Abstract
Process-based numerical models developed to perform hydraulic/hydrologic/water quality analysis of watersheds and rivers have become highly sophisticated, with a corresponding increase in their computation time. However, for incidents such as water pollution, rapid analysis and decision-making are critical. This paper proposes an optimized parallelization scheme to reduce the computation time of the Environmental Fluid Dynamics Code-National Institute of Environmental Research (EFDC-NIER) model, which has been continuously developed for water pollution or algal bloom prediction in rivers. An existing source code and a parallel computational code with open multi-processing (OpenMP) and a message passing interface (MPI) were optimized, and their computation times compared. Subsequently, the simulation results for the existing EFDC model and the model with the parallel computation code were compared. Furthermore, the optimal parallel combination for hybrid parallel computation was evaluated by comparing the simulation time based on the number of cores and threads. When code parallelization was applied, the performance improved by a factor of approximately five compared to the existing source code. Thus, if the parallel computational source code applied in this study is used, urgent decision-making will be easier for events such as water pollution incidents.
Highlights
Published: 30 August 2021In areas with monsoon climates, including South Korea, changes in hydraulic characteristics throughout the year are significant because weather conditions such as precipitation and air temperature change throughout the year [1,2]
Source Code Analysis for the EFDC-National Institute of Environmental Research (NIER) Model. In models such as EFDC-NIER, which rely on data-intensive calculations, it is important to identify the time-consuming calculation codes in the program before creating the parallelization code
We identified 20 subroutines and calculation statements as hotspots among approximately 250 subroutines executed in the source code of EFDC-NIER
Summary
In areas with monsoon climates, including South Korea, changes in hydraulic characteristics throughout the year are significant because weather conditions such as precipitation and air temperature change throughout the year [1,2]. During the summer, when the temperature is high, stratification develops and sometimes causes various environmental problems [3]. Changes in hydraulic characteristics affect water quality [4]. The vertical layers need to be classified to precisely simulate hydraulics and water quality for these conditions. Cyanobacteria, which are generated in large quantities during the summer, often have different distribution characteristics along the lateral direction of a river, and the water quality distribution worsens downstream around basic environmental facilities or confluences of major pollutant sources. Integrated 2D or x-z 2D models are limited in their ability to reproduce these 3D variation characteristics. The application of a 3D model with an appropriate vertical/horizontal resolution is required, Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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