8.9 Environment Variables

HP-MPI on HP XC provides the following additional environment variables:

8.9.1 MPIRUN_OPTIONS

MPIRUN_OPTIONS is a mechanism for specifying additional command line arguments to mpirun. If this environment variable is set, then any mpirun command will behave as if the arguments in MPIRUN_OPTIONS had been specified on the mpirun command line. For example:

%export MPIRUN_OPTIONS="-v -prot"

%$MPI_ROOT/bin/mpirun -np 2 /path/to/program.x

The above commands are equivalent to the following:

%$MPI_ROOT/bin/mpirun -v -prot -np 2 /path/to/program.x

8.9.2MPIRUN_SYSTEM_OPTIONS

The MPIRUN_SYSTEM_OPTIONS environment variable allows a system administrator to preset options which will be inserted before MPIRUN_OPTIONS and any explicit mpirun options on the command line. This is most useful for establishing a preferred IP address/hostname for TCP communications in the situation where a user explicitly requests TCP via the -TCPoption, or when default system interconnection selection chooses TCP. This environment variable can be overridden.

8.9.3 MPI_IC_ORDER

The MPI_IC_ORDER environment variable, whose default contents are

"elan:gm:itapi:TCP", instructs HP-MPI to search in a specific order for the presence of a system interconnect. Lowercase selections imply use if detected, otherwise keep searching. An uppercase option demands that the system interconnect option be used, and if it cannot be selected the application will terminate with an error. For example:

%export MPI_IC_ORDER="elan:TCP:gm:itapi"

%export MPIRUN_SYSTEM_OPTIONS="-subnet 192.168.1.1"

%export MPIRUN_OPTIONS="-prot"

%$MPI_ROOT/bin/mpirun -srun -n4 ./a.out

The command line for the above will appear to mpirun as:

$ MPI_ROOT/bin/mpirun -subnet 192.168.1.1 -prot -srun -n4

./a.out

The system interconnect decision will look for the presence of Elan and use it if found. Otherwise, TCP will be used and the communication path will be on the subnet

192.168.1.1.

The following is an example of using TCP over Gigabit Ethernet, assuming Gigabit Ethernet is installed and 192.168.1.1 corresponds to the Ethernet interface with Gigabit Ethernet. Note the implicit use of -subnet 192.168.1.1 is required to effectively get TCP over the proper subnet.

%export MPI_IC_ORDER="elan:TCP:gm:itapi"

%export MPIRUN_SYSTEM_OPTIONS="-subnet 192.168.1.1"

%$MPI_ROOT/bin/mpirun -prot -TCP -srun -n4 ./a.out

8.9.4MPI_PHYSICAL_MEMORY

MPI_PHYSICAL_MEMORY allows you to specify the amount of physical memory in kilobytes available on the system. MPI normally attempts to determine the amount of physical memory

8-10Using HP-MPI