[petsc-users] Advice on how to tackle with in place operation for a Matrix

[Matthew Knepley]

On Tue, May 18, 2010 at 3:58 AM, Umut Tabak <u.tabak at tudelft.nl> wrote:

> Matthew Knepley wrote:
>
>> 1) This must be a dense matrix, so you could directly copy in the values
>> with a strided loop
>>
>>  Dear Matt,
> Thanks for the immediate reply, I guess I did not understand this.
>
>  2) Is there a reason for the output to be a matrix, rather than a
>> collection of vectors?
>>
>>  Collection of vectors? not sure on this point. After the
> orthogonalization, I extract some parts of the matrix and continue operation
> with these extracted parts. Are there better ways of conducting operations
> for these kinds of tasks?
>

Well, you generally do not want the parallel organization of a MPIDENSE when
you make
these sorts of updates. You want to access 1 column at a time, with the
layout of a vector.
Thus is generally makes more sense to me to use a Vec[] than a MPIDENSE.

    Matt

-- 
What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
lead.
-- Norbert Wiener
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