[petsc-users] [PATCH 2/2] Call KSPSetFromOptions before setting fieldsplit-specific options

[Dave May]

It's stuck in  one of the inner solves. Turn on the montitors for
fieldsplit_2

On Sunday, 8 September 2013, Umut Tabak wrote:

> On 09/08/2013 04:19 PM, Jed Brown wrote:
>
>> Umut Tabak <u.tabak at tudelft.nl> writes:
>>
> Dear Jed and others,
>
> Thanks a lot for your help.
>
> One last question, trying to run with
>
> ./ex3 -pc_type fieldsplit -pc_fieldsplit_type schur -pc_fieldsplit_schur_*
> *factorization_type diag -fieldsplit_1_pc_type icc -fieldsplit_1_ksp_type
> minres -fieldsplit_2_pc_type icc -fieldsplit_2_ksp_type minres
> -ksp_converged_reason -ksp_monitor_short
>
> With this input, I would expect to see a flow of residual information even
> if increasing, but no information is being printed on the screen, what
> could be the reason for this?
>
>  On 09/08/2013 03:57 PM, Jed Brown wrote:
>>>
>>>> In the second call, ISCreateBlock looks at the array of block indices of
>>>> length n2 starting from inputindices+n1.  That references
>>>> inputindices[n1], which is off the end of the array you created above.
>>>> Simply extending that array won't work either because you can't describe
>>>> the starting point correctly for one "block" of different length.  I.e.,
>>>> if inputindices[1] == 1, then the second call above would be creating
>>>> the index set
>>>>
>>>>     {sz2, sz2+1,..., 2*sz2-1}
>>>>
>>>> This should be obvious if you look at ISView().
>>>>
>>> Yes, but then there is a problem with my understanding of the block
>>> structure.
>>>
>>> What I would like to do at the end is to create a first block of size
>>> 1490 and then create a block of size 2432 and stack these. This is how
>>> the original system is built up.
>>>
>> Then use the code I sent.
>>
>>  Of what if I use the below code,
>>>
>>> PetscInt sz1 = 1490, sz2 = 2432;
>>>
>>>     /* ----- */
>>>
>>>     PetscInt n1=1, n2=1,
>>>         inputindices1[]={0}, inputindices2[]={1}; /* block size is 2 */
>>>
>>>     ISCreateBlock(PETSC_COMM_SELF,**sz1,n1,inputindices1,
>>>                   PETSC_COPY_VALUES,&is_row1);
>>>     ISCreateBlock(PETSC_COMM_SELF,**sz2,n2,inputindices2,
>>>                   PETSC_COPY_VALUES,&is_row2);
>>>
>>> Because if I look at
>>>
>>> http://www.mcs.anl.gov/petsc/**petsc-current/docs/**
>>> manualpages/IS/ISCreateBlock.**html<http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/IS/ISCreateBlock.html>
>>>
>>> I am getting the impression that bs and n are the same and on top idx is
>>> the global block number of the large matrix blocks.
>>>
>> What gives you this impression?
>>
>> ISCreateBlock is meant to describe index sets like the following (bs=2):
>>
>>    {0,1,8,9,10,11,16,17,20,21}
>>
>> via
>>
>>    ISCreateBlock(comm,2,5,[0,4,5,**8,10],&is);
>>
>
>
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