Q

3 – Using InfiniPath MPI InfiniPath MPI Limitations

Symbolic debugging is easier than machine language debugging. To enable symbolic debugging you must have compiled with the -goption to mpicc so that the compiler will have included symbol tables in the compiled object code.

To run your MPI program with a debugger use the -debugor -debug-no-pauseand -debuggeroptions to mpirun. See the man pages to pathdb, gdb, and strace for details. When you run under a debugger, you get an xterm window on the front end machine for each node process. Thus, you can control the different node processes as desired.

To use strace with your MPI program, the syntax would be: $ mpirun -npn -mmpihosts strace program-name

The following features of InfiniPath MPI especially facilitate debugging:

■Stack backtraces are provided for programs that crash.

■-debugand -debug-no-pauseoptions are provided for mpirun that can make each node program start with debugging enabled. The -debugoption allows you to set breakpoints, and start running programs individually. The -debug-no-pauseoption allows postmortem inspection. Note that you should set -q 0 when using -debug.

■Communication between mpirun and node programs can be printed by specifying the mpirun -verboseoption.

■MPI implementation debug messages can be printed by specifying the mpirun -psc-debug-leveloption. Note that this can substantially impact the performance of the node program.

■Support is provided for progress timeout specifications, deadlock detection, and generating information about where a program is stuck.

■Several misconfigurations (such as mixed use of 32-bit/64-bit executables) are detected by the runtime.

■A formatted list containing information useful for high-level MPI application profiling is provided by using the -print-statsoption with mpirun. Statistics include minimum, maximum and median values for message transmission protocols as well as a more detailed information for expected and unexpected message reception. See appendix C.8.13 for more information and a sample output listing.

3.12

InfiniPath MPI Limitations

The current version of InfiniPath MPI has the following limitations:

By default, at most eight node programs per node with the QHT7140 are allowed, and at most four node programs per node with the QLE7140. The error message when this limit is exceeded is:

IB6054601-00 D

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Q-Logic IB6054601-00 D manual InfiniPath MPI Limitations
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IB6054601-00 D specifications

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