CERN Openlab Report: CMS Heterogeneous Pixel Track Reconstruction using SYCL

The CMS software framework (CMSSW) has been recently extended to perform part of the physics reconstruction with NVIDIA GPUs. To avoid writing different implementations of the code for each back-end the decision was to use a performance portability library and so Alpaka has been chosen as the solution for Run-3. In the meantime different studies have been performed to test the track reconstruction and clustering algorithms on different back-ends like CUDA and Alpaka. With the idea of exploring new solutions, Intel GPUs have been considered as a new possible back-end and their implementation is currently under development. This is achieved using SYCL, that is a cross-platform abstraction C++ programming model for heterogeneous computing. It allows developers to reuse code across different hardware and also perform custom tuning for a specific accelerator. The SYCL implementation used is the Data Parallel C++ library (DPC++) in the Intel oneAPI Toolkit. In this report, we will present strengths and weaknesses of this heterogeneous programming model as well as the performance of a physics reconstruction algorithm (clustering) on different hardware