DMDAGetOwnershipRanges
> On Nov 11, 2015, at 10:47 PM, Gianluca Meneghello <[email protected]> wrote:
>
> Hi,
>
> thanks for the very quick reply.
>
> One more question: is there a way to get the lx and ly from the first dm and
> use them (modified) for the second dm? DMDAGetInfo does not seem to provide
> this information.
>
> Thanks again for your help
>
> Gianluca
>
> On Wed, Nov 11, 2015 at 8:12 PM, Barry Smith <[email protected]> wrote:
>
> When you create the 2 DM you must be set the lx, ly arguments (the ones you
> set to 0) in your code carefully to insure that the vectors for the 2 DM you
> create have compatible layout to do the matrix vector product.
>
> You can run a very small problem with 2 processors and printing out the
> vectors to see the layout to make sure you get it correct.
>
> The 2 DM don't have any magically way of knowing that you created another
> DMDA and want it to be compatible automatically.
>
> Barry
>
> DMDACreate2d(PETSC_COMM_WORLD , DM_BOUNDARY_GHOSTED , DM_BOUNDARY_GHOSTED ,
> DMDA_STENCIL_BOX ,
> Mx , Nx , PETSC_DECIDE , PETSC_DECIDE , 1 , 0 , 0 , 0 , &dax);
> DMDACreate2d(PETSC_COMM_WORLD , DM_BOUNDARY_NONE , DM_BOUNDARY_NONE ,
> DMDA_STENCIL_BOX ,
> Mx-2*bs , Nx-2*bs , PETSC_DECIDE , PETSC_DECIDE , 1 , 0 , 0 , 0 , &daf);
>
> > On Nov 11, 2015, at 10:05 PM, Gianluca Meneghello <[email protected]>
> > wrote:
> >
> > Hi,
> >
> > I am trying to do something apparently really simple but with no success.
> >
> > I need to perform a matrix-vector multiplication x = B f , where the length
> > of x is bigger than the length of f (or viceversa). Thus, B cannot be
> > created using DMCreateMatrix.
> >
> > Both x and f are obtained from different DMs, the smaller covering only a
> > subdomain of the larger. The application is to apply a control f to a
> > system, e.g. \dot{x} = A x + B f.
> >
> > The problem is, when running on more than one core, the vector x is not
> > organized as I would expect (everything works fine on a single core).
> >
> > I attach a short example where B is intended to map f to the interior of x.
> >
> > mpirun -n 1 ./test -draw_pause -1 works fine while
> > mpirun -n 2 ./test -draw_pause -1 shows the problem
> >
> > I have not found any example with non square matrices in the src folder,
> > any help is very welcome.
> >
> > Thanks for your time,
> >
> > Gianluca
> > <test.cpp>
>
>
