[MOAB-dev] Question about iMesh and Fortran 90/2003

[Chris Eldred]

Hey Tim,

Using an integer tag to number vertices/faces/edges myself seems like
the easiest option. I should just be able to use the handle array as
an input into iMesh_getIntArrData to get the integer tag array, which
is basically converting from handles to some form of (global) integer
id.

Thanks,
Chris

On Fri, Nov 15, 2013 at 1:14 PM, Tim Tautges <tautges at mcs.anl.gov> wrote:
> Hi Chris,
>   Using the id associated with handles in C++ MOAB is dicey, since there
> aren't any guarantees that integer space is contiguous, and in parallel that
> gives local ids but not global ones.  The quick answer to your question is
> that you may want to use an integer tag and number your vertices yourself,
> then use the handle array you get back as connectivity as input to the
> function to get that integer tag data for those vertices.
>
> Secondly, I just this morning committed another example that shows how to
> use iMesh from F90 that may help.  It's not exactly what you're doing, but
> it may show some more things about accessing MOAB through ISO_C_BINDING.
> It's on my to-do list to document F90+iMesh/MOAB better.
>
> I'll also look over your code in a minute, but wanted to get this answer out
> quickly.
>
> - tim
>
>
> On 11/14/2013 08:20 PM, Chris Eldred wrote:
>>
>> Hey Moab-Dev,
>>
>> I am trying to write a Fortran code that uses iMesh to call MOAB, and
>> I keep running into errors. What I would like to be able to do it is
>> to convert an adjacency returned by iMesh_getEntAdj from type(c_ptr)
>> to integers. In MOAB using C++ this seems to be trivial (use id =
>> id_from_handle(HANDLE) . It would also be useful to have the dual of
>> this operator (handle = handle_from_id(ID) ). I can't seem to get it
>> to work in Fortran however. My code is:
>>
>> subroutine get_adjacency(entity, entity_requested, adjacencyptr,
>> adjacency_size)
>> implicit none
>>
>> integer(kind=c_int) :: alloc, adjacency_size
>> integer(kind=c_int) :: entity_requested
>> integer(kind=c_int), pointer, dimension(:) :: adjacency
>> type(c_ptr) :: entity
>> type(c_ptr) :: adjacencyptr_C
>> type(c_ptr), pointer, dimension(:) :: adjacencyptr
>>
>> alloc = 0
>> call iMesh_getEntAdj( mesh, entity, entity_requested, adjacencyptr_C,
>> alloc, adjacency_size, ierr)
>> CHECK("Couldn't get adjacencies")
>> call C_F_POINTER(adjacencyptr_C, adjacencyptr, [alloc])
>> adjacency = transfer(adjacencyptr,adjacency,adjacency_size)
>>
>> end subroutine get_adjacency
>>
>> I have tried using the transfer function, but that produces memory
>> (segmentation fault) errors. Everything before this line works fine. I
>> am using the Fortran 2003 modules (iMesh_iso.F03) from
>>
>> https://redmine.scorec.rpi.edu/anonsvn/itaps/software/trunk/interfaces/iMesh/examples/FindAdjacency/.
>> I've also looked through the iBase and iMesh documentation, but there
>> is very little information there about using Fortran instead of C/C++.
>> I am not very familiar with mixed C/Fortran programming, so it is
>> entirely possible that I just don't understand what is going on.
>>
>> Thanks,
>> Chris Eldred
>>
>
> --
> ================================================================
> "You will keep in perfect peace him whose mind is
>   steadfast, because he trusts in you."               Isaiah 26:3
>
>              Tim Tautges            Argonne National Laboratory
>          (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
>  phone (gvoice): (608) 354-1459      1500 Engineering Dr.
>             fax: (608) 263-4499      Madison, WI 53706
>



-- 
Chris Eldred
DOE Computational Science Graduate Fellow
Graduate Student, Atmospheric Science, Colorado State University
B.S. Applied Computational Physics, Carnegie Mellon University, 2009
chris.eldred at gmail.com / celdred at atmos.colostate.edu