ROOT I/O Meeting

Friday 23 Aug 2019, 16:00 → 17:40 Europe/Zurich

32/1-A24 (CERN)

Brian Paul Bockelman (University of Nebraska-Lincoln (US)), Philippe Canal (Fermi National Accelerator Lab. (US))

Attendees: Philippe, Jim, Pratyush Das, Guilherme, Oksana, Jakob.

Oksana: Catching up on older task and prepare for next week Sprint.  I want to achieve the following:
    * RTuple and (ZSTD) Compression discussion and plans.
    * ZTD, compression dictionary and TTree.
    * Benchmarking.
    * Discuss Jim with and etc.

Amadio: RAS.

Jakob: Exciting week with many merges in RTuple.  Most visible added parallel support for RDataFrame.  Added support for more types including std::variant.  Enough functionality for CMS NanoAOD, so ready for benchmarking.
2nd implementation of page storage class ( “RawFile” ).  

Philippe: RawFile will eventually need a vector interface.

[Discussion on granularity of reads and write …  one idea: cache whole cluster and when storing make sure the branch’s data is stored consecutively … no matter what readv is needed for the case of sparse reads].

Philippe: Why was the name was remove from Column?

Jakob: I found that keeping a column name because it is already stored in the meta data.

Jim: Finally working C++ implementation of awkward-array and trying to understand how it relates to RTuple.

Pratyush: RAS.

Philippe: Made progress on schema evolution of split sub-objects. (need to make ‘whole’ StreamerInfo as being cached and maybe repeated).

Philippe: ART is reporting yet another pch-file-is-out-of-date problem, what do we do?

Axel: The long term plan (needed by Windows by the SDK changes all files) is to ‘disable’ carefully the ‘stat-ing’ of the file (we have a copy inside the pch) but in the short term we could simply make sure the error message is convenient/clear enough and added the offending file to our list of file we ‘cache’ locally.

Philippe: There will be an I/O meeting next to provide for a debrief of next week’s I/O sprint.

 

16:00 → 16:20 Round Table