[petsc-dev] PCRedundant problem

[Hong Zhang]

Stefano,
Checking PCRedundant, I see that  current PCRedundant is hard-coded using
PETSC_SUBCOMM_INTERLACED
which  'avoid data scattering from subcomm back to original comm'
See ~petsc/src/sys/objects/subcomm.c - PetscSubcommCreate_interlaced()
Unless you write a new implementation, PETSC_SUBCOMM_CONTIGUOUS cannot be
used
for PCRedundant.

Hong

On Mon, Oct 15, 2012 at 4:37 PM, Hong Zhang <hzhang at mcs.anl.gov> wrote:

> Stefano :
>
>> Hong, INTERLACED is the default since
>> http://petsc.cs.iit.edu/petsc/petsc-dev/rev/67df4fdba5bd
>>
>> See also http://petsc.cs.iit.edu/petsc/petsc-dev/rev/c04222d17a3d
>
>
> Hmm, you are correct :-(
>
>
>> Hong, in petsc-dev, default is interlaced. I ran some tests, I got malloc
>>> errors when inserting mat values using subcomm of contiguous type. I think
>>> that PCRedundant with PETSC_SUBCOMM_CONTIGUOUS is buggy.
>>
>>
> PETSC_SUBCOMM_CONTIGUOUS was introduced for  multiprocessor bjacobi
> preconditioner,
> which has not been used/tested in other situations, likely causes problems.
> Can you send us a stand-alone code that reproduces the malloc errors?
>
> Hong
>
>>
>>>
>>> 2012/10/15 Hong Zhang <hzhang at mcs.anl.gov>
>>>
>>>> Stefano :
>>>>
>>>>>
>>>>> is it possible to use PCRedundant with PETSC_SUBCOMM_CONTIGUOUS as
>>>>> subcomm type?
>>>>>
>>>> I think "PETSC_SUBCOMM_CONTIGUOUS" is the default for PCRedundant.
>>>>
>>>> Hong
>>>>
>>>
>>>
>>>
>>> --
>>> Stefano
>>>
>>
>>
>>
>> --
>> Stefano
>>
>
>
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