* 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
* $a_{ij} = \int_\Omega a(x) \nabla\phi_i(x) \nabla\phi_j(x) dx$,
* 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.
* 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.
* 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,