Parallel Programming Guide for HP-UX Systems

MPI
Running
Chapter 230
allocated to these objects before you call MPI_Finalize. In C, this is
analogous to making calls to malloc() and free() for each object created
during program execution.
Setting the l option may decrease application performance.
f Forces MPI errors to be fatal. Using the f option sets the
MPI_ERRORS_ARE_FATAL error handler, ignoring the programmer’s
choice of error handlers. This option can help you detect nondeterministic
error problems in your code.
If your code has a customized error handler that does not report that an MPI
call failed, you will not know that a failure occurred. Thus your application
could be catching an error with a user-written error handler (or with
MPI_ERRORS_RETURN) which masks a problem.
i Turns on language interoperability concerning the MPI_BOTTOM constant.
MPI_BOTTOM Language Interoperability—Previous versions of HP MPI were
not compliant with Section 4.12.6.1 of the MPI-2 Standard which requires
that sends/receives based at MPI_BOTTOM on a data type created with
absolute addresses must access the same data regardless of the language in
which the data type was created. If compliance with the standard is desired,
set MPI_FLAGS=i to turn on language interoperability concerning the
MPI_BOTTOM constant. Compliance with the standard can break source
compatibility with some MPICH code.
s[a|p][ # ] Selects signal and maximum time delay for guaranteed message
progression. The sa option selects SIGALRM. The sp option selects SIGPROF.
The # option is the number of seconds to wait before issuing a signal to
trigger message progression. The default value for the MPI library is
sp604800, which issues a SIGPROF once a week. If the application uses both
signals for its own purposes, you must disable the heart-beat signals. A time
value of zero seconds disables the heart beats.
This mechanism is used to guarantee message progression in applications
that use nonblocking messaging requests followed by prolonged periods of
time in which HP MPI routines are not called.
Generating a UNIX signal introduces a performance penalty every time the
application processes are interrupted. As a result, while some applications
will benefit from it, others may experience a decrease in performance. As
part of tuning the performance of an application, you can control the
behavior of the heart-beat signals by changing their time period or by