Add Universe_size

[bn222]

As part of development of MPIExecutor.jl, a package inspired by mpi4py that I'm working on, I need to be able to get the universe size to provide sane defaults.

[simonbyrne]

Would also be good to add a test and docstring if possible.

[simonbyrne]

Looks like MPICH doesn't define it unless specified as part of mpiexec or as an environment variable.

[bn222]

What do you propose to proceed? Can we throw an exception if running with MPICH for example?

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On Fri, Jun 28, 2019 at 5:26 PM Simon Byrne ***@***.***> wrote: Looks like MPICH doesn't define it unless specified as part of mpiexec or as an environment variable. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#280?email_source=notifications&email_token=AJOKSAW4Z244IL5J2CIIAUTP4YUTNA5CNFSM4H3ZNWSKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODY2MNZI#issuecomment-506775269>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AJOKSAULMYJDJ4ZH6KXCKE3P4YUTNANCNFSM4H3ZNWSA> .

[simonbyrne]

Supposedly MPICH should allow setting the universe size by the MPIEXEC_UNIVERSE_SIZE environment variable, but I couldn't get it to work.

Instead I changed it to return nothing if the attribute is not defined. Also since it is only attached tgo MPI.COMM_WORLD, I just made it a zero-argument function.

[simonbyrne]

@beltedmetric Does this work for you?

[bn222]

Yes, this should be fine. Thanks.

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On Mon, Jul 1, 2019 at 5:04 AM Simon Byrne ***@***.***> wrote: @beltedmetric <https://github.com/beltedmetric> Does this work for you? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#280?email_source=notifications&email_token=AJOKSAQYYKV7DZTBSWNWIATP5FX3XA5CNFSM4H3ZNWSKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGODY43TVY#issuecomment-507099607>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AJOKSAUYTDCZZJ6QA2AZF3LP5FX3XANCNFSM4H3ZNWSA> .