[petsc-users] Output question for ex29.

[Alan Wei]

ooops, sorry, here it is.
^_^

Alan

On Fri, Jun 10, 2011 at 3:09 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Jun 10, 2011 at 3:05 PM, <zhenglun.wei at gmail.com> wrote:
>
>> Dear Matt,
>> Following your suggestions, I modified the VecView_VTK in
>> /src/ksp/ksp/example/tutorial/ex29.c to
>>
>> PetscFunctionBegin;
>> PetscViewerASCIIOpen(comm, filename, &viewer);
>> PetscViewerSetFormat(viewer, PETSC_VIEWER_ASCII_MATLAB);
>>
>
> I told you to use ASCII_VTK, not ASCII_MATLAB.
>
>
>> DMView(x, viewer);
>> VecView(x, PETSC_VIEWER_STDOUT_WORLD);
>> PetscViewerDestroy(&viewer);
>> PetscFunctionReturn(0);
>>
>> However, I always give me some error. Could you please briefly check if
>> there is any obvious coding problem here.
>>
>
> How can I possibly know what went wrong if you do not send the ENTIRE error
> message.
>
>    Matt
>
>
>> thanks,
>> Alan
>>
>>
>> On , Matthew Knepley <knepley at gmail.com> wrote:
>> > On Thu, Jun 9, 2011 at 6:18 PM, Matthew Knepley knepley at gmail.com>
>> wrote:
>> >
>> > On Thu, Jun 9, 2011 at 6:01 PM, zhenglun.wei at gmail.com> wrote:
>> >
>> >
>> > Dear Sir/Madam,
>> > I'm still studying on the ex29 of /src/ksp/ksp/example/tutorial. Before
>> I met a problem on VecView_VTK in parallel computation. I'm trying to modify
>> it in order to output some data from the computation.
>> >
>> >
>> >
>> >
>> > Here is a better answer. If you want output, throw away this old
>> function which is broken, and use
>> >
>> >
>> >   PetscViewerASCIIOpen()
>> >   PetscViewerASCIISetFormat(PETSC_VIEWER_ASCII_VTK)
>> >
>> >   DMView()
>> >   VecView()
>> >   PetscViewerDestroy()
>> >
>> >
>> >     Thanks,
>> >
>> >
>> >        Matt
>> >
>> >
>> > 1) My first questions is that what does this section do in VecView_VTK:
>> >
>> > 272: MPI_Comm_rank(comm, &rank);
>> >
>> > 273: MPI_Comm_size(comm, &size);
>> > 274: MPI_Reduce(&n, &maxn, 1, MPIU_INT, MPI_MAX, 0, comm);
>> >
>> > 275: tag = ((PetscObject) viewer)->tag;
>> > 276: if (!rank) {
>> > 277: PetscMalloc((maxn+1) * sizeof(PetscScalar), &values);
>> > 278: for(i = 0; i 279: PetscViewerASCIIPrintf(viewer, "%G\n",
>> PetscRealPart(array[i]));
>> >
>> >
>> > 280: }
>> > 281: for(p = 1; p 282: MPI_Recv(values, (PetscMPIInt) n, MPIU_SCALAR, p,
>> tag, comm, &status);
>>
>> > 283: MPI_Get_count(&status, MPIU_SCALAR, &nn);
>> > 284: for(i = 0; i
>> >
>> > 285: PetscViewerASCIIPrintf(viewer, "%G\n", PetscRealPart(array[i]));
>> > 286: }
>> > 287: }
>> > 288: PetscFree(values);
>> > 289: } else {
>> > 290: MPI_Send(array, n, MPIU_SCALAR, 0, tag, comm);
>> >
>> >
>> > 291: }
>> >
>> > What I understand is: it gather all the data from different process in
>> parallel computation, and output it to the 'viewer'. I comment out
>> everything in VecView_VTK except this part, there is no error message coming
>> up in my parallel computation so far.
>> >
>> >
>> >
>> > 2) however, I really don't know how did it split the domain for parallel
>> computation. For example, if I use 4 processes, is the domain split like:
>> >
>> >
>> > The DMDA describes the domain splitting.
>> >
>> >
>> >
>> >
>> >    Matt
>> >
>> > a)
>> > |
>> > 0 | 1
>> > |
>> >
>> >
>> > ---------------|--------------
>> > |
>> > 2 | 3
>> > |
>> >
>> > b)
>> > |
>> > 0 | 2
>> > |
>> > ---------------|--------------
>> > |
>> >
>> >
>> > 1 | 3
>> > |
>> >
>> > c)
>> > | | | |
>> > | | | |
>> > 0 | | 2 | |
>> > | 1 | | 3 |
>> > | | | |
>> > | | | |
>> >
>> >
>> >
>> > d)
>> > 0
>> > ------------------------
>> > 1
>> > ------------------------
>> > 2
>> > ------------------------
>> > 3
>> >
>> > thanks in advance,
>> > Alan
>> >
>> >
>> >
>> >
>> > --
>> > 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
>> >
>>
>
>
>
> --
> 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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