time? I was wondering what is the idiomatic clojure way in this case? You know that (map f seq1 seq2) means call f with one argument from seq1 and one from seq2 in turn, until one of the sequences has been exhausted? Does = (map #(vector %1 %2) [1 2 3] ['a 'b 'c]) ([1 a] [2 b] [3 c]) Seem like the result you would expect or not, when you talk about run over several sequences in parallel? Lars Nilsson -- 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
Re: How to loop over several sequences in parallel for side-effects?
Hi, to add to Lars answer: (doseq [[a b c] (map vector s1 s2 s3)] (side-effect-fn a b c)) This should do the trick. Sincerely Meikel -- 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
Re: How to loop over several sequences in parallel for side-effects?
On Jan 20, 2012, at 2:41 PM, Lars Nilsson wrote: = (map #(vector %1 %2) [1 2 3] ['a 'b 'c]) ([1 a] [2 b] [3 c]) Sorry if I'm drifting a bit off topic, but I just wanted to point out that it's convenient to use just the function name if the arguments are already in the appropriate order. Also, it is sometimes convenient to quote a vector rather than the individual elements. For example, the following is an equivalent expression: (map vector [1 2 3] '[a b c]) Of course, wrapping the expression in dorun is necessary if you care about forcing side-effects. -- 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
Re: How to loop over several sequences in parallel for side-effects?
But I don't see any reason why this would be faster than (dorun (map side-effect-fn s1 s2 s3)). You're creating and then dismantling a three-element vector at every iteration to no purpose. On Jan 20, 12:40 pm, Meikel Brandmeyer m...@kotka.de wrote: Hi, to add to Lars answer: (doseq [[a b c] (map vector s1 s2 s3)] (side-effect-fn a b c)) This should do the trick. Sincerely Meikel -- 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
