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From: George Bosilca (bosilca_at_[hidden])
Date: 2007-10-25 00:11:24


Now you cast a doubt on me. As far as I remember, there is a trick in
MPI2 to do this. You can merge your inter-communicators into one
intra-communicators with MPI_Intercomm_merge and then use
MPI_Intercomm_create to spawn a new inter-comm over the 2 childs
world (using the common parent as a bridge process) ... I have to try
it to refresh my memory :)

   george.

On Oct 24, 2007, at 8:47 PM, Jeff Squyres wrote:

> 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.
>>
>> http://www.lam-mpi.org/MailArchives/lam/2003/06/6226.php
>>
>> 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
>
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