[petsc-users] MatSetSizes with blocked matrix

[Matthew Knepley]

On Tue, Mar 15, 2016 at 11:04 AM, Steena Monteiro <steena.hpc at gmail.com>
wrote:

> I pass a binary, matrix data file at the command line and load it into the
> matrix:
>
> PetscInitialize(&argc,&args,(char*)0,help);
> ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
>
> /* converted mtx to dat file*/
> ierr = PetscOptionsGetString(NULL,"-f",file,PETSC_MAX_PATH_LEN,&flg);
> CHKERRQ(ierr);
>
> if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER,"specify matrix dat file
> with -f");
>
>  /* Load matrices */
> ierr =
> PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);CHKERRQ(ierr);
> ierr =
> PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);CHKERRQ(ierr);
> ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
> ierr = MatSetFromOptions(A);CHKERRQ(ierr);
>

Nothing above loads a matrix. Do you also call MatLoad()?

  Matt


> Thanks,
> Steena
>
> On 15 March 2016 at 08:58, Matthew Knepley <knepley at gmail.com> wrote:
>
>> On Tue, Mar 15, 2016 at 10:54 AM, Steena Monteiro <steena.hpc at gmail.com>
>> wrote:
>>
>>> Thank you, Dave.
>>>
>>> Matt: I understand the inconsistency but MatMult with non divisible
>>> block sizes (here, 2) does not throw any errors and fail, when MatSetSize
>>> is commented out. Implying that 1139905 global size does work with block
>>> size 2.
>>>
>>
>> If you comment out MatSetSize(), how does it know what size the Mat is?
>>
>>    Matt
>>
>>
>>> On 15 March 2016 at 00:12, Dave May <dave.mayhem23 at gmail.com> wrote:
>>>
>>>>
>>>> On 15 March 2016 at 04:46, Matthew Knepley <knepley at gmail.com> wrote:
>>>>
>>>>> On Mon, Mar 14, 2016 at 10:05 PM, Steena Monteiro <
>>>>> steena.hpc at gmail.com> wrote:
>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> I am having difficulty getting MatSetSize to work prior to using
>>>>>> MatMult.
>>>>>>
>>>>>> For matrix A with rows=cols=1,139,905 and block size = 2,
>>>>>>
>>>>>
>>>>> It is inconsistent to have a row/col size that is not divisible by the
>>>>> block size.
>>>>>
>>>>
>>>>
>>>> To be honest, I don't think the error message being thrown clearly
>>>> indicates what the actual problem is (hence the email from Steena). What
>>>> about
>>>>
>>>> "Cannot change/reset row sizes to 400000 local 1139906 global after
>>>> previously setting them to 400000 local 1139905 global. Local and global
>>>> sizes must be divisible by the block size"
>>>>
>>>>
>>>>>
>>>>>   Matt
>>>>>
>>>>>
>>>>>> rank 0 gets 400000 rows and rank 1 739905 rows,  like so:
>>>>>>
>>>>>> /*Matrix setup*/
>>>>>>
>>>>>> ierr=PetscViewerBinaryOpen(PETSC_COMM_WORLD,file,FILE_MODE_READ,&fd);
>>>>>> ierr = MatCreate(PETSC_COMM_WORLD,&A);
>>>>>> ierr = MatSetFromOptions(A);
>>>>>> ierr = MatSetType(A,MATBAIJ);
>>>>>> ierr = MatSetBlockSize(A,2);
>>>>>>
>>>>>> /*Unequal row assignment*/
>>>>>>
>>>>>>  if (!rank) {
>>>>>>     ierr = MatSetSizes(A, 400000, PETSC_DECIDE,
>>>>>> 1139905,1139905);CHKERRQ(ierr);
>>>>>>    }
>>>>>> else {
>>>>>>     ierr = MatSetSizes(A, 739905, PETSC_DECIDE,
>>>>>> 1139905,1139905);CHKERRQ(ierr);
>>>>>> }
>>>>>>
>>>>>> MatMult (A,x,y);
>>>>>>
>>>>>> /************************************/
>>>>>>
>>>>>> Error message:
>>>>>>
>>>>>> 1]PETSC ERROR: [0]PETSC ERROR: No support for this operation for this
>>>>>> object type
>>>>>> Cannot change/reset row sizes to 400000 local 1139906 global after
>>>>>> previously setting them to 400000 local 1139905 global
>>>>>>
>>>>>> [1]PETSC ERROR: [0]PETSC ERROR: Cannot change/reset row sizes to
>>>>>> 739905 local 1139906 global after previously setting them to 739905 local
>>>>>> 1139905 global
>>>>>>
>>>>>> -Without messing with row assignment,  MatMult works fine on this
>>>>>> matrix for block size = 2, presumably because an extra padded row is
>>>>>> automatically added to facilitate blocking.
>>>>>>
>>>>>> -The above code snippet works well for block size = 1.
>>>>>>
>>>>>> Is it possible to do unequal row distribution *while using blocking*?
>>>>>>
>>>>>> Thank you for any advice.
>>>>>>
>>>>>> -Steena
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> What most experimenters take for granted before they begin their
>>>>> experiments is infinitely more interesting than any results to which their
>>>>> experiments lead.
>>>>> -- Norbert Wiener
>>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> What most experimenters take for granted before they begin their
>> experiments is infinitely more interesting than any results to which their
>> experiments lead.
>> -- Norbert Wiener
>>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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