From 4cfc87d6767ba8d352f1340ab7b98fefcdf34cee Mon Sep 17 00:00:00 2001 From: wolf Date: Thu, 14 Jan 1999 13:24:05 +0000 Subject: [PATCH] Doc update for FESystem. git-svn-id: https://svn.dealii.org/trunk@729 0785d39b-7218-0410-832d-ea1e28bc413d --- deal.II/deal.II/include/numerics/matrices.h | 22 +++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) diff --git a/deal.II/deal.II/include/numerics/matrices.h b/deal.II/deal.II/include/numerics/matrices.h index b417f8179b..ad19460c3b 100644 --- a/deal.II/deal.II/include/numerics/matrices.h +++ b/deal.II/deal.II/include/numerics/matrices.h @@ -69,6 +69,15 @@ class dSMatrix; * the assemblage is much faster. However, no coefficient can be * given. * + * Note that the effect of the two ways of setting up the mass + * matrix is not the same if you use finite elements which are + * composed of several subelements. In this case, using the + * quadrature free way (without coefficient) results in a matrix + * which does not couple the subelements, as described in the + * #FESystem::get_local_mass_matrix# documentation, while the + * way using quadrature sets up the full matrix, i.e. with the + * cross coupling of shape functions belonging to different subelements. + * * \item #create_laplace_matrix#: there are two versions of this; the * one which takes the #Function# object creates * $a_{ij} = \int_\Omega a(x) \nabla\phi_i(x) \nabla\phi_j(x) dx$, @@ -172,7 +181,10 @@ class MatrixCreator { * If the coefficient is constant, it * may be more adequate to use the * functions assembling the mass matrix - * without quadrature. + * without quadrature. However, the + * two functions have different effects + * for finite elements composed of + * several subobjects. * * See the general doc of this class * for more information. @@ -193,7 +205,10 @@ class MatrixCreator { * If the coefficient is constant, it * may be more adequate to use the * functions assembling the mass matrix - * without quadrature. + * without quadrature. However, the + * two functions have different effects + * for finite elements composed of + * several subobjects. * * See the general doc of this class * for more information. @@ -222,6 +237,9 @@ class MatrixCreator { * previously in the matrix, so if you want * the pure mass matrix, you have to clear * the matrix beforehand. + * + * See the general doc of this class + * for more information. */ static void create_mass_matrix (const DoFHandler &dof, const FiniteElement &fe, -- 2.39.5