HP-MPI V2.3 for Linux Release Note

included with HP-MPI attempt to link MPI applications in such a way as to make

this possible. If you choose not to link your application with the provided compiler

wrappers, you must either ensure that libmpi.so precedes libc.so on the

linker command line or specify "-e LD_PRELOAD=%LD_PRELOAD:libmpi.so"

on the mpirun command line.

• Whether mpirun is invoked on a host where at least one MPI process is running

or on a host remote from all MPI processes, HP-MPI writes the instrumentation

output file prefix.instr to the working directory on the host that is running

rank 0 (when instrumentation for multihost runs is enabled). When using -ha,

the output file is located on the host that is running the lowest existing rank number

at the time the instrumentation data is gathered during MPI_Finalize().

• Applications that use the ScaLAPACK library must use the HP-MPI mpich

compatibility mode. When the application is built, mpicc.mpich or

mpif77.mpich or mpif90.mpich must be used. At runtime, mpirun.mpich

must be used to launch the application.

• HP-MPI uses shared memory for communications between processes on the same

node and may attempt to allocate a shared-memory segment that is larger than

the operating system allows. The most common issue you might experience is an

error message like:

Cannot create shared memory segment of <size> bytes.

To increase the maximum allowed shared memory segment size, enter the following

command as root:

# /sbin/sysctl -w kernel.shmmax=<size in bytes>

To make changes to the kernel.shmmax setting persist across a reboot, add the

line:

kernel.shmmax=<size in bytes>

to the /etc/sysctl.conf file.

• The MPI_FLUSH_FCACHE environment variable is silently ignored if the

-cpu_bind option is not specified. This limitation will be removed in a future

release. See the mpienv(1) manpage for more information.

• HP-MPI uses the $MPI_REMSH command to launch on remote machines. The

commands constructed are of the general form "$MPI_REMSH <host> -n

<command>". If a remote shell command is desired for which the -n in the above

syntax is not appropriate, a shell script such as the following can be constructed

and used for the MPI_REMSH command:

#!/bin/sh

host="$1"

shift

ssh $host "$@"

28 Known Problems and Workarounds