From: Michael Povolotskyi <povolotskyi@in...>  20050217 18:00:40

Hello, the situation gets clearer. I have just checked the matrix. It turnes that: a) if I don't call dof_map.constrain_element_matrix_and_vector(), then the matrix comes out as I intend; b) if I call dof_map.constrain_element_matrix_and_vector(), then the corresponding raw has additional elements. In case a) the boundary nodes are okay, but the solution is discontinuous. In case b) the solution is continuous, but the boundary conditions are disturbed. The question is: is it possible somehow to have both continuous solution and apply boundary conditions in our way (not with a penalty method)? Thank you for your help, Michael. Roy Stogner wrote: > On Thu, 17 Feb 2005, Michael Povolotskyi wrote: > >> we set boundary condition in such a way that a row in the matrix that >> correspond to >> the boundary node i looks like this: >> >> 0 .... 0 1 0 .... 0, >> >> where 1 stands at the ith position. >> >> We apply the boundary condition while assembling the matrix. >> Not all the Dirichlet boundary points are wrong  just a few. >> And not always the same. > > > Have you checked the assembled system matrix, to make sure those rows > came out the way you intended? Have you checked the solution vector, > to make sure the Dirichlet node errors are there and not just another > GMVrelated glitch? Are you sure the nodes end up exactly right with > uniform refinement? >  > Roy Stogner >   Michael Povolotskyi, Ph.D. University of Rome "Tor Vergata" Department of Electronic Engineering Viale Politecnico, 1  00133 Rome  Italy Phone + 39 06 72597367 Fax + 39 06 2020519 http://www.optolab.uniroma2.it/pages/moshe/moshe.html  