Multigrid Solver on Fugaku

TL;DR

This paper presents a highly optimized multigrid solver for Clover fermions on the Fugaku supercomputer, demonstrating good scalability and performance using the Bridge++ framework and QWS library.

Contribution

It introduces a novel implementation of a multigrid solver utilizing the QWS library's domain decomposed preconditioner as a smoother on Fugaku.

Findings

The solver scales well on Fugaku's architecture.

It achieves improved performance over previous implementations.

The code demonstrates effective use of A64FX CPU features.

Abstract

We report an implementation of a multigrid solver for the Clover fermion on supercomputer Fugaku, which uses A64FX CPU with Arm architecture. On Fugaku, a highly optimized implementation of BiCGStab solver with domain decomposed preconditioner for the Clover fermion, called QCD Wide SIMD library (QWS), is available. We use the preconditioner in QWS as a smoother of the multigrid solver. Our implementation shows reasonably good scaling and performance. The code is developed by using Bridge++ code framework and its extension.