From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Fri, 24 Feb 2023 11:52:20 +0000 (-0700)
Subject: Reference the glossary entry relating to the lumped mass matrix.
X-Git-Tag: v9.5.0-rc1~517^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F14830%2Fhead;p=dealii.git

Reference the glossary entry relating to the lumped mass matrix.
---

diff --git a/doc/doxygen/headers/glossary.h b/doc/doxygen/headers/glossary.h
index d93eb2a96e..3ce2463379 100644
--- a/doc/doxygen/headers/glossary.h
+++ b/doc/doxygen/headers/glossary.h
@@ -1332,10 +1332,15 @@
  * where the sum extends over those cells on which $\varphi_i$ is nonzero.
  * The so-computed mass matrix is therefore diagonal.
  *
- * Whether or not this particular choice of quadrature formula is sufficient
- * to retain the convergence rate of the discretization is a separate
- * question. For the usual $Q_k$ finite elements, the appropriate
- * quadrature formulas are of QGaussLobatto type.
+ * Whether or not this particular choice of quadrature formula is
+ * sufficient to retain the convergence rate of the discretization is
+ * a separate question. For the usual $Q_k$ finite elements
+ * (implemented by FE_Q and FE_DGQ), the appropriate quadrature
+ * formulas are of QGaussLobatto type. Mass lumping can also be done
+ * with FE_SimplexP_Bubbles, for example, if appropriate quadrature rules
+ * are chosen.
+ *
+ * For an example of where lumped mass matrices play a role, see step-69.
  * </dd>
  *
  *
diff --git a/examples/step-69/doc/intro.dox b/examples/step-69/doc/intro.dox
index 15acd85da7..edafa046b6 100644
--- a/examples/step-69/doc/intro.dox
+++ b/examples/step-69/doc/intro.dox
@@ -267,7 +267,8 @@ the (explicit time stepping) scheme as:
 @f}
 where
   - $m_i \dealcoloneq \int_{\Omega} \phi_i \, \mathrm{d}\mathbf{x}$
-    is the lumped @ref GlossMassMatrix "mass matrix"
+    is the @ref GlossLumpedMassMatrix "lumped"
+    @ref GlossMassMatrix "mass matrix"
   - $\tau$ is the time step size
   - $\mathbf{c}_{ij} \dealcoloneq \int_{\Omega} \nabla\phi_j\phi_i \,
     \mathrm{d}\mathbf{x}$ (note that $\mathbf{c}_{ij}\in \mathbb{R}^d$)
diff --git a/examples/step-69/step-69.cc b/examples/step-69/step-69.cc
index 7e229edfa1..c013a95546 100644
--- a/examples/step-69/step-69.cc
+++ b/examples/step-69/step-69.cc
@@ -178,7 +178,9 @@ namespace Step69
   //
   // The class <code>OfflineData</code> contains pretty much all components
   // of the discretization that do not evolve in time, in particular, the
-  // DoFHandler, SparsityPattern, boundary maps, the lumped @ref GlossMassMatrix "mass matrix",
+  // DoFHandler, SparsityPattern, boundary maps, the
+  // @ref GlossLumpedMassMatrix "lumped" lumped
+  // @ref GlossMassMatrix "mass matrix",
   // $\mathbf{c}_{ij}$ and $\mathbf{n}_{ij}$ matrices. Here, the term
   // <i>offline</i> refers to the fact that all the class
   // members of <code>OfflineData</code> have well-defined values
diff --git a/include/deal.II/matrix_free/operators.h b/include/deal.II/matrix_free/operators.h
index 647c85a1db..f6bfcfe0d9 100644
--- a/include/deal.II/matrix_free/operators.h
+++ b/include/deal.II/matrix_free/operators.h
@@ -766,7 +766,8 @@ namespace MatrixFreeOperators
     compute_diagonal() override;
 
     /**
-     * Compute the lumped @ref GlossMassMatrix "mass matrix". This is equal to the mass matrix times a
+     * Compute the @ref GlossLumpedMassMatrix "lumped mass matrix".
+     * This is equal to the mass matrix times a
      * vector of all ones and is equivalent to approximating the mass matrix
      * with a nodal quadrature rule.
      *