Franck,
Thank you for your reply. I have tried what you suggested still the problem
persists.
It is exactly the same linear solver as in step43 which I plan to write the
parallel. I have not write every thing but just the darcy part in it simple
way that.
I attach the file in case you want to have a look and a possible suggestion.
You are asking for too much -- we cannot debug your code for you.
If your solver does not converge, there are two possibilities: (i) The solver
or preconditioner you have can not be applied to the matrix you have (for
example, if you try to solve a non-symmetric system with CG). You can test
this by trying SparseDirectUMFPACK on the matrix and see whether that gives
you the correct solution. If UMFPACK gives you a correct solution but your
iterative solver does not, then the problem is with the iterative solver.
(ii) The matrix is not invertible. In that case, UMFPACK will either fail, or
will give you a nonsensical solution as you refine the mesh. In that case, the
problem is with the way you assemble the system, or with your formulation.
Which of these is the problem for you I don't know. You'll have to debug this
yourself.
> is it possible in dealii to deal with parallel upwinding as in step21 using
> workstream or some like that?
One step at a time. Get your solver to work on a simple, small mesh,
single-processor problem first before you try to solve something in parallel.
Best
W.
--
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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