[petsc-dev] horrid bug

[Dmitry Karpeev]

The problem is most likely in the creation routine or, rather, in the
arguments passed into it:
is it possible that the Vecs fed into VecScatterCreate have different block
sizes on different procs?

Dmitry.

On Fri, May 18, 2012 at 7:20 AM, Mark F. Adams <mark.adams at columbia.edu>wrote:

> I've got a bug with block sizes in multigrid that is getting harry and
> wanted to see if I could get some help.
>
> The crux of the problem seems to be that different versions of
> VecScatterEnd are being called.  I've added a print statement in:
>
> PetscErrorCode PETSCMAP1(VecScatterEnd)(VecScatter ctx,Vec xin,Vec
> yin,InsertMode addv,ScatterMode mode)
>
> in vpscat.h. and with a two processor run see this:
>
> *****[0]VecScatterEnd_3 start, N=27 Xin.bs=3 yin.bs=1
> *****[1]VecScatterEnd_3 start, N=27 Xin.bs=3 yin.bs=1
> *****[0]VecScatterEnd_2 start, N=27 Xin.bs=3 yin.bs=1
> *****[1]VecScatterEnd_1 start, N=27 Xin.bs=3 yin.bs=1
> [1]PETSC ERROR: VecScatterEnd_1() line 217 in
> /Users/markadams/Codes/petsc-dev/include/../src/vec/vec/utils/vpscat.h
> [1]PETSC ERROR: VecScatterEnd() line 1620 in
> /Users/markadams/Codes/petsc-dev/src/vec/vec/utils/vscat.c
> [1]PETSC ERROR: MatMultAdd_MPIAIJ() line 1118 in
> /Users/markadams/Codes/petsc-dev/src/mat/impls/aij/mpi/mpiaij.c
> [1]PETSC ERROR: MatMultAdd() line 2372 in
> /Users/markadams/Codes/petsc-dev/src/mat/interface/matrix.c
> [1]PETSC ERROR: MatInterpolateAdd() line 7439 in
> /Users/markadams/Codes/petsc-dev/src/mat/interface/matrix.c
> [1]PETSC ERROR: PCMGMCycle_Private() line 52 in
> /Users/markadams/Codes/petsc-dev/src/ksp/pc/impls/mg/mg.c
>
>
> This is a two level solve and the coarse grid is all on proc 0 and has a
> block size of 3. The fine grid has a block size of 2.  THis error, as you
> can see, comes from the interpolation from coarse to fine.  You can see
> from this output that the code called VecScatterEnd_3 successfully (the
> coarse grid) but when it does the interpolation proc 0 calls
> VecScatterEnd_2 (the destination is block size 2) and proc 1 calls
> VecScatterEnd_1 -- clearly wrong.
>
> Anyway, I'll keep digging, but any ideas would be welcome.
>
> Mark
>
>
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