Model Coupling between the Weather Research and Forecasting Model and the DPRI Large Eddy Simulator for Urban Flows on GPU-accelerated Multicore Systems

TL;DR

This paper introduces the Glasgow Model Coupling Framework (GMCF), enabling efficient coupling of weather and urban flow models on multicore systems with GPU accelerators, demonstrated by significant speed-ups and minimal code modifications.

Contribution

The paper presents a novel framework for model coupling on shared-memory multicore systems with accelerators, including an OpenCL port of LES and successful coupling of WRF and LES models.

Findings

OpenCL port of LES achieves 7x speed-up on GPU.

GMCF enables minimal-code-change coupling of models.

Coupled system performs efficiently on multicore GPU systems.

Abstract

In this report we present a novel approach to model coupling for shared-memory multicore systems hosting OpenCL-compliant accelerators, which we call The Glasgow Model Coupling Framework (GMCF). We discuss the implementation of a prototype of GMCF and its application to coupling the Weather Research and Forecasting Model and an OpenCL-accelerated version of the Large Eddy Simulator for Urban Flows (LES) developed at DPRI. The first stage of this work concerned the OpenCL port of the LES. The methodology used for the OpenCL port is a combination of automated analysis and code generation and rule-based manual parallelization. For the evaluation, the non-OpenCL LES code was compiled using gfortran, fort and pgfortran}, in each case with auto-parallelization and auto-vectorization. The OpenCL-accelerated version of the LES achieves a 7 times speed-up on a NVIDIA GeForce GTX 480 GPGPU, compared to the fastest possible compilation of the original code running on a 12-core Intel Xeon E5-2640. In the second stage of this work, we built the Glasgow Model Coupling Framework and successfully used it to couple an OpenMP-parallelized WRF instance with an OpenCL LES instance which runs the LES code on the GPGPI. The system requires only very minimal changes to the original code. The report discusses the rationale, aims, approach and implementation details of this work.