[petsc-users] Scatter context for MatMult

[John Fettig]

On Fri, Aug 17, 2012 at 5:03 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
> On Aug 17, 2012, at 1:48 PM, John Fettig <john.fettig at gmail.com> wrote:
>
>> On Fri, Aug 17, 2012 at 2:33 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>> Why do you want raw access?
>>
>> I'm trying to write my own RAP operator for AMG.
>
>    Why? Our's is not fast enough and you think you can make it better?  You want to support an R that is not the transpose of P?  Regardless why not start with the current source code we have and fork your own routine instead of starting from scratch? Doing a full efficient RAP from scratch is a major project.

Yes, I'm having problems getting MatPtAP to work efficiently with my
projection matrices.  It is especially problematic in parallel, and
I'm not really sure why since it seems to do ok for GAMG.  I'm trying
to code up a simple RAP currently, and I'll let you know how it goes.

John