Porting CMS Heterogeneous Pixel Reconstruction to Kokkos

TL;DR

This paper demonstrates porting CMS's heterogeneous pixel reconstruction code to Kokkos, enabling multi-architecture support and comparing performance across GPU and CPU implementations.

Contribution

It presents a practical case study of adapting HEP reconstruction software to Kokkos, highlighting portability and performance implications.

Findings

Kokkos enables multi-architecture support for HEP reconstruction code.

Performance comparison shows GPU and CPU throughput differences.

Porting effort maintains core functionality across architectures.

Abstract

Programming for a diverse set of compute accelerators in addition to the CPU is a challenge. Maintaining separate source code for each architecture would require lots of effort, and development of new algorithms would be daunting if it had to be repeated many times. Fortunately there are several portability technologies on the market such as Alpaka, Kokkos, and SYCL. These technologies aim to improve the developer productivity by making it possible to use the same source code for many different architectures. In this paper we use heterogeneous pixel reconstruction code from the CMS experiment at the CERNL LHC as a realistic use case of a GPU-targeting HEP reconstruction software, and report experience from prototyping a portable version of it using Kokkos. The development was done in a standalone program that attempts to model many of the complexities of a HEP data processing framework such as CMSSW. We also compare the achieved event processing throughput to the original CUDA code and a CPU version of it.