ELSI: A unified software interface for Kohn–Sham electronic structure solvers

Solving the electronic structure from a generalized or standard eigenproblem is often the bottleneck in large scale calculations based on Kohn–Sham density-functional theory. This problem must be addressed by essentially all current electronic structure codes, based on similar matrix expressions, and by high-performance computation. We here present a unified software interface, ELSI, to access different strategies that address the Kohn–Sham eigenvalue problem. Currently supported algorithms include the dense generalized eigensolver library ELPA, the orbital minimization method implemented in libOMM, and the pole expansion and selected inversion (PEXSI) approach with lower computational complexity for semilocal density functionals. The ELSI interface aims to simplify the implementation and optimal use of the different strategies, by offering (a) a unified software framework designed for the electronic structure solvers in Kohn–Sham density-functional theory; (b) reasonable default parameters for a chosen solver; (c) automatic conversion between input and internal working matrix formats, and in the future (d) recommendation of the optimal solver depending on the specific problem. Comparative benchmarks are shown for system sizes up to 11,520 atoms (172,800 basis functions) on distributed memory supercomputing architectures.基于科恩-沈吕九密度泛函理论（Kohn–Sham density-functional theory）的大规模计算中，通过广义或标准本征问题求解电子结构往往是计算瓶颈。当前几乎所有基于相似矩阵表述的电子结构计算程序，以及高性能计算场景，均需解决该类问题。本文提出一款统一软件接口ELSI，用于调用各类求解科恩-沈吕九本征值问题的策略。当前支持的算法包括稠密广义本征求解器库ELPA、libOMM实现的轨道最小化方法，以及针对半局域密度泛函具有更低计算复杂度的极点展开与选择性反演（PEXSI）方法。ELSI接口旨在通过以下方式简化各类策略的实现与优化调用：(a) 为科恩-沈吕九密度泛函理论下的电子结构求解器设计统一软件框架；(b) 为选定的求解器提供合理的默认参数；(c) 实现输入矩阵格式与内部工作矩阵格式间的自动转换；未来还将支持(d) 根据具体问题推荐最优求解器。本文在分布式内存超级计算架构上，针对原子数至多11520、基函数数达172800的体系开展了对比基准测试。