23,643 research outputs found
A GPU-enabled implicit Finite Volume solver for the ideal two-fluid plasma model on unstructured grids
This paper describes the main features of a pioneering unsteady solver for
simulating ideal two-fluid plasmas on unstructured grids, taking profit of
GPGPU (General-purpose computing on graphics processing units). The code, which
has been implemented within the open source COOLFluiD platform, is implicit,
second-order in time and space, relying upon a Finite Volume method for the
spatial discretization and a three-point backward Euler for the time
integration. In particular, the convective fluxes are computed by a multi-fluid
version of the AUSM+up scheme for the plasma equations, in combination with a
modified Rusanov scheme with tunable dissipation for the Maxwell equations.
Source terms are integrated with a one-point rule, using the cell-centered
value. Some critical aspects of the porting to GPU's are discussed, as well as
the performance of two open source linear system solvers (i.e. PETSc,
PARALUTION). The code design allows for computing both flux and source terms on
the GPU along with their Jacobian, giving a noticeable decrease in the
computational time in comparison with the original CPU-based solver. The code
has been tested in a wide range of mesh sizes and in three different systems,
each one with a different GPU. The increased performance (up to 14x) is
demonstrated in two representative 2D benchmarks: propagation of circularly
polarized waves and the more challenging Geospace Environmental Modeling (GEM)
magnetic reconnection challenge.Comment: 22 pages, 7 figure
Odeint - Solving ordinary differential equations in C++
Many physical, biological or chemical systems are modeled by ordinary
differential equations (ODEs) and finding their solution is an every-day-task
for many scientists. Here, we introduce a new C++ library dedicated to find
numerical solutions of initial value problems of ODEs: odeint (www.odeint.com).
odeint is implemented in a highly generic way and provides extensive
interoperability at top performance. For example, due to it's modular design it
can be easily parallized with OpenMP and even runs on CUDA GPUs. Despite that,
it provides a convenient interface that allows for a simple and easy usage.Comment: 4 pages, 1 figur
QuTiP: An open-source Python framework for the dynamics of open quantum systems
We present an object-oriented open-source framework for solving the dynamics
of open quantum systems written in Python. Arbitrary Hamiltonians, including
time-dependent systems, may be built up from operators and states defined by a
quantum object class, and then passed on to a choice of master equation or
Monte-Carlo solvers. We give an overview of the basic structure for the
framework before detailing the numerical simulation of open system dynamics.
Several examples are given to illustrate the build up to a complete
calculation. Finally, we measure the performance of our library against that of
current implementations. The framework described here is particularly
well-suited to the fields of quantum optics, superconducting circuit devices,
nanomechanics, and trapped ions, while also being ideal for use in classroom
instruction.Comment: 16 pages, 12 figure
Numerical simulation of the stress-strain state of the dental system
We present mathematical models, computational algorithms and software, which
can be used for prediction of results of prosthetic treatment. More interest
issue is biomechanics of the periodontal complex because any prosthesis is
accompanied by a risk of overloading the supporting elements. Such risk can be
avoided by the proper load distribution and prediction of stresses that occur
during the use of dentures. We developed the mathematical model of the
periodontal complex and its software implementation. This model is based on
linear elasticity theory and allows to calculate the stress and strain fields
in periodontal ligament and jawbone. The input parameters for the developed
model can be divided into two groups. The first group of parameters describes
the mechanical properties of periodontal ligament, teeth and jawbone (for
example, elasticity of periodontal ligament etc.). The second group
characterized the geometric properties of objects: the size of the teeth, their
spatial coordinates, the size of periodontal ligament etc. The mechanical
properties are the same for almost all, but the input of geometrical data is
complicated because of their individual characteristics. In this connection, we
develop algorithms and software for processing of images obtained by computed
tomography (CT) scanner and for constructing individual digital model of the
tooth-periodontal ligament-jawbone system of the patient. Integration of models
and algorithms described allows to carry out biomechanical analysis on
three-dimensional digital model and to select prosthesis design.Comment: 19 pages, 9 figure
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
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