From: Peter Munch Date: Mon, 24 May 2021 12:54:44 +0000 (+0200) Subject: Write text X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e7d0863d811813d72dd77e5b4d57b9b4dabafb41;p=release-papers.git Write text --- diff --git a/9.3/paper.bib b/9.3/paper.bib index d156b88..9d105c2 100644 --- a/9.3/paper.bib +++ b/9.3/paper.bib @@ -1119,3 +1119,34 @@ doi = {10.1016/0096-3003(82)90191-6} Year = {2019}, Url = {https://arxiv.org/abs/1907.06696} } + +@article{logg2012, +author = {Logg, Anders}, +year = {2012}, +month = {05}, +pages = {}, +title = {Efficient Representation of Computational Meshes}, +volume = {4}, +journal = {Int. J. Computational Science and Engineering Int. J. Computational Science and Engineering}, +doi = {10.1504/IJCSE.2009.029164} +} + +@article{becker2000multigrid, + title={Multigrid techniques for finite elements on locally refined meshes}, + author={Becker, Roland and Braack, Malte}, + journal={Numerical linear algebra with applications}, + volume={7}, + number={6}, + pages={363--379}, + year={2000}, + publisher={Wiley Online Library} +} + +@inproceedings{sundar2012parallel, + title={Parallel geometric-algebraic multigrid on unstructured forests of octrees}, + author={Sundar, Hari and Biros, George and Burstedde, Carsten and Rudi, Johann and Ghattas, Omar and Stadler, Georg}, + booktitle={SC'12: Proceedings of the International Conference on High Performance Computing, Networking, Storage and Analysis}, + pages={1--11}, + year={2012}, + organization={IEEE} +} diff --git a/9.3/paper.tex b/9.3/paper.tex index 0f54dff..4ee008a 100644 --- a/9.3/paper.tex +++ b/9.3/paper.tex @@ -244,7 +244,13 @@ GNU Lesser General Public License (LGPL). Downloads are available at The major changes of this release are: % \begin{itemize} - \item TODO. + \item An experimental support for simplex and mixed meshes (see Section~\ref{subsec:simplex}); + \item Improved flexibility of the particle infrastructure (see Section~\ref{subsec:particles}); + \item Support for global-coarsening multigrid algorithms (see Section~\ref{subsec:mg}); + \item Advances in the matrix-free infrastructure (see Section~\ref{subsec:mf}); + \item Usage of MPI-3.0 shared-memory features to reduce memory footprint (see Section~\ref{subsec:sm}); + \item Improved support for evaluation and integration at arbitrary points (see Section~\ref{subsec:fepointvalues}); + \item Nine new tutorial programs and a new code gallery program (see Section~\ref{subsec:steps}). \end{itemize} % These major changes are discussed in detail in Section~\ref{sec:major}. There @@ -252,9 +258,13 @@ are a number of other noteworthy changes in the current \dealii{} release that we briefly outline in the remainder of this section: % \begin{itemize} - \item globally unique cell IDs: TODO + \item Each non-artificial cell posses now an globally unique index, which can be queried + for active cells via \texttt{CellAccessor::global\_active\_cell\_index()} and for level cells + via \texttt{::global\_\allowbreak level\_\allowbreak cell\_\allowbreak index()}. The information + can be used to efficiently access global cell vectors. Users have been able to construct the + same information by distributing \texttt{FE\_DGQ(0)} in a \texttt{DoFHandler}. \item In addition to the macro \texttt{DEAL\_II\_DEPRECATED}, we have introduced - the \texttt{DEAL\_II\_DEPRECATED\_EARLY} macro, which indicates that a feature will be + the \texttt{DEAL\_II\_DEPRECATED\_\allowbreak EARLY} macro, which indicates that a feature will be deprecated in the next release. In contrast to the first macro, it will only give warnings if \dealii{} has been configured with \texttt{-D DEAL\_II\_EARLY\_DEPRECATIONS=ON}. \item After each update of the master branch of \dealii{}, we build a new Docker image @@ -263,7 +273,7 @@ that we briefly outline in the remainder of this section: particular useful when used in the contiguous-integration processes of user codes. \end{itemize} % -The changelog lists more than 240 other +The changelog lists more than ?? other features and bugfixes. @@ -286,10 +296,10 @@ can be found %\newpage %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\subsection{Simplex and mixed mesh support} +\subsection{Experimental simplex and mixed mesh support} \label{subsec:simplex} -\begin{figure}[!h] +\begin{figure}[!t] \centering @@ -514,7 +524,7 @@ can be found \end{tabular} \end{table} -The current release of \dealii adds support for simplex meshes (consisting of triangles in 2D; tetrahedra in 3D) and mixed meshes (consisting of triangles and/or +The current release of \dealii adds an experimental support for simplex meshes (consisting of triangles in 2D; tetrahedra in 3D) and mixed meshes (consisting of triangles and/or quadrilaterals in 2D; tetrahedra, pyramids, wedges, and/or hexahedra in 3D). Many freely available mesh-generation tools produce such kind of meshes; while users of \dealii used to have to pre-process such meshes and convert them to pure hex meshes, they can now directly work with them. @@ -528,7 +538,7 @@ The template parameters of the internal data structures of \texttt{Triangulation have been removed and the type of each cell and of each face (only in 3D) is stored. The function \texttt{Triangulation::create\_\allowbreak triangulation()}, which converts a given list of cells and vertices to the internal data structures, has been rewritten -inspired by \citep{logg09} and a speed-up of up to 5 has been reached. Minor adjustments +inspired by \citep{logg2012} and a speed-up of up to 5 has been reached. Minor adjustments have been made to \texttt{parallel::shared::Triangulation} and \texttt{parallel::\allowbreak fullydistributed::\allowbreak Triangulation} such that the new mesh types can be processed also in parallel. @@ -536,14 +546,14 @@ The internal data structures of \texttt{DoFHandler} used to be hard-coded for pu hypercube meshes, while the \texttt{hp::DoFHandler} used to be built around CRS-like data structures. Due to the need of CRS data structures in the \texttt{DoFHandler} in the context of more general meshes, we have merged -\texttt{hp::DoFHandler} into the \texttt{DoFHandler}. The class \texttt{hp::DoFHandler}, which is now a dummy derivation of \texttt{DoFHandler}, currently only exists for compatibility reasons. For -more details see Subsection~\ref{TODO}. +\texttt{hp::DoFHandler} into the \texttt{DoFHandler}. The class \texttt{hp::DoFHandler}, which is now a dummy derivation of \texttt{DoFHandler}, currently only exists for compatibility reasons and has +been deprecated, see Section~\ref{subsec:deprecated}. \subsubsection{Generating meshes} The most obvious way to generate a simplex or a mixed mesh is to read the mesh from a file generated by an external mesh generator. Currently, we support the -file formats \texttt{VTK}, \texttt{MSH}, \texttt{EXODUS II}. +file formats \texttt{VTK}, \texttt{MSH}, and \texttt{EXODUS II}. Alternatively, one can create a pure hypercube mesh with the known functions in the \texttt{GridGenerator} namespace and convert the obtained mesh to a @@ -567,7 +577,7 @@ dof_handler.distribute_dofs(fe); FEValues fe_values(mapping, fe, quad, flags); \end{c++} The list of currently supported finite-element classes is provided in Table~\ref{tab:simplex:fe}. Currently, -only linear iso-parametric mapping (\texttt{MappingFE} and \texttt{MappingFEFields}) is available. For quadrature, the classes \texttt{QGaussSimplex}, \texttt{QWitherdenVincentSimplex}, +only linear iso-parametric mapping (\texttt{MappingFE} and \texttt{MappingFEFields}) is available. For quadrature, the classes \texttt{QDuffy}, \texttt{QGaussSimplex}, \texttt{QWitherdenVincentSimplex}, \texttt{QGaussPyamid}, and \texttt{QGaussWedge} are available. @@ -676,11 +686,14 @@ supported. \subsubsection{Miscellanea} -We have created two new tutorials presenting the new simplex (\texttt{step-3b}) and mixed mesh features -(\texttt{step-3c}). Similarly as \texttt{step-3}, they solve a Poisson problem, however, focus -on the changed workflow. +Further information can be found on the new module page ``Simplex support (experimental)'', see +\begin{center} + \url{https://www.dealii.org/current/doxygen/deal.II/group__simplex.html} +\end{center} +As an example, it shows how to solve a simple Poisson problem like in \texttt{step-3} +on simplex and mixed meshes, with the focus on on the changed workflow. -By the time of writing, there have been 74 tests (in the folder \texttt{tests/simplex}) +By the time of writing, there have been 92 tests (in the folder \texttt{tests/simplex}) targeting the new simplex and mixed mesh support. In particular, the folder also contains ported variants of the following tutorials: 1, 2, 3, 4, 6, 7, 8, 12, 17, 18, 20, 23, 31, 38, 40, 55, 67, 68, and 74. These might be also good starting points. @@ -700,7 +713,7 @@ Until now, \dealii has only supported local smoothing multigrid algorithms~\citep{ClevengerHeisterKanschatKronbichler2019}; in local smoothing algorithms, smoothers only act on the cells of a given refinement level, skipping those parts of the mesh that are not adaptively refined to that level. -The current release now also has support for global coarsening~\citep{becker00} when +The current release now also has support for global coarsening~\citep{becker2000multigrid, sundar2012parallel} when using continuous (\texttt{FE\_Q}, \texttt{FE\_SimplexP}) and discontinuous (\texttt{FE\_DGQ}, \texttt{FE\_SimplexDGP}) elements. Global coarsening builds multigrid levels for the entire @@ -727,16 +740,16 @@ smoothing algorithms, but have to deal with hanging nodes within each level and general require more computational work per iteration overall. -The transfer operators between two levels has been implemented in the new class \texttt{MGTwoLevelTransfer}, which can be set up via the functions \texttt{MGTwoLevelTransfer::\allowbreak reinit\_\allowbreak geometric\_\allowbreak transfer()} or \texttt{MGTwo\allowbreak LevelTransfer::\allowbreak reinit\_\allowbreak polynomial\_\allowbreak transfer()} for given +The transfer operators between two levels have been implemented in the new class \texttt{MGTwoLevel\allowbreak Transfer}, which can be set up via the functions \texttt{MGTwoLevel\allowbreak Transfer::\allowbreak reinit\_\allowbreak geometric\_\allowbreak transfer()} or \texttt{MGTwo\allowbreak LevelTransfer::\allowbreak reinit\_\allowbreak polynomial\_\allowbreak transfer()} for given \texttt{DoFHandler} and \texttt{AffineConstraint} classes of two levels. The resulting transfer operators can then be collected in a single -\texttt{MGTransferGlobalCoarsening} object that can be used just as the previous workhorse \texttt{MGTransferMatrixFree} within the \texttt{Multigrid} +\texttt{MGTransfer\allowbreak GlobalCoarsening} object that can be used just as the previous workhorse \texttt{MGTransferMatrixFree} within the \texttt{Multigrid} algorithm. %Several common operations are encoded in utility %functions in the \texttt{MGTransferGlobalCoarseningTools} %namespace. To facilitate the construction of matrix diagonals with matrix-free methods as well as a matrix representation of the coarse level matrix, new utility functions \texttt{create\_diagonal()} and \texttt{create\_matrix()} from -the \texttt{MatrixFreeTools} namespace have been added. (see also Subsection~\ref{subsec:mf}). +the \texttt{MatrixFreeTools} namespace have been added (see also Subsection~\ref{subsec:mf}). The usage of the new transfer operators (and of some of the utility functions) in the context of a hybrid multigrid algorithm @@ -803,7 +816,7 @@ in the context of a hybrid-multigrid solver. -\subsection{MPI-3.0 shared-memory support} +\subsection{MPI-3.0 shared-memory support}\label{subsec:sm} In many large computations, certain pieces of data are computed once and then treated as read-only. If this information is needed by more than one MPI process, it is more efficient to store this information only @@ -819,7 +832,7 @@ The feature is also used in the \texttt{MatrixFree} and \texttt{MatrixFree::create\_dof\_vector()} creates vectors that share information among all processes on one node. As a consequence, the \texttt{FEEvaluation} classes can access vector elements owned by -other processes and in certain cases local +other processes and in certain cases node-local communication can be skipped. To prevent race conditions, \texttt{MatrixFree} uses local barriers at the beginning and the end of loops (\texttt{loop()}, \texttt{cell\_loop()}, \texttt{loop\_cell\_centric()}). @@ -827,7 +840,7 @@ The new \texttt{step-76} tutorial program illustrates this latter case in the context of the solution of the Euler equations. \texttt{step-76} reaches a speed-up of 27\% compared to the original version, \texttt{step-67}, by using the new feature. -For more details and use of the feature in the library \texttt{hyper.deal}, see \citep{munch2020hyperdeal}. +For more details and the usage of the feature in the library \texttt{hyper.deal}, see \citep{munch2020hyperdeal}. @@ -838,8 +851,8 @@ For more details and use of the feature in the library \texttt{hyper.deal}, see In a number of circumstances, finite element solutions need to be evaluated on arbitrary reference points that change from one element to next. Two important examples are particle simulations coupled to a finite element solution, or -algorithms on non-matching grids. The existing \texttt{FEValues} class a poor -fit for this task, as it relies on tabulating all information before use, +algorithms on non-matching grids. The existing \texttt{FEValues} class is a poor +fit for this task, as it relies on tabulating all information before its usage, necessitating a separate setup for every cell. The new class \texttt{FEPointEvaluation} provides a more convenient interface for this task. For tensor product finite elements (\texttt{FE\_Q}, \texttt{FE\_DGQ}) @@ -862,11 +875,11 @@ phi_normal.reinit(cell, reference_points); phi_force.reinit(cell, reference_points); phi_normal.evaluate(normal_values, EvaluationFlags::values); for (unsigned int q = 0; q < n_points; ++q) - phi_force.submit_value(phi_normal.get_value(q) * - phi_curvature.get_value(q) * JxW[q], q); + phi_force.submit_value(phi_curvature.get_value(q) * + phi_normal.get_value(q) * JxW[q], q); phi_force.integrate(force_values, EvaluationFlags::values); \end{c++} -The quadrature points and the related \texttt{JxW} value can, e.g., come from +The quadrature points (at reference positions - \texttt{reference\_points}) and the related \texttt{JxW} value can, e.g., come from a mesh of codimension one. Determining to which \texttt{cell} a quadrature point belongs to on the background mesh, including the reference-cell coordinates \texttt{reference\_points}, can be determined with functions like @@ -875,20 +888,20 @@ functions have been available in \dealii{} previously, their performance has been considerably enhanced with the aforementioned more optimized code paths for selected mappings. +While \texttt{FEPointEvaluation} assumes that evaluation points are already sorted according to +the owning cells and such can concentrate on cell-local operations, the new class +\texttt{RemovePointEvaluation} is responsible to determine the owning cells in a distributed +context and for providing efficient communication patterns for the data exchange. In \texttt{deal.II}, +the class has been successfully applied together with \texttt{FEPointEvaluation} to evaluate a distributed +solution vector at arbitrary points (see \texttt{VectorTools::evaluate\_at\_points()}). + %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \subsection{New and improved tutorials and code gallery programs} \label{subsec:steps} Many of the \dealii{} tutorial programs were revised in a variety of -ways as part of this release. A particular example is that we have -converted a number of programs to use range-based for loops (a C++11 -feature) for loops over a range of integer indices such as loops over -all quadrature points or all indices of degrees of freedom during -assembly. This makes sense given that the -range-based way of writing loops seems to be the idiomatic approach -these days, and that we had previously already converted loops over -all cells in this way. +ways as part of this release. TODO In addition, there are a number of new tutorial programs: \begin{itemize} @@ -957,7 +970,7 @@ In addition, there are a number of new tutorial programs: \item \texttt{step-79} TODO \end{itemize} -There are also new programs in the code gallery (a collection of +There is also a new program in the code gallery (a collection of user-contributed programs that often solve more complicated problems than tutorial programs, and intended as starting points for further research rather than as teaching tools): @@ -968,7 +981,7 @@ research rather than as teaching tools): %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -\subsection{Incompatible changes} +\subsection{Incompatible changes}\label{subsec:deprecated} The 9.3 release includes \href{https://dealii.org/developer/doxygen/deal.II/changes_between_9_2_0_and_9_3_0.html}