Q-Logic IB6054601-00 D Manuel D’Utilisation

3 – Using InfiniPath MPI
File I/O in MPI

3-18

IB6054601-00 D

Q

The Multi-Purpose Daemon (MPD) was developed by Argonne National Laboratory 
(ANL), as part of the MPICH-2 system. While the ANL MPD had certain advantages 
over the use of their 

mpirun

 (faster launching, better cleanup after crashes, better 

tolerance of node failures), the InfiniPath 

mpirun

 offers the same advantages.

The disadvantage of MPD is reduced security, since it does not use 

ssh

 to launch 

node programs. It is also a little more complex to use than 

mpirun

 because it 

requires starting a ring of MPD daemons on the nodes. Therefore, most users should 
use the normal 

mpirun

 mechanism for starting jobs as described in the previous 

chapter. However, for users who wish to use MPD, it is included in the InfiniPath 
software.

To start an MPD environment, use the 

mpdboot

 program. You must provide 

mpdboot

 

with a file listing the machines on which to run the 

mpd

 daemon. The format of this 

file is the same as for the mpihosts file in the 

mpirun

 command.

Here is an example of how to run mpdboot:

$ mpdboot -f hostsfile

After 

mpdboot

 has started the MPD daemons, it will print a status message and 

drop you into a new shell.

To leave the MPD environment, exit from this shell. This will terminate the daemons.

To run an MPI program from within the MPD environment, use the 

mpirun

 command. 

You do not need to provide a 

mpihosts

 file or a count of CPUs; by default, 

mpirun

 

will use all nodes and CPUs available within the MPD environment.

To check the status of the MPD daemons, use the 

mpdping

 command

To use MPD, the software package mpi-frontend-2.0*.rpm must be 
installed on all nodes. See the InfiniPath Install Guide for more details on 
software installation. 

File I/O in MPI is discussed briefly in the following two sections.

MPI node programs are Linux programs, which can do file I/O to local or remote 
files in the usual ways through APIs of the language in use. Remote files are