Graphical applications¶

Running graphical applications on UCT HPC¶

Some research workflows require graphical interfaces, such as:

visualisation tools
IDEs
MATLAB or similar environments

On HPC, graphical applications run on compute nodes, with output displayed remotely.

Recommended approach¶

For most users, graphical applications should be run via:

→ Open OnDemand (web-based access)

This provides a more stable, accessible, and persistent interface.

See:

Open OnDemand → Reference > HPC

Alternative approach: X11 forwarding¶

X11 forwarding allows graphical applications to display on your local machine over SSH.

This approach:

is older and less reliable
depends on local configuration
can be slow over typical network connections

Use X11 only when:

the application is not available via Open OnDemand
you need a lightweight graphical tool
you understand the limitations

Login nodes are for:

connecting to the system
editing files
submitting jobs

They are not designed for running applications.

Always use interactive jobs.

Interactive job example¶

srun --partition=ada --nodes=1 --ntasks=1 --time=02:00:00 --pty bash

Using X11 forwarding¶

Connect with X forwarding¶

ssh -X username@hpc.uct.ac.za

or

ssh -Y username@hpc.uct.ac.za

Start an interactive job¶

srun --partition=ada --nodes=1 --ntasks=1 --time=02:00:00 --pty bash

Test¶

xclock

Running applications (examples)¶

MATLAB¶

module load matlab
matlab

R¶

module load R/R-4.3.3
R

Python¶

module load python/miniconda3-py3.12
python

Performance considerations¶

X11 forwarding can be:

slow
laggy
sensitive to network quality

Prefer:

saving outputs to file
viewing results locally
using Open OnDemand where possible

Alternatives to GUI workflows¶

Many workflows are better without graphical interfaces.