[petsc-users] how to output components of a section

[Matthew Knepley]

On Mon, Nov 7, 2016 at 4:17 AM, Sander Arens <Sander.Arens at ugent.be> wrote:

> Ok, I see what happened.
> If you create a a vector with DMGetGlobalVector, the VecView function is
> overloaded with some DM-specific VecView function (e.g. VecView_Plex), but
> this doesn't happen with the vec that you get from VecGetSubVector. So one
> way to solve this would be to create a global vector from your subdm and do
> the scatters yourself.
> But I think it would be better if these VecView operations could be copied
> from the original vec in VecGetSubVector?
>

You are right. I am moving this to petsc-dev temporarily for discussion.

  Thanks,

    Matt


> Thanks,
> Sander
>
> On 7 November 2016 at 09:08, leejearl <leejearl at 126.com> wrote:
>
>> Hi Sander:
>>     Thank your for your assistance, but it is still not works. The code
>> is now as follows:
>>         Vec subX, X;
>>         DM subdm;
>>         IS subIS;
>>         PetscInt numSubFields = 2;
>>         PetscInt subFields[2];
>>         subFields[0] = 0; subFields[1] =1 ;
>>         ierr = DMCreateSubDM(dm, numSubFields, subFields, &subIS,
>> &subdm);CHKERRQ(ierr);
>>         ierr = DMGetGlobalVector(dm, &X);CHKERRQ(ierr);
>>         ierr = VecGetSubVector(X,subIS,&subX);CHKERRQ(ierr);
>>         ierr = VecSetDM(subX, dm);CHKERRQ(ierr);
>>
>>>         ierr = PetscObjectSetName((PetscObject) subX,
>>> "sol.");CHKERRQ(ierr);
>>>         ierr = PetscViewerSetType(*viewer, PETSCVIEWERVTK);CHKERRQ(ierr);
>>>        ierr = PetscViewerPushFormat(*viewer,
>>> PETSC_VIEWER_VTK_VTU);CHKERRQ(ierr);
>>>         ierr = PetscViewerFileSetName(*viewer,
>>> "subsol.vtu");CHKERRQ(ierr);
>>>         ierr = VecView(subX, viewer);CHKERRQ(ierr);
>>>         ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
>>>         ierr = VecRestoreSubVector(X, subIS, &subX);CHKERRQ(ierr);
>>>         DMDestroy(&subdm);
>>>         ierr = DMRestoreGlobalVector(dm, &X);CHKERRQ(ierr);
>>>
>>
>>
>> I have add "VecSetDm", but it has not output file.
>>
>> Thanks
>> leejearl
>>
>> On 2016年11月07日 15:35, Sander Arens wrote:
>>
>> Does it work if you put
>> ierr = VecSetDM(subX, subdm);CHKERRQ(ierr);
>> before the VecView?
>>
>> Thanks,
>> Sander
>>
>> On 7 November 2016 at 03:50, leejearl <leejearl at 126.com> wrote:
>>
>>> Hi, Barry:
>>>     I must have some make some mistakes. I post the code as follows:
>>>         Vec subX, X;
>>>         DM subdm;
>>>         IS subIS;
>>>         PetscInt numSubFields = 2;
>>>         PetscInt subFields[2];
>>>         subFields[0] = 0; subFields[1] =1 ;
>>>         ierr = DMCreateSubDM(dm, numSubFields, subFields, &subIS,
>>> &subdm);CHKERRQ(ierr);
>>>         ierr = DMGetGlobalVector(dm, &X);CHKERRQ(ierr);
>>>         ierr = VecGetSubVector(X,subIS,&subX);CHKERRQ(ierr);
>>>         ierr = PetscObjectSetName((PetscObject) subX,
>>> "sol.");CHKERRQ(ierr);
>>>         ierr = PetscViewerSetType(*viewer, PETSCVIEWERVTK);CHKERRQ(ierr);
>>>        ierr = PetscViewerPushFormat(*viewer,
>>> PETSC_VIEWER_VTK_VTU);CHKERRQ(ierr);
>>>         ierr = PetscViewerFileSetName(*viewer,
>>> "subsol.vtu");CHKERRQ(ierr);
>>>         ierr = VecView(subX, viewer);CHKERRQ(ierr);
>>>         ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
>>>         ierr = VecRestoreSubVector(X, subIS, &subX);CHKERRQ(ierr);
>>>         DMDestroy(&subdm);
>>>         ierr = DMRestoreGlobalVector(dm, &X);CHKERRQ(ierr);
>>>
>>> There are three fields in dm, and I want to obtain the vector of the two
>>> of them. But, I can not
>>> get the output file “subsol.vtu”. Can you help me with the code?
>>>
>>> Thanks
>>> leejearl
>>>
>>> On 2016年11月06日 12:21, Barry Smith wrote:
>>>
>>>> On Nov 5, 2016, at 8:36 PM, leejearl <leejearl at 126.com> wrote:
>>>>>
>>>>> Hi Sander:
>>>>>      Thank you for your advices, and it works. But it is only
>>>>> available in th local vector.
>>>>>
>>>>    This should work on the global vector. Please send the full output
>>>> of the error messages when used with a global vector.
>>>>
>>>>     Barry
>>>>
>>>> Is there any methods to reach this purposes in the global vector?
>>>>>      Thanks
>>>>> leejearl
>>>>> On 2016年11月05日 19:29, Sander Arens wrote:
>>>>>
>>>>>> You can first obtain an IS with
>>>>>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/
>>>>>> DM/DMCreateSubDM.html
>>>>>> and with that you can obtain a subvector with
>>>>>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/
>>>>>> Vec/VecGetSubVector.html
>>>>>> which you can then view the usual way.
>>>>>>
>>>>>> Thanks,
>>>>>> Sander
>>>>>>
>>>>>> On 5 November 2016 at 12:17, leejearl <leejearl at 126.com> wrote:
>>>>>> Hi, all:
>>>>>>
>>>>>>      I meet a problems which I can not overcome. The programe is like
>>>>>> the code in
>>>>>>
>>>>>> "http://www.mcs.anl.gov/petsc/petsc-current/src/dm/impls/ple
>>>>>> x/examples/tutorials/ex1.c.html".
>>>>>>
>>>>>>     The code create a section which has three fields: u,v,w. How can
>>>>>> I output the fields u and v without together with w?
>>>>>>
>>>>>>     Thanks!
>>>>>>
>>>>>>
>>>>>> leejearl
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>
>>>
>>
>>
>


-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20161107/f53fd9dc/attachment.html>