Exploiting repeated matrix block structures for more efficient CFD on modern supercomputers
Abstract
Computational Fluid Dynamics (CFD) simulations are often constrained by the memory-bound nature of sparse matrix-vector operations, which eventually limits performance on modern high-performance computing (HPC) systems. This work introduces a novel approach to increase arithmetic intensity in CFD by leveraging repeated matrix block structures. The method transforms the conventional sparse matrix-vector product (SpMV) into a sparse matrix-matrix product (SpMM), enabling simultaneous processing of multiple right-hand sides. This shifts the computation towards a more compute-bound regime by reusing matrix coefficients. Additionally, an inline mesh-refinement strategy is proposed: simulations initially run on a coarse mesh to establish a statistically steady flow, then refine to the target mesh. This reduces the wall-clock time to reach transition, leading to faster convergence with equivalent computational cost. The methodology is evaluated using theoretical performance bounds and validated through three test cases: a turbulent channel flow, Rayleigh-B\'{e}nard convection, and an industrial airfoil simulation. Results demonstrate substantial speed-ups - from modest improvements in basic configurations to over 50% in the mesh-refinement setup - highlighting the benefits of integrating SpMM across all CFD operators, including divergence, gradient, and Laplacian.
Cite
@article{arxiv.2508.06710,
title = {Exploiting repeated matrix block structures for more efficient CFD on modern supercomputers},
author = {Josep Plana-Riu and F. Xavier Trias and Àdel Alsalti-Baldellou and Xavier Álvarez-Farré and Guillem Colomer and Assensi Oliva},
journal= {arXiv preprint arXiv:2508.06710},
year = {2026}
}