[petsc-users] Question about MatGetRow

Sat Feb 4 02:24:36 CST 2023

Following your comments, that works in multi processes.
After extracting procedure from 'newmat' which is submatrix.

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)

I did 'ISDestroy(&isrow); PetscFree(indices);'
However I got an error 'double free'.
So I deleted PetscFree.
Is this correct response of that error?
If not, how should I deal with that error??

Thanks,
Hyung Kim

2023년 2월 3일 (금) 오후 11:33, Matthew Knepley <knepley at gmail.com>님이 작성:

> On Fri, Feb 3, 2023 at 9:04 AM 김성익 <ksi2443 at gmail.com> wrote:
>
>> 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.
>>
>
> Did you run and see what you get? If it is on all processes, it should
> work.
>
>   Thanks,
>
>      Matt
>
>
>> 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/>
>>>
>>
>
> --
> 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/>
>
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