Portable implementation model for CFD simulations. Application to hybrid CPU/GPU supercomputers

Oyarzun, Guillermo; Borrell, R.; Gorobets, A.; Oliva, A.

doi:10.1080/10618562.2017.1390084

Cited by 13 publications

(15 citation statements)

References 27 publications

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“…The final speedup of the GPUs according to the CPUs of the node is of 5.44 and 3.48 times for the sphere and airplane meshes respectively. These results match other unstructured CFD codes running on GPUs [33,34]. Figure 14 (right) shows the speedup of the best GPU implementation according to the optimal CPU version at the node level.…”

Section: Gpu Performance Analysissupporting

confidence: 73%

Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

Borrell

Dosimont

García-Gasulla

et al. 2020

Future Generation Computer Systems

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High fidelity Computational Fluid Dynamics simulations are generally associated with large computing requirements, which are progressively acute with each new generation of supercomputers. However, significant research efforts are required to unlock the computing power of leadingedge systems, currently referred to as pre-Exascale systems, based on increasingly complex architectures. In this paper, we present the approach implemented in the computational mechanics code Alya. We describe in detail the parallelization strategy implemented to fully exploit the different levels of parallelism, together with a novel co-execution method for the efficient utilization of heterogeneous CPU/GPU architectures. The latter is based on a multi-code co-execution approach with a dynamic load balancing mechanism. The assessment of the performance of all the proposed strategies has been carried out for airplane simulations on the POWER9 architecture accelerated with NVIDIA Volta V100 GPUs. * c 2020 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ https://doi.

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Section: Gpu Performance Analysissupporting

confidence: 73%

Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

Borrell

Dosimont

García-Gasulla

et al. 2020

Future Generation Computer Systems

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“…In previous works of Oyarzun et al [18] and Álvarez et al [23], an algebra-based implementation model was proposed for the DNS and LES of incompressible turbulent flows such that the algorithm of the time-integration phase reduces to a set of only three algebraic kernels: SpMV, axpy and dot. However, a close look at Equations 17 and 18, for instance, reveals that this set is insufficient to fulfill the implementation of the flux limiter because it comprises non-linear operations.…”

Section: Algebraic Implementationmentioning

confidence: 99%

“…By casting discrete operators and mesh functions into sparse matrices and vectors, it has been shown that nearly 90% of the calculations in a typical CFD algorithm for the direct numerical simulation (DNS) and large eddy simulation (LES) of incompressible turbulent flows boil down to the following basic linear algebra subroutines: sparse matrix-vector product (SpMV), linear combination of vectors (axpy) and dot product (dot) [18]. Moreover, after the generalizations detailed in Section 3.2 this value will be raised to 100%.…”

Section: Introductionmentioning

confidence: 99%

On the implementation of flux limiters in algebraic frameworks

Valle,

Álvarez-Farré,

Gorobets

et al. 2021

Preprint

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The use of flux limiters is widespread within the scientific computing community to capture shock discontinuities and are of paramount importance for the temporal integration of high-speed aerodynamics, multiphase flows and hyperbolic equations in general.Meanwhile, the breakthrough of new computing architectures and the hybridization of supercomputer systems pose a huge portability challenge, particularly for legacy codes, since the computing subroutines that form the algorithms, the so-called kernels, must be adapted to various complex parallel programming paradigms. From this perspective, the development of innovative implementations relying on a minimalist set of kernels simplifies the deployment of scientific computing software on state-of-the-art supercomputers, while it requires the reformulation of algorithms, such as the aforementioned flux limiters.Equipped with basic algebraic topology and graph theory underlying the classical mesh concept, a new flux limiter formulation is presented based on the adoption of algebraic data structures and kernels. As a result, traditional flux limiters are cast into a stream of only two types of computing kernels: sparse matrix-vector multiplication and generalized pointwise binary operators. The newly proposed formulation eases the deployment of such a numerical technique in massively parallel, potentially hybrid, computing systems and is demonstrated for a canonical advection problem.

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“…As a future work, the authors are interested in extending the implementation of the framework to a hybrid MPI-openMP paradigm and study its effect on the computational efficiency. The code also has a multi-threading capability with CUDA or openCL to use GPUs as co-processors on a hybrid machine [50][51][52]. This configuration was not used in this work and we focused on CPU-only clusters.…”

Section: Single-physics Solversmentioning

confidence: 99%

A scalable framework for the partitioned solution of fluid–structure interaction problems

et al. 2020

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In this work, we present a scalable and efficient parallel solver for the partitioned solution of fluid-structure interaction problems through multi-code coupling. Two instances of an in-house parallel software, Ter-moFluids, are used to solve the fluid and the structural sub-problems, coupled together on the interface via the preCICE coupling library. For fluid flow, the Arbitrary Lagrangian-Eulerian form of the Navier-Stokes equations is solved on an unstructured conforming grid using a second-order finitevolume discretization. A parallel dynamic mesh method for unstructured meshes is used to track the moving boundary. For the structural problem, the nonlinear elastodynamics equations are solved on an unstructured grid using a second-order finite-volume method. A semi-implicit FSI coupling method is used which segregates the fluid pressure term and couples it strongly to the structure, while the remaining fluid terms and the geometrical nonlinearities are only loosely coupled. A robust and advanced multivector quasi-Newton method is used for the coupling iterations between the solvers. Both the fluid and the structural solver use distributed-memory parallelism. The intra-solver communication required for data update in the solution process is carried out using non-blocking point-to-point communicators. The inter-code communication is fully parallel and point-to-point, avoiding any central communication unit. Inside each single-physics solver, the load is balanced by dividing the computational domain into fairly equal blocks for each process. Additionally, a load balancing model is used at the inter-code level to minimize the overall idle time of the processes. Two strating the accuracy and computational efficiency of the coupled solver. Strong scalability test results show a parallel efficiency of 83% on 10,080 CPU cores.

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Portable implementation model for CFD simulations. Application to hybrid CPU/GPU supercomputers

Cited by 13 publications

References 27 publications

Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

Heterogeneous CPU/GPU co-execution of CFD simulations on the POWER9 architecture: Application to airplane aerodynamics

On the implementation of flux limiters in algebraic frameworks

A scalable framework for the partitioned solution of fluid–structure interaction problems

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