[petsc-users] petscviewerduplicate?

[Barry Smith]

  Why not just use one file, if Matlab is going to read them, it saves you typing both when saving the matrices and when reading them in Matlab?

  If the matrices are not tiny you likely also want to use the binary viewer, it will be much faster and work in parallel.

   Barry

On Mar 20, 2013, at 1:28 PM, Nachiket Gokhale <gokhalen at gmail.com> wrote:

> I have this in my code:
> 
> ierr = PetscViewerCreate(PETSC_COMM_WORLD,&RightViewer);CHKERRQ(ierr);
> ierr = PetscViewerSetType(RightViewer,PETSCVIEWERASCII);CHKERRQ(ierr);
> ierr = PetscViewerFileSetMode(RightViewer,FILE_MODE_WRITE);CHKERRQ(ierr);
> ierr = PetscViewerSetFormat(RightViewer,PETSC_VIEWER_ASCII_MATLAB);CHKERRQ(ierr);
> 	
> ierr = PetscViewerCreate(PETSC_COMM_WORLD,&LeftViewer);CHKERRQ(ierr);
> ierr = PetscViewerSetType(LeftViewer,PETSCVIEWERASCII);CHKERRQ(ierr);
> ierr = PetscViewerFileSetMode(LeftViewer,FILE_MODE_WRITE);CHKERRQ(ierr);
> ierr = PetscViewerSetFormat(LeftViewer,PETSC_VIEWER_ASCII_MATLAB);CHKERRQ(ierr);
> 
> It would have been nice to create the LeftViewer from the RightViewer.
> That is what I am trying to do.
> 
> At other places I use only one viewer to output left and right matrices:
> 
> // projection matrices in ascii
>  ierr = PetscViewerCreate(PETSC_COMM_WORLD,&ProjMatViewer);CHKERRQ(ierr);
>  ierr = PetscViewerSetType(ProjMatViewer,PETSCVIEWERASCII);CHKERRQ(ierr);
>  ierr = PetscViewerFileSetMode(ProjMatViewer,FILE_MODE_WRITE);CHKERRQ(ierr);
>  ierr = PetscViewerSetFormat(ProjMatViewer,PETSC_VIEWER_ASCII_MATLAB);CHKERRQ(ierr);
>  // right
>  ierr = PetscViewerFileSetName(ProjMatViewer,projfileasciiright);CHKERRQ(ierr);
>  ierr = MatView(ProjMatRight,ProjMatViewer);CHKERRQ(ierr);
>  // left
>  ierr = PetscViewerFileSetName(ProjMatViewer,projfileasciileft);CHKERRQ(ierr);
>  ierr = MatView(ProjMatLeft,ProjMatViewer);CHKERRQ(ierr);
>  // destroy
>  ierr = PetscViewerDestroy(&ProjMatViewer);CHKERRQ(ierr);
> 
> But I think switching the filename is inconvenient - I'd rather create
> a separate viewer Left and Right Matrices and have it copy the same
> parameters from an already created viewer.
> 
> -Nachiket
> 
> On Wed, Mar 20, 2013 at 2:16 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> What would it mean to duplicate a viewer? What are you actually trying to
>> do?
>> 
>> On Mar 20, 2013 12:59 PM, "Nachiket Gokhale" <gokhalen at gmail.com> wrote:
>>> 
>>> Not a show stopper, but would it be possible to add a
>>> PetscViewerDuplicate function? I don't see such a function here -
>>> 
>>> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Viewer/index.html
>>> 
>>> Cheers, -Nachiket