[mpich-discuss] Process Mapping in MPICH2

[vaibhav dutt]

Hi,

I am doing some experiments in quantum chemistry software GAMESS
 using an old version of MPICH2.
I was wondering how the process mapping is done in mpich2.
For example  I have a hostfile which contains hosts like

host1
host2
...

hostn

and each host has 8 cores. When I spawn 32 processes, could you please tell
me
what will be the order of ranks spawned. I mean would it be  like

1) rank 0 to 7 on host 1, rank 8 to 15 on host2 ...
 or
2) rank 0 on host 1, rank 1 on host2......rank n on host n, rank n+1 on
host 1.


Moreover, how can I change the rank mapping within a node , for example if
I want to
have certain ranks together on a die of a socket.

Thanks
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