On Mon, Jan 9, 2012 at 10:31 AM, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:
> I have tested default GMRES+ILU(0) solver for problem of size ~200000 and > I observed that both convergence rate and accuracy degrade when I increase > number of processes. > E.g., number of iterations almost doubles when going from 1 to 4 > processors. > > I noticed that ILU(0) is somehow represented by sequential matrices > internally and feel that this might be a reason? > The default is Block Jacobi+ILU(0) and GMRES(30) which will definitely degrade as the number of processes is increased. You would need to use an optimal preconditioner like Multigrid if you want a constant number of iterates. Matt > Regards, > Alexander > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120109/1d556ad6/attachment-0001.htm>
