block matrices

[Manav Bhatia]

Hi,

I was reading the Petsc manual pages and came across the following  
functions: MatCreateBlockMat, MatCreateSeqAIJWithArrays and  
MatCreateSeqBAIJ.

1> So, if I have the S1,S2,...,S5, and I want to build the B matrix as  
mentioned below, would the BAIJ matrix be better to use than the AIJ?  
How about BlockMat?

2> And which one of the above three methods would be best to create B ?

I would appreciate any comments on this.

Thanks,
Manav


On Sep 21, 2008, at 12:50 PM, Hong Zhang wrote:

>
> Manav,
>
> On Sun, 21 Sep 2008, Manav Bhatia wrote:
>
>> Hi,
>>
>>   I have an application in which I have multiple sparse matrices,
>> which together form one bigger matrix. For example: if S1, S2, S3, S4
>> and S5 are my sparse matrices, I need to create a matrix B of the
>> following form
>>
>> B = 3 x 3 blocks
>>
>> row 1 of B = 0, S1, 0
>> row 2 of B = S2, 0 , S3
>> row 3 of B = S4, S5, 0
>>
>> If I build the S1... S5 independently, is there a way for me to
>> directly embed these matrices into B without having to explicitly  
>> copy
>> the values from each matrix?
>
> No, we do not have this function.
> You can use MatSetValues()
> http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatSetValues.html
>
> to insert a block of values.
>
> Hong
>
>> I would appreciate any help. Please also, let me know if there is an
>> example code somewhere about this.
>>
>> Regards,
>> Manav
>>
>>
>>
>>
>