Effect of implementations of the N-body problem on the performance and portability across GPU vendors

Since Aurora entered the TOP500 list in November 2023, the top ten systems saw some shifts in the ratio of GPU vendors represented. With each vendor supplying their own preferred programming models for their hardware, it becomes relevant to compare the portability of these models on other hardware platforms. For the present paper we implemented the N-body problem with different optimizations using native and portable programming frameworks. For each of those we determined the best performing optimized version on one target architecture and compared the performance achieved for each platform. • Portable programming models can achieve native performance. • OpenMP, pSTL, and SYCL work very well for writing portable code for GPUs. • Portable code optimized for Nvidia GH200 may need further optimizations for other GPU vendors. • Minor code changes can make a big difference.