From: Matthias Maier Date: Thu, 9 Mar 2017 21:47:58 +0000 (-0600) Subject: Restructure and reword Section 2.3 LinearOperator X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a2fd9f463059a60294a1c7d2f62047bcadc408dd;p=release-papers.git Restructure and reword Section 2.3 LinearOperator --- diff --git a/8.5/paper.tex b/8.5/paper.tex index 1ae6776..97b9eeb 100644 --- a/8.5/paper.tex +++ b/8.5/paper.tex @@ -136,7 +136,7 @@ The major changes of this release are: approximations of the manifold. TODO: Luca -\item The \texttt{LinearOperator} class has been extended by a generic +\item the \texttt{LinearOperator} class has been extended by a generic ``payload'' mechanism that allows to attach arbitrary additional information to a \texttt{LinearOperator}. The mechanism was used to implement a \texttt{TrilinosPayload} class to have full support for using @@ -197,18 +197,30 @@ This release of \dealii{} contains a number of large and significant changes that will be discussed in the following sections. It of course also contains a vast number of smaller changes and added functionality; the details of these can be found -\href{https://www.dealii.org/8.5.0/doxygen/deal.II/changes_between_8_4_and_8_5.html}{in the file that lists all changes for this release} (see \cite{changes85}) -and that is linked to from the web site of each release as well as the -release announcement. +\href{https://www.dealii.org/8.5.0/doxygen/deal.II/changes_between_8_4_and_8_5.html}{in +the file that lists all changes for this release}; see \cite{changes85}. +(The file is also linked to from the web site of each release as well as +the release announcement.) \subsection{The \texttt{CellDataStorage} class and friends} -The \texttt{CellDataStorage} class is an integrated mechanism to safely store user-defined data, such as that required at each computation point, within each cell. -Although the same was previously achieved through the use of a cell \texttt{user\_pointer}, it required users to manage this data themselves. -As this data is now treated as a first-class citizen to \dealii{}, through the abstract \texttt{TransferableQuadraturePointData} we have provided a generic interface to facilitate several low-level operations that were previously tedious or technically challenging to implement. -For instance, the \texttt{parallel::distributed::ContinuousQuadratureDataTransfer} class assists in the transfer of arbitrary data (that is continuous within a cell) stored at quadrature points when performing h-adaptive refinement of \texttt{parallel::distributed::Triangulation}. -Not only does it perform an $\mathcal{L}^2$ projection of the specified user data between quadrature points, but it also ships the data automatically between MPI processes. +The \texttt{CellDataStorage} class is an integrated mechanism to safely +store user-defined data, such as that required at each computation point, +within each cell. Although the same was previously achieved through the use +of a cell \texttt{user\_pointer}, it required users to manage this data +themselves. This data is now treated as a first-class citizen to \dealii{}. + +Through the abstract \texttt{TransferableQuadraturePointData} we have +provided a generic interface to facilitate several low-level operations +that were previously tedious or technically challenging to implement. For +instance, the +\texttt{parallel::distributed::ContinuousQuadratureDataTransfer} class +assists in the transfer of arbitrary data (that is continuous within a +cell) stored at quadrature points when performing h-adaptive refinement of +\texttt{parallel::distributed::Triangulation}. Not only does it perform an +$\mathcal{L}^2$-projection of the specified user data between quadrature +points, but it also ships the data automatically between MPI processes. \subsection{The \texttt{MappingManifold} class} @@ -216,23 +228,30 @@ TODO: Luca \subsection{Extension of the \texttt{LinearOperator} class} -By introduction of an arbitrary \texttt{Payload} base class, the -\texttt{LinearOperator} class can be extended to seamlessly exploit the -native features and operations offered by external linear algebra -libraries. We have thus developed a \texttt{TrilinosPayload} class, through -which full support for the suite of {\trilinos} parallel iterative solvers -and preconditioners has been achieved. In the case of the construction of -an \texttt{inverse\_operator}, both \dealii's built in solvers and those -offered by {\trilinos} can be selected. This has been achieved by using the -\texttt{Epetra\_Operator} as the basis for the \texttt{TrilinosPayload}, -for which the result of both standard and composite operations involving -forward (\texttt{Apply()}) and inverse (\texttt{ApplyInverse()}) -matrix-vector multiplication are collated using lambda functions. It is -envisaged that, in the future, similar can be done for the {\petsc} +The \texttt{LinearOperator} class has been extended by a generic +``payload'' mechanism that allows to attach arbitrary additional +information to a \texttt{LinearOperator}. This was achieved by introducing +a generic \texttt{Payload} base class. The main use case of the new +mechanism is to extend the \texttt{LinearOperator} class to seamlessly +exploit the native features and operations offered by external linear +algebra libraries. We have thus developed a \texttt{TrilinosPayload} class, +that provides full support for the suite of {\trilinos} parallel iterative +solvers and preconditioners. + +A particular interesting case is the construction of an +\texttt{inverse\_operator}. Now both, \dealii's built in solvers and those +offered by {\trilinos}, can be selected. This has been achieved by using +the \texttt{Epetra\_Operator} as the basis for the +\texttt{TrilinosPayload}, for which the result of standard and composite +operations involving forward (\texttt{Apply()}) and inverse +(\texttt{ApplyInverse()}) matrix-vector multiplication are collated using +lambda functions. + +It is envisaged that, in the future, similar can be done for the {\petsc} iterative solvers. An additional feature of the \texttt{LinearOperator} suite is the defintion -of a \texttt{schur\_complement} operator, and its associated condensation +of a \texttt{schur\_complement} operator and its associated condensation and post-processing \texttt{PackagedOperation}s. An operator representing the Schur complement of a block system can be declared and, though the delayed evaluation offered by \texttt{PackagedOperation}s, reused on any