From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Mon, 22 May 2023 22:59:32 +0000 (-0600)
Subject: Update the Trilinos section.
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=38aab597655094a7b41c02be4d4aa1e7f359031a;p=release-papers.git

Update the Trilinos section.
---

diff --git a/9.5/paper.tex b/9.5/paper.tex
index eded50a..8474a41 100644
--- a/9.5/paper.tex
+++ b/9.5/paper.tex
@@ -259,35 +259,43 @@ can be found
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \subsubsection{Interfaces to Trilinos' Belos and NOX packages}\label{sec:trilinos}
 
-We have added a new wrapper to \texttt{Belos}. The package
-\texttt{Belos}  is the
-successor of \texttt{AztecOO} and provides basic and advanced iterative solvers
+Trilinos is a large collection of individual sub-packages. \dealii{}
+has long had interfaces to the Trilinos packages that provide parallel
+vector and matrix classes (both \texttt{Epetra} and \texttt{Tpetra}),
+as well as a small number of linear algebra packages for iterative
+solvers and preconditions. In the current release, there are now also
+interfaces to two additional packages: \texttt{Belos} and \texttt{NOX}.
+
+\texttt{Belos} is the
+successor of the Trilinos package \texttt{AztecOO} and provides basic and advanced iterative solvers
 that heavily rely on multivector operations. The interface of the
-wrapper is similar to the one of the native iterative solvers
-provided by \dealii:
-
+wrapper is similar to \dealii{}'s own iterative solvers:
 \begin{c++}
 TrilinosWrappers::SolverBelos<VectorType> solver(/*...*/);
 solver.solve(matrix, x, r, preconditioner);
 \end{c++}
-
-Via additional data, the user can select the actual iterative
-solver to be used and set its configurations.
-
-Furthermore, we have added a wrapper to \texttt{NOX}. This is a
-nonlinear-solver library similar to \texttt{KINSOL} from \texttt{SUNDIALS}
-and to \texttt{SNES} from \texttt{PETSc}. The basic interface
-of the \texttt{NOX} wrapper is similar to the one of the other wrappers
-mentioned before:
-
+The omitted constructor arguments allow selecting the actual iterative
+solver to be used, along with other configuration options.
+
+Secondly, we have added a wrapper to \texttt{NOX}, a
+nonlinear solver library similar to the \texttt{KINSOL} solver from
+the \texttt{SUNDIALS} package to which we already had interfaces, as
+well as to \texttt{SNES} from \texttt{PETSc} (see also
+Section~\ref{sec:petsc}). The interfaces to these three solvers are
+essentially the same and require setting function objects for
+computing the residual of the nonlinear problem, along with setting
+up, applying, and solving with the Jacobian matrix:
 \begin{c++}
 TrilinosWrappers::NOXSolver<VectorType> solver(/*...*/);
 
-solver.residual            = [ ](const auto &src, auto &dst) {/*...*/};
-solver.setup_jacobian      = [&](const auto &src) {/*...*/};
-solver.apply_jacobian      = [&](const auto &src, auto &dst) {/*...*/};
-solver.solve_with_jacobian = 
-  [&](const auto &src, auto &dst, const auto tol) {/*...*/};
+solver.residual            = [ ](const VectorType &src,
+                                 VectorType       &dst) {/*...*/};
+solver.setup_jacobian      = [&](const VectorType &src) {/*...*/};
+solver.apply_jacobian      = [&](const VectorType &src,
+                                 VectorType       &dst) {/*...*/};
+solver.solve_with_jacobian = [&](const VectorType &src,
+                                 VectorType       &dst,
+                                 const double      tol) {/*...*/};
 
 solver.solve(solution);
 \end{c++}
@@ -298,6 +306,10 @@ In particular, we have added the possibility to reuse the preconditioner between
 nonlinear steps (also known as \textit{preconditioner lagging}), which is
 unfortunately natively only  supported in the official \texttt{EPetra} implementations.
 
+\todo[inline]{I don't understand this last sentence. Can you
+  elaborate? At least in the KINSOL interfaces, you only update the
+  preconditioner whenever setup\_jacobian() is called.}
+
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \subsubsection{Uniform structure of callbacks}\label{sec:callbacks}