[petsc-users] global index distributed arrays

[Jed Brown]

On Sat, Dec 11, 2010 at 01:53, Matthew Knepley <knepley at gmail.com> wrote:

> What are you guys talking about? He is asking ("global index for any given
> 3-d index") for a map
>
>   (i, j, k) -->  ((k*N + j)*M + i)*C + c
>
> I can't imagine what you are searching for? The process which owns a given
> index does not involve a search.
>

The "global index" is in the "PETSc ordering".  He wants this index for an
arbitrary (i,j,k) which are not in the ghosted patch of the current process.
 You either have to store the full mapping, on search lx,ly,lz to locate the
owner, then compute the index relative to that process.  I don't think that
code exists in PETSc.  It wouldn't be too hard to write, but it's not the
most beautiful thing to do.
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