Updated 2023-02-24

Run Root on the Cluster


  • ROOT is a framework for data processing, born at CERN, at the heart of the research on high-energy physics. Every day, thousands of physicists use ROOT applications to analyze their data or to perform simulations. With ROOT you can:
    • Save data
    • Access data
    • Mine data
    • Publish results
    • Run interactively or build your own application
    • Use ROOT within other languages


  • In this guide we will run Root in python as an example. Using an interpreted language allows us to run Root interactively, but for the purposes of this guide, we will generate a 2D line plot with no interactive elements.
  • Since Root is a graphical application, we will need to run it through the Interactive Desktop on Phoenix OnDemand.

Walkthrough: Run Root on the Cluster

  • This walkthrough will use Python and Root to generate a 2D line plot that will be viewed through Phoenix OnDemand.
  • The code used in this example comes from Root's GitHub repo.
  • graph.py can be found here
  • You can transfer the file to your account on the cluster to follow along. The file transfer guide may be helpful.

Set up Interactive Desktop on Phoenix OnDemand

  • In order to access Phoenix OnDemand you must be connected to the GT VPN. If you do not already have the VPN set up, visit Configure the GT VPN
  • Once connected to the VPN you can access the application at Phoenix OnDemand.
  • Choose the Slurm Interactive Apps tab and select Interactive Desktop to setup and launch.
  • Setting up Interactive Desktop:
    • Charge Account: gts-<PI username> ("phx-pace-staff" works for trial. Required.)
    • Quality of Service: inferno
    • Node Type: GPU Tesla V100-16B or GPU Tesla V100-32B
    • Nodes: 1
    • Cores Per Node: 8 (Number of cores (CPUs) per node. Max: 24 cores per node.)
    • GPUs Per Node: 1
    • Memery Per Crore (GB): Leave blank if unsure. Total memory for job is: nodes × cores × memory per core
    • Number of hours: 1
  • After the preceding details are entered, clik the Launch button
  • Once the Launch Interactive Desktop is an available option, click the button to open a Phoenix OnDemand Interactive Desktop to use for Root

Part 2: Load and Start Root on Phoenix OnDemand

  • Open terminal in the Interactive Desktop by clicking top left Activities > search for terminal
  • All commands here on will be typed in the terminal
  • You can find which versions are available for any module with module avail [software].
  • Run the following commands to load the necessary modules:
    • module load gcc/10.3.0
    • module load root/6.26.04
  • Navigate to the directory containing the graph.py file.
  • View the graph with python graph.py.


  • Congratulations! You successfully ran Root on the cluster.