[petsc-users] about MatTranspose

[Matthew Knepley]

On Wed, Aug 31, 2011 at 2:17 AM, Likun Tan <likunt at andrew.cmu.edu> wrote:

>
> Thank you very much. So i should create the transpose matrix as MPIDense
> and partition it corresponding? That is, if the matrix is partitioned into
> 3 parts by row, then the transpose matrix will be partitioned into 3 parts
> by column?
>

1 part per process.


> I have two more questions:
> 1. I define a DA with PETSC_COMM_SELF, where is the array stored? Could i
> use this array in every process?
>

It does not store anything, but with PETSC_COMM_SELF, the array will not be
partitioned.


> 2. I vaguely remember that matrix can only be partitioned by row, is that
> true?
>

Sparse matrices are generally partitioned by row. This is how the AIJ
classes work,
and also our dense classes to mirror it.

   Matt


> best,
> Likun
>
>
> On Tue, August 30, 2011 10:07 pm, Matthew Knepley wrote:
> > On Wed, Aug 31, 2011 at 12:48 AM, Likun Tan <likunt at andrew.cmu.edu>
> > wrote:
> >
> >
> >>
> >> I have MPIDense matrix, if i want to get the tranpose of the matrix,
> >> what should i do? Or i should use MPISparse instead?
> >
> >
> > If it is rectangular, create the transpose matrix first, then call
> > MatTranspose.
> >
> >
> > Matt
> >
> >
> >
> >> On Tue, August 30, 2011 7:08 pm, Matthew Knepley wrote:
> >>
> >>> On Tue, Aug 30, 2011 at 10:59 PM, Likun Tan <likunt at andrew.cmu.edu>
> >>> wrote:
> >>>
> >>>
> >>>
> >>>>
> >>>> Dear all,
> >>>>
> >>>>
> >>>>
> >>>> Can MatTranspose be used on non-squra matrix? I have a matrix with
> >>>> size 200*27, and i want to get the tranpose of it.
> >>>>
> >>>>
> >>>>
> >>>
> >>> I assume you are talking about dense matrices. If so, yes.
> >>>
> >>>
> >>>
> >>>
> >>>> Second question is, if the 200*27 is partitioned by row, how is the
> >>>>  tranpose stored in each processor? Is it stored by column?
> >>>>
> >>>
> >>> For MPIDENSE, you cannot in-place transpose unless it is square.
> >>> Otherwise,
> >>> you provide the transpose matrix, so you determine the layout.
> >>>
> >>> Matt
> >>>
> >>>
> >>>
> >>>
> >>>> Thanks,
> >>>> Likun
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>> --
> >>> 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
> >>>
> >>>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > --
> > 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
> >
> >
>
>
>
>
>


-- 
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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