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From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2007-10-24 20:47:29

I believe that the second scenario that Sriram described is
incorrect: you cannot merge independent intercommunicators into a
single communicator (either intra or inter).

On Oct 18, 2007, at 4:36 PM, Murat Knecht wrote:

> Hi,
> I have a question regarding merging intracommunicators.
> Using MPI_Spawn, I create on designated machines child processes,
> retrieving an intercommunicator each time.
> With MPI_Intercomm_Merge it is possible to get an intracommunicator
> containing the master process(es) and the newly spawned child process.
> The problem is to merge the intracommunicators into a single one.
> I understand there is the possibilty to use the so created
> intracommunicator from the first try in order to spawn the second
> child,
> merge this one into the intracomm and continue like this.
> This brings some considerable adminstrative overhead with it, as all
> already spawned children must (be informed to) participate in the
> spawn
> call.
> I would rather merge all intercommunicators together in the end using
> only the master process for spawning.
> Both these possibilites have been mentioned in the following post.
> While I understand the first one, I do not follow the second - I
> cannot
> seem to find any method to merge multiple inter- or intracomms into a
> single intracomm.
> Groups cannot be used either, to collect the children and retrieve the
> intracomm, because this is only used for subgrouping within an already
> existing intracommunicator-group.
> Is there a way to merge them the easy way, or did I misread the
> post above?
> Thanks & best regards,
> Murat
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Jeff Squyres
Cisco Systems