157 research outputs found
ParMooN - a modernized program package based on mapped finite elements
{\sc ParMooN} is a program package for the numerical solution of elliptic and
parabolic partial differential equations. It inherits the distinct features of
its predecessor {\sc MooNMD} \cite{JM04}: strict decoupling of geometry and
finite element spaces, implementation of mapped finite elements as their
definition can be found in textbooks, and a geometric multigrid preconditioner
with the option to use different finite element spaces on different levels of
the multigrid hierarchy. After having presented some thoughts about in-house
research codes, this paper focuses on aspects of the parallelization for a
distributed memory environment, which is the main novelty of {\sc ParMooN}.
Numerical studies, performed on compute servers, assess the efficiency of the
parallelized geometric multigrid preconditioner in comparison with some
parallel solvers that are available in the library {\sc PETSc}. The results of
these studies give a first indication whether the cumbersome implementation of
the parallelized geometric multigrid method was worthwhile or not.Comment: partly supported by European Union (EU), Horizon 2020, Marie
Sk{\l}odowska-Curie Innovative Training Networks (ITN-EID), MIMESIS, grant
number 67571
Toward Performance-Portable PETSc for GPU-based Exascale Systems
The Portable Extensible Toolkit for Scientific computation (PETSc) library
delivers scalable solvers for nonlinear time-dependent differential and
algebraic equations and for numerical optimization.The PETSc design for
performance portability addresses fundamental GPU accelerator challenges and
stresses flexibility and extensibility by separating the programming model used
by the application from that used by the library, and it enables application
developers to use their preferred programming model, such as Kokkos, RAJA,
SYCL, HIP, CUDA, or OpenCL, on upcoming exascale systems. A blueprint for using
GPUs from PETSc-based codes is provided, and case studies emphasize the
flexibility and high performance achieved on current GPU-based systems.Comment: 15 pages, 10 figures, 2 table
Simulating water-entry/exit problems using Eulerian-Lagrangian and fully-Eulerian fictitious domain methods within the open-source IBAMR library
In this paper we employ two implementations of the fictitious domain (FD)
method to simulate water-entry and water-exit problems and demonstrate their
ability to simulate practical marine engineering problems. In FD methods, the
fluid momentum equation is extended within the solid domain using an additional
body force that constrains the structure velocity to be that of a rigid body.
Using this formulation, a single set of equations is solved over the entire
computational domain. The constraint force is calculated in two distinct ways:
one using an Eulerian-Lagrangian framework of the immersed boundary (IB) method
and another using a fully-Eulerian approach of the Brinkman penalization (BP)
method. Both FSI strategies use the same multiphase flow algorithm that solves
the discrete incompressible Navier-Stokes system in conservative form. A
consistent transport scheme is employed to advect mass and momentum in the
domain, which ensures numerical stability of high density ratio multiphase
flows involved in practical marine engineering applications. Example cases of a
free falling wedge (straight and inclined) and cylinder are simulated, and the
numerical results are compared against benchmark cases in literature.Comment: The current paper builds on arXiv:1901.07892 and re-explains some
parts of it for the reader's convenienc
Introduction and verification of FEDM, an open-source FEniCS-based discharge modelling code
This paper introduces the FEDM (Finite Element Discharge Modelling) code,
which was developed using the open-source computing platform FEniCS
(https://fenicsproject.org). Building on FEniCS, the FEDM code utilises the
finite element method to solve partial differential equations. It extends
FEniCS with features that allow the automated implementation and numerical
solution of fully-coupled fluid-Poisson models including an arbitrary number of
particle balance equations. The code is verified using the method of exact
solutions and benchmarking. The physically based examples of a time-of-flight
experiment, a positive streamer discharge in atmospheric-pressure air and a
low-pressure glow discharge in argon are used as rigorous test cases for the
developed modelling code and to illustrate its capabilities. The performance of
the code is compared to the commercial software package COMSOL
Multiphysics\textsuperscript{\textregistered} and a comparable parallel
speed-up is obtained. It is shown that the iterative solver implemented by FEDM
performs particularly well on high-performance compute clusters.Comment: 17 pages, 12 figures, revision submitted to Plasma Sources Science
and Technolog
Enhancing speed and scalability of the ParFlow simulation code
Regional hydrology studies are often supported by high resolution simulations
of subsurface flow that require expensive and extensive computations. Efficient
usage of the latest high performance parallel computing systems becomes a
necessity. The simulation software ParFlow has been demonstrated to meet this
requirement and shown to have excellent solver scalability for up to 16,384
processes. In the present work we show that the code requires further
enhancements in order to fully take advantage of current petascale machines. We
identify ParFlow's way of parallelization of the computational mesh as a
central bottleneck. We propose to reorganize this subsystem using fast mesh
partition algorithms provided by the parallel adaptive mesh refinement library
p4est. We realize this in a minimally invasive manner by modifying selected
parts of the code to reinterpret the existing mesh data structures. We evaluate
the scaling performance of the modified version of ParFlow, demonstrating good
weak and strong scaling up to 458k cores of the Juqueen supercomputer, and test
an example application at large scale.Comment: The final publication is available at link.springer.co
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