Thanks for the feedback so far. It seems that there are pros and cons to all of the options.

What about the following: We go with the somewhat random min(8, number of threads) and print a warning once if "number of threads" > 8 (telling the user to export SAGE_NUM_THREADS)? Note that this won't affect doctests as SAGE_NUM_THREADS=2 in that context. That way, we provide a good experience for the typical laptop/desktop user and don't risk angry emails from admins after somebody convinced them to install Sage on their shiny server. What do you think? julian PS: I am also fine with "number of threads" as a default. But I am opposed to "1" as that provides a poor experience for the casual user who won't dig into the documentation to find out what's going on. On Monday, July 9, 2018 at 6:35:22 PM UTC+2, Julian Rüth 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 :) > > julian > -- 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.