Console I/O in MPI Programs

3 – Using InfiniPath MPI InfiniPath MPI Details

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 section 3.3.1, you can use the command line option -m: $ mpirun -npn -m mpihosts [other options] program-name

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

2.If the -moption 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 -moption 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.

3.5.7

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 -loption 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, stdin 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 -stdinoption can be used to redirect a file as standard input to all nodes or to a particular node as specified by the -stdin-targetoption.

3.5.8

Environment for Node Programs

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

3-12	IB6054601-00 D

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Q-Logic IB6054601-00 D manual Console I/O in MPI Programs, Environment for Node Programs

Models: IB6054601-00 D