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

[Jed Brown]

That particular issue is an output diagnostic quirk that will be fixed
eventually. Don't worry about it now.
On Jun 25, 2012 6:44 PM, "TAY wee-beng" <zonexo at gmail.com> wrote:

> On 25/6/2012 5:57 PM, Barry Smith wrote:
>
>>    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
>>
>
> I have switched to a 2d case. The matrix size is much smaller (still more
> than 1024). The matrix is now saved to a txt file. However, when running 2
> cpu, I got:
>
> Matrix Object: 1 MPI processes
>  type: mpiaij
> row 0: (0, -2)  (132, 3)  (264, -1)
> row 1: (1, -2)  (133, 3)  (265, -1)
> row 2: (2, -2)  (134, 3)  (266, -1)
> ...
>
> Shouldn't it be 2 MPI processes? Like in a vector:
>
> Vector Object:Vec_84000004_0 2 MPI processes
>  type: mpi
> Process [0]
> 0
> 0
> ...
>
> I used :
>
> call PetscViewerASCIIOpen(MPI_COMM_**WORLD,'A_semi.txt',viewer,**ierr)
>
> call MatView(A_semi,viewer,ierr)
>
> call PetscViewerDestroy(viewer,**ierr)
>
> Is there some error in my matrix? I also noticed that the matrix creating
> w/o using DM gives the same "1 MPI processes" output.
>
> I create it using :
>
> call DMDACreate2d(MPI_COMM_WORLD,**DMDA_BOUNDARY_NONE,DMDA_**
> BOUNDARY_NONE,DMDA_STENCIL_**STAR,size_x,size_y,&
> PETSC_DECIDE,num_procs,i1,i1,**PETSC_NULL_INTEGER,PETSC_NULL_**
> INTEGER,da,ierr)
>
> call DMCreateMatrix(da,MATAIJ,A_**semi,ierr)
>
> Thanks!
>
>
>
>> 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
>>>>>>
>>>>>>
>>>>>>
>>>
>
>
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