On Sep 6, 2005, at 11:02 AM, Michael Lees wrote:
> Hi,
>
> I understand that lam doesn't implement MPI_Cancel for send requests.
Correct.
> If a program attempts to terminate without canceling a non-blocking
> receive, what happens?
> Does MPI_Finalize wait until all posted non blocking receives have
> finished or been canceled? What if there are still pending sends which
> haven't finished?
On abnormal termination (segmentation fault, etc.), the peer processes
will either:
a) Abort, since the default behavior in MPI, or
b) If the program setup an error handler, the operation will return an
erroneous return code indicating the peer has failed.
Some sections of the message may have been received, but the data in
the buffer should not be relied upon. The buffer is however free for
use at this time, since the request has completed.
In the normal termination case, where a program calls MPI_Finalize()
then exits, the standard say'ith that:
"The user must ensure that all pending communication involving a
process completes before the process calls MPI_FINALIZE"
So to be conformant to the standard, the program should explicitly wait
for all requests to finish before exiting. LAM/MPI waits for all
requests to finish from within MPI_Finalize, as a convenience to the
user.
>
> If a program will terminate with pending communication is it
> safe/recommended to do so?
A 'correct' program would not terminate with pending communication, per
the standard. So it is not recommended that a MPI program to terminate
with pending communication.
>
>
> Thanks
> --
> Mike
>
>
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----
Josh Hursey
jjhursey_at_[hidden]
http://www.lam-mpi.org/
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