mpiexec -hosts differences in MPICH and Intel MPI

[zelenko__yauheni]

What is differences in handling mpiexec -hosts in MPICH and Intel MPI? It seems that Inte MPI doesn't recognize <host>:<number processes> syntax.

[Dmitry_G_Intel]

Hi,

Could you please provide full command line and version of Intel MPI?

[zelenko__yauheni]

I tried MPICH 2 1.5 and MPICH 3.3 and Intel MPI 2018.4.

Command line was simple: mpiexec -host "host1:2,host2:2" <cpi> example.

MPICH mpiexec (Hydra) launched 4 processes. Intel MPI mpiexec launched number of CPUs on both hosts processes.

[James_T_Intel]

This is the expected behavior.  Intel® MPI Library does not support this syntax for the -hosts option.  There was no specification for the number of ranks in a recognized manner, therefore the default is to put a number of ranks equal to the number of cores.  In order to achieve your desired behavior, please use the -machinefile <file> option.  The specified file should contain the <host>:<ranks> syntax, with one host per line.

[zelenko__yauheni]

But if Intel MPI mpiexec is based on MPICH Hydra why Hydra's -host syntax could not be supported? I don't think that creating temporary files for -machinefile is better solution then more flexible -hosts.