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Subject: Re: [OMPI users] Dynamic process tutorials?
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-07-12 15:38:28


On Jul 12, 2010, at 11:12 AM, Brian Budge wrote:

> HI Ralph -
>
> Thanks for the reply. I think this patch sounds great! The idea in
> our software is that it won't be known until after the program is
> running whether or not MPI is needed, so it would be best if the
> communication initialization could be done programmatically instead of
> through an external program like mpirun. Is there a plan for this to
> enter the mainline?

Just to clarify: while the revised OMPI will allow singleton connect/accept, it will still only do so in the presence of a running ompi-server. There is no way to wireup singletons without that external agent.

However, ompi-server is not specific to any job, so it can be allowed to run in the background as a daemon, used only when required.

>
> Brian
>
> On Mon, Jul 12, 2010 at 8:29 AM, Ralph Castain <rhc_at_[hidden]> wrote:
>>
>> On Jul 12, 2010, at 9:07 AM, Brian Budge wrote:
>>
>>> Hi Jody -
>>>
>>> Thanks for the reply. is there a way of "fusing" intercommunicators?
>>> Let's say I have a higher level node scheduler, and it makes a new
>>> node available to a COMM that is already running. So the master
>>> spawns another process for that node. How can the new process
>>> communicate with the other already started processes?
>>
>> They can connect/accept via ompi-server - checkout "man ompi-server". You can also have them all rendezvous at a common mpirun if you prefer by using the appropriate mca param to give the required contact info.
>>
>>>
>>> Also, how can you specify with MPI_Comm_spawn/multiple() how do you
>>> specify IP addresses on which to start the processes?
>>
>> Look at "man MPI_Comm_spawn"
>>
>>>
>>> If my higher level node scheduler needs to take away a process from my
>>> COMM, is it good/bad for that node to call MPI_Finalize as it exits?
>>
>> The entire job will automatically abort if it fails to call Finalize as this is considered an abnormal termination event.
>>
>>>
>>> I would prefer not to use any of the MPI command-line utilities
>>> (mpirun/mpiexec) if that's possible.
>>
>> Not possible at the moment. I have provided a patch to another user on this list that made it possible to use ompi-server as a rendezvous point for singletons, but that isn't in any formal release yet.
>>
>>>
>>> Thanks,
>>> Brian
>>>
>>> On Sat, Jul 10, 2010 at 11:53 PM, jody <jody.xha_at_[hidden]> wrote:
>>>> Hi Brian
>>>> When you spawn processes with MPI_Comm_spawn(), one of the arguments
>>>> will be set to an intercommunicator of thes spawner and the spawnees.
>>>> You can use this intercommunicator as the communicator argument
>>>> in the MPI_functions.
>>>>
>>>> Jody
>>>> On Fri, Jul 9, 2010 at 5:56 PM, Brian Budge <brian.budge_at_[hidden]> wrote:
>>>>> Hi all -
>>>>>
>>>>> I've been looking at the dynamic process features of mpi-2. I have managed
>>>>> to actually launch processes using spawn, but haven't seen examples for
>>>>> actually communicating once these processes are launched. I am additionally
>>>>> interested in how processes created through multiple spawn calls can
>>>>> communicate.
>>>>>
>>>>> Does anyone know of resources that describe these topics? My google-fu must
>>>>> not be up to par :)
>>>>>
>>>>> Thanks,
>>>>> Brian
>>>>>
>>>>> _______________________________________________
>>>>> users mailing list
>>>>> users_at_[hidden]
>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>>
>>>>
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