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
