On Nov 1, 2012, at 9:03 PM, Roy Stogner <royst...@ices.utexas.edu> wrote:
>
> On Thu, 1 Nov 2012, Kirk, Benjamin (JSC-EG311) wrote:
>
>> Roy - I'd like to have a default constructor for the MessageTag so I
>> can create a vector of them. I have a use case where I need a
>> number of tags, and this is the easiest way to store them so I can
>> then loop through the tags and receive from any source but in a
>> predictable order on the content.
>
> Definitely sounds reasonable.
>
>> I was thinking a static MessageTag::invalid_tag =
>> std::numeric_limits<int>::min() or something like that,
>
> Something we can libmesh_assert() against? Yeah, that sounds good.
>
> I'd prefer for the default constructor to give something valid, but we
> can't get a unique valid tag without a Communicator argument...
>
>> but wasn't sure where to initialize it with this being header-only
>> now.
>
> I cheated and put Communicator_World (and now CommWorld) in libmesh.C,
> but there's no reason other than my laziness not to just create a
> parallel.C for those.
Here's what I currently want to do:
// on all processors
for (unsigned int blk=0; blk<num_blks; blk++)
{
...
Parallel::MessageTag id_tag =
Parallel::Communicator_World.get_unique_tag(100*num_blks + blk);
// send the data for this block
Parallel::send (0, ids, id_requests[blk], id_tag);
}
if (libMesh::processor_id() == 0)
{
...
for (unsigned int blk=0; blk<num_blks; blk++)
for (unsigned int comm_step=0; comm_step<libMesh::n_processors();
comm_step++)
{
...
Parallel::MessageTag id_tag =
Parallel::Communicator_World.get_unique_tag(100*num_blks + blk);
// receive data for this block, imposing no particular order on
processor
Parallel::receive (Parallel::any_source, ids, id_tag);
}
}
If I do this I don't need a container. But there is a problem, at least in
DEBUG mode, there is a collective assertion in get_unique_tag(), preventing me
from creating one inside the "if (libMesh::processor_id() == 0)" bit
See the issue? What would your proposed path forward be?
-Ben
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