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

Understanding HP-MPI
MPI options
Chapter 3148
prefix[:l][:nc][:off]
where
prefix Specifies the instrumentation output file prefix. The
rank zero process writes the application’s
measurement data to prefix.instr in ASCII. If the
prefix does not represent an absolute pathname, the
instrumentation output file is opened in the working
directory of the rank zero process when MPI_Init is
called.
l Locks ranks to CPUs and uses the CPU’s cycle counter
for less invasive timing. If used with gang scheduling,
the :l is ignored.
nc Specifies no clobber. If the instrumentation output file
exists, MPI_Init aborts.
off Specifies counter instrumentation is initially turned off
and only begins after all processes collectively call
MPIHP_Trace_on.
Refer to “Using counter instrumentation” on page 175 for more
information.
Even though you can specify profiling options through the MPI_INSTR
environment variable, the recommended approach is to use the mpirun
command with the -i option instead. Using mpirun to specify profiling
options guarantees that multihost applications do profiling in a
c o n s i s te n t m a n n e r. R e f e r t o “ m p i r u n ” o n p a g e 7 4 f o r m or e i n f o r m a t i o n .
Counter instrumentation and trace-file generation are mutually
exclusive profiling techniques.
NOTE When you enable instrumentation for multihost runs, and invoke mpirun
either on a host where at least one MPI process is running, or on a host
remote from all your MPI processes, HP-MPI writes the instrumentation
output file (prefix.instr) to the working directory on the host that is
running rank 0.