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

[Barry Smith]

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

>> 
>> 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
>> 
>> 
> 
>