[MPICH] Asking about some details of mpi in a cluster?

[Rajeev Thakur]

> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of zyh
> Sent: Thursday, December 27, 2007 9:58 AM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] Asking about some details of mpi in a cluster?
> 
>  
> Hi,
>   I'd like to know some details about mpich in a cluster:
>  
> 1.Is udp or tcp used to communicate when using mpi_send and mpi_recv?

TCP.

> 2.I guess when a mpi programm is run by "mpirun -np 
> process-number mpiprogramme",the mpiprogramme is sent to 
> other computers to run.
> Is this right?

No. The executable file must be accessible from that machine either via a
shared file system or copied by the user onto the local file system.

> 3.What does mpi_init do?

Initializes internal data structures of MPICH.

> 4.When using mpi_comm_size,how to get the size?I guess there 
> are two ways:
> the first is getting from "mpirun -np process-numbler 
> mpiprogramme";the second is after judging all the computers 
> in the file "hostlist" is alive or not.  Which is right?
> 4.And when using mpi_comm_rank,how to get the rank of every computer?

Both comm_size and comm_rank are obtained from the process manager via the
PMI (process manager interface) in MPICH.

Rajeev