Installing ROOT with CUDA support in a Conda environment


I work with users at Purdue CMS Analysis Facility (Purdue AF), who would like to be able to accelerate ROOT with GPUs (specifically, RooFit’s EvalBackend functionality). RooFit operations take dozens of hours in some cases, and users are excited about the possibility of accelerating that using available GPU resources.

At Purdue AF, we manage software stacks via Conda, so an ideal solution would be to keep it that way, and somehow enable CUDA for ROOT installation in a given Conda environment.

What is the best way to achieve this? Could you please provide specific instructions for installing ROOT in such a way, if it is possible?

OS: AlmaLinux 8
ROOT version: the latest will do (6.30.06)
CUDA version: 12.2

Thank you!

  • Dmitry

Hi Dmitry,

Thanks for reaching out. This sounds like a great use case. Actually, we’d also be very interested in understanding more of the great work you do at Purdue to understand how to best support you: that’s perhaps for a private message at a later stage with which we can reach out to you perhaps?

To come back to your question, let me ask two things for me to understand better the context. I see in the JL session the cms cvmfs mount point is available:

  • Have you checked with the curator of the content of that repository whether CMS distributes a CUDA enabled root as part of the CMSSW releases?
  • The SFT group distributes software stacks, e.g. for individual analysers, ATLAS, LHCb and SWAN. Among the type of releases, CUDA flavoured stacks are made available (e.g. /cvmfs/ These look very much like CMSSW externals, i.e. a few hundred packages coherently compiled and distributed. Have you considered mounting on your AF?

Cheers and thanks again for the interesting post.


1 Like

Hi Danilo,

Thank you very much for quick reply!

In general, we try to avoid using CVMFS distributions, as the setup scripts there tend to break existing environments by overwriting environment variables such as LD_LIBRARY_PATH. For this reason, most of our researchers are already used to not mixing CMSSW with Pythonic analysis workflows.

That said, I did try to use SFT builds, the only Alma8 build of latest ROOT that I found is this:
However, I cannot use pyROOT with it (I’m not sure if it is the problem of the build, or whether it interferes with ROOT that is already installed in our image):

[dkondra@purdue-af-1]$ source /cvmfs/
[dkondra@purdue-af-1]$ python3
Python 3.10.14 | packaged by conda-forge | (main, Mar 20 2024, 12:45:18) [GCC 12.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ROOT as rt
cling (LLVM option parsing): for the --optimize-regalloc option: may only occur zero or one times!

What we are trying to achieve at Purdue AF is being able to use ROOT with CUDA within a given Conda environment (Jupyter kernel), such that the environment variables and dependencies in that kernel are respected. This has already been working well with ROOT installed from conda-forge, but there is no CUDA support there.

Please feel free to message me privately for further discussion on Mattermost or email.


Hi Dmitry,

Let’s move the discussion somewhere (I am contacting you now) and then we may decide to post the solution we find here.