HP-MPI User's Guide (11th Edition)

Understanding HP-MPI
MPI options
Chapter 3144
The single, fun, serial, and mult options are mutually exclusive. For
example, if you specify the serial and mult options in MPI_MT_FLAGS,
only the last option specified is processed (in this case, the mult option).
If no runtime option is specified, the default is mult.
For more information about using MPI_MT_FLAGS with the
thread-compliant library, refer to “Thread-compliant library” on page 57.
MPI_ROOT MPI_ROOT indicates the location of the HP-MPI tree. If you
move the HP-MPI installation directory from its default location in
/opt/mpi for HP-UX and /opt/hpmpi for Linux, set the MPI_ROOT
environment variable to point to the new location. See “Directory
structure for HP-UX and Linux” on page 24 for more information.
MPI_WORKDIR MPI_WORKDIR changes the execution directory. This
variable is ignored when srun or prun is used.
CPU Bind environment variables
MPI_BIND_MAP MPI_BIND_MAP allows specification of the integer CPU
numbers, ldom numbers, or CPU masks. These are a list of integers
separated by commas (,).
MPI_CPU_AFFINITY MPI_CPU_AFFINITY is an alternative method to
using -cpu_bind on the command line for specifying binding strategy. The
possible settings are LL, RANK, MAP_CPU, MASK_CPU, LDOM,
CYCLIC, BLOCK, RR, FILL, PACKED, SLURM, and MAP_LDOM.
MPI_CPU_SPIN MPI_CPU_SPIN allows selection of spin value. The default
is 2 seconds.
MPI_FLUSH_FCACHE MPI_FLUSH_FCACHE clears the file-cache
(buffer-cache). Add "-e MPI_FLUSH_FCACHE[=x]" to the mpirun
command line and the file-cache will be flushed before the code starts;
where =x is an optional percent of memory at which to flush. If the
memory in the file-cache is greater than x, the memory is flushed. The
default value is 0 (in which case a flush is always performed). Only the
lowest rank# on each host flushes the file-cache; limited to one flush per
host/job.
Setting this environment variable saves time if, for example, the
file-cache is currently using 8% of the memory and =x is set to 10. In this
case, no flush is performed.
Example output: