On Wed, Feb 1, 2012 at 04:47, gouarin <loic.gouarin at math.u-psud.fr> wrote:
> Hi, > > I sent some email on Stokes solver using DMComposite grid (one for the > velocity and an other one for the pressure). > > Now, I try to use PCMG to precondition the velocity part with fieldsplit > and PETSc command line options only. > > This is an example of my options: > > ./test -stokes_ksp_type fgmres > -stokes_pc_type fieldsplit > -stokes_fieldsplit_0_ksp_type preonly > -stokes_fieldsplit_0_pc_type mg > -stokes_fieldsplit_0_pc_mg_**levels 2 > -stokes_fieldsplit_0_pc_mg_**galerkin > ... > -stokes_fieldsplit_1_ksp_type preonly > -stokes_fieldsplit_1_pc_type jacobi > > It doesn't work because we need to call PCFieldSplitGetSubKSP to get the > subpc[0] to create the interpolation matrices. So, we have to call > KSPSetUp before PCFieldSplitGetSubKSP. But, if we call KSPSetUp, we have an > error because the interpolation matrices are not created ! > The interpolation matrices for PCMG? Those should be constructed by the DM. It looks from your code like you have a DMComposite, in which case you shouldn't have to do anything special. Try "make runex28_4". (It's broken with a change that went into petsc-dev a few days ago. I'll be able to push the fix whenever I find a wireless network in this airport that doesn't block ssh.) > > But If I do: > > ------ > PCSetDM(pc, dom->get_pack()); > PCSetType(pc, PCFIELDSPLIT); > KSPSetUp(solver); > PCFieldSplitGetSubKSP(pc, &nsplits, &subksp); > PetscMalloc(sizeof(PC)***nsplits, &subpc); > > KSPSetType(subksp[0], KSPPREONLY); > KSPGetPC(subksp[0], &subpc[0]); > PCSetType(subpc[0], PCMG); > > create the interpolation matrices > > KSPSetFromOptions(solver); > ------ > > It works but we can't set the mg_levels with the command line options > anymore. Moreover, I have some warning of this type: > > Option left: name:-stokes_fieldsplit_0_pc_**mg_multiplicative_cycles > value: 3 > > Is there a way to do that only with the command line option ? > > Thanks, > Loic > > -- > Loic Gouarin > Laboratoire de Math?matiques > Universit? Paris-Sud > B?timent 425 > 91405 Orsay Cedex > France > Tel: (+33) 1 69 15 60 14 > Fax: (+33) 1 69 15 67 18 > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120201/94839de6/attachment.htm>
