MatGetSubMatrix question

Barry Smith bsmith at
Tue May 26 17:03:07 CDT 2009

    I think this change may make sense. The switch would be done by  
putting the ISAllGather() inside each current implementation. (The  
current implementations are already not scalable, so this will not  
change that).

    Anybody want to try this change?


   By the way, whoever wrote MatGetSubMatrixRaw() deserves a good  
beating; what an ugly POS.

On May 25, 2009, at 8:20 AM, Jed Brown wrote:

> Is it really necessary that iscol be a sequential index set that  
> covers
> all columns, with csize selecting the local columns?  I realize this
> might be natural/easy for AIJ formats, but it feels clumsy (not to
> mention not scalable due to the ISAllGather).
> I'm guessing this is a relic from when IS was not a real parallel
> object.  Am I missing some deep reason for this interface, or could
> iscol be parallel and csize be dropped?
> Jed

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