DDT is a tool for debugging C, C++ and Fortran parallel programs. It is available on the MACS and XCI systems as part of the Forge suite.


To use DDT you will need to load the Forge module. On MACS the command is

module load allinea/forge

and on the XCI system the command is

module load tools/arm-forge

When you have loaded the module you can start the DDT graphical interface by running the command ddt &.

Example session

This example uses an interactive job running in the XCI arm-dev queue to debug a parallel program.

Start by compiling your program with a -g flag to retain extra debugging information. For example to compile a C program called myprog.c run

cc -g -o myprog myprog.c

which will produce an executable file called myprog.

Next start an interactive job by running the command

qsub -I -X -q arm-dev -l select=1 -l walltime=1:00:00

This starts an interactive job (-I) with X11 graphics forwarding (-X) using 1 compute node for up to 1 hour.

When the job starts load the Forge module

module load tools/arm-forge

We can now run ddt and tell it to start our program

ddt aprun -n 2 ./myprog

This example runs myprog with with 2 MPI processes. The ddt graphical interface will open and from here you can launch and debug your program.