]> https://gitweb.dealii.org/ - dealii-svn.git/commitdiff
Doc update for FESystem.
authorwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Thu, 14 Jan 1999 13:24:05 +0000 (13:24 +0000)
committerwolf <wolf@0785d39b-7218-0410-832d-ea1e28bc413d>
Thu, 14 Jan 1999 13:24:05 +0000 (13:24 +0000)
git-svn-id: https://svn.dealii.org/trunk@729 0785d39b-7218-0410-832d-ea1e28bc413d

deal.II/deal.II/include/numerics/matrices.h

index b417f8179b9a467cc6d2bc9a8a178775235b6830..ad19460c3b57e9b5b261d643f11901c106a71ce1 100644 (file)
@@ -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<dim># 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<dim>    &dof,
                                    const FiniteElement<dim> &fe,

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