QLogic OFED+ Host Software User Guide, Rev. B

4–Running QLogic MPI on QLogic Adapters
QLogic MPI Details
Table 4-7. Environment Variables (Continued)
Name
IPATH_HCA_SELECTION_ALG
Description
This variable provides user-level support to specify
Host Channel Adapter/port selection algorithm
through the environment variable. The default
option is Round Robin that allocates the Host
Channel Adapters in a round robin fashion. The
older mechanism option is Packed that fills all
contexts on a Host Channel Adapter before allocating
from the next Host Channel Adapter.
For example: In the case of using two single-port
Host Channel Adapters, the default or
IPATH_HCA_SELECTION_ALG="Round Robin"
setting, will allow 2 or more MPI processes per
node to use both Host Channel Adapters and to
achieve performance improvements compared to
what can be achieved with one Host Channel
Adapter.
Running Multiple Versions of TrueScale or MPI
The variable MPICH_ROOT sets a root prefix for all InfiniPath-related paths. It is
used by mpirun to try to find the mpirun-ipath-ssh executable, and it also
sets up the LD_LIBRARY_PATH for new programs. Consequently, multiple
versions of the TrueScale software releases can be installed on some or all
nodes, and QLogic MPI and other versions of MPI can be installed at the same
time. It may be set in the environment, in mpirun.defaults, or in an rcfile (such
as .mpirunrc, .bashrc, or .cshrc) that will be invoked on remote nodes.
If you have installed the software into an alternate location using the --prefix
option with rpm, --prefix would have been set to $MPICH_ROOT.
If MPICH_ROOT is not set, the normal PATH is used unless mpirun is invoked with
a full pathname.
NOTE:
mpirun-ssh was renamed mpirun-ipath-ssh to avoid name conflicts
with other MPI implementations.
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