Solving the Bethe-Salpeter equation on massively parallel architectures

TL;DR

This paper demonstrates how integrating a modern parallel eigensolver into a legacy code for the Bethe-Salpeter equation significantly improves computational speed and scalability on parallel architectures, enabling advanced material studies.

Contribution

It introduces the integration of the ChASE eigensolver into a legacy BSE code, enhancing performance and scalability on parallel computing systems.

Findings

Remarkable speedup achieved with ChASE integration

Improved scaling on multi- and many-core architectures

Enables study of complex materials previously computationally infeasible

Abstract

The last ten years have witnessed fast spreading of massively parallel computing clusters, from leading supercomputing facilities down to the average university computing center. Many companies in the private sector have undergone a similar evolution. In this scenario, the seamless integration of software and middleware libraries is a key ingredient to ensure portability of scientific codes and guarantees them an extended lifetime. In this work, we describe the integration of the ChASE library, a modern parallel eigensolver, into an existing legacy code for the first-principles computation of optical properties of materials via solution of the Bethe-Salpeter equation for the optical polarization function. Our numerical tests show that, as a result of integrating ChASE and parallelizing the reading routine, the code experiences a remarkable speedup and greatly improved scaling behavior on both multi- and many-core architectures. We demonstrate that such a modernized BSE code will, by fully exploiting parallel computing architectures and file systems, enable domain scientists to accurately study complex material systems that were not accessible before.