[petsc-users] parallel ILU

[Barry Smith]

On Feb 16, 2010, at 1:46 PM, Craig Tanis wrote:

>>> On Mon, 15 Feb 2010 12:45:21 -0500, Craig Tanis <craig- 
>>> tanis at utc.edu> wrote:
>>>> It is possible to do ILU-k preconditioning on an MPI matrix, right?
>>>
>>> Note that ILU (regardless of fill) scales very poorly, so it  
>>> really only
>>> makes sense on a small number of cores, and even then, only if you  
>>> can't
>>> find anything else that works.  As Matt says, build with Hypre, then
>>>
>>> -pc_type hypre -pc_hypre_type euclid -pc_hypre_euclid_levels k
>>>
>>> Jed
>>
>> Also note that there is no support for BAIJ matrices. It is only a  
>> "scalar" ILU, not one that works on little blocks.
>>
>>   Barry
>>
>
>
> could you clarify this?  i'm running the euclid preconditioner on a  
> mpibaij matrix, and  I get no errors or warnings.  a ksp_view  
> verifies that things are configured as expected.
>
> thanks
> craig

   As the matrix is passed to hypre it is passed as a AIJ matrix  
without a block size. This is because hypre has no concept of a BAIJ  
matrix. So yes, your PETSc part of the code is using a BAIJ matrix but  
hypre is doing a scalar ILU without a block size.


    Barry