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ROOT I/O Meeting
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VIDYO
VIDYO
Viktor: Working from CERN, ROOT4J update to put ROOT I/O in Spark. Support Tree, TBranch and TLeaf but not yet TBranchElement. 2 questions away from reading his ntuples and after that CMS MiniAOD.
Danilo: On my plate improving support of collection of unique_ptr. Shared_ptr might have priority. I am also thinking of the JITed collection proxy.
Philippe: I will resend my preliminary draft of how we could support shrared_ptr.
Brian: Is there a good write up about JITed collection proxy?
Danilo: not really.
Brian: Two things worth mentioning. I just checked the ticket on the implicit parallel writing and it is ready to go.
Philippe: fair enough I’ll merge it then
Brian: There is actually a follow-up merge request that have been heavily test by CMS. Factor 2 improvement in CMSSW by reducing Amdahl in real Reco on KNL.
Brian: I am also developing/prototyping the bulk I/O API … I am almost ready for numerical types … I will present at the next meeting.
Brian: Dave A has made a version of zlib that makes a run-time selection of the actually (de)compression routines to find the best assembly supported by the CPU. It is in the development branch of CMSSW. He is going to make a merge request to CloudFlare and another one for the built-in one in ROOT. It probably only work for GCC at the moment.
Brian: My student is stuck in Boston by snow. He is working on two things. One is the per-entry compression. Need input to decide what is the next step. The other was an improved version of the parallel unzipper (the current version is not optimal due to fine grained locks and possibly due to pthread). Part of the reason to address this was a class project and it might help because the de-compression could be ask earlier and the data would be ready ‘faster’. It would also help in the case the user call Branch::GetEntry ….
Peter: I am glad to see this series of meeting starting. Vassil will start in January working on I/O. Working on parallelization.
Next meeting: January 6th.
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