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

[Barry Smith]

   So you run with -mat_ascii_output_large and it hangs? How big is the matrix?

   If it truly hangs and doesn't just take a long time you can run with -start_in_debugger and then hit control c in the debugger after it has been "hanging" to see where it is.

    But why not just run with a matrix less than 1024 to check that the matrix is correct.

   Barry

On Jun 25, 2012, at 4:39 PM, TAY wee-beng wrote:

> 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
>>>> 
>>>> 
>>> 
> 
>