Q-Logic IB6054601-00 D Manual De Usuario

3 – Using InfiniPath MPI
InfiniPath MPI Details

3-12

IB6054601-00 D

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programs will be started on that host before using the next entry in the 

mpihosts

 

file. If the full 

mpihosts

 file is processed, and there are still more processes 

requested, processing starts again at the start of the file.

You have several alternative ways of specifying the 

mpihosts

 file.

1. First, as noted in 

, you can use the command line option

 -m

:

$

mpirun -np n -m mpihosts [other options] program-name

In this case, if the named file cannot be opened, the MPI job fails. 

2. If the 

-m

 option is omitted, 

mpirun

 checks the environment variable 

MPIHOSTS

 

for the name of the MPI hosts file. If this variable is defined and the file it names 
cannot be opened, then the MPI job fails.

3. In the absence of both the 

-m

 option and the 

MPIHOSTS

 environment variable, 

mpirun

 uses the file

./mpihosts

, if it exists.

4. If none of these three methods of specifying the hosts file are used, 

mpirun

 

looks for the file  

~/.mpihosts

.

If you are working in the context of a batch queuing system, it may provide you with 
a job submission script that generates an appropriate 

mpihosts

 file.

mpirun

 sends any output printed to 

stdout

  or 

stderr

 by any node program to the 

terminal.  This output is line-buffered, so the lines output from the various node 
programs will be non-deterministically interleaved on the terminal.  Using the 

 -l 

option to 

mpirun

 will label each line with the rank of the node program that produced 

it.

Node programs do not normally use interactive input on 

stdin

, and by default, 

stdi

n is bound to /dev/null. However, for applications that require standard input 

redirection, InfiniPath MPI supports two mechanisms to redirect stdin:

1. If 

mpirun

 is run from the same node as MPI rank 0, all input piped to the 

mpirun

 

command will be redirected to rank 0.

2. If 

mpirun

 is not run from the same node as MPI rank 0 or if the input must be 

redirected to all or specific MPI processes, the 

-stdin

 option can be used to 

redirect a file as standard input to all nodes or to a particular node as specified 
by the 

-stdin-target

 option.

The environment variables existing on the front end node on which you run 

mpirun 

are not propagated to the other nodes. You can set the paths, such as