Re: leave my rows alone

[Satish Balay <balay@xxxxxxxxxxx>]

On Wed, 16 Aug 2006, Thomas Geenen wrote:

> dear petsc users,
> 
> is there a way to prevent Petsc during the assembly phase from redistributing 
> matrix rows over cpu's ??

The row distribution is done at matrix creation time - and you can set
the row distribution with MatSetSizes() [or MatCreateMPIAIJ() etc..]
by using the correct distribution value - instead of PETSC_DECIDE

> i like the way the rows are assigned to the cpu's during the
> setvalues phase.

I don't understand this statement. The row assignment doesn't change

> apparently petsc assigns the first nrows to cpu0 the second nrows to cpu1 etc.

yes. this fact can't be changed.

> I could of course renumber my matrix but I would rather convince
> petsc that it should keep the distribution of the matrix rows.

If you have some other global numbering scheme which is inconsitant
with the matrix row numbering scheme - then you can use 'AO' object
and associated routines to convert between mappings.

Note: 'row distribution' is different from 'row numbering'.

Satish