• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.3
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• pp.171-178
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• 2020

In this study, we develop MPI-OpenMP hybrid parallelization for multibody peridynamic simulations. Peridynamics is suitable for analyzing complicated dynamic fractures and various discontinuities. However, compared with a conventional finite element method, nonlocal interactions in peridynamics cost more time and memory. In multibody peridynamic analysis, the costs increase due to the additional interactions that occur when computing the nonlocal contact and ghost interlayer models between adjacent bodies. The costs become excessive when further refinement and smaller time steps are required in cases of high-velocity impact fracturing or similar instances. Thus, high computational efficiency and performance can be achieved by parallelization and optimization of multibody peridynamic simulations. The analytical code is developed using an Intel Fortran MPI compiler and OpenMP in NURION of the KISTI HPC center and parallelized through MPI-OpenMP hybrid parallelization. Further parallelization is conducted by hybridizing with OpenMP threads in each MPI process. We also try to minimize communication operations by model-based decomposition of MPI processes. The numerical results for the impact fracturing of multiple bodies show that the computing performance improves significantly with MPI-OpenMP hybrid parallelization.

• Atmosphere
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• v.22 no.1
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• pp.109-115
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• 2012

We parallelized the CFD_NIMR model, which is a numerical meteorological model, for best performance on both of distributed and shared memory parallel computers. This hybrid parallelization uses MPI (Message Passing Interface) to apply horizontal 2-dimensional sub-domain out of the 3-dimensional computing domain for distributed memory system, as well as uses OpenMP (Open Multi-Processing) to apply vertical 1-dimensional sub-domain for utilizing advantage of shared memory structure. We validated the parallel model with the original sequential model, and the parallel CFD_NIMR model shows efficient speedup on the distributed and shared memory system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.71-79
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• 2014

A parallelization of the bi-conjugate gradient solver for the pressure equation of the CUPID (component unstructured program for interfacial dynamics) code, which was developed for analyzing the components of a pressurized water-cooled reactor, was studied in a symmetric multi-processing system. The parallel performance was investigated for three typical parallel programming models (MPI, OpenMP, Hybrid) by solving incompressible backward-facing step flow at various grid resolutions. It was confirmed that parallel performance was low when problem size was small or the memory requirement for each thread was considerably higher than the cache memory. Furthermore, it was shown that MPI was better than OpenMP regardless of the problem size, and Hybrid was the best when the number of threads was relatively small.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.7-7
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• 2018

1차원 하수관로 해석 모형과 2차원 지표면 유출 해석 모형을 연계한 1D-2D 결합 도시침수 모델은 도시지역의 유출 현상과 침수 모의에 널리 이용되고 있다. 그러나 도시 지역의 복잡한 지형이 지표면 유출 흐름에 미치는 영향을 보다 자세히 파악하기 위해서는 보다 높은 해상도의 지형자료를 활용한 모의가 필요하다. 본 연구에서는 도시침수 해석을 위한 1D-2D 결합 하이브리드(Hybrid) 병렬화 코드(H12)를 개발하여 넓은 도시 유역에 대해서 고해상도 지형자료를 활용한 모의가 유역단위로 가능하도록 하였다. H12는 Open Multi-Processing(OpenMP)와 Message Passing Interface(MPI) 병렬 계산을 동시에 수행하여 매우 넓은 지역에 대해서도 도로의 형태를 확인 할 수 있는 수준의 고해상도 침수 해석 모의가 가능하다. 또한 도시지역의 복잡한 지형을 자세히 재현하고 계산의 효율을 높이기 위하여 격자세분화 기법이 적용되었다. H12의 적용성을 평가하기 위하여 미국 텍사스 알링턴 지역의 Johnson Creek 유역(${\sim}40km^2$)유역에 대한 시범 모의를 수행하였으며 도시유역의 지형을 표현하기 위하여 1m 해상도의 LiDAR자료를 사용하여 침수발생시 보다 자세한 유출수의 흐름을 해석할 수 있도록 하였다. 모의 결과 하이브리드 병렬 계산은 순차적 계산에 비하여 최고 79배 이상 빠른 계산속도 효율 향상을 보여주었으며, OpenMP나 MPI를 단독으로 사용하는 것에 비하여 더욱 효율적인 계산속도 효율 향상을 보여주었다.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.3902-3909
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• 2021

SACOS series of subchannel analysis codes have been developed by XJTU-NuTheL for many years and are being used for the thermal-hydraulic safety analysis of various reactor cores. To achieve fine whole core pin-level analysis, the input preprocessing and parallel capabilities of the code have been developed in this study. Preprocessing is suitable for modeling rectangular and hexagonal assemblies with less error-prone input; parallelization is established based on the domain decomposition method with the hybrid of MPI and OpenMP. For domain decomposition, a more flexible method has been proposed which can determine the appropriate task division of the core domain according to the number of processors of the server. By performing the calculation time evaluation for the several PWR assembly problems, the code parallelization has been successfully verified with different number of processors. Subsequent analysis results for rectangular- and hexagonal-assembly core imply that the code can be used to model and perform pin-level core safety analysis with acceptable computational efficiency.