Debugging GEOSgcm.x with Arm Forge at NCCS

Overview

This describes how to debug GEOS5 on NCCS systems (Discover) using the Arm Forge debugger (formerly Allinia DDT) and the remote client.

1 Prerequisites

1.1 Build GEOS in Debugging Mode

You first need to build GEOS with the debug CMake options. See the GEOS5 build instructions for this.

1.2 Install the Arm Forge Remote Client

Next, you need the Arm Forge remote client. This run on your local machine and provides a tunnel into the machine where your code actually runs. This is really the only practical way to debug as if you run Arm Forge on Discover it will be unusably slow due to needing to forward X.

The remote client can be found at:

https://developer.arm.com/tools-and-software/server-and-hpc/downloads/arm-forge

and need to be installed on your local machine.

2 Running GEOSgcm.x in the Debugger

It is important to note that NCCS has a limited number of Arm Forge licenses on the order of 100 to 200. What users need to know is that each license allows one MPI process to run. Practically, a user can only run an application with about 100 to 200 MPI tasks. Therefore a user needs to have an experiment that can be run with up to 200 MPI processes.