The ch_nexus device allows you to use Nexus debugging facilities only if you link against the debug version of mpich and Nexus. You can then pass the following parameters to your program using mpirun:
- -Dnexus: This command sets the trace level (0-9). 0 will give you nothing, and 9 will give you more than you can effectively use. Suggested values are 2 or 3.
- -debug_display: This command gives the X windows screen name that the debugger should be displayed on. One debugger will start for each process (except the starting node). Use the go command within the debugger to start your program with the right parameters.
- -debug_command: This command tells where to find the script to start up a debugger for each process. This should be generated automatically with configure -device=ch_nexus in either /usr/local/mpi/bin/rundbx or /usr/local/mpi/bin/rungdb.
So, to run a program at trace level 3, one would enter:
mpirun -np 2 program -mpi -Dnexus 3Be sure to include the -mpi before any of the debugging flags. See the debugging section of the Nexus User's Guide for more details on how to debug ch_nexus programs.