[petsc-users] ML and linear elasticity

[Jed Brown]

We don't keep coordinates, just use the provided null space.

We should make MatDiagonalScale update the near null space.
On Apr 2, 2012 4:38 PM, "Mark F. Adams" <mark.adams at columbia.edu> wrote:

>
> On Apr 2, 2012, at 7:24 PM, Jed Brown wrote:
>
> On Mon, Apr 2, 2012 at 07:44, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>
>> The block size is used if you don't provide any other information. The
>> preferred approach with petsc-dev is to use MatSetNearNullSpace(). (I'll
>> make sure this is currently working with ML and reply to this message.)
>
>
> I pushed ML support for user-provided null spaces to petsc-dev. Call
> MatSetNearNullSpace() to provide the information. You can use
> MatNullSpaceCreateRigidBody() if you have nodal coordinates.
>
>
> Mark, what is the best way to make PCGAMG use this interface?
>
>
> It looks like you are adding this to the Mat, so I can check to see if
> coordinates have been set and if not check the matrix.  This should be easy
> to do; I'll look at the ML code to clone the API.
>
> One thing to keep in mind is that diagonal scaling breaks the null space
> (ie, the rigid body modes have to be scaled appropriately).  Who owns the
> diagonal scaling? If it is Mat then we might want MatSetNearNullSpace to do
> this, otherwise we should think of a good way to deal with this.  It is
> very error prone to not do the right thing here, we should at least throw
> an error.
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120402/d18642d0/attachment.htm>