Using a debugger

• We can start up multiple MPI processes under the control of a debugger like GDB. An example is shown below. The option -enable-x is required in the lab but not needed if you are running mpiexec locally on your system.

  mpiexec -enable-x -n 2 konsole -e gdb spmd_sum_3 1000
  

  This can be convenient in pinpointing a specific problem. However, this is a bit like one person riding multiple bikes!

• Use a commercial parallel debugger, such as TotalView or DDT, that understands MPI jobs and can deal with multiple processes at once. These are much more sophisticated. But they are also expensive.