From: Wolfgang Bangerth 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. * * * 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 OfflineData 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 // offline refers to the fact that all the class // members of OfflineData 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. *