[petsc-users] output

[Matthew Knepley]

On Thu, Jan 24, 2013 at 10:03 AM, Kharche, Sanjay <
Sanjay.Kharche at liverpool.ac.uk> wrote:

>
> Hi Barry, All
>
> I am still taking the first few steps towards getting started.
>
> Yesterday, I was trying to output a vector in a specific format,
> essentially a row of 10 numbers only rather than a column of
> numbers+metadata. The suggestion for that was to output the vector as a
> binary, and then read it in using VecLoad from another standalone program
> and do whatever I wanted. Both my programs are serial, so there is no issue
> of parallel. In my standalone, I do something like:
>
> PetscViewer viewer;
> PetscViewerBinaryOpen(PETSC_COMM_WORLD,"ubu.bin",FILE_MODE_READ,&viewer);
> VecLoad(u, viewer);
> PetscViewerDestroy(&viewer);
>
> // check that u has the values you think it should have.
> VecView(u, PETSC_VIEWER_STDOUT_WORLD); // yes it does.
>
> // Now test if u now visible to printf so I can do this:
> for(i=0;i<10;i++)
> fprintf(my_non_petscfile,"%f ",u[i]);
> fprintf(my_non_petscfile,"\n");
> // but this does not work - the values of u are not as shown by VecView!
>
> And I still cannot output the vector u as a row into the non_petscfile.
> Can you help?
>

This is not the whole code. Where is the call to VecGetArray()?

   Matt


> thanks
> Sanjay
>
>
> ________________________________________
> From: petsc-users-bounces at mcs.anl.gov [petsc-users-bounces at mcs.anl.gov]
> on behalf of Barry Smith [bsmith at mcs.anl.gov]
> Sent: 23 January 2013 20:53
> To: PETSc users list
> Subject: Re: [petsc-users] output
>
>    Sanjay,
>
>      Since you are wanting ASCII output you don't need to worry about
> absolute scalability. Thus what I would do is in your parallel PETSc
> application code save the vectors with VecView() to binary format. Then
> write a stand-alone sequential program in C, Matlab, Python that reads in
> the binary vectors with VecLoad() and outputs them in any way you want.
>  Trying to do fancy ASCII output in parallel is not worth spending time.
>
>     Barry
>
> On Jan 23, 2013, at 2:18 PM, "Kharche, Sanjay" <
> Sanjay.Kharche at liverpool.ac.uk> wrote:
>
> >
> > Dear All
> >
> > I am an absolute beginner to PetSc. I am trying to output PetSc vectors
> in a specific format. This may have been discussed before, but I have so
> far not found a solution.
> >
> > For 2 or 3 vectors, I do this:
> >
> > /*
> > now write it to file.
> > I would like row 1 to be u, row 2 to be b, and row 3 to be u. that way I
> can use
> > gnuplots surf, and also all my existin matlab code for plotting/analysis.
> > */
> > PetscViewer viewer; // a Petsc file pointer.
> > PetscViewerASCIIOpen(PETSC_COMM_WORLD,"ubx.dat",&viewer);
> > VecView(u,viewer); // this comes out with information that I dont want,
> and in a column - I need to put it as a row.
> > VecView(b,viewer);
> > VecView(x,viewer);
> > PetscViewerDestroy( &viewer );
> >
> > However, I have not been able to get rid of the information about procs,
> and also the vectors u, b, and u need to be in row format as:
> > 1 2 1 1 1
> > 0 0 0 1 0
> > -1 2 -1 0
> >
> > rather than what I have now:
> >
> > Vector Object: 1 MPI processes
> >  type: seq
> > 1
> > 2
> > 1
> > 1
> > 1
> > etc....
> >
> >
> > Any suggestions on how to do this will be appreciated.
> >
> > thanks
> > Sanjay
>
>


-- 
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/20130124/3b05f307/attachment.html>