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

[Richard Tran Mills]

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.)

--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 
> <mailto: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 <mailto:rmills at ornl.gov>  V: 865-241-3198
>     <tel:865-241-3198> http://climate.ornl.gov/~rmills
>     <http://climate.ornl.gov/%7Ermills>
>
>


-- 
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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