[petsc-dev] MetSetBlockSize issue

[Mark F. Adams]

On Apr 24, 2012, at 2:55 PM, Barry Smith wrote:

> 
> On Apr 24, 2012, at 1:39 PM, Mark F. Adams wrote:
> 
>> Now I'm getting this error with code like this:
>> 
>>     ierr = MatGetSubMatrix( Cmat, new_eq_indices, new_eq_indices, MAT_INITIAL_MATRIX, &mat );
>>     CHKERRQ(ierr);
>>     ierr = MatSetBlockSize( mat, cbs );      CHKERRQ(ierr);
>> 
>> and like this:
>> 
>> ierr = MatPtAP( Amat_fine, Pold, MAT_INITIAL_MATRIX, 2.0, &Cmat ); CHKERRQ(ierr);
>> ierr = MatSetBlockSize( Cmat, cbs );      CHKERRQ(ierr);
> 
>   Right you cannot do this. The matrix already exists so you cannot now set its size.   
> 
>   Does Cmat have a block size of cbs
> 
>    What about Amat?   By default these routines should create the new matrix with the correct blocksize. 
> 
>    The harder part is if the blocksize of mat would be different than Cmat?
> 

It seems like MatGetSubMatrix should just inherit the block size but PtAP is harder.  The block size of the Cmat is the column block size of P.  But I can not set a column block size (!= row block size) so I don't set block size on P at all.  Here cbs is this column block size of P, or what it should be.

Mark

>   Barry
> 
>> 
>> Mark
>> 
>> On Apr 23, 2012, at 9:09 PM, Barry Smith wrote:
>> 
>>> 
>>> Yes, look, for example how ex32 is handled at the bottom of the makefile.
>>> 
>>> Thanks
>>> 
>>> Barry
>>> 
>>> On Apr 23, 2012, at 5:50 PM, Mark F. Adams wrote:
>>> 
>>>> 
>>>> On Apr 23, 2012, at 5:59 PM, Barry Smith wrote:
>>>> 
>>>>> 
>>>>> It was changed a while ago that MatSetBlockSize() couldn't be set after the matrix was full instantiated. I guess that example did not get fixed because it is not listed in the makefile to run in the makeall.
>>>> 
>>>> May I add it?
>>>> 
>>>>> 
>>>>> I have fixed the example to call MatSetBlockSize() at a safe point.
>>>>> 
>>>>> Barry
>>>>> 
>>>>> On Apr 23, 2012, at 4:29 PM, Mark F. Adams wrote:
>>>>> 
>>>>>> ex55.c in ksp is failing with:
>>>>>> 
>>>>>> [0]PETSC ERROR: --------------------- Error Message ------------------------------------
>>>>>> [0]PETSC ERROR: Arguments are incompatible!
>>>>>> [0]PETSC ERROR: Cannot change block size 1 to 2!
>>>>>> [0]PETSC ERROR: ------------------------------------------------------------------------
>>>>>> 
>>>>>> on this line 57 of ex55.c:
>>>>>> 
>>>>>> ierr = MatSetBlockSize(Amat,2);      CHKERRQ(ierr);
>>>>>> 
>>>>>> Any idea what happened here?  
>>>>>> 
>>>>>> Mark
>>>>> 
>>>>> 
>>>> 
>>> 
>>> 
>> 
> 
>