An Empirical Study of High Performance Computing (HPC) Performance Bugs

Abstract

Performance efficiency and scalability are the major design goals for high performance computing (HPC) applications. However, it is challenging to achieve high efficiency and scalability for such applications due to complex underlying hardware architecture, inefficient algorithm implementation, suboptimal code generation by the compilers, inefficient parallelization, and so on. As a result, the HPC community spends a significant effort detecting and fixing the performance bugs frequently appearing in scientific applications. However, it is important to accumulate the experience to guide the scientific software engineering community to write performance-efficient code.In this paper, we investigate open-source HPC applications to categorize the performance bugs and their fixes and measure the programmer’s effort and experience to fix them. For this purpose, we first perform a large-scale empirical analysis on 1729 HPC performance commits collected from 23 real-world projects. Through our manual analysis, we identify 186 performance issues from these projects. Furthermore, we study the root cause of these performance issues and generate a performance bug taxonomy for HPC applications. Our analysis identifies that inefficient algorithm implementation (39.3%), inefficient code for target micro-architecture (31.2%), and missing parallelism and inefficient parallelization (14.5%) are the top three most prevalent categories of performance issues for HPC applications. Additionally, to understand how the performance bugs are fixed, we analyze the performance fix commits and categorize them into eight performance fix types. We further measure the developer’s efforts and expertise required to fix performance bugs. The analysis identified that performance bug fixes are complicated with a median patch size (LOC) of 35 lines and are mostly fixed by experienced developers.