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（Kohn–Sham）密度泛函理论的大规模计算中，求解广义或标准本征问题的电子结构往往是整个计算的瓶颈。当前几乎所有基于相似矩阵表达的电子结构计算程序，以及高性能计算场景，均需解决这一问题。本文提出一款统一软件接口ELSI，用于对接各类求解科恩-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中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接口旨在简化各类求解方案的实现与优化使用，具体通过以下途径实现：(a) 为科恩-沈吕九密度泛函理论中的电子结构求解器构建统一软件框架；(b) 为选定的求解器提供合理的默认参数；(c) 实现输入与内部工作矩阵格式的自动转换；未来还将新增(d) 根据具体问题推荐最优求解器的功能。本文在分布式内存超级计算机架构上，针对原子数至多11520个（基函数至多172800个）的体系规模开展了对比基准测试。