> On May 7, 2018, at 3:25 PM, Xiangdong <[email protected]> wrote:
>
> Hello everyone,
>
> I have a 2D DMDA with Nx=6 and Ny=4. If I set refine_x=3 and refine_y=2, I
> can get a coarse DMDA by DMCoarsen(). However, when I tried to call the
> DMCreateRestriction between these two DMDAs, I got error about " No support
> for this operation for this object type. DMCreateRestriction not implemented
> for this type."
>
> Can you help me get around this?
Us DMCreateInterpolation() and then use MatMultTranspose() for example to
apply the restriction.
>
> Another simple question, where can I find the explanation/meaning of DMDA_Q0
> and DMDA_Q1?
This is finite element terminology, Q0 means piecewise constant basis
functions (and hence piecewise constant interpolation) while Q1 means linear
interpolation.
For Q0 you should think of the unknowns as living on the centers of each
element while for Q1 the unknowns live on the vertices of the elements.
Barry
>
> Below is my test example.
>
> Thank you.
>
> Best,
> Xiangdong
>
> #include <petsc.h>
>
> int main(int argc, char **argv)
> {
> PetscErrorCode ierr;
>
> PetscInitialize(&argc, &argv, PETSC_NULL, PETSC_NULL);
>
> int Nx=6, Ny=4, Nz=1;
>
> DM da;
>
> ierr = DMDACreate2d(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,DM_BOUNDARY_NONE,
> DMDA_STENCIL_STAR,Nx,Ny,PETSC_DECIDE,
> PETSC_DECIDE,1,1,NULL,NULL,&da);CHKERRQ(ierr);
>
> int refine_x=3, refine_y=2, refine_z=1;
> ierr = DMDASetRefinementFactor(da,refine_x,refine_y,refine_z);
>
> ierr = DMDASetInterpolationType(da,DMDA_Q0);
>
> ierr = DMSetFromOptions(da); CHKERRQ(ierr);
> ierr = DMSetUp(da); CHKERRQ(ierr);
>
> DM dac;
> ierr = DMCoarsen(da,NULL,&dac);
>
> Mat M;
> Vec V;
>
> ierr = DMCreateRestriction(dac,da,&M);
>
> MatView(M,PETSC_VIEWER_STDOUT_WORLD);
>
>
> ierr = PetscFinalize(); CHKERRQ(ierr);
> PetscFunctionReturn(0);
> }
>
