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
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
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.
%\newpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\subsection{Simplex and mixed mesh support}
+\subsection{Experimental simplex and mixed mesh support}
\label{subsec:simplex}
-\begin{figure}[!h]
+\begin{figure}[!t]
\centering
\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.
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.
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
FEValues<dim, spacedim> 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.
\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.
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
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
-\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
\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()}).
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}.
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})
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
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}
\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):
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\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}
projects / release-papers.git / commitdiff