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

Understanding HP-MPI
MPI options
Chapter 3 139
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
turning them off. This is accomplished by setting the
time period of the s option in the MPI_FLAGS
environment variable (for example: s600). Time is in
seconds.
You can use the s[a][p]# option with the
thread-compliant library as well as the standard non
thread-compliant library. Setting s[a][p]# for the
thread-compliant library has the same effect as setting
MPI_MT_FLAGS=ct when you use a value greater than 0
for #. The default value for the thread-compliant
library is sp0. MPI_MT_FLAGS=ct takes priority over
the default MPI_FLAGS=sp0.
Refer to “MPI_MT_FLAGS” on page 143 and
“Thread-compliant library” on page 57 for additional
information.
Set MPI_FLAGS=sa1 to guarantee that MPI_Cancel
works for canceling sends.
To use gprof on XC systems, set to environment
variables:
MPI_FLAGS=s0
GMON_OUT_PREFIX=/tmp/app/name
These options are ignored on HP-MPI for Windows.
y[#] Enables spin-yield logic. # is the spin value and is an
integer between zero and 10,000. The spin value
specifies the number of milliseconds a process should
block waiting for a message before yielding the CPU to
another process.
How you apply spin-yield logic depends on how well
synchronized your processes are. For example, if you
have a process that wastes CPU time blocked, waiting
for messages, you can use spin-yield to ensure that the