[petsc-users] global index distributed arrays

[Jed Brown]

On Sat, Dec 11, 2010 at 01:40, Matthew Knepley <knepley at gmail.com> wrote:

> I know that I could use some MPI commands to pass those indices among
>> processors, but I was wondering if there a clean and neat way with which
>> each processor can have access to the global index for any given 3-d index.
>>
>
> ((k*N + j)*M + i)*C + c
>

Matt, you have seriously missed the point.

Mohamad, there is not an easy way to calculate it for an arbitrary index, it
necessarily involves a search.  Do you need it for arbitrary indices, or do
you know in advance which global indices are needed?  DAGetAO() can give you
what you are after, but there is usually a way to avoid using that code
since it is not scalable.

Jed
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