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ROOT I/O Worshop October 2011

ROOT I/O Worshop October 2011. Summary. v5.34 External Contributions. Allow more than one TTreeCache per file (automatically) - Peter Resolve the issue of the TTreeCache startup time – Peter Reimplementation of OptimizeBaskets – Brian Fast Merging sort by cluster and branches - Brian

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ROOT I/O Worshop October 2011

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  1. ROOT I/O WorshopOctober 2011 Summary Philippe Canal, FNAL

  2. v5.34 External Contributions • Allow more than one TTreeCache per file (automatically) - Peter • Resolve the issue of the TTreeCache startup time – Peter • Reimplementation of OptimizeBaskets – Brian • Fast Merging sort by cluster and branches - Brian • Testing of parallel prefetching – Brian • I/O Customization: Write Rules – Chris • Test environment - Ilija/Wahid Philippe Canal, FNAL

  3. Gathering Statistics • Proposal to allow instrumentation to understand what is the real fraction of the file are being read. • For example by enabling a statistic dump of the fraction of files each jobs read and share that information with CERN IT? • This really need to be done only for a sub set of the jobs. • Should use TTreePerfStats • Need to make TTreePerfStats flexible and thread safe. Philippe Canal, FNAL

  4. Discussions • Strong interest in new Parallel Merger • Caveat: how to deal with luminosity blocks is still unresolved. • Oddities in the results presented by LCHb and by ATLAS (multi sites tests) • Need to be investigated and/or re-measured. • LHCb issues: probably due LHCb and/or too small of a cluster size. • ATLAS tests: probably due to temporary change in ROOT/Athena releases. • Understand why ATLAS reading is seemingly 30% faster when not split. Philippe Canal, FNAL

  5. Conclusion • Very Good participation and collaborations. • Active participation from both CMS and ATLAS. • Next ROOT I/O workshop in February • Exact date to be announced soon. Philippe Canal, FNAL

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