From: Guido Kanschat Date: Mon, 27 Aug 2012 14:44:44 +0000 (+0000) Subject: clarift form of lines X-Git-Tag: v8.0.0~2234 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e450e3829718484081f27507bf4c719281005d1c;p=dealii.git clarift form of lines git-svn-id: https://svn.dealii.org/trunk@26131 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/include/deal.II/lac/constraint_matrix.h b/deal.II/include/deal.II/lac/constraint_matrix.h index f857a5aaf6..446aebe8b9 100644 --- a/deal.II/include/deal.II/lac/constraint_matrix.h +++ b/deal.II/include/deal.II/lac/constraint_matrix.h @@ -82,9 +82,23 @@ namespace internals *

Description of constraints

* * Each "line" in objects of this class corresponds to one constrained degree - * of freedom, with the number of the line being i, and the entries in - * this line being pairs - * (ji,aiji). + * of freedom, with the number of the line being i, entered by + * using add_line() or add_lines(). The entries in + * this line are pairs of the form + * (j,aij), which are added by add_entry() or + * add_entries(). The organization is essentially a + * SparsityPattern, but with only a few lines containing nonzero + * elements, and therefore no data wasted on the others. For each + * line, which has been added by the mechanism above, an elimination + * of the constrained degree of freedom of the form + * @f[ + * x_i = \sum_j a_{ij} x_j + b_i + * @f] + * is performed, where bi is optional and set by + * set_inhomogeneity(). Thus, if a constraint is formulated for + * instance as a zero mean value of several degrees of freedom, one of + * the degrees has to be chosen to be eliminated. + * * Note that the constraints are linear * in the xi, and that there might be a constant (non-homogeneous) term in * the constraint. This is exactly the form we need for hanging node