HP-MPI Version 1.2 for Windows Release Note

1.5 Running HP-MPI from HPCS
There are two ways to run HP-MPI under HPCS: command line and scheduler GUI. Both ways
can be used to access the functionality of the scheduler. The command line scheduler options
are similar to the GUI options.
The following instructions are in the context of the GUI, but equivalent command line options
are also listed.
The HPCS job scheduler uses the term "job" to refer to an allocation of resources, while a "task"
is a command that is scheduled to run using a portion of a job allocation. HP-MPI’s mpirun
must be submitted as a task that uses only a single processor. This enables the remaining resources
within the job to be used for the creation of the remaining application ranks (and daemons). This
is different from MSMPI, which requires that all of the processors in the job be allocated to the
MSMPI mpiexec task.
Figure 1 shows the relationship between HP-MPI processes and the job allocation. A single task,
Task 1 is submitted and assigned a single CPU resource inside a larger job allocation. This task
contains the mpirun command. Solid lines show the creation of local deamons and ranks using
standard process creation calls. The creation of remote ranks are handled by mpirun by creating
additional tasks within the job allocation. Only the task which starts mpirun is submitted by the
user.
Figure 1-1 Job Allocation
To run an MPI application, submit the mpirun command to the scheduler. HP-MPI uses the
environment of the task and job where mpirun is executing to launch the required mpids that
start the ranks.
mpirun must use only a single processor for its task within the job so the resources can be used
by the other processes within the MPI application. (This is the opposite of MSMPI, which requires
all of the processor to be allocated to the mpiexec task by the MPI application.)
You must submit the mpirun task as an exclusive task. Click the Exclusive box in the GUI
for both Job and Task, or include the /exclusive:true flag on the job commands for both
Job Creation and Task Addition. You must include exclusive for mpirun. Otherwise, all the
processes started by mpirun are bound to a single CPU. This is due to the new scheduler affinity
rules and the use of the legacy API by HP-MPI for this version. You can also schedule the mpirun
task with the number of processors equal to the CPU count for the node. If you do not know
what this number is, use of the exclusive flag is preferred.
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