how to extract a subvector?

Barry Smith bsmith at
Fri Jan 2 13:46:36 CST 2009

    VecScatter is for this purpose.

    Rational: extracting subparts of vectors for ghost points etc  
takes place many times in a simulation; maybe millions.
Thus separating it into a set-up followed by many uses is a   
worthwhile optimization. Extracting submatrices occur
much less often in a simulation, maybe tens, hundreds or thousands of  
times so it is not worth the extra complexity
of having separate set-up followed by many uses. One could argue that  
uniformity of design means we should have
handled matrices with a MatScatter concept to parallel the Vec  
approach, but it is too late now :-).


On Jan 2, 2009, at 1:41 PM, Yujie wrote:

> Like MatGetSubMatrix(), whether is there a function to get a  
> subvector in parallel mode? I have checked some scatter functios,  
> they don't likely work. thanks a lot.
> Regards,
> Yujie

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