Thank you so much Hui. Really appreciate it. I now understand it. From: Zhou, Hui <[email protected]> Date: Monday, July 1, 2024 at 4:37 PM To: Niyaz Murshed <[email protected]>, [email protected] <[email protected]>, Jenke, Joachim <[email protected]> Cc: nd <[email protected]> Subject: Re: Custom rank for processes Yes, you can use rankmap to simply list out the node assignment for each rank. "-rankmap (vector,1,1,0,0,0)" is a list of 5 node ids, one for each rank. So rank 0 gets node 1, rank 1 gets node 1, rank 2 gets node 0, and so on. The -hosts options is convenient if you have somewhat uniform assignment. If you want arbitrary assignment, just use -rankmap option. -- Hui ________________________________ From: Niyaz Murshed <[email protected]> Sent: Monday, July 1, 2024 4:30 PM To: Zhou, Hui <[email protected]>; [email protected] <[email protected]>; Jenke, Joachim <[email protected]> Cc: nd <[email protected]> Subject: Re: Custom rank for processes 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 ZjQcmQRYFpfptBannerStart This Message Is From an External Sender This message came from outside your organization. ZjQcmQRYFpfptBannerEnd 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 <[email protected]> Date: Monday, July 1, 2024 at 4:09 PM To: Niyaz Murshed <[email protected]>, [email protected] <[email protected]>, Jenke, Joachim <[email protected]> Cc: nd <[email protected]> Subject: Re: Custom rank for processes

root@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