[petsc-users] Question about MatView

[Barry Smith]

   Use 

>> MatCreate(PETSC_COMM_SELF, &mat);
>>  PetscViewerBinaryOpen(PETSC_COMM_SELF, "mat.bin", FILE_MODE_READ, &viewer);


    If it one program running that both views and loads the matrix you can use MatCreateRedundantMatrix() to reproduce the entire matrix on each MPI rank. It is better than using the filesystem to do it.


> On Mar 17, 2023, at 9:45 AM, user_gong Kim <ksi2443 at gmail.com> wrote:
> 
> Following your comments,  I did an test.
> However, if I run the application in parallel. 
> In all processes, it is not possible to obtain values at all positions in the matrix through MatGetValue.
> As in the previous case of saving in binary, it is read in parallel divided form.
> Is it impossible to want to get the all value in the whole process?
> 
> 
> Thanks,
> Hyung Kim
> 
> 2023년 3월 17일 (금) 오후 7:35, Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com>>님이 작성:
>> On Fri, Mar 17, 2023 at 5:51 AM user_gong Kim <ksi2443 at gmail.com <mailto:ksi2443 at gmail.com>> wrote:
>>> Hello,
>>> 
>>>  
>>> I have 2 questions about MatView.
>>> 
>>>  
>>> 1.    I would like to ask if the process below is possible.
>>> When running in parallel, is it possible to make the matrix of the mpiaij format into a txt file, output it, and read it again so that the entire process has the same matrix?
>>> 
>> No. However, you can do this with a binary viewer. I suggest using
>> 
>>   MatViewFromOptions(mat, NULL, "-my_view");
>> 
>> and then the command line argument
>> 
>>   -my_view binary:mat.bin
>> 
>> and then you can read this in using
>> 
>>   MatCreate(PETSC_COMM_WORLD, &mat);
>>   PetscViewerBinaryOpen(PETSC_COMM_WORLD, "mat.bin", FILE_MODE_READ, &viewer);
>>   MatLoad(mat, viewer);
>>   ViewerDestroy(&viewer);
>> 
>>   THanks,
>> 
>>      Matt
>> 
>>  
>>> 2.    If possible, please let me know which function can be used to create a txt file and how to read the txt file.
>>> 
>>>  
>>> 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/>

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