Generally you do want to use FieldSplit but Vanka might work. I'm not sure what to use as the smoother KSP. -mg_levels_ksp_type [gmres | richardson]. If you use richardson you will probably want to fiddle with the damping.
On Tue, Sep 22, 2020 at 11:23 PM Barry Smith <bsm...@petsc.dev> wrote: > > Raju, > > If you call MatSetBlockSize(mat,4) then GAMG will keep the 4 variables > together through all the levels. > > You might consider using the point block Jacobi smoother with it > instead of the default Jacobi smoother -mg_levels_pc_type pbjacobi > > There is also PCPATCH which supports Vanka smoothing (though it is to > well hidden) PCPatchSetConstructType(pc,PC_PATCH_VANKA) > -pc_patch_construct_type vanka > > > For coupled Navier stokes you might also consider using PCFIELDSPLIT > and GAMG just for the pressure solve inside it. > > Barry > > > On Sep 22, 2020, at 9:24 PM, Raju Mandhapati via petsc-users < > petsc-users@mcs.anl.gov> wrote: > > > > Hello, > > > > Does Petsc have an option to solve block matrices using AMG > solver/preconditioner. My block matrix is coming from solving u,v,w,p > (coupled Navier stokes) at each cell. > > > > thanks > > Raju. > >
