Hi W B 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. is it possible in dealii to deal with parallel upwinding as in step21 using workstream or some like that? Best F75 On Monday, 17 July 2017 04:45:11 UTC+2, Wolfgang Bangerth wrote: > > On 07/16/2017 11:11 AM, 'franck75' via deal.II User Group wrote: > > I am having that error message when I run in parallel with 2 processor > like this > > mpirun -n 2 ./darcyparl > > > > and when I run with one MPI process with mpirun -n 1 ./darcyparl I have > this > > error message > > > > An error occurred in line <474> of file > </home/franckm/darcyparl/darcyparl.cc> > > in function > > void Step43::LinearSolvers::InverseMatrix<Matrix, > > Preconditioner>::vmult(VectorType&, const VectorType&) const [with > VectorType > > = dealii::TrilinosWrappers::MPI::Vector; Matrix = > > dealii::TrilinosWrappers::SparseMatrix; Preconditioner = > > dealii::TrilinosWrappers::PreconditionIC] > > The violated condition was: > > false > > Additional information: > > > > -------------------------------------------------------- > > An error occurred in line <590> of file > > > </home/franckm/deal.ii-candi/deal.II-v8.5.0/include/deal.II/lac/solver_cg.h> > > > in function > > void dealii::SolverCG<VectorType>::solve(const MatrixType&, > VectorType&, > > const VectorType&, const PreconditionerType&) [with MatrixType = > > dealii::TrilinosWrappers::SparseMatrix; PreconditionerType = > > dealii::TrilinosWrappers::PreconditionIC; VectorType = > > dealii::TrilinosWrappers::MPI::Vector] > > The violated condition was: > > false > > Additional information: > > Iterative method reported convergence failure in step 81. The residual > in the > > last step was 49.0941. > > This error message can indicate that you have simply not allowed a > > sufficiently large number of iterations for your iterative solver to > converge. > > > > how large should be the number of iterations for it to converge? > > linear solver being the same as in step-43 > > That depends on the size of your problem. I suspect that the problem > you're > trying to solve has only 81 unknowns. In that case, your solver should > converge in fewer than 81 iterations, and if it doesn't, then your matrix > is > likely either nor symmetric or not positive definite. > > It also depends on the tolerance you require. If, for example, the entries > of > your matrix and rhs vector are very large, then you ought to use a > tolerance > that is only small *relative to these entries*. If it is small in absolute > terms, then you may not reach convergence. > > Best > W. > > -- > ------------------------------------------------------------------------ > Wolfgang Bangerth email: [email protected] > <javascript:> > www: http://www.math.colostate.edu/~bangerth/ > > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
step43parl.tar.gz
Description: Binary data
