[petsc-dev] Need mechanism to set LocalToGlobal mapping in a DMShell

[Peter Brune]

On Thu, Feb 21, 2013 at 12:58 PM, Dmitry Karpeev <karpeev at mcs.anl.gov>wrote:

>
>
> On Thu, Feb 21, 2013 at 12:54 PM, Richard Tran Mills <rtm at eecs.utk.edu>wrote:
>
>>  Hi Jed,
>>
>> The reason is that in the PFLOTRAN code we currently have some code like
>> this:
>>
>>   select case(discretization%itype)
>>     case(STRUCTURED_GRID,STRUCTURED_GRID_MIMETIC)
>>       call
>> DMLocalToGlobalBegin(dm_ptr%sgdm,local_vec,INSERT_VALUES,global_vec,ierr)
>>       call
>> DMLocalToGlobalEnd(dm_ptr%sgdm,local_vec,INSERT_VALUES,global_vec,ierr)
>>    case(UNSTRUCTURED_GRID)
>>       call VecScatterBegin(dm_ptr%ugdm%scatter_ltog,local_vec,global_vec,
>> &
>>                            INSERT_VALUES,SCATTER_FORWARD,ierr)
>>       call VecScatterEnd(dm_ptr%ugdm%scatter_ltog,local_vec,global_vec, &
>>                          INSERT_VALUES,SCATTER_FORWARD,ierr)
>>   end select
>>
>> where in the STRUCTURED_GRID case we have a DMDA.  In the
>> UNSTRUCTURED_GRID case we have no DM, and I want to pack things into a
>> DMShell so that have a DM and the various DM calls work (and then I can
>> eliminate these 'select case' statements).
>>
>> (Eventually I'd like to be using more of the PETSc infrastructure and not
>> even calling DMLocalToGlobalBegin(), etc., in the PFLOTRAN code, but that
>> can wait a bit.)
>>
> I would vote for DMGetLocalToGlobalMapping() etc.
> That has the flexibility to be used with  DM-impl-oblivious codes.
>

The Set is the issue at hand; and it probably belongs in DMShell as a
Set/SetCreate pair like everything else in DMShell.


> Dmitry.
>
>>
>>
>> --Richard
>>
>>
>>
>> On 2/21/13 1:42 PM, Jed Brown wrote:
>>
>> It would be natural to have a matching interface, but why do you need it?
>> You're in charge of making the matrices and vectors so you can give them
>> local-to-global mappings. The only solver that calls
>> DMGetLocalToGlobalMapping is PCEXOTIC, which only works with DMDA anyway.
>>
>>
>> On Thu, Feb 21, 2013 at 12:35 PM, Richard Tran Mills <rtm at eecs.utk.edu>wrote:
>>
>>> Hi Folks,
>>>
>>> I want to set a LocalToGlobal mapping in a DMShell object.  Should we
>>> add a DMShell routine to do this, or just add a DMSetLocalToGlobalMapping()
>>> routine?
>>>
>>> Thanks,
>>> Richard
>>>
>>> --
>>> Richard Tran Mills, Ph.D.
>>> Computational Earth Scientist      | Joint Assistant Professor
>>> Hydrogeochemical Dynamics Team     | EECS and Earth & Planetary Sciences
>>> Oak Ridge National Laboratory      | University of Tennessee, Knoxville
>>> E-mail: rmills at ornl.gov  V: 865-241-3198 http://climate.ornl.gov/~rmills
>>>
>>>
>>
>>
>> --
>> Richard Tran Mills, Ph.D.
>> Computational Earth Scientist      | Joint Assistant Professor
>> Hydrogeochemical Dynamics Team     | EECS and Earth & Planetary Sciences
>> Oak Ridge National Laboratory      | University of Tennessee, Knoxville
>> E-mail: rmills at ornl.gov  V: 865-241-3198 http://climate.ornl.gov/~rmills
>>
>>
>
>
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