MatGetLocalSize() and MatDenseGetLocalMatrix()

[Matthew Knepley]

On Tue, Jan 6, 2009 at 1:55 PM, Yujie <recrusader at gmail.com> wrote:

> I am sorry, Matthew. I can't understand what you said. You mean it is not
> bug? However, practically, the dimension of local matrix in proc1 is 56*108?
> if it is, how to obtain its accurate dimension? thanks a lot.
>
For rowwise storage,  the number of columns is always the global number.

   Matt

> Regards,
>
> Yujie
>
> On Tue, Jan 6, 2009 at 11:45 AM, Matthew Knepley <knepley at gmail.com>wrote:
>
>> On Tue, Jan 6, 2009 at 1:43 PM, Yujie <recrusader at gmail.com> wrote:
>>
>>> Dear Matthew:
>>>
>>> Two processors are used. The matrix dimension is 105*108;
>>>
>>> MatGetOwnershipRange()
>>>
>>> proc1: 0->56
>>>
>>> proc2: 56->105
>>>
>>> Mat->camp.rstart; Mat->cmap.rend
>>>
>>> proc1: 0->54
>>>
>>> proc2: 54->108
>>>
>>> MatGetLocalSize()
>>>
>>> proc1: row 56 col 54
>>>
>>> porc2: row 49 col 54
>>>
>>> MatDenseGetLocalMatrix()
>>>
>>> proc1: 56*108
>>>
>>> proc2: 49*108
>>>
>>
>> Since PETSc matrices are all stored row-wise, even if columns are assigned
>> to one process
>> for the other, the storage is divided by row. This GetLocalMatrix()
>> returns all the rows
>> associated with a given process.
>>
>>    Matt
>>
>>
>>> thanks.
>>>
>>> Yujie
>>>
>>> On Tue, Jan 6, 2009 at 11:33 AM, Matthew Knepley <knepley at gmail.com>wrote:
>>>
>>>> On Tue, Jan 6, 2009 at 11:52 AM, Yujie <recrusader at gmail.com> wrote:
>>>>
>>>>> Dear PETSc developers:
>>>>>
>>>>> I am trying to use MatGetArray() and MatSetValues() to combine several
>>>>> MPIDense matrices into one matrix. At the beginning, I use
>>>>>
>>>>> MatGetOwnershipRange() and Mat->camp.rstart; Mat->cmap.rend (2.3.3-p8
>>>>> version) to get the start, end row and column. I can calculate the local
>>>>> rows and columns.
>>>>>
>>>>> I also use MatGetLocalSize() to confirm the accuracy. However, I always
>>>>> find some data loses in the combined matrix.
>>>>>
>>>>> And then, I try to use MatDenseGetLocalMatrix() to get the lcoal matrix
>>>>> and output it. I find column information by MatGetLocalSize() is not
>>>>> consistent with by MatDenseGetLocalMatrix(), is it bug? could you give me
>>>>> some advice? thanks a lot.
>>>>>
>>>> What information?
>>>>
>>>>   Matt
>>>>
>>>>
>>>>> Regards,
>>>>>
>>>>> Yujie
>>>>>
>>>> --
>>>> 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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