VecDuplicate does NOT copy the vector values over to the newly created
vector. You must call VecCopy() after the VecDuplicate() if you want to copy
the values over.
Barry
On Dec 17, 2011, at 8:55 AM, Juha J?ykk? wrote:
> Hi all!
>
> I am at a loss: my vector entries get zeroed when I am not even using the
> vector.
>
> I have the vectors:
>
> ierr = DACreateGlobalVector(lattice.da, &Fields); CHKERRQ(ierr);
>
> ierr = VecDuplicate(Fields, &lattice.prev_state); CHKERRQ(ierr);
> ...
> TSSolve(lattice.ts, Fields);
>
> Later on, in a my RHS function PETSc has kindly provided me with my
> "lattice.da" as part of my context (it is now called simply "da"), it has
> also
> given me Fields, so I can do:
>
> DALocalInfo l_da;
> ahcs_field ***fields, ***rhs, ***pfields;
> Vec lfields, lpfields;
> begin_using_petsc_DA_step_1(da, &l_da, Fields, &lfields, &fields);
>
> where
>
> PetscErrorCode begin_using_petsc_DA_step_1(DA da, DALocalInfo *l_da, Vec
> Fields, Vec *lfields, void *fields) {
>
> PetscErrorCode ierr;
> ierr = DAGetLocalInfo(da, l_da); CHKERRQ(ierr);
> ierr = DAGetLocalVector(da, lfields); CHKERRQ(ierr);
> ierr = DAGlobalToLocalBegin(da, Fields, INSERT_VALUES, *lfields);
>
> At this point, the other vector in lattice.prev_state gets (some of) its
> entries zeroed!
>
> What am I doing wrong? Obviously, DAGlobalToLocalBegin working on Fields
> should not alter anything in a duplicated vector, let alone INTERNAL values
> of
> that vector (i.e. non-ghost points, which is what happens here).
>
> Cheers,
> Juha
>
> --
> -----------------------------------------------
> | Juha J?ykk?, juhaj at iki.fi |
> | http://www.maths.leeds.ac.uk/~juhaj |
> -----------------------------------------------
