Solvers for Large-Scale Electronic Structure Theory: ELPA and ELSI

TL;DR

This paper presents the ELPA library and ELSI interface, which enable efficient large-scale electronic structure calculations by supporting various solvers and hardware architectures, including recent GPU optimizations.

Contribution

It introduces the ELPA solver library and ELSI interface, highlighting their capabilities, support for multiple architectures, and recent performance improvements for large-scale DFT calculations.

Findings

Significant GPU performance improvements for eigenproblem solutions.

ELSI provides a flexible interface supporting multiple solvers.

ELPA supports CPU and GPU architectures, including NVIDIA, AMD, and Intel GPUs.

Abstract

In this contribution, we give an overview of the ELPA library and ELSI interface, which are crucial elements for large-scale electronic structure calculations in FHI-aims. ELPA is a key solver library that provides efficient solutions for both standard and generalized eigenproblems, which are central to the Kohn-Sham formalism in density functional theory (DFT). It supports CPU and GPU architectures, with full support for NVIDIA and AMD GPUs, and ongoing development for Intel GPUs. Here we also report the results of recent optimizations, leading to significant improvements in GPU performance for the generalized eigenproblem. ELSI is an open-source software interface layer that creates a well-defined connection between "user" electronic structure codes and "solver" libraries for the Kohn-Sham problem, abstracting the step between Hamilton and overlap matrices (as input to ELSI and the respective solvers) and eigenvalues and eigenvectors or density matrix solutions (as output to be passed back to the "user" electronic structure code). In addition to ELPA, ELSI supports solvers including LAPACK and MAGMA, the PEXSI and NTPoly libraries (which bypass an explicit eigenvalue solution), and several others.