.zip synchronizes its input streams because it requires one element from each for every output, .merge consumes its inputs independently (as long as there is downstream demand).
Regards, Roland > 21 dec. 2016 kl. 22:20 skrev Anil Gursel <[email protected]>: > > Thanks Endre and Roland! Yes, when I add a buffer just before zip.in0, both > tests pass: > > unzip.out0.buffer(10, OverflowStrategy.backpressure) ~> zip.in0 > > So, adding the buffer is enabling the parallelism. However, why does not the > first test (the one without zip/unzip) need a buffer to enable parallelism > (e.g., just before merge)? > > Thanks, > Anil > > On Wed, Dec 21, 2016 at 2:40 AM, Endre Varga <[email protected] > <mailto:[email protected]>> wrote: > Yes, that might be the case. > > On Wed, Dec 21, 2016 at 9:39 AM, Roland Kuhn <[email protected] > <mailto:[email protected]>> wrote: > I think what is happening here is that zip does not pull until the delayed > element has come out, meaning that the second (less delayed) element will not > overtake it. mapAsync is effectively a buffer, so you'll need a buffer in > front of zip.in0 as well to enable parallelism. > > Regards, Roland > > Sent from my iPhone > > On 21 Dec 2016, at 09:34, Endre Varga <[email protected] > <mailto:[email protected]>> wrote: > >> >> >> On Tue, Dec 20, 2016 at 11:34 PM, Anil Gursel <[email protected] >> <mailto:[email protected]>> wrote: >> I see that unzip does not pull the next element when fusing is on. I >> understand that when fusing is on, a message goes through the entire stream >> and then the next message goes through. >> >> This is not true, messages are handled concurrently even in fused islands, >> it is just that they are not parallel. I.e. same thread, but event order is >> unspecified. In fact, fused islands are fair in that even in the case of >> long-running cycles other parts of the graph can still progress (which would >> not be true if what you said would be true) >> >> However, is it still the case when `mapAsyncUnordered` is used? >> >> mapAsync wait on asynchronous events, so that needs to wait until those are >> ready. In the meantime the rest of the graph can progress. >> >> >> Please see the two tests at >> https://gist.github.com/anilgursel/aa70497a9431fc8b498c599d9d469e2b >> <https://gist.github.com/anilgursel/aa70497a9431fc8b498c599d9d469e2b>. The >> two tests are identical except the second one does an unzip then a zip. The >> first one succeeds and the second one fails. The first one succeeding means >> that when `mapAsyncUnordered` is used, it is not actually waiting for the >> previous message to go through the entire stream. >> >> Again, there is no "previous message go through the entire stream". That >> would lead to starving scenarios that you describe. What fusing changes is >> that it removes buffers and hence prefetches. Try out higher delays and see >> what happens. >> >> -Endre >> >> >> >> I will appreciate if you can shed some light on what's going on in this >> samples. >> >> Thanks, >> Anil >> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ <http://akka.io/docs/> >> >>>>>>>>>> Check the FAQ: >> >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >> >>>>>>>>>> <http://doc.akka.io/docs/akka/current/additional/faq.html> >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> >>>>>>>>>> <https://groups.google.com/group/akka-user> >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at https://groups.google.com/group/akka-user >> <https://groups.google.com/group/akka-user>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. >> >> >> -- >> >>>>>>>>>> Read the docs: http://akka.io/docs/ <http://akka.io/docs/> >> >>>>>>>>>> Check the FAQ: >> >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html >> >>>>>>>>>> <http://doc.akka.io/docs/akka/current/additional/faq.html> >> >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user >> >>>>>>>>>> <https://groups.google.com/group/akka-user> >> --- >> You received this message because you are subscribed to the Google Groups >> "Akka User List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at https://groups.google.com/group/akka-user >> <https://groups.google.com/group/akka-user>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > >>>>>>>>>> Read the docs: http://akka.io/docs/ <http://akka.io/docs/> > >>>>>>>>>> Check the FAQ: > >>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html > >>>>>>>>>> <http://doc.akka.io/docs/akka/current/additional/faq.html> > >>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user > >>>>>>>>>> <https://groups.google.com/group/akka-user> > --- > You received this message because you are subscribed to the Google Groups > "Akka User List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/akka-user > <https://groups.google.com/group/akka-user>. > For more options, visit https://groups.google.com/d/optout > 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