[petsc-users] Question about MatGetRow

[김성익]

Actually in the last mail, below scripts are running in all processes.

IS isrow;
PetscInt *indices;
PetscMalloc1(1, &indices);
Indices[0] = 0;
ISCreateGenreral(PETSC_COMM_WORLD, 1, indices, PETSC_OWN_POINTER, &isrow);
MatCreateSubMatrix(mat,isrow,NULL,MAT_INITIAL_MATRIX,&newmat);
(extract from newmat)

However, you said it cannot get the values of first row of global matrix.
Please let me know how can I fix this scripts for getting the 1st row of
global matrix in all processes.

Hyung Kim







2023년 2월 3일 (금) 오후 10:54, Matthew Knepley <knepley at gmail.com>님이 작성:

> On Fri, Feb 3, 2023 at 8:52 AM 김성익 <ksi2443 at gmail.com> wrote:
>
>> I want to extract same row values of global matrix in all processes.
>> Then how can I do this??
>>
>
> Create the same IS on each process.
>
>   THanks,
>
>     Matt
>
>
>> The case of same problem of vector, I just use vecscattertoall.
>> However, I can't find same function for matrix.
>>
>> Hyung Kim
>>
>> 2023년 2월 3일 (금) 오후 10:47, Matthew Knepley <knepley at gmail.com>님이 작성:
>>
>>> On Fri, Feb 3, 2023 at 8:45 AM 김성익 <ksi2443 at gmail.com> wrote:
>>>
>>>> Following your comments,
>>>> If I extract first row of below matrix.
>>>> [image: image.png]
>>>> IS isrow;
>>>> PetscInt *indices;
>>>> PetscMalloc1(1, *indices);
>>>>
>>>
>>> That should be &indices.
>>>
>>>
>>>> Indices[0] = 0;
>>>> ISCreateGenreral(PETSC_COMM_WORLD, 1, indices, PETSC_COPY_VALUES,
>>>> &isrow);
>>>>
>>>
>>> You should use PETSC_OWN_POINTER.
>>>
>>>
>>>> MatCreateSubMatrix(mat,isrow,NULL,MAT_INITIAL_MATRIX,&newmat);
>>>>
>>>> Then can I get the array about first row of global matrix in all
>>>> processes?
>>>>
>>>
>>> No, just on the process which gives 0. If you do that on every process,
>>> every rank with get row 0.
>>>
>>>   Thanks,
>>>
>>>      Matt
>>>
>>>
>>>> Hyung Kim
>>>>
>>>> 2023년 2월 3일 (금) 오후 10:26, Matthew Knepley <knepley at gmail.com>님이 작성:
>>>>
>>>>> On Fri, Feb 3, 2023 at 8:06 AM 김성익 <ksi2443 at gmail.com> wrote:
>>>>>
>>>>>> Following your comments,
>>>>>> I want to check below things.
>>>>>> For example, the global dense matrix are as below.
>>>>>> [image: image.png]
>>>>>> If I want to get first row ('1 2 0 0 3 0 0 4') in Proc 1.
>>>>>> Then I should put 'MatCreateSubMatrix
>>>>>> <https://petsc.org/main/docs/manualpages/Mat/MatCreateSubMatrix/>(mat
>>>>>> , isrow, NULL, MAT_INITIAL_MATRIX, *&*newmat)'
>>>>>> and isrow will be [0 1 2 3 4 5 6 7].
>>>>>>
>>>>>> In this case, How can I make isrow?
>>>>>> Actually I can't understand the procedure of handling isrow.
>>>>>>
>>>>>
>>>>> You create an IS object of type ISGENERAL and give it the array of
>>>>> global indices that you want to extract.
>>>>>
>>>>>   Thanks,
>>>>>
>>>>>      Matt
>>>>>
>>>>>
>>>>>> Hyung Kim
>>>>>>
>>>>>> 2023년 2월 3일 (금) 오후 9:03, Mark Adams <mfadams at lbl.gov>님이 작성:
>>>>>>
>>>>>>> https://petsc.org/main/docs/manualpages/Mat/MatCreateSubMatrix/
>>>>>>>
>>>>>>> Note, PETSc lets you give NULL arguments if there is a reasonable
>>>>>>> default.
>>>>>>> In this case give NULL for the column IS and you will get the whole
>>>>>>> columns.
>>>>>>>
>>>>>>> Mark
>>>>>>>
>>>>>>> On Fri, Feb 3, 2023 at 4:05 AM 김성익 <ksi2443 at gmail.com> wrote:
>>>>>>>
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>>
>>>>>>>> By using MatGetRow, user can get vectors from local matrix (at each
>>>>>>>> process).
>>>>>>>>
>>>>>>>> However, I need other process's row values.
>>>>>>>> So I have 2 questions.
>>>>>>>>
>>>>>>>> 1. Is there any function for getting arrays from other process's??
>>>>>>>>
>>>>>>>> 2. Or is there any function like matrix version of vecscattertoall??
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>> Hyung Kim
>>>>>>>>
>>>>>>>
>>>>>
>>>>> --
>>>>> 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
>>>>>
>>>>> https://www.cse.buffalo.edu/~knepley/
>>>>> <http://www.cse.buffalo.edu/~knepley/>
>>>>>
>>>>
>>>
>>> --
>>> 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
>>>
>>> https://www.cse.buffalo.edu/~knepley/
>>> <http://www.cse.buffalo.edu/~knepley/>
>>>
>>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230203/c3bbbdb2/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 6931 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230203/c3bbbdb2/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image.png
Type: image/png
Size: 7950 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230203/c3bbbdb2/attachment-0003.png>