[petsc-users] reordering the dmda dof

Matthew Knepley knepley at gmail.com
Fri Oct 11 08:13:42 CDT 2013

On Fri, Oct 11, 2013 at 8:09 AM, Bishesh Khanal <bisheshkh at gmail.com> wrote:

> Dear all,
> By default, dmda puts all dof at a given node logically in consecutive
> order. The corresponding vectors and matrices created also follow this
> order. What should I do to change it so that it puts all the grid nodes for
> a 1st dof consecutively, then do the same for 2nd dof and so on. I also
> want the same behavior for the matrix it creates so that the rows
> corresponding to a particular dof are put in a consecutive manner instead
> of interleaving different dofs.

What do you really want to accomplish? This ordering is disastrous for
cache architectures.

1) If you want segregated solves, use PCFIELDSPLIT.

2) If you want to mess around with a single field, use



> Bishesh

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
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