[mpich-discuss] Custom rank for processes

[Niyaz Murshed]

Sorry to bother you again with silly questions.

How do I read the below :
-rankmap (vector,1,1,0,0,0)

I have 5 processes. 1 1 => means node1 will get first 2 processes ?

-hosts 192.168.2.100:2,192.168.2.200:3 : this will give 2 process in 100 and 3 in 200 .. Still won’t be able to specify which ranks goes to which node. Rank0 will be on node 100 .. what If I want Rank0 on node 200?


From: Zhou, Hui <zhouh at anl.gov>
Date: Monday, July 1, 2024 at 4:09 PM
To: Niyaz Murshed <Niyaz.Murshed at arm.com>, discuss at mpich.org <discuss at mpich.org>, Jenke, Joachim <jenke at itc.rwth-aachen.de>
Cc: nd <nd at arm.com>
Subject: Re: Custom rank for processes
> root at ampere-altra-2-1:/# mpirun -n 5   -bind-to user:10,11,12,13 -hosts 192.168.2.200,192.168.2.100 /mpitutorial/tutorials/mpi-hello-world/code/mpi_hello_world
Hello world from processor ampere-altra-2-1, rank 1 out of 5 processors
Hello world from processor ampere-altra-2-1, rank 3 out of 5 processors
Hello world from processor dpr740, rank 0 out of 5 processors
Hello world from processor dpr740, rank 4 out of 5 processors
Hello world from processor dpr740, rank 2 out of 5 processors

> -bind-to user:10,11,12,13
> This would mean on host 192.168.2.100
> P0=>10 , P2=>11
> This would mean on host 192.168.2.200
> P0=>10 , P2=>11, P3=12
> Is this correct understanding ?  Is it also possible to say which rank process will be pinned to which core ?

Yes, that is correct. The ranks are assigned to hosts as shown in the hello world output.


> About the rankmap:, trying to understand if I can select where a particular rank would be from > list of hosts. Currently, the first host in the list always get rank0.
> Can I specify the below ranks?
> mpirun -n 5   -bind-to user:10,11,12,13 -hosts 192.168.2.200,192.168.2.100 /mpitutorial/tutorials/mpi-hello-world/code/mpi_hello_world
>
> Hello world from processor ampere-altra-2-1, rank 1 out of 5 processors => rank0
> Hello world from processor ampere-altra-2-1, rank 3 out of 5 processors. => rank1
> Hello world from processor dpr740, rank 0 out of 5 processors           =>rank2
> Hello world from processor dpr740, rank 4 out of 5 processors           =>rank3
> Hello world from processor dpr740, rank 2 out of 5 processors           =>rank4

Yes. You can use "-rankmap (vector,1,1,0,0,0)". Alternatively, you can use "-hosts 192.168.2.100:2,192.168.2.200:3", the colon syntax specifies how many processes you want to assign to each host.

--
Hui
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