SU3\_Bench is a microbenchmark developed to explore performance portability across multiple programming models/methodologies using a simple, but nontrivial, mathematical kernel. This kernel has been derived from the MILC lattice quantum chromodynamics (LQCD) code. SU3\_Bench is bandwidth bound and generates regular compute and data access patterns. Therefore, on most traditional CPU and GPU-based systems, its performance is mainly determined by the achievable memory bandwidth. Although SU3\_Bench is a simple kernel, experience says its subtleties require a certain amount of tweaking to achieve peak performance for a given programming model and hardware, making performance portability challenging. In this paper, we share some of the challenges in obtaining the peak performance for SU3\_Bench on a state-of-the-art Intel Xeon machine, due to the nuances of variable definition, the nature of compiler-provided default constructors, how memory is accessed at object creation time, and the NUMA effects on the machine. We discuss how to tackle those challenges to improve SU3\_Bench's performance by \(2\times\) compared to the original OpenMP implementation available at Github. This provides a valuable lesson for other similar kernels. Expanding on the performance portability aspects, we also show early results obtained porting SU3\_Bench to the new Intel Programmable Integrated Unified Memory Architecture (PIUMA), characterized by a more balanced flops-to-byte ratio. This paper shows that it is not the usual bandwidth or flops, rather the pipeline throughput, that determines SU3\_Bench's performance on PIUMA. Finally, we show how to improve performance on PIUMA and how that compares with the performance on Xeon, which has around one order of magnitude more flops-per-byte.
翻译:SU3 ⁇ Bench 是用来探索多种编程模型/方法的可移动性的一个微小基准, 使用简单但非三进制的数学内核, 这个内核来自 MILC 的 lattice 量子化学动力( LQCD) 代码。 SU3 ⁇ Bench 是带宽约束的, 产生定期的计算和数据访问模式。 因此, 在大多数传统的 CPU 和基于 GPU 的系统中, 它的性能主要由可实现的内存带宽度决定。 虽然 SU3 ⁇ Bench是一个简单的内核内核, 经验表明, 它的微妙性能需要一定量的精细度, 才能达到某个特定的编程性能, P3 ⁇ Bench 的性能也比常规性能更强。 在OFI3中, 我们讨论如何应对这些挑战, 将SU3A3的性能比普通的性能, 将SUMTLO 展示到其它有价值的性能。