[petsc-dev] MATSCATTER Transpose

Barry Smith bsmith at mcs.anl.gov
Mon Mar 29 16:23:30 CDT 2010

On Mar 29, 2010, at 2:42 PM, Dmitry Karpeev wrote:

> Good point.  Actually, should this be pushed all the way to the level
> of VecScatter?
> That would necessitate an introduction of something like  
> VecScatterTranspose
> (by analogy with the induced linear operator) or VecScatterInvert.
> The implementation of VecScatterTranspose is trivially carried out at
> the interface level
> with a flag, which would cause an appropriate change in the
> ScatterMode submitted to
> ops->scatterbegin, ops->scatterend.

    Yuck, unless there is a good reason for VecScatterInvert/Transpose? 
() I'd much prefer that you just work inside the MATSCATTER matrix  


> Then, MatTranspose for MATSCATTER could be implemented by transposing
> the underlying
> VecScatter (incurring extra storage) or transposing the underlying
> scatter on MatScatterGetVecScatter
> (this is much less clean, though).
> Any thoughts?
> Thanks.
> Dmitry.
> On Mon, Mar 29, 2010 at 1:14 PM, Jed Brown <jed at 59a2.org> wrote:
>> On Mon, 29 Mar 2010 12:57:53 -0600, Dmitry Karpeev <karpeev at mcs.anl.gov 
>> > wrote:
>>> Is there any reason why MATSCATTER doesn't implement MatTranspose?
>>> It seems to me that it would be easy to accomplish by reversing
>>> MatMultXXX and MatMultTransposeXXX
>>> in MATSCATTER's ops vtable.
>> Makes sense to me, just be careful with MatScatterGetVecScatter().
>> Jed

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