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arXiv · 2607.07687

Scaling WaterLily.jl with MPI and an improved geometric multigrid solver

Bernat Font·Marin Lauber·Tzu-Yao Huang·Gabriel D. Weymouth
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Abstract

We present recent performance-oriented developments in WaterLily, a scale-resolving incompressible flow solver written in pure Julia that runs seamlessly on CPUs and GPUs of any vendor. Supported by the newly added MPI-based parallelism, strong-scalability tests display a near-ideal linear trend, and weak-scaling efficiency is kept above 85% before node memory-concurrency contention dominates parallel performance. Inter-node weak scalability is sustained above 96% with grid size up to 1 billion cells. We further benchmark improvements to the geometric multigrid Poisson solver enabled by an adaptive under-relaxed red-black Gauss-Seidel smoother together with anisotropic coarsening operators.

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Bernat Font, Marin Lauber, Tzu-Yao Huang, Gabriel D. Weymouth. 2026-07-08. Scaling WaterLily.jl with MPI and an improved geometric multigrid solver. https://arxiv.org/abs/2607.07687

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