Abstract
The High-Luminosity upgrade of the Large Hadron Collider (LHC) will see the accelerator reach an instantaneous luminosity of 7 × 1034 cm−2 s−1 with an average pileup of 200 proton-proton collisions. These conditions will pose an unprecedented challenge to the online and offline reconstruction software developed by the experiments. The computational complexity will exceed by far the expected increase in processing power for conventional CPUs, demanding an alternative approach. Industry and High-Performance Computing (HPC) centers are successfully using heterogeneous computing platforms to achieve higher throughput and better energy efficiency by matching each job to the most appropriate architecture. In this paper we will describe the results of a heterogeneous implementation of pixel tracks and vertices reconstruction chain on Graphics Processing Units (GPUs). The framework has been designed and developed to be integrated in the CMS reconstruction software, CMSSW. The speed up achieved by leveraging GPUs allows for more complex algorithms to be executed, obtaining better physics output and a higher throughput.
Highlights
The High-Luminosity upgrade of the Large Hadron Collider (LHC) (Apollinari et al, 2017) will pose unprecedented challenges to the reconstruction software used by the experiments due to the increase both in instantaneous luminosity and readout rate
The results shown in this article are based on the Open Data and the data formats released (CMS Collaboration, 2018)
This article is organized as follows: Section 2 will describe the CMS heterogeneous framework, Section 3 will discuss the algorithms developed in the Patatrack pixel track and vertex reconstruction workflow, Section 4 will describe the physics results and computational performance and compare them to the CMS pixel track reconstruction used at the High Level Trigger (HLT) for data taking in 2018, while Section 5 will contain our conclusions
Summary
The High-Luminosity upgrade of the LHC (Apollinari et al, 2017) will pose unprecedented challenges to the reconstruction software used by the experiments due to the increase both in instantaneous luminosity and readout rate. In order to investigate the feasibility of a heterogeneous approach in a typical High Energy Physics experiment, the authors developed a novel pixel tracks and vertices reconstruction chain within the official CMS reconstruction software CMSSW (Jones et al, 2006), using the CUDA parallel computing platform (Nickolls et al, 2008). The input to this chain is represented by RAW data coming out directly from the detector’s front-end electronics, while the output is represented by legacy pixel tracks and vertices that could be transparently re-used by other components of the CMS reconstruction. This article is organized as follows: Section 2 will describe the CMS heterogeneous framework, Section 3 will discuss the algorithms developed in the Patatrack pixel track and vertex reconstruction workflow, Section 4 will describe the physics results and computational performance and compare them to the CMS pixel track reconstruction used at the HLT for data taking in 2018, while Section 5 will contain our conclusions
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