[petsc-users] Vec I/O using different parallel layout

[Barry Smith]

On Oct 10, 2011, at 7:41 PM, Mohamad M. Nasr-Azadani wrote:

> Thanks Barry, 
> 
> I am still not 100% sure if I can do this. 
> Say I have save the global vector obtained by a DA (3D) that is shared amongst 16 processors. 
> Can I load that data into a vector obtained from a DA (3D, same size obviously) that is shared on 1 processor? 

  ABSOLUTELY. Or a DA on 2 processes etc.

   Barry

> 
> Thanks, 
> Best, 
> Mohamad
> 
> 
> On Mon, Oct 10, 2011 at 5:36 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> On Oct 10, 2011, at 7:31 PM, Mohamad M. Nasr-Azadani wrote:
> 
> > Hi
> > I was wondering if it would be possible if I write a global vector (associated with a certain 3D distributed array)  to file
> > via:
> >
> >             ierr = PetscViewerBinaryOpen(PCW1, filename, FILE_MODE_WRITE, &writer);
> >             ierr = VecView(vec_data, writer);
> >             ierr = PetscViewerDestroy(writer);
> >
> > And then load the data into a global vector which is not created using the same parallel layout?
> > A simple example for this case would be to write the runtime data (parallel vector) to file and then just load the saved vector to do some simple SERIAL post processing.
> 
>  YES.
> 
>   The vector is saved to the file in the "natural ordering" that is starting with the logically 0,0,0 coordinate then increasing through the x axis, then the y axis then the z axis. To load back in in parallel you need to pass to VecLoad() a vector obtained with the appropriate DMCreateGlobalVector().
> 
> 
>  Barry
> 
> >
> > Thanks in advance,
> > Best
> > Mohamad
> >
> >
> >
> >
> 
>