Correction on this, this problem only occurs (with OpenMPI 1.2) when
I don't use mpirun to launch my process.
I know seems strange to most mpi users, it turns out that when using
OpenMPI and only needing one process (because I spawn everything else
I need), I had found it quicker just to launch the executable directly.
I have only confirmed my test code works with OpenMPI 1.2 (if I have
trouble I'll test 1.1), below is the proper output for my test of
spawning, disconnecting, and respawning:
>mpirun -np 1 parent2
parent: 0 of 1
parent: How many processes total?
2
parent: Calling MPI_Comm_spawn to start 1 subprocesses.
child starting
parent returned from Comm_Spawn call
parent: Calling MPI_BCAST with btest = 17 . child = 3
child 0 of 1: Parent 3
parent: Calling MPI_Comm_spawn to start 1 subprocesses.
child 0 of 1: Receiving 17 from parent
child calling COMM_FREE
child calling FINALIZE
child exiting
Maximum user memory allocated: 0
child starting
parent: Calling MPI_BCAST with btest = 17 . child = 3
child 0 of 1: Parent 3
child 0 of 1: Receiving 17 from parent
child calling COMM_FREE
child calling FINALIZE
Michael
On Apr 25, 2006, at 2:57 PM, Michael Kluskens wrote:
I'm running OpenMPI 1.1 (v9704)and when a spawned processes exits
the parent does not die (see previous discussions about
1.0.1/1.0.2); however, the next time the parent tries to spawn a
process MPI_Comm_spawn does not return.
My test output below:
parent: 0 of 1
parent: How many processes total?
2
parent: Calling MPI_Comm_spawn to start 1 subprocesses.
child starting
parent returned from Comm_Spawn call
parent: Calling MPI_BCAST with btest = 17 . child = 3
child 0 of 1: Parent 3
parent: Calling MPI_Comm_spawn to start 1 subprocesses.
child 0 of 1: Receiving 17 from parent
child calling COMM_FREE
child calling FINALIZE
child exiting
Notice there is no message saying "parent returned from Comm_Spawn"
and the parent just sits there and obviously the second set of
processes don't get launched.
Quick note on code fixes, my child process now calls MPI_COMM_FREE
(parent,ierr) to free the communicator to the parent before
exiting, in earlier version of 1.1 this crashed the code. I'm
guessing this is the right thing to do, the Complete Reference book
has an example without it and the Using MPI-2 book has a more
detailed example with this in. In either case, I get the same
results regardless.
Background from previous discussion on this follows. It will cost
me less to test new versions of Open MPI handling this than work
around this issue in my project.
Michael
On Mar 2, 2006, at 1:55 PM, Ralph Castain wrote:
We expect to have much better support for the entire comm_spawn
process in the next incarnation of the RTE. I don't expect that to
be included in a release, however, until 1.1 (Jeff may be able to
give you an estimate for when that will happen).
Jeff et al may be able to give you access to an early non-release
version sooner, if better comm_spawn support is a critical issue
and you don't mind being patient with the inevitable bugs in such
versions.
Ralph
Edgar Gabriel wrote:
Open MPI currently does not fully support a proper disconnection
of parent and child processes. Thus, if a child dies/aborts, the
parents will abort as well, despite of calling
MPI_Comm_disconnect. (The new RTE will have better support for
these operations, Ralph/Jeff can probably give a better estimate
when this will be available.) However, what should not happen is,
that if the child calls MPI_Finalize (so not a violent death but
a proper shutdown), the parent goes down at the same time. Let me
check that as well... Brignone, Sergio wrote:
Hi everybody, I am trying to run a master/slave set. Because of
the nature of the problem I need to start and stop (kill) some
slaves. The problem is that as soon as one of the slave dies,
the master dies also.
<child2.f90>
<parent2.f90>
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