Intel® MPI Library Developer Guide for Linux* OS

ID 768728
Date 12/16/2022

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Interoperability with Other Tools Through -gtool

To simplify interoperability with other analysis tools, Intel® MPI Library provides the -gtool option (also available as the I_MPI_GTOOL environment variable). Using the -gtool option, you can analyze specific MPI processes with VTune™ Profiler, Intel® Advisor, Valgrind,* and other tools through the mpiexec.hydra or mpirun commands.

The Intel Advisor CLI uses -gtool to analyze MPI applications. For sample command lines and example scenarios, including the Weather Research and Forecasting (WRF) Model, see Analyze Vectorization and Memory Aspects of an MPI Application.

If you are not using the -gtool option, to analyze an MPI process with, for example, VTune Profiler, you must specify the relevant command in the corresponding argument set:

$ mpirun -n 3 ./myprog : -n 1 vtune -c advanced-hotspots -r ah -- ./myprog

The -gtool option allows you to specify a single analysis command for all argument sets (separated by colons ':') at once. Even though it is allowed to use -gtool within a single argument set, it is not recommended to use it in several sets at once and combine the two analysis methods (with -gtool and argument sets).

For example, to analyze processes 3, 5, 6, and 7 with the VTune Profiler, you can use the following command line:

$ mpirun -n 8 -gtool "vtune -collect hotspots -r result:3,5-7" ./myprog

The -gtool option also provides several methods for finer process selection. For example, you can easily analyze only one process on each host, using the exclusive launch mode:

$ mpirun -n 8 -ppn 4 -hosts node1,node2 -gtool "vtune -collect hotspots -r result:all=exclusive" ./myprog

You can also use the -gtoolfile option to specify -gtool parameters in a configuration file. All the same rules apply. Additionally, you can separate different command lines with section breaks.

For example, if gtool_config_file contains the following settings:

env VARIABLE1=value1 VARIABLE2=value2:3,5,7-9; env VARIABLE3=value3:0,11
env VARIABLE4=value4:1,12

The following command sets VARIABLE1 and VARIABLE2 for processes 3, 5, 7, 8, and 9 and sets VARIABLE3 for processes 0 and 11, while VARIABLE4 is set for processes 1 and 12:

$ mpirun -n 16 -gtoolfile gtool_config_file a.out

Using -gtool for Debugging

The -gtool runtime option can help you with debugging, when attaching to several processes at once. Instead of attaching to each process individually, you can specify all the processes in a single command line. For example:

$ mpirun -n 16 -gtool "gdb:3,5,7-9=attach" ./myprog

The command line above attaches the GNU* Debugger (GDB*) to processes 3, 5, 7, 8 and 9.

Do not use the -gdb and -gtool options together. Use one option at a time.