[petsc-users] PetscSplitOwnerShip()

[Matthew Knepley]

If you do your own partitioning, you need to use VecLoadIntoVector() with a
Vec you get from the DA.

   Matt

On Tue, Mar 9, 2010 at 5:16 PM, (Rebecca) Xuefei YUAN
<xy2102 at columbia.edu>wrote:

> Hi,
>
> I ran np=4 for a small (-da_grid_x 6, -da_grid_y 5) problem, with
> PETSC_STENCIL_BOX and width=2, dof = 4.
>
> When I use vecLoad() to load the binary file with the following set:
>
>    PetscViewerBinaryOpen(PETSC_COMM_WORLD,fileName,FILE_MODE_READ,&viewer);
>    VecLoad(viewer,PETSC_NULL,&FIELD);
>    ierr = DAVecGetArray(da2_4,FIELD,&field);CHKERRQ(ierr);
>
>    ierr = DAVecRestoreArray(da2_4,FIELD,&field);CHKERRQ(ierr);
>    ierr = VecDestroy(FIELD);CHKERRQ(ierr);
>    ierr = DADestroy(da2_4);CHKERRQ(ierr);
>    ierr = PetscViewerDestroy(viewer);CHKERRQ(ierr);
>
> However, I got the error messages as below:
>
> [0]PETSC ERROR: DAVecGetArray() line 53 in src/dm/da/src/dagetarray.c
> Vector local size 32 is not compatible with DA local sizes 36 100
>
> [1]PETSC ERROR: DAVecGetArray() line 53 in src/dm/da/src/dagetarray.c
> Vector local size 32 is not compatible with DA local sizes 36 100
>
> [2]PETSC ERROR: DAVecGetArray() line 53 in src/dm/da/src/dagetarray.c
> Vector local size 28 is not compatible with DA local sizes 24 80
>
> [3]PETSC ERROR: DAVecGetArray() line 53 in src/dm/da/src/dagetarray.c
> Vector local size 28 is not compatible with DA local sizes 24 80
>
> Then I tracked down and tried to find how this 32,32,28,28 coming from.
>
> It turns out that my da2_4 has the parameters at each processor:
>
>
>      xs xe ys ye x y Xs Xe Ys Ye Nl base nlocal Nlocal
> p0:   0  12 0  3 12 3 0  20 0  5  100 0   100    36
> p1:   12 24 0  3 12 3 4  24 0  5  100 36  100    36
> p2:   0  12 3  5 12 2 0  20 1  5  80  72   80    24
> p3:   12 24 3  5 12 2 4  24 1  5  80  96   80    24
>
> and deep in
>
> #0  PetscSplitOwnership (comm=-2080374782, n=0x8a061b4, N=0x8a061b8)
>    at psplit.c:81
> #1  0x08628384 in PetscLayoutSetUp (map=0x8a061b0) at pmap.c:140
> #2  0x08618320 in VecCreate_MPI_Private (v=0x8a05c50, alloc=PETSC_TRUE,
>    nghost=0, array=0x0) at pbvec.c:182
> #3  0x08618ba7 in VecCreate_MPI (vv=0x8a05c50) at pbvec.c:232
> #4  0x085f1554 in VecSetType (vec=0x8a05c50, method=0x885dd0b "mpi")
>    at vecreg.c:54
> #5  0x085ec4f0 in VecSetTypeFromOptions_Private (vec=0x8a05c50)
>    at vector.c:1335
> #6  0x085ec909 in VecSetFromOptions (vec=0x8a05c50) at vector.c:1370
> #7  0x085d7a7e in VecLoad_Binary (viewer=0x89f70b0, itype=0x885ce3d "mpi",
>    newvec=0xbfe148e4) at vecio.c:228
> #8  0x085d70e4 in VecLoad (viewer=0x89f70b0, outtype=0x885ce3d "mpi",
>    newvec=0xbfe148e4) at vecio.c:134
> #9  0x0804f140 in FormInitialGuess_physical (dmmg=0x89a2880, X=0x89b34f0)
>    at vecviewload_out.c:390
> #10 0x08052ced in DMMGSolve (dmmg=0x89a2720) at damg.c:307
> #11 0x0804d479 in main (argc=-1, argv=0xbfe14cd4) at vecviewload_out.c:186
>
> it says that
>
>      *n = *N/size + ((*N % size) > rank);
>
> where *N = 30; size = 4; rank = 0,1,2,3, in such a case, this gives me
>
> *n = 32,32,28,28 for pro0,1,2,3, separately.
>
> Where could be wrong with this mismatch of the local vector size and da
> local size(excluding ghost pts or including ghost pts)?
>
> Thanks so much!
>
> Rebecca
>
>


-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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