GPU Implementation of the OVERFLOW CFD Code

Charles W. Jackson; David Appelhans; Joseph M. Derlaga; Pieter G. Buning

NASA NTRS · 20230016176

GPU Implementation of the OVERFLOW CFD Code

Charles W. Jackson·David Appelhans·Joseph M. Derlaga·Pieter G. Buning

Abstract

The high-performance computing (HPC) landscape is quickly changing to systems where most of the performance comes from specialized chips, specifically graphics processing units (GPUs). Such GPU systems are throughput machines, where efficient use of the GPU often requires code refactoring to expose a few orders of magnitude more fine grain parallelism than was previously used on the CPU. Recent modifications to OVERFLOW, an overset, structured grid, computational fluid dynamics flow solver, written in Fortran will be presented. These modifications include both code modernization efforts and algorithmic changes to enable OVERFLOW to efficiently utilize GPUs. Many of these algorithmic changes would likely also be applicable for other structured grid, stencil-based codes wanting to utilize GPUs. The capabilities that have been ported to run on the GPUs are presented, along with the performance gains of the GPU version relative the CPU version of OVERFLOW.

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GPU Programming Computational Fluid Dynamics OpenACC HPC

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BibTeX RIS

Charles W. Jackson, David Appelhans, Joseph M. Derlaga, Pieter G. Buning. GPU Implementation of the OVERFLOW CFD Code. https://ntrs.nasa.gov/citations/20230016176

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GPU Implementation of the OVERFLOW CFD Code

GPU Programming↗

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Strategies for the GPU Implementation of the OVERFLOW CFD Code

Wondering how to port a large, computational fluid dynamics (CFD) solver, written in Fortran, to run effectively on GPUs? Join this talk to learn about the strategies NASA’s OVERFLOW CFD code has used to effectively utilize GPUs to greatly improve the time to solution compared to CPUs. OVERFLOW is an overset, structured grid, computational fluid dynamics (CFD) flow solver developed by NASA and widely used by government, US industry, and academia. It is known for its effective use of CPU hardware, but this talk will discuss recent efforts to modify the code to run efficiently on GPUs. We will describe our use of OpenACC, CUDA Fortran, and CUDA C++, discussing why and how we use each to map our problem onto NVIDIA GPUs. We will also describe structural changes we made in the code to expose enough parallelism to effectively use the GPU hardware. Finally, we will present the performance benefits from running OVERFLOW on GPUs compared to the well optimized CPU version of the code.

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