Root 5 containers?


Do you have available root containers for older versions of ROOT, e.g. v5.32 (or similar compatible) or could you think of building one? I’m asking because of CMS Open data compatibility. In open data workflows, in particular, in a cloud environment, we could benefit from having one.


Best, Kati

ROOT Version: 5
Platform: Not Provided
Compiler: Not Provided

Hi @kati,

ROOT 5 is totally unsupported since a few years. If you use it, you are on your own (no bug fixes or new features, uses the old CINT, etc.). Why do you want to use such an old version of ROOT? ROOT data files created with ROOT 5.32 should be readable by the latest ROOT release.

If you really insist on using ROOT v5.32, the only thing I can suggest is that you build from source: GitHub - root-project/root at v5-32-04, using the instructions here.


Hi @jalopezg ,

ok, sure, I understand this. We need to use this old version of root for the CMS public data for the first steps in the analysis and we are exploring the best options for the analysis flow, e.g. in the cloud environment. We do have it in the CMSSW open data images, but for some cases, in certain workflow steps, it would be practical not to use the full large image with all CMSSW but only with root. But we can also exclude such cases, or build one if needed. Of course, we are better off with the new root versions and we will use it whenever possible.

However, keep in mind that CERN has now an open data policy, and experiments are expected to provide a working environment compatible with the data ("Virtual computing environments that are compatible with the data and software will be made available. "). No one expects the old versions to be supported years after, but it is good to keep this data preservation and long-term usability aspect in mind. Obviously, the most important factor is the readability of data files created with old version, and as long that holds we are in a good position.

Best, Kati

@Axel and @pcanal might be able to comment further, but ROOT 5 data should be readable with ROOT 6.

If you get around to produce a ROOT 5 Docker image, feel free to contribute the corresponding Dockerfile at GitHub - root-project/root-docker: Docker recipes for ROOT , we currently do not provide one.


Yes, indeed, ROOT 5 data is readable with ROOT 6 with no problem and that’s great. This was just a further detail. Thanks a lot!

Best, Kati

1 Like

Thanks, Kati! Apologies for not replying before Enrico did, and then not having anything to add :slight_smile:

Indeed if you want old histogram bugs (!) then using ROOT5 is the way to go. For archival / reproducibility purposes that’s maybe ideal? But for open data / open science I’d argue that ROOT’s backward compatibility is the preferred path, as you point out.

Hi @kati,

Sorry for not replying before! I have nothing to add to what Axel and Enrico already said, but I’m happy to here that you managed to read in ROOT 6 data saved by ROOT 5.
We know that backward (and forward!) compatibility is a must, and we do our best to achieve it! In general, backward compatibility is ensured, and forward compatibility works also pretty well: we were able to (partially) read in ROOT 3.02 a .root file generated by ROOT 6.24!


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