From: wolf Date: Mon, 15 Mar 2004 23:45:29 +0000 (+0000) Subject: Extend the docs a little more. X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74f52ae6bf132c169c73d330bc21d7e9efb161cc;p=dealii-svn.git Extend the docs a little more. git-svn-id: https://svn.dealii.org/trunk@8760 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/lac/include/lac/sparsity_pattern.h b/deal.II/lac/include/lac/sparsity_pattern.h index 7e3d751e97..5c530be0d3 100644 --- a/deal.II/lac/include/lac/sparsity_pattern.h +++ b/deal.II/lac/include/lac/sparsity_pattern.h @@ -742,23 +742,35 @@ class SparsityPattern : public Subscriptor * uses special convention for * quadratic matrices. * - * A return value true - * means that diagonal elements - * are stored first in each - * row. This is required by - * relaxation methods like - * Jacobi() and SOR(). A side - * effect of this scheme is that - * each row contains at least one - * element. + * A return value true means + * that diagonal elements are stored + * first in each row. A number of + * functions in this class and the + * library in general, for example + * relaxation methods like Jacobi() and + * SOR(), require this to make their + * operations more efficient, since they + * need to quickly access the diagonal + * elements and do not have to search for + * them if they are the first element of + * each row. A side effect of this scheme + * is that each row contains at least one + * element, even if the row is empty + * (i.e. the diagonal element exists, but + * has value zero). * - * A return value false - * means that diagonal elements - * are stored anywhere in the - * row. In particular, a row or - * even the whole matrix may be - * empty. - */ + * A return value false means + * that diagonal elements are stored + * anywhere in the row, or not at all. In + * particular, a row or even the whole + * matrix may be empty. This can be used + * if you have block matrices where the + * off-diagonal blocks are quadratic but + * are never used for operations like the + * ones mentioned above. In this case, + * some memory can be saved by not using + * the diagonal storage optimization. + */ bool optimize_diagonal () const; /**