[petsc-users] about MatTranspose

[Likun Tan]

Thanks,

so what I want to do is using MatMatSolve() to solve Ax=B, where A is a
27*27 dense matrix, B is a 27*4000 dense matrix.

1. For efficiency, i want to generate the matrix B in parallel. Since it
cannot be partitioned by row, i generated a 4000*27 matrix and try to get
the transpose of it. Should i use MatCreateTranspose()?

2. Does MatMatSolve() solve Ax=B in parallel? If so, since A is not
partitioned, is A visible in every process? or other steps i should do?

3. I have a 3D array (with PETSC_COMM_SELF) that will be used to generate
all the elements of matrix B, how could I make it available in every
process?

Thanks,
Likun


On Wed, August 31, 2011 4:07 am, Matthew Knepley wrote:
> 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
>
>