[petsc-users] Geometric multigrid with a cell-centered discretization

Tue Jan 9 09:37:33 CST 2018

On Tue, Jan 9, 2018 at 10:32 AM, Buesing, Henrik <
hbuesing at eonerc.rwth-aachen.de> wrote:

> [3]
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: Arguments are incompatible
> [0]PETSC ERROR: Ratio between levels: (mx - 1)/(Mx - 1) must be integer:
> mx 1536 Mx 768
>
>
>
> It looks like you give it the number of vertices, not cells, so +1 to your
> grid size.
>
>
> [Buesing, Henrik] Yes! But, I do not want that. I want to give the cells…
>
>
>
> That is the interface. You will get m-1 cells so give it m = num_cells + 1.
>
>
> [Buesing, Henrik] Ok, I can do that. But, does the space discretization
> matter for the coarsening and refining.
>

No. We are careful to separate topology from the numerics.

> With DMDA_Q0, I tell him it is cell-centered two-point flux approximation,
> right?
>

Not sure. You specific that you want one variable per cell someplace (not
edge or vertex), look at examples and/or documentation.

>
>
>
>
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html
> for trouble shooting.
> [0]PETSC ERROR: Petsc Development GIT revision: v3.8.2-48-g851ec02  GIT
> Date: 2017-12-05 09:52:17 -0600
> [0]PETSC ERROR: /rwthfs/rz/cluster/work/hb111949/EoCoE/aixcelerate17/
> gge_gnu/bench_run/000023/000000_copy_sub_launch/work/shem_fw64gnu_const.x
> on a gnu_openmpi named linuxbmc0008.rz.RWTH-Aachen.DE by hb111949 Tue
> Jan  9 16:04:39 2018
> [0]PETSC ERROR: Configure options --download-fblaslapack --with-cc=mpicc
> -with-fc=mpif90 --with-cxx=mpicxx --download-hypre --download-superlu_dist
> --download-suitesparse --download-scalapack --download-blacs
> --download-hdf5 --download-parmetis --download-metis --with-debugging=0
> --download-mumps
> [0]PETSC ERROR: #1 DMCreateInjection_DA_3D() line 1195 in
> /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/impls/da/dainterp.c
> [0]PETSC ERROR: #2 DMCreateInjection_DA() line 1283 in
> /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/impls/da/dainterp.c
> [0]PETSC ERROR: #3 DMCreateInjection() line 1082 in
> /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/interface/dm.c
> [0]PETSC ERROR: #4 DMCoarsen_DA() line 1219 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/dm/impls/da/da.c
> [0]PETSC ERROR: #5 DMCoarsen() line 2427 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/dm/interface/dm.c
> [0]PETSC ERROR: #6 PCSetUp_MG() line 618 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/ksp/pc/impls/mg/mg.c
> [0]PETSC ERROR: #7 PCSetUp() line 924 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: #8 KSPSetUp() line 381 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: #9 KSPSolve() line 612 in /rwthfs/rz/cluster/work/
> hb111949/Code/petsc/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: [1]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
>
>
> --
> Dipl.-Math. Henrik Büsing
> Institute for Applied Geophysics and Geothermal Energy
> E.ON Energy Research Center
> RWTH Aachen University
> ------------------------------------------------------
> Mathieustr. 10
> <https://maps.google.com/?q=Mathieustr.+10&entry=gmail&source=g>
>   |    Tel +49 (0)241 80 49907
> 52074 Aachen, Germany     |    Fax +49 (0)241 80 49889
> ------------------------------------------------------
> http://www.eonerc.rwth-aachen.de/GGE
> hbuesing at eonerc.rwth-aachen.de
> ------------------------------------------------------
>
> > -----Ursprüngliche Nachricht-----
> > Von: Smith, Barry F. [mailto:bsmith at mcs.anl.gov]
> > Gesendet: 09 January 2018 15:10
> > An: Buesing, Henrik <hbuesing at eonerc.rwth-aachen.de>
> > Cc: petsc-users <petsc-users at mcs.anl.gov>
> > Betreff: Re: [petsc-users] Geometric multigrid with a cell-centered
> > discretization
>
> >
> >
> >   With cell centered elements each element is sliced in half in each of
> > the three directions for refinement (or you can refine only in 1 or 2 of
> > the dimensions if you like). This means that the ratio of mx to MX needs
> > to be 2 (or 4).So your numbers are fine.
> >
> > > On Jan 9, 2018, at 7:59 AM, Buesing, Henrik <hbuesing at eonerc.rwth-
> <hbuesing at eonerc.rwth-%0b>> aachen.de> wrote:
> > >
> > > Dear all,
> > >
> > > I am using DMDACreate3d to generate my domain and a cell-centered
> > > two-point flux approximation as discretization. I use geometric
> > > Multigrid (-pc_type mg) with DMDASetInterpolationType(petsc_da,
> > > DMDA_Q0, petsc_ierr). With DM_BOUNDARY_GHOSTED as boundary type in
> > > DMDACreate3d, I get
> > >
> > > [0]PETSC ERROR: Arguments are incompatible [0]PETSC ERROR: Ratio
> > > between levels: (mx - 1)/(Mx - 1) must be integer: mx 1536 Mx 768
> >
> >   We need ALL the output from the error (always). It should never be
> > doing this check in your case so something is wrong with the order of
> > your code perhaps.
> >
> >    Barry
> >
> > >
> > > With DM_BOUNDARY_PERIODIC, I get invalid accesses when I assemble the
> > matrix.
> > >
> > > Can I somehow tell him, that I have a cell-centered grid, or do I have
> > to resort to using N+1 in my dimensions?
> > >
> > > Thank you!
> > > Henrik
> > >
> > >
> > > --
> > > Dipl.-Math. Henrik Büsing
> > > Institute for Applied Geophysics and Geothermal Energy E.ON Energy
> > > Research Center RWTH Aachen University
> > > ------------------------------------------------------
> > > Mathieustr. 10
> <https://maps.google.com/?q=Mathieustr.+10&entry=gmail&source=g>
>   |    Tel +49 (0)241 80 49907 <+49%20241%208049907>
> > > 52074 Aachen, Germany     |    Fax +49 (0)241 80 49889
> <+49%20241%208049889>
> > > ------------------------------------------------------
> > > http://www.eonerc.rwth-aachen.de/GGE
> > > hbuesing at eonerc.rwth-aachen.de
> > > ------------------------------------------------------
>
>
>
>
>
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