Escali Escali, LLC Network Router 4.4 User Manual
Section: 3.7 Debugging and profiling
Scali MPI Connect Release 4.4 Users Guide
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3.7.2 Built-in-tools for debugging
Built-in tools for debugging in Scali MPI Connect covers discovery of the MPI calls used through
tracing and timing, and an attachment point to processes that fault with segmentation
violation. The tracing and timing is covered in Chapter 4.
tracing and timing, and an attachment point to processes that fault with segmentation
violation. The tracing and timing is covered in Chapter 4.
3.7.2.1 Using built-in segment protect violation handler
When running applications that terminate with a SIGSEGV-signal it is often useful to be able
to freeze the situation instead of exiting, the default behavior. The built-in SIGSEGV-handler
can be made to do this by defining the environment-variable
SCAMPI_INSTALL_SIGSEGV_HANDLER.
to freeze the situation instead of exiting, the default behavior. The built-in SIGSEGV-handler
can be made to do this by defining the environment-variable
SCAMPI_INSTALL_SIGSEGV_HANDLER.
Legal options are:
6. The handler dumps all registers and starts looping. Attaching with a debugger will then
make it possible to examine the situation which resulted in the segment protect violation.
7. The handler dumps all registers but all processes will exit afterwards.
All other values will disable the installation of the handler.
To attach to process <pid> on a machine with the GNU debugger (gdb) do;
user% gdb /proc/<pid>/exe <pid>
In general, this will allow gdb to inspect the stack trace and identify the functions active when
the sigsegv occurred, and disssasemble the functions. If the application is compiled with
debug info (-g) and the source code is available, then source level debugging can be carried
out.
3.7.3 Assistance for external profiling
Profiling parallel applications is complicated by having multiple processes at the same time. But
Scali MPI Connect comes to assistance; through the SCAMPI_PROFILE_APPLICATION
Scali MPI Connect comes to assistance; through the SCAMPI_PROFILE_APPLICATION
environment variable together with the -separate_output option (SCAMPI_SEPARATE_OUTPUT)
the output from the application runs is directed at one file per process for easier use.
The environment variables SCAMPI_PROFILE_APPLICATION_START and
SCAMPI_PROFILE_APPLICATION_END are also available for steering the range of memory
SCAMPI_PROFILE_APPLICATION_END are also available for steering the range of memory
addresses applicable to profiling.
3.7.4 Debugging with Etnus Totalview
SMC applications can be debugged using the Etnus Totalview, see http://www.etnus.com
for more information about this product.
for more information about this product.
To start the Etnus Totalview debugger with a Scali MPI application, use the tvmpimon wrapper
script. This wrapper script accepts the regular options that mpimon accepts, and sets up the
environment for Totalview. The totalview binary must be in the search path when launching
tvmpimon. If the mpirun script is the preferred way of starting jobs, it accepts the “standard”
-tv option, however the same rules applies with regards to the search path.
script. This wrapper script accepts the regular options that mpimon accepts, and sets up the
environment for Totalview. The totalview binary must be in the search path when launching
tvmpimon. If the mpirun script is the preferred way of starting jobs, it accepts the “standard”
-tv option, however the same rules applies with regards to the search path.