Re: [Boost-users] [mpi] irecv / send problem

Subject: Re: [Boost-users] [mpi] irecv / send problem
From: tom fogal (tfogal_at_[hidden])
Date: 2009-07-01 23:09:42

Nick Collier <nick.collier_at_[hidden]> writes:
> I running into an issue where an irecv followed by a send results in  
> deadlock. A simple test case,
[snip]
> 	int other = world.rank() == 0 ? 1 : 0;
> 	cout << world.rank() << " irecv from " << other << endl;
> 	receipt.request = world.irecv(other, 0, receipt.items);
> 	cout << world.rank() << " sending to " << other << endl;
> 	world.send(other, 0, msg);
[snip]

Does this even work with non-boost MPI?  My reading (skimming) of the
MPI spec does not generate the implication that synchronous sends can
be asynchronously received.

See:

  http://www.mpi-forum.org/docs/mpi21-report/node58.htm#Node58

Note the emphasized part in:

   The fields in a status object returned by a call to
   MPI_WAIT, MPI_TEST, or any of the other derived functions *(
   MPI_{TEST|WAIT}{ALL|SOME|ANY}), where the request corresponds to
   a send call, are undefined, with two exceptions: The error status
   field will contain valid information if the wait or test call
   returned with MPI_ERR_IN_STATUS; and the returned status can be
   queried by the call MPI_TEST_CANCELLED.*

_Wait and _Test not working *does* imply, to me, that synchronous and
asynchronous communication may not be mixed for the same communication.

-tom