Implementation of the ATLAS Run 2 event data model

Buckley, A. , Eifert, T., Elsing, M., Gillberg, D., Koeneke, K., Krasznahorkay, A., Moyse, E., Nowak, M., Snyder, S. and van Gemmeren, P. (2015) Implementation of the ATLAS Run 2 event data model. Journal of Physics: Conference Series, 664(7), 072045. (doi:10.1088/1742-6596/664/7/072045)

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Abstract

During the 2013-2014 shutdown of the Large Hadron Collider, ATLAS switched to a new event data model for analysis, called the xAOD. A key feature of this model is the separation of the object data from the objects themselves (the 'auxiliary store'). Rather than being stored as member variables of the analysis classes, all object data are stored separately, as vectors of simple values. Thus, the data are stored in a 'structure of arrays' format, while the user still can access it as an 'array of structures'. This organization allows for on-demand partial reading of objects, the selective removal of object properties, and the addition of arbitrary user- defined properties in a uniform manner. It also improves performance by increasing the locality of memory references in typical analysis code. The resulting data structures can be written to ROOT files with data properties represented as simple ROOT tree branches. This paper focuses on the design and implementation of the auxiliary store and its interaction with ROOT.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Buckley, Dr Andy
Authors: Buckley, A., Eifert, T., Elsing, M., Gillberg, D., Koeneke, K., Krasznahorkay, A., Moyse, E., Nowak, M., Snyder, S., and van Gemmeren, P.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Journal of Physics: Conference Series
Publisher:IOP Publishing
ISSN:1742-6588
ISSN (Online):1742-6596
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Journal of Physics: Conference Series 664(7): 072045
Publisher Policy:Reproduced under a Creative Commons License

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