Collaborative Research: SI2-SSI: ELSI - Infrastructure for Scalable Electronic Structure Theory

Routine applications of electronic structure theory to molecules and periodic systems need to compute the electron density from given Hamiltonian and overlap matrices. System sizes can range from few to thousands or (in some cases) millions of atoms. Different discretization schemes (basis sets) and different system geometries (finite non-periodic vs. infinite periodic boundary conditions) dictate matrices with different structure. The ELectronic Structure Infrastructure (ELSI) project provides an open-source software interface to facilitate the implementation and optimal use of high-performance solver libraries covering cubic scaling eigensolvers, linear scaling density-matrix-based algorithms, and other reduced scaling methods in between. We cover the ELSI interface software itself, solvers connected to the interface, as well as practical handling (e.g., routines for density matrix extrapolation in geometry optimization and molecular dynamics calculations and general utilities such as parallel matrix I/O and JSON output). Finally, we present benchmarks comparing different solvers, carried out using the ELSI infrastructure on massively parallel supercomputers.