From: Johannes Heinz Date: Fri, 16 Jun 2023 10:28:52 +0000 (+0200) Subject: add text for Intersected meshes section X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fdc3737fe7ac4b895bd89273ad48ebe36f28985d;p=release-papers.git add text for Intersected meshes section --- diff --git a/9.5/paper.tex b/9.5/paper.tex index 22e8f71..33cfca5 100644 --- a/9.5/paper.tex +++ b/9.5/paper.tex @@ -493,17 +493,41 @@ and (ii) multigrid with non-nested levels. In the following, we describe these in more detail. \subsubsection{Intersected meshes} +In the current release, we added experimental support to compute intersections on parallel::distributed::Triangulation objects using \texttt{CGAL}~\cite{cgal-user-ref}. +For this purpose we introduced a free function which computes intersections and relevant information for communication from \texttt{intersection\_requests}. +\texttt{intersection\_requests} is a vector that contains entities for which intersections are computed on a given triangulation (in the form of \texttt{GridTools::Cache}). +Each entity (faces or cells) is described by a vector of vertices. -\todo[inline]{Complete.} +\begin{c++} +// compute intersections on distributed triangulation +auto intersection_data = + GridTools::internal::distributed_compute_intersection_locations( + cache, intersection_requests, global_bboxes, marked_vertices, + tolerance); +\end{c++} -\begin{itemize} -\item uses \texttt{CGAL}~\cite{cgal-user-ref} -\item data can be used to fill \texttt{RemotePointEvaluation} (communication-free) -\item used successfully in \cite{heinz2023high} to perform Nitsche-type mortaring in the context -of the conservative formulation of acoustic equations discretized with -DG, in order to suppress artificial modes -\end{itemize} +For the common case of Nitsche-type mortaring, quadrature points must be distributed on the intersections where relevant quantities are evaluated. +The \texttt{intersection\_data} returned by the function above can convert itself to data which can be used to fill \texttt{RemotePointEvaluation}. +The whole procedure is done communication-free. + +\begin{c++} +// distribute n_points_1D quadrature points to the intersections +auto point_data = intersection_data.template + convert_to_distributed_compute_point_locations_internal( + n_points_1D, tria, mapping, + // following parameter is optional would need additional + // communication + consistent_numbering_of_sender_and_receiver); + +// use point_data to reinit RemotePointEvaluation +Utilities::MPI::RemotePointEvaluation rpe; +rpe.reinit(point_data,tria, mapping); +\end{c++} + +This functionality is handy since \texttt{RemotePointEvaluation} can now be used to access quantities in quadrature points on intersections without further ado. +To reduce the user's effort, we plan to add a wrapper that takes care of the described procedure and provides interfaces like \texttt{FEEvaluation} to access quantities easily, e.g., in a matrix-free loop. +Described implementation and an early version of the wrapper have been used successfully in~\cite{heinz2023high} to perform Nitsche-type mortaring in the context of the conservative formulation of acoustic equations discretized with DG to suppress artificial modes. \subsubsection{Non-nested multigrid} \dealii has provided support for geometric multigrid methods%