[petsc-users] petscviewerbinaryread

[Matthew Knepley]

On Mon, Jun 17, 2013 at 2:47 PM, Frederik Treue <frtr at fysik.dtu.dk> wrote:

> OK, so I got a little further: Now I can read 1D fields on any amount of
> processors, and 2D fields on 1 processor :). My code:
>

What are you trying to do? Why not just use VecView() and VecLoad(), which
work in parallel, and are scalable. I doubt you want to reproduce that code.

   Matt


> MPI_Comm_size(PETSC_COMM_WORLD,&cs);
> MPI_Comm_rank(MPI_COMM_WORLD,&rank);
>
> ierr = VecGetArray(dummy,&dump); CHKERRQ(ierr);
> ierr = VecGetArray(ReRead,&readarray); CHKERRQ(ierr);
>
> ierr=PetscViewerBinaryOpen(PETSC_COMM_WORLD,"./testvector",FILE_MODE_READ,&fileview);CHKERRQ(ierr);
>
> for (i=0;i<rank;i++) {
> printf("Rank BEFORE: %d\n",rank);
>
> ierr=PetscViewerBinaryRead(fileview,(void*)dump,nx*ny/cs,PETSC_SCALAR);CHKERRQ(ierr);
> }
>
>
> ierr=PetscViewerBinaryRead(fileview,(void*)readarray,nx*ny/cs,PETSC_SCALAR);CHKERRQ(ierr);
>
> for (i=rank+1;i<cs;i++) {
> printf("Rank: AFTER: %d\n",rank);
>
> ierr=PetscViewerBinaryRead(fileview,(void*)dump,nx*ny/cs,PETSC_SCALAR);CHKERRQ(ierr);
> }
>
> However, this fails for 2D with more than one processor: The resulting
> vector is garbled and I get memory corruption. Am I on the right track,
> or is there another way to achieve an MPI version of binary read? The
> above code seems somewhat cumbersome...
>
> /Frederik Treue
>
> On Mon, 2013-06-17 at 11:06 +0200, Matthew Knepley wrote:
> > On Mon, Jun 17, 2013 at 10:59 AM, Frederik Treue <frtr at fysik.dtu.dk>
> > wrote:
> >         Hi guys,
> >
> >         is petscviewerbinaryread working? The examples given at the
> >         webpage
> >         either fails with out of memory error issues (ex65 and ex65dm)
> >         or
> >         doesn't compile (ex61) for me?
> >
> >         Oddly I have problems only when trying to use mpi. My code:
> >
> >
> ierr=DMDACreate1d(PETSC_COMM_WORLD,DMDA_BOUNDARY_GHOSTED,156,1,1,PETSC_NULL,&da);CHKERRQ(ierr);
> >
> >         ierr=DMCreateGlobalVector(da,&ReRead);CHKERRQ(ierr);
> >
> >         ierr=VecAssemblyBegin(ReRead);CHKERRQ(ierr);
> >         ierr=VecAssemblyEnd(ReRead);CHKERRQ(ierr);
> >
> >         double *workarray=(double*)malloc(156*sizeof(double));
> >
> >         ierr = VecGetArray(ReRead,&workarray); CHKERRQ(ierr);
> >
> >
> > 1) This does not make sense. You allocate an array, but then overwrite
> > that
> > array with the one inside the vector ReRead.
> >
> >
> ierr=PetscViewerBinaryOpen(PETSC_COMM_WORLD,"./testvector",FILE_MODE_READ,&fileview);CHKERRQ(ierr);
> >
> >
> ierr=PetscViewerBinaryRead(fileview,&dummy,1,PETSC_SCALAR);CHKERRQ(ierr);
> >
> >
> ierr=PetscViewerBinaryRead(fileview,(void*)workarray,156,PETSC_SCALAR);CHKERRQ(ierr);
> >         printf("TEST: %g\n",workarray[144]);
> >         ierr=VecRestoreArray(ReRead,&workarray);
> >
> >
> > 2) In parallel, the local array in your vector ReRead will be smaller
> > than the global size 156. Thus this read also
> >     does not makes sense.
> >
> >
> >    Matt
> >
> >         VecView(ReRead,PETSC_VIEWER_DRAW_WORLD);
> >
> >         This works fine as long as I'm on a single processor. The file
> >         read also
> >         works on mpi with 2 processors, as evidenced by the result of
> >         the printf
> >         statement (which gives the right result from both processors).
> >         However
> >         the VecView statement fails with "Vector not generated from a
> >         DMDA!".
> >         Why?
> >
> >         And second question: How do I generalize to 2d? Can I give a
> >         2d array to
> >         PetscViewerBinaryRead and expect it to work? And how should it
> >         be
> >         malloc'ed? Or does one give a 1d array to
> >         PetscViewerBinaryRead and let
> >         VecRestoreArray do the rest? Or what?
> >
> >         /Frederik Treue
> >
> >
> >
> >
> >
> > --
> > 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
>
>
>


-- 
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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