Root analysis and implications to analysis model in ATLAS

An impressive amount of effort has been put in to realize a set of frameworks to support analysis in this new paradigm of GRID computing. However, much more than half of a physicist's time is typically spent after the GRID processing of the data. Due to the private nature of this level of analysis, there has been little common framework or methodology. While most physicists agree to use ROOT as the basis of their analysis, a number of approaches are possible for the implementation of the analysis using ROOT: conventional methods using CINT/ACLiC, development using g++, alternative interface through python, and parallel processing methods such as PROOF are some of the choices currently available on the market. Furthermore, in the ATLAS collaboration an additional layer of technology adds to the complexity because the data format is based on the POOL technology, which tends to be less portable. In this study, various modes of ROOT analysis are profiled for comparison with the main focus on the processing speed. Input data is or derived from the ATLAS Full-Dress-Rehearsal, which was meant to stress test the whole computing system of ATLAS.