On Mon, Jul 9, 2018 at 6:35 PM Julian Rüth <julian.ru...@fsfe.org> wrote: > > Hello. > > since Sage 8.2 sage.parallel.ncpus.ncpus() returns 1 if you have no > environment variables such as MAKE, SAGE_NUM_THREADS, MAKEOPTS set. > > This number is used by the @parallel decorator and similar constructions to > determine the number of processes to run in parallel. (Unless during > doctests, then it's set to 2 I think.) > > The question is: What is a good default for things such as @parallel when > SAGE_NUM_THREADS has not been set? I think that 1 is not a good one. The > actual number of cores/threads on a system probably isn't either on servers > with lots of cores. At some point we had `min(8, number of threads)` which > appears reasonable to me. > > Please join the discussion at https://trac.sagemath.org/ticket/24937 :)
For the sake of reference, the standard library's `multiprocessing.Pool` [1] just uses `os.cpu_count()` by default, and I don't really see a problem with that. If I want to limit parallelization on a machine that I'm concurrently using for other work, that's kind of a decision a human has to make. If I have 32 cores why would I want it limited to 8, by default, for example? (No, most people's personal machines won't have 32 cores, though that's not going to be so uncommon forever...) [1] https://docs.python.org/3.7/library/multiprocessing.html?highlight=process#multiprocessing.pool.Pool -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
