[petsc-users] AMG for block matrices

[Barry Smith]

  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 at 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.