From: wolf Date: Wed, 24 Mar 2004 16:17:02 +0000 (+0000) Subject: Add some words to the documentation. X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f1253b9b479ff6815d911c6cb9788b1c26809ff0;p=dealii-svn.git Add some words to the documentation. git-svn-id: https://svn.dealii.org/trunk@8858 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/deal.II/include/dofs/dof_constraints.h b/deal.II/deal.II/include/dofs/dof_constraints.h index 6efc8fd2e4..6470d056b5 100644 --- a/deal.II/deal.II/include/dofs/dof_constraints.h +++ b/deal.II/deal.II/include/dofs/dof_constraints.h @@ -57,11 +57,17 @@ class BlockIndices; * degrees of freedom. When building the global system matrix and the right * hand sides, you normally build them without taking care of the constraints, * purely on a topological base, i.e. by a loop over cells. In order to do - * actual calculations, you have to 'condense' these matrices: eliminate - * constrained degrees of freedom and distribute the appropriate values to - * the unconstrained dofs. This changes the sparsity pattern of the sparse + * actual calculations, you have to 'condense' the linear system: eliminate + * constrained degrees of freedom and distribute the appropriate values to the + * unconstrained dofs. This changes the sparsity pattern of the sparse * matrices used in finite element calculations und is thus a quite expensive - * operation. + * operation. The general scheme of things is that you build your system, you + * eliminate (condense) away constrained nodes using the condense() functions + * of this class, then you solve the remaining system, and finally you compute + * the values of constrained nodes from the values of the unconstrained ones + * using the distribute() function. Note that the condense() function is + * applied to matrix and right hand side of the linear system, while the + * distribute() function is applied to the solution vector. * * Condensation is done in four steps: first the large matrix sparsity pattern * is created (e.g. using @ref{DoFHandler}@p{::create_sparsity_pattern}), then the