From: Wolfgang Bangerth Date: Wed, 6 Jun 2012 21:22:38 +0000 (+0000) Subject: Add one more paragraph as suggested by Joerg. X-Git-Tag: v8.0.0~2521 X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=05dd50d2e79b15bf903f6d28d9c12496eeb99055;p=dealii.git Add one more paragraph as suggested by Joerg. git-svn-id: https://svn.dealii.org/trunk@25609 0785d39b-7218-0410-832d-ea1e28bc413d --- diff --git a/deal.II/doc/doxygen/headers/constraints.h b/deal.II/doc/doxygen/headers/constraints.h index b4493e1564..9a74e6f85c 100644 --- a/deal.II/doc/doxygen/headers/constraints.h +++ b/deal.II/doc/doxygen/headers/constraints.h @@ -302,7 +302,7 @@ * First approach: * - Apply the ConstraintMatrix::distribute_local_to_global() function to the * system matrix and the right-hand-side with the parameter - * use_inhomogeneities_for_rhs = false (default) + * use_inhomogeneities_for_rhs = false (i.e., the default) * - Set the solution to zero in the inhomogeneous constrained components * using the ConstraintMatrix::set_zero() function (or start with a solution * vector equal to zero) @@ -382,6 +382,15 @@ * ConstraintMatrix::distribute() before solving the linear system * (and then, as necessary, a second time after solving). * + * In addition to these considerations, consider the case where we have + * inhomogeneous constraints of the kind $x_{3}=\tfrac 12 x_1 + \tfrac 12$, + * e.g., from a hanging node constraint of the form $x_{3}=\tfrac 12 (x_1 + + * x_2)$ where $x_2$ is itself constrained by boundary values to $x_2=1$. + * In this case, the ConstraintMatrix can of course not figure out what + * the final value of $x_3$ should be and, consequently, can not set the + * solution vector's third component correctly. Thus, the second approach will + * not work and you should take the first. + * * *

Dealing with conflicting constraints

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