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From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-04-02 12:23:42

On Apr 1, 2007, at 3:12 PM, Ralph Castain wrote:

> I can't help you with the BTL question. On the others:

Yes, you can "sorta" call BTL's directly from application programs
(are you trying to use MPI alongside other communication libraries,
and using the BTL components as a sample?), but there are issues
involved with this.

First, you need to install Open MPI with all the development
headers. Open MPI normally only installs "mpi.h" and a small number
of other heads; installing *all* the headers will allow you to write
applications that use OMPI's internal headers (such as btl.h) while
developing outside of the Open MPI source tree.

Second, you probably won't want to access the BTL's directly. To
make this make sense, here's how the code is organized (even if the
specific call sequence is not exactly this layered for performance/
optimization reasons):

MPI layer (e.g., MPI_SEND)
  -> PML
    -> BML
      -> BTL

You have two choices:

1. Go through the PML instead (this is what we do in the MPI
collectives, for example) -- but this imposes MPI semantics on
sending and receiving, which assumedly you are trying to avoid.
Check out ompi/mca/pml/pml.h.

2. Go through the BML instead -- the BTL Management Layer. This is
essentially a multiplexor for all the BTLs that have been
instantiated. I'm guessing that this is what you want to do
(remember that OMPI has true multi-device support; using the BML and
multiple BTLs is one of the ways that we do this). Have a look at
ompi/mca/bml/bml.h for the interface.

There is also currently no mechanism to get the BML and BTL pointers
that were instantiated by the PML. However, if you're just doing
proof-of-concept code, you can extract these directly from the MPI
layer's global variables to see how this stuff works.

To have full interoperability of the underlying BTLs and between
multiple upper-layer communication libraries (e.g., between OMPI and
something else) is something that we have talked about a little, but
have not done much work on.

To see the BTL interface (just for completeness), see ompi/mca/btl/

You can probably see the pattern here... In all of Open MPI's
frameworks, the public interface is in <level>/mca/<framework>/
<framework>.h, where <level> is one of opal, orte, or ompi, and
<framework> is the name of the framework.

> 1. states are reported via the orte/mca/smr framework. You will see
> the
> states listed in orte/mca/smr/smr_types.h. We track both process
> and job
> states. Hopefully, the state names will be somewhat self-
> explanatory and
> indicative of the order in which they are traversed. The job states
> are set
> when *all* of the processes in the job reach the corresponding state.

Note that these are very coarse-grained process-level states (e.g.,
is a given process running or not?). It's not clear what kind of
states you were asking about -- the Open MPI code base has many
internal state machines for various message passing and other

What information are you looking for, specifically?

> 2. I'm not sure what you mean by mapping MPI processes to "physical"
> processes, but I assume you mean how do we assign MPI ranks to
> processes on
> specific nodes. You will find that done in the orte/mca/rmaps
> framework. We
> currently only have one component in that framework - the round-robin
> implementation - that maps either by slot or by node, as indicated
> by the
> user. That code is fairly heavily commented, so you hopefully can
> understand
> what it is doing.
> Hope that helps!
> Ralph
> On 4/1/07 1:32 PM, "pooja_at_[hidden]" <pooja_at_[hidden]> wrote:
>> Hi
>> I am Pooja and I am working on a course project which requires me
>> -> to track the internal state changes of MPI and need me to
>> figure out
>> how does ORTE maps MPi Process to actual physical processes
>> ->Also I need to find way to get BTL transports work directly with
>> MPI
>> level calls.
>> I just want to know is this posible and if yes what procedure I
>> should
>> follow or I should look into which files (for change).
>> Please Help
>> Thanks and Regards
>> Pooja
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
> _______________________________________________
> devel mailing list
> devel_at_[hidden]

Jeff Squyres
Cisco Systems