[petsc-users] user defined grids

[praveen kumar]

Thanks Barry. I think I didn’t put the question properly.

I want to generate a 3D non uniform grid. I went through the archieves and
read about DMSetCoordinates. As I have large No. of grid points, it is
difficult to assign coordinates manually.


Thanks,

Praveen

On Thu, Mar 3, 2016 at 12:21 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Mar 2, 2016, at 9:01 AM, praveen kumar <praveenpetsc at gmail.com>
> wrote:
> >
> > Dear all,
> >
> > I am employing PETSc for DD in a serial fortran code and I would be
> using the solver from serial code itself. In my programme there is
> subroutine which reads an input file for the grids.  I have two questions:
> >
> >
> >
> > 1.  The input file contains : No. of segments in each direction, Length
> of each segment, Grid expansion ratio for each segment, dx(min) and dx(max)
> (min and max size of sub-division for each segment),
>
>    I don't understand what this grid expansion ratio means.
>
> > No. of uniform sub-divisions in each segment. Will I be able to include
> all these details in DMDAcreate3D?
>
>    The DMDACreate3d() only defines the topology of the mesh (number of
> mesh points in each direction etc), not the geometry. If you want to
> provide geometry information (i.e. length of grid segments) then you use
> DMDAGetCoordinateArray() to set the local values. See DMDAVecGetArray for
> the form of the "coordinates" array.
>
> >  Is there any example? If no, then is there any way to retain the input
> file section and still use PETSc?
>
>    Should be possible but you will need to do a little programming and
> poking around to use all the information.
>
>   Barry
>
> >
> >
> >
> > 2. Moreover application requires that, I call the Grid subroutine after
> some fixed number of iterations.
> >
> >
> >
> > Would you suggest how to fix the above two?
> >
> >
> >
> > Thanks,
> >
> > Praveen
> >
>
>
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