[petsc-users] DM and HDF5 Viewer

[Gianluca Meneghello]

I need both right and left vectors for use in a SLEPc SVD decomposition; it
is my understanding that the correct layout is obtained with MatCreateVecs
and that only the layout for the right vector is created with
DMCreateGlobalVector.

Or I might be wrong and there is actually no difference! If so I will
use DMCreateGlobalVector
without any problem

Thanks

Gianluca





On Thu, Jul 16, 2015 at 9:14 AM, Jed Brown <jed at jedbrown.org> wrote:

> Gianluca Meneghello <gianmail at gmail.com> writes:
>
> > Hi again,
> >
> > I am now trying to write a vector to an HDF5, this time using a DM
> > structure to impose the vector layout.
> >
> > Creating the vector with (as in src/dm/examples/tutorials/ex10.c)
> >
> > DMCreateGlobalVector(da2D,&gauss);
> >
> > every works fine, i.e. the hdf5 file has the correct layout given by the
> > dimension of the DM. On the other side, if I use:
> >
> > VecCreate(PETSC_COMM_WORLD,&gauss);
> > VecSetSizes(gauss,PETSC_DECIDE,Nx*Ny);
> > VecSetDM(gauss,da2D);
>
> VecSetDM only associates a DM with the Vec.  It does not interpose
> itself into VecView.
>
> Should we change this so that creating a Vec of the correct size/block
> size/layout and associating a DM is equivalent?  Perhaps, but it's more
> nuanced than it might seem.
>
> Why don't you want to just call DMCreateGlobalVector()?
>
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