Martin, the problem statement should be OK, because I chose the problem from step-11 (f=-2, g=1). But I found the solution by myself. I have to choose finite elements of order 1, then it runs well. At the moment I don't know why, but I will figure out.
Thank you for your help, Markus On Fri March 20 2009 7:02 pm, Martin Kronbichler wrote: > Markus, > > I tried your program and could not easily resolve the convergence > problem. I even tested step-11 with distribute_local_to_global instead > of the condense function on the matrix, and there everything works fine > (with Neumann conditions all over the boundary), so I don't think the > problem is due to the ConstraintMatrix::distribute_local_to_global > function itself. I'd guess that something else (something with the > problem statement) makes the system matrix and RHS incompatible and > destroys the convergence of the iterative solver (not even BiCGStab > converges on your system), like e.g. that the Neumann boundary function > and the right hand side function do not satisfy the condition stated in > the tutorial step-11 introduction. Do you think anything like that > could cause the error (or some other incompatibility)? Or has anyone > else an idea? > > Best regards, > Martin _______________________________________________ dealii mailing list http://poisson.dealii.org/mailman/listinfo/dealii
