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

[TAY wee-beng]

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 
> <mailto: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 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
>
>


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