[petsc-users] about VecScatterCreate()

[Yujie]

Thanks, Matt.
I think the manpage should point out this. In MatGetSubmatrix().
"isrow" and "iscol" have good explanations.

Regards,
Yujie

On Thu, May 27, 2010 at 10:07 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Fri, May 28, 2010 at 1:02 PM, Yujie <recrusader at gmail.com> wrote:
>>
>> Dear PETSc Developers,
>>
>> I got the following information from VecScatterCreate() manpage.
>> "
>> PetscErrorCode  VecScatterCreate(Vec xin,IS ix,Vec yin,IS iy,VecScatter
>> *newctx)
>>
>> Collective on Vec
>>
>> Input Parameters
>>        xin     - a vector that defines the shape (parallel data layout of
>> the
>> vector) of vectors from which we scatter
>>        yin     - a vector that defines the shape (parallel data layout of
>> the
>> vector) of vectors to which we scatter
>>        ix      - the indices of xin to scatter (if PETSC_NULL scatters all
>> values)
>>        iy      - the indices of yin to hold results (if PETSC_NULL fills
>> entire
>> vector yin)
>> "
>> My question is about "ix". If xin and yin are parallel Vec, how about ix?
>>
>> Is "ix"  an IS only containing local index set or a parallel IS
>> containing all the index set on all the processors (each local index
>> set on its processor)? Thanks a lot.
>
> ix contains some indices for that process. The indices can be different on
> each process.
> We take the union.
>    Matt
>
>>
>> Regards,
>> Yujie
>
>
>
> --
> What most experimenters take for granted before they begin their experiments
> is infinitely more interesting than any results to which their experiments
> lead.
> -- Norbert Wiener
>