Integrating LHCb Offline Workflows on Supercomputers State of Practice

Abstract

To better understand experimental conditions and performances of its experiment, the LHCb collaboration executes tens of thousands of looselycoupled and CPU-intensive Monte Carlo simulation workflows per hour. To meet the increasing LHC computing needs, funding agencies encourage the collaboration to exploit High-Performance Computing resources, and more specifically supercomputers, which offer a significant additional amount of computing resources but also come with higher integration challenges. This state-ofpractice paper outlines years of integration of LHCb simulation workflows on several supercomputers. The main contributions of this paper are: (i) an extensive description of the gap to address to run High-Energy Physics Monte Carlo simulation workflows on supercomputers; (ii) various methods and proposals to maximize the use of allocated CPU resources; (iii) a comprehensive analysis of LHCb production workflows running on diverse supercomputers.