ROOT I/O Meeting

Friday 27 Apr 2018, 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, Danilo, Zhe, Oksana, Brian.

Oksana: I was able to reproduce the problem on linux.  A ‘tree’ function is calling the CRC function (original version and intrinsic version have different version).    The behavior is very stable/reproducable on linux but on MacOS it is unstable (end result changes).  And indeed valgrind is not clean on valgrind.  I am analyzing the 4 lines of code (or so) that are suspicious.

Brian: In the fallback case, we should not be using the heavily optimized version especially if it is suspicious.  

Oksana: To use the intrinsic version on MacOS we are missing the ‘architecture’ based trampoline function supported by the compiler.

Brian: Proposal mode until May 1st.

Danilo: Finalizing the feature for the release.   I was able to read CMS opendata with RDataFrame.  

Guilherme [Danilo reporting]: Not much new on Parallel Buffer.

Brian: Did we give you any of the NanoAOD data files?

Danilo: Not yet, we are very interested (of course :) ).  Especially since the regular data file require dictionary for full reading.

Brian: Andrea Ricci might be able to give you some information.

Danilo: DataFrame vs BulkIO and overhead.  TDataFrame ‘just’ filling a data frame from ‘just’ created data (i.e. no I/O involved).  TDataFrame’s overhead is  of the order of magnitude as the histogram filling.

Danilo: I will look into the TBranch::SetAddress probably next week.

Zhe: RAS.

Philippe: Significant enhancement to the TTreeCache FillBuffer algorithm.

Brian: What is the guidance on the TTreeCache, still the same or different?

Philippe: Yes, it is just sturdier and more stable :).  If you want to stay within a strict budget, set the cache to half of the cluster size.  The rules is as follow:  Use up to 4 times the requested amount to fit at least one basket per branch, Use up to 2 times the requested amount to fit the first cluster.  Use only up to the requested size to fit extra cluster.

Brian: Friday the 11th, I will be at Fermilab.  

 

16:00 → 16:20 Round Table