User guide

4–Running MPI on QLogic Adapters
Open MPI
4-16 IB0054606-02 A
Open MPI adds the base-name of the current node’s bindir (the directory where
Open MPI’s executables are installed) to the prefix and uses that to set the PATH
on the remote node. Similarly, Open MPI adds the base-name of the current
node’s libdir (the directory where Open MPI’s libraries are installed) to the
prefix and uses that to set the LD_LIBRARY_PATH on the remote node. For
example:
Local bindir: /local/node/directory/bin
Local libdir: /local/node/directory/lib64
If the following command line is used:
% mpirun --prefix /remote/node/directory
Open MPI will add /remote/node/directory/bin to the PATH and
/remote/node/directory/lib64 to the D_LIBRARY_PATH on the remote
node before attempting to execute anything.
Note that --prefix can be set on a per-context basis, allowing for different
values for different nodes.
The --prefix option is not sufficient if the installation paths on the remote node
are different than the local node (for example, if /lib is used on the local node
but /lib64 is used on the remote node), or if the installation paths are
something other than a subdirectory under a common prefix.
Note that executing mpirun using an absolute pathname is equivalent to
specifying --prefix without the last subdirectory in the absolute pathname to
mpirun. For example:
% /usr/local/bin/mpirun ...
is equivalent to
% mpirun --prefix /usr/local
Exported Environment Variables
All environment variables that are named in the form OMPI_* will automatically be
exported to new processes on the local and remote nodes. The -x option to
mpirun can be used to export specific environment variables to the new
processes. While the syntax of the -x option allows the definition of new
variables. Note that the parser for this option is currently not very sophisticated, it
does not understand quoted values. Users are advised to set variables in the
environment and use -x to export them, not to define them.