Even with 64 cores your process takes 3hrs… unless they are all external requests - so essentially unlimited cores.
> On Jan 27, 2019, at 2:32 PM, Michael Jones <michael.jo...@gmail.com> wrote: > > Glad you saw it. Lots of ways to do it but small-seeming details shape the > approach: > > Are the tasks of similar effort? If yes, good, if not it is VERY desirable to > start the hard ones first and on different workers. > > Do you know how many tasks? If you do not—if you only know when you’re done > with new tasks—then that means you need to signal completion. > > Can you wait for the last result before sending the first output? Could mean > a big stall and is very different than the single-thread case, but, it allows > sorting and easy load balancing. > > Might you want to quit early and abandon processing? This is not so natural > to the mechanisms so requires finesse in your code (as suggested by various > debates about the context idea). > > My snippet is one path through this decision matrix. > > Also, it uses an outer ask/answer channel pair for uniformity between serial > and parallel modes. This is fine for my case (ten thousand minute long tasks) > with a max rate of channel sending on my laptop of about 3M sends/sec. > overhead here is about zero but if the tasks were itsy-bitsy then the > overhead would matter. So you’d want to batch them—or restructure. > > On Sun, Jan 27, 2019 at 3:51 AM Tom Payne <twpa...@gmail.com > <mailto:twpa...@gmail.com>> wrote: > Yes, I did, thank you! My reply was to the previous message (robert engels' > post about it being "straightforward" but not providing code) and I think we > just both hit send at about the same time. > > On Sat, 26 Jan 2019 at 02:52, Michael Jones <michael.jo...@gmail.com > <mailto:michael.jo...@gmail.com>> wrote: > Did you notice that I sent you the complete code above? > > On Fri, Jan 25, 2019 at 2:48 PM <twpa...@gmail.com > <mailto:twpa...@gmail.com>> wrote: > For what it's worth > http://www.golangpatterns.info/concurrency/parallel-for-loop > <http://www.golangpatterns.info/concurrency/parallel-for-loop> > implements an order-preserving parallel map, but does not limit the number of > workers. > > In my case, I want to limit the number of workers because I'm making a lot of > system calls and don't want to overload the kernel. runtime.NumCPU() seems > like a reasonable limit. > > > > On Friday, January 25, 2019 at 8:04:31 PM UTC+1, twp...@gmail.com > <mailto:twp...@gmail.com> wrote: > Hi, > > I have a number of slow tasks that I want to run concurrently across > runtime.NumCPU() workers in a single process. The tasks have a specific input > order, but they are completely independent of each other and can execute in > any order. I would like to print the output of each task in the same order as > the input order of tasks. > > This can be implemented by including each task's index in the input order as > it is distributed via a channel to the workers, and the final collection of > results assembled using these task indexes before the results are printed. > > Assumptions: > - Small number of tasks (~10,000 max), i.e. this easily fits in memory. > - Single Go process, i.e. I don't want/need a distributed system. > > This feels like it should be common problem and there's probably either a > library or a standard Go pattern out there which can do it. My web search > skills didn't find such a library though. Do you know of one? > > Cheers, > Tom > > > Background info to avoid the XY problem <http://xyproblem.info/>: this is to > make chezmoi <https://github.com/twpayne/chezmoi> run faster. I want to run > the doctor checks > <https://github.com/twpayne/chezmoi/blob/ed27b49f9ca4cd3662e6a59908dee24b0d295b79/cmd/doctor.go#L102-L163> > (basically os.Exec'ing a whole load of binaries to get their versions) > concurrently in the short term. In the long term I want to make chezmoi's > apply concurrent, so it runs faster too. In the first case, the order > requirement is because I want all users to see the output in the same order > so that it's easy to compare. In the second case, the order requirement comes > because I need to ensure that parent directories are in the correct state > before checking their children. > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com > <mailto:golang-nuts+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > > > -- > Michael T. Jones > michael.jo...@gmail.com <mailto:michael.jo...@gmail.com>-- > Michael T. Jones > michael.jo...@gmail.com <mailto:michael.jo...@gmail.com> > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com > <mailto:golang-nuts+unsubscr...@googlegroups.com>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
