Modernizing an Operational Real-time Tsunami Simulator to Support Diverse Hardware Platforms

TL;DR

This paper describes a minimally invasive migration of a real-time tsunami simulation system to modern CPUs and GPUs, significantly improving performance and enabling broader access to accurate tsunami forecasts.

Contribution

It introduces a directive-based approach for performance portability of tsunami simulation code across diverse hardware platforms.

Findings

Simulation runs in under 2.5 minutes on 32 CPUs

Simulation completes in 1.5 minutes on 32 GPUs

Code achieves performance portability across CPUs, GPUs, and vector processors

Abstract

To issue early warnings and rapidly initiate disaster responses after tsunami damage, various tsunami inundation forecast systems have been deployed worldwide. Japan's Cabinet Office operates a forecast system that utilizes supercomputers to perform tsunami propagation and inundation simulation in real time. Although this real-time approach is able to produce significantly more accurate forecasts than the conventional database-driven approach, its wider adoption was hindered because it was specifically developed for vector supercomputers. In this paper, we migrate the simulation code to modern CPUs and GPUs in a minimally invasive manner to reduce the testing and maintenance costs. A directive-based approach is employed to retain the structure of the original code while achieving performance portability, and hardware-specific optimizations including load balance improvement for GPUs are applied. The migrated code runs efficiently on recent CPUs, GPUs and vector processors: a six-hour tsunami simulation using over 47 million cells completes in less than 2.5 minutes on 32 Intel Sapphire Rapids CPUs and 1.5 minutes on 32 NVIDIA H100 GPUs. These results demonstrate that the code enables broader access to accurate tsunami inundation forecasts.