[petsc-users] MatView and PetscViewerASCIIOpen problem when cpu > 1

[TAY wee-beng]

On 25/6/2012 4:24 PM, Barry Smith wrote:
> On Jun 25, 2012, at 4:18 PM, TAY wee-beng wrote:
>
>> On 25/6/2012 3:40 PM, Jed Brown wrote:
>>> On Mon, Jun 25, 2012 at 12:25 PM, TAY wee-beng <zonexo at gmail.com> wrote:
>>> Hi,
>>>
>>> I'm trying to use DMDA to solve my linear equation.
>>>
>>> It works fine with 1 cpu. However, problem arise when cpu > 1. I get segmentation error.
>>>
>>> I tried to use  MatView and PetscViewerASCIIOpen to view my matrix to check if it's correct.
>     It only makes sense to view the matrix in this case for small matrices. You should check the matrix for a very small problem, how are you going to compare the ASCII output to see if it is correct for a huge matrix. Always debug with very small data sets.
>
>     Barry
I just want to get a quick view of the matrix. I have the correct matrix 
generated without using DM. So,  I use a file difference comparison 
software to check the difference, which is rather fast. I just wonder 
why it takes a long time to view the matrix on screen, or write to file. 
I guess it should be easy to just view the matrix and spot the error.
>>> It works with 1 cpu. However now, it shows the error below when I use 2 cpu.
>>>
>>> [0]PETSC ERROR: --------------------- Error Message ------------------------------------
>>> [0]PETSC ERROR: Argument out of range!
>>> [0]PETSC ERROR: ASCII matrix output not allowed for matrices with more than 1024 rows, use binary format instead.
>>> You can override this restriction using -mat_ascii_output_large.!
>>>
>>>   To view the matrix, my command is :
>>>
>>> call PetscViewerASCIIOpen(MPI_COMM_WORLD,"A_semi.txt",viewer,ierr)
>>>
>>> call MatView(A_semi,viewer,ierr)
>>>
>>> call PetscViewerDestroy(viewer,ierr)
>>>
>>> I tried to use -mat_ascii_output_large but then it just hangs there forever.
>>>
>>> It may just be very slow.
>> I tried using 1 cpu and I got it in a few minutes. Should i take a long time if I use 2 cpu? Also, I got the error:
>>
>> [0]PETSC ERROR: Argument out of range!
>> [0]PETSC ERROR: ASCII matrix output not allowed for matrices with more than 1024 rows, use binary format instead.
>>
>> It doesn't happen when I use 1 cpu. Is it normal to get it when I use 2 cpu?
>>
>> I also tried to use :
>>
>> call MatView(A_semi,PETSC_VIEWER_STDOUT_WORLD ,ierr)
>>
>> but the same error occurs. It just hangs there when 2 cpu are used.
>>
>>
>>> Why do you need ASCII? Writing anything large in ASCII is hopeless. Please use binary.
>>>   
>>> I create the matrix using DMCreateMatrix. I don't have to use MatCreateAIJ, right?
>>>
>>> Also, I check for the ierr value when I use MatSetValuesStencil to ensure there's no error. Btw There's no problem with VecView.
>>>
>>> So how can I view the matrix?
>>>
>>> Thank you!
>>>
>>> -- 
>>> Yours sincerely,
>>>
>>> TAY wee-beng
>>>
>>>
>>