[mpich-discuss] mpiexec and -n option

[Jain, Rohit]

I am running mpiexec in following format without any binding:
mpiexec a1.out : a2.out : a3.out

I was expecting that hydra would launch only 3 processes. But, I am seeing it is launching 12 processes (4 each). Isn't default value of -n is 1?

-verbose option shows following output which confirms my suspicion:
# --version 1.5a1 --iface-ip-env-name MPICH_INTERFACE_HOSTNAME --hostname dxyv117 --global-core-map 0,4,0 --filler-process-map 0,4,0 --global-process-count 12 --auto-cleanup 1 --pmi-rank -1 --pmi-kvsname kvs_61149_0 --pmi-process-mapping (vector,(0,1,4)) --ckpoint-num -1

What is causing this behavior?

Regards,
Rohit

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