Parallel Event Selection on HPC Systems

Conference · Tue Jan 01 00:00:00 EST 2019 · EPJ Web Conf.

DOI:https://doi.org/10.1051/epjconf/201921404059· OSTI ID:1581426

Paterno, Marc ^[1]; Kowalkowski, Jim ^[1]; Sehrish, Saba ^[1]

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1. Fermilab

In their recent measurement of the neutrino oscillation parameters,NOvA uses a sample of approximately 25 million reconstructed spills to searchfor electron-neutrino appearance events. These events are stored in an n-tupleformat, in 250 thousand ROOT files. File sizes range from a few hundred KiB toa few MiB; the full dataset is approximately 1.4 TiB. These millions of eventsare reduced to a few tens of events by the application of strict event selectioncriteria, and then summarized by a handful of numbers each, which are used inthe extraction of the neutrino oscillation parameters.The NOvA event selection code is currently a serial C++ program that readsthese n-tuples. The current table data format and organization and the selection/reduction processing involved provides us with an opportunity to explorealternate approaches to represent the data and implement the processing. Werepresent our n-tuple data in HDF5 format that is optimized for the HPC environmentand which allows us to use the machine’s high-performance parallelI/O capabilities. We use MPI, numpy and h5py to implement our approach andcompare the performance with the existing approach. We study the performanceimplications of using thousands of small files of different sizes as comparedwith one large file using HPC resources. This work has been done as part of theSciDAC project, “HEP analytics on HPC” in collaboration with the ASCR teamsat ANL and LBNL.

• Research Organization: Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 1581426
• Report Number(s): FERMILAB-CONF-18-667-CD; oai:inspirehep.net:1761011
• Journal Information: EPJ Web Conf., Vol. 214; Conference: 23rd International Conference on Computing in High Energy and Nuclear Physics, Sofia, Bulgaria, 07/09-07/13/2018
• Country of Publication: United States
• Language: English