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Default differences

How does the default behaviour of HPCx differ from other IBM eServer 575 clusters?

Environment Variables

The following environment variables have been reset.

MP_SHARED_MEMORY=yes
MP_POLLING_INTERVAL=1000000
MP_TIMEOUT=300

whereas the IBM defaults are

MP_SHARED_MEMORY=no
MP_POLLING_INTERVAL=400000 (for US and 180000 for IP)
MP_TIMEOUT=150

LPARs

We define our LPARs (Logical PARtions) to be the same as two MCMs (Multi-Chip Modules), which are tightly coupled, so that we may use all the switch channels to allow maximum communication through-put. For HPCx, each LPAR has 16 processors.

LoadLeveler

If your job is a parallel job, then you must specify job_type=parallel and node_usage=not_shared

If your job is a serial job, then you must specify job_type=serial and node_usage=shared

If your job is an interactive job, then you must specify job_type=parallel and node_usage=shared

LoadLeveler imposes a maximum memory per task to be 14.4GB/(number-of-processes), where number-of-processes is the number_of_tasks in a purely MPI job, or number_of_tasks*OMP_NUM_THREADS, in a mixed-mode code.

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