The Experts below are selected from a list of 18852 Experts worldwide ranked by ideXlab platform
Y. Kwak - One of the best experts on this subject based on the ideXlab platform.
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An IMPES scheme for a two-phase flow in heterogeneous porous media using a Structured Grid
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Gwanghyun Jo, Y. KwakAbstract:Abstract We develop a numerical scheme for a two-phase immiscible flow in heterogeneous porous media using a Structured Grid finite element method, which has been successfully used for the computation of various physical applications involving elliptic interface equations (Li et al., 2003, 2004; Chou et al., 2010; Kwak et al., 2010; Chang and Kwak, 2011). The proposed method is based on the implicit pressure-explicit saturation procedure. To solve the pressure equation, we use an IFEM based on the Rannacher–Turek Rannacher and Turek (1992) nonconforming space, which is a modification of the work in Kwak et al. (2010) where ‘broken’ P 1 nonconforming element of Crouzeix–Raviart (1973) [1] was developed. For the Darcy velocity, we apply the mixed finite volume method studied in Chou et al. (2003) and Kwak et al. (2010) on the basis of immersed finite element method (IFEM). In this way, the Darcy velocity of the flow can be computed cheaply (locally) after we solve the pressure equation. The computed Darcy velocity is used to solve the saturation equation explicitly. The whole procedure can be implemented on a Structured Grid which is independent of the underlying heterogeneous porous media. In fact, we apply a new version of multiGrid algorithm to solve the pressure equation for which the CPU time grows like O ( N ) . Numerical tests for analytic problems show that our method is almost optimal in all variables. Problem with sources/sinks is also computed and it seems to work well.
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An IMPES scheme for a two-phase flow in heterogeneous porous media using a Structured Grid
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Gwanghyun Jo, Y. KwakAbstract:Abstract We develop a numerical scheme for a two-phase immiscible flow in heterogeneous porous media using a Structured Grid finite element method, which has been successfully used for the computation of various physical applications involving elliptic interface equations (Li et al., 2003, 2004; Chou et al., 2010; Kwak et al., 2010; Chang and Kwak, 2011). The proposed method is based on the implicit pressure-explicit saturation procedure. To solve the pressure equation, we use an IFEM based on the Rannacher–Turek Rannacher and Turek (1992) nonconforming space, which is a modification of the work in Kwak et al. (2010) where ‘broken’ P 1 nonconforming element of Crouzeix–Raviart (1973) [1] was developed. For the Darcy velocity, we apply the mixed finite volume method studied in Chou et al. (2003) and Kwak et al. (2010) on the basis of immersed finite element method (IFEM). In this way, the Darcy velocity of the flow can be computed cheaply (locally) after we solve the pressure equation. The computed Darcy velocity is used to solve the saturation equation explicitly. The whole procedure can be implemented on a Structured Grid which is independent of the underlying heterogeneous porous media. In fact, we apply a new version of multiGrid algorithm to solve the pressure equation for which the CPU time grows like O ( N ) . Numerical tests for analytic problems show that our method is almost optimal in all variables. Problem with sources/sinks is also computed and it seems to work well.
Gregory Levitin - One of the best experts on this subject based on the ideXlab platform.
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optimal resource allocation for maximizing performance and reliability in tree Structured Grid services
IEEE Transactions on Reliability, 2007Co-Authors: Yuanshun Dai, Gregory LevitinAbstract:The paper considers a Grid computing systems in which the resource management systems (RMS) can divide service tasks into execution blocks (EB), and send these blocks to different resources. To provide a desired level of service reliability, the RMS can assign the same EB to several independent resources for parallel (redundant) execution. According to the optimal schedule for service task partition, and distribution among resources, one can achieve the greatest possible expected service performance (i.e. least execution time), or reliability. For solving this optimization problem, the paper suggests an algorithm that is based on graph theory, Bayesian approach, and the evolutionary optimization approach. A virtual tree-structure model is constructed in which failure correlation in common communication channels is taken into account. Illustrative examples are presented.
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performance and reliability of tree Structured Grid services considering data dependence and failure correlation
IEEE Transactions on Computers, 2007Co-Authors: Yuanshun Dai, Gregory Levitin, Kishor S TrivediAbstract:Grid computing is a newly emerging technology aimed at large-scale resource sharing and global-area collaboration. It is the next step in the evolution of parallel and distributed computing. Due to the largeness and complexity of the Grid system, its performance and reliability are difficult to model, analyze, and evaluate. This paper presents a model that relaxes some assumptions made in prior research on distributed systems that were inappropriate for Grid computing. The paper proposes a virtual tree-Structured model of the Grid service. This model simplifies the physical structure of a Grid service, allows service performance (execution time) to be efficiently evaluated, and takes into account data dependence and failure correlation. Based on the model, an algorithm for evaluating the Grid service time distribution and the service reliability indices is suggested. The algorithm is based on Graph theory and probability theory. Illustrative examples and a real case study of the BioGrid are presented.
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reliability and performance of tree Structured Grid services
IEEE Transactions on Reliability, 2006Co-Authors: Yuanshun Dai, Gregory LevitinAbstract:Grid computing is a new emerging technology aiming at large-scale resource sharing, and global-area collaboration. It is a next step in an evolution of parallel and distributed computing. Due to the large scale and complexity of the Grid system, its performance and reliability are difficult to model, analyse, and evaluate. This paper presents a model that relaxes some assumptions unsuitable for Grid computing systems that have been made in the existed works studying the distributed systems. The paper proposes a virtual tree model of the Grid service. This model simplifies the physical structure of a Grid service, allows service performance (execution time) to be estimated, and takes into account the common cause failures in communication channels. Based on the model, an algorithm for evaluating the Grid service performance distribution and the service reliability indices is suggested. The algorithm is based on graph theory, and Bayesian analysis. Illustrative examples are presented in which the results of the suggested algorithm are compared with simulation results.
Brian W Oshea - One of the best experts on this subject based on the ideXlab platform.
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k athena a performance portable Structured Grid finite volume magnetohydrodynamics code
IEEE Transactions on Parallel and Distributed Systems, 2021Co-Authors: Philipp Grete, Forrest W Glines, Brian W OsheaAbstract:Large scale simulations are a key pillar of modern research and require ever-increasing computational resources. Different novel manycore architectures have emerged in recent years on the way towards the exascale era. Performance portability is required to prevent repeated non-trivial refactoring of a code for different architectures. We combine Athena++ , an existing magnetohydrodynamics (MHD) CPU code, with Kokkos , a performance portable on-node parallel programming paradigm, into K-Athena to allow efficient simulations on multiple architectures using a single codebase. We present profiling and scaling results for different platforms including Intel Skylake CPUs, Intel Xeon Phis, and NVIDIA GPUs. K-Athena achieves $>10^8$ > 10 8 cell-updates/s on a single V100 GPU for second-order double precision MHD calculations, and a speedup of 30 on up to 24 576 GPUs on Summit (compared to 172,032 CPU cores), reaching $1.94\times 10^{12}$ 1 . 94 × 10 12 total cell-updates/s at 76 percent parallel efficiency. Using a roofline analysis we demonstrate that the overall performance is currently limited by DRAM bandwidth and calculate a performance portability metric of 62.8 percent. Finally, we present the implementation strategies used and the challenges encountered in maximizing performance. This will provide other research groups with a straightforward approach to prepare their own codes for the exascale era. K-Athena is available at https://gitlab.com/pgrete/kathena .
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k athena a performance portable Structured Grid finite volume magnetohydrodynamics code
arXiv: Distributed Parallel and Cluster Computing, 2019Co-Authors: Philipp Grete, Forrest W Glines, Brian W OsheaAbstract:Large scale simulations are a key pillar of modern research and require ever-increasing computational resources. Different novel manycore architectures have emerged in recent years on the way towards the exascale era. Performance portability is required to prevent repeated non-trivial refactoring of a code for different architectures. We combine Athena++, an existing magnetohydrodynamics (MHD) CPU code, with Kokkos, a performance portable on-node parallel programming paradigm, into K-Athena to allow efficient simulations on multiple architectures using a single codebase. We present profiling and scaling results for different platforms including Intel Skylake CPUs, Intel Xeon Phis, and NVIDIA GPUs. K-Athena achieves $>10^8$ cell-updates/s on a single V100 GPU for second-order double precision MHD calculations, and a speedup of 30 on up to 24,576 GPUs on Summit (compared to 172,032 CPU cores), reaching $1.94\times10^{12}$ total cell-updates/s at 76% parallel efficiency. Using a roofline analysis we demonstrate that the overall performance is currently limited by DRAM bandwidth and calculate a performance portability metric of 62.8%. Finally, we present the implementation strategies used and the challenges encountered in maximizing performance. This will provide other research groups with a straightforward approach to prepare their own codes for the exascale era. K-Athena is available at this https URL .
Gwanghyun Jo - One of the best experts on this subject based on the ideXlab platform.
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An IMPES scheme for a two-phase flow in heterogeneous porous media using a Structured Grid
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Gwanghyun Jo, Y. KwakAbstract:Abstract We develop a numerical scheme for a two-phase immiscible flow in heterogeneous porous media using a Structured Grid finite element method, which has been successfully used for the computation of various physical applications involving elliptic interface equations (Li et al., 2003, 2004; Chou et al., 2010; Kwak et al., 2010; Chang and Kwak, 2011). The proposed method is based on the implicit pressure-explicit saturation procedure. To solve the pressure equation, we use an IFEM based on the Rannacher–Turek Rannacher and Turek (1992) nonconforming space, which is a modification of the work in Kwak et al. (2010) where ‘broken’ P 1 nonconforming element of Crouzeix–Raviart (1973) [1] was developed. For the Darcy velocity, we apply the mixed finite volume method studied in Chou et al. (2003) and Kwak et al. (2010) on the basis of immersed finite element method (IFEM). In this way, the Darcy velocity of the flow can be computed cheaply (locally) after we solve the pressure equation. The computed Darcy velocity is used to solve the saturation equation explicitly. The whole procedure can be implemented on a Structured Grid which is independent of the underlying heterogeneous porous media. In fact, we apply a new version of multiGrid algorithm to solve the pressure equation for which the CPU time grows like O ( N ) . Numerical tests for analytic problems show that our method is almost optimal in all variables. Problem with sources/sinks is also computed and it seems to work well.
-
An IMPES scheme for a two-phase flow in heterogeneous porous media using a Structured Grid
Computer Methods in Applied Mechanics and Engineering, 2017Co-Authors: Gwanghyun Jo, Y. KwakAbstract:Abstract We develop a numerical scheme for a two-phase immiscible flow in heterogeneous porous media using a Structured Grid finite element method, which has been successfully used for the computation of various physical applications involving elliptic interface equations (Li et al., 2003, 2004; Chou et al., 2010; Kwak et al., 2010; Chang and Kwak, 2011). The proposed method is based on the implicit pressure-explicit saturation procedure. To solve the pressure equation, we use an IFEM based on the Rannacher–Turek Rannacher and Turek (1992) nonconforming space, which is a modification of the work in Kwak et al. (2010) where ‘broken’ P 1 nonconforming element of Crouzeix–Raviart (1973) [1] was developed. For the Darcy velocity, we apply the mixed finite volume method studied in Chou et al. (2003) and Kwak et al. (2010) on the basis of immersed finite element method (IFEM). In this way, the Darcy velocity of the flow can be computed cheaply (locally) after we solve the pressure equation. The computed Darcy velocity is used to solve the saturation equation explicitly. The whole procedure can be implemented on a Structured Grid which is independent of the underlying heterogeneous porous media. In fact, we apply a new version of multiGrid algorithm to solve the pressure equation for which the CPU time grows like O ( N ) . Numerical tests for analytic problems show that our method is almost optimal in all variables. Problem with sources/sinks is also computed and it seems to work well.
Yuanshun Dai - One of the best experts on this subject based on the ideXlab platform.
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optimal resource allocation for maximizing performance and reliability in tree Structured Grid services
IEEE Transactions on Reliability, 2007Co-Authors: Yuanshun Dai, Gregory LevitinAbstract:The paper considers a Grid computing systems in which the resource management systems (RMS) can divide service tasks into execution blocks (EB), and send these blocks to different resources. To provide a desired level of service reliability, the RMS can assign the same EB to several independent resources for parallel (redundant) execution. According to the optimal schedule for service task partition, and distribution among resources, one can achieve the greatest possible expected service performance (i.e. least execution time), or reliability. For solving this optimization problem, the paper suggests an algorithm that is based on graph theory, Bayesian approach, and the evolutionary optimization approach. A virtual tree-structure model is constructed in which failure correlation in common communication channels is taken into account. Illustrative examples are presented.
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performance and reliability of tree Structured Grid services considering data dependence and failure correlation
IEEE Transactions on Computers, 2007Co-Authors: Yuanshun Dai, Gregory Levitin, Kishor S TrivediAbstract:Grid computing is a newly emerging technology aimed at large-scale resource sharing and global-area collaboration. It is the next step in the evolution of parallel and distributed computing. Due to the largeness and complexity of the Grid system, its performance and reliability are difficult to model, analyze, and evaluate. This paper presents a model that relaxes some assumptions made in prior research on distributed systems that were inappropriate for Grid computing. The paper proposes a virtual tree-Structured model of the Grid service. This model simplifies the physical structure of a Grid service, allows service performance (execution time) to be efficiently evaluated, and takes into account data dependence and failure correlation. Based on the model, an algorithm for evaluating the Grid service time distribution and the service reliability indices is suggested. The algorithm is based on Graph theory and probability theory. Illustrative examples and a real case study of the BioGrid are presented.
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reliability and performance of tree Structured Grid services
IEEE Transactions on Reliability, 2006Co-Authors: Yuanshun Dai, Gregory LevitinAbstract:Grid computing is a new emerging technology aiming at large-scale resource sharing, and global-area collaboration. It is a next step in an evolution of parallel and distributed computing. Due to the large scale and complexity of the Grid system, its performance and reliability are difficult to model, analyse, and evaluate. This paper presents a model that relaxes some assumptions unsuitable for Grid computing systems that have been made in the existed works studying the distributed systems. The paper proposes a virtual tree model of the Grid service. This model simplifies the physical structure of a Grid service, allows service performance (execution time) to be estimated, and takes into account the common cause failures in communication channels. Based on the model, an algorithm for evaluating the Grid service performance distribution and the service reliability indices is suggested. The algorithm is based on graph theory, and Bayesian analysis. Illustrative examples are presented in which the results of the suggested algorithm are compared with simulation results.
