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Subject: Re: [OMPI devel] MPI_Bcast
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-11-19 07:13:31


+1 on what George says.

In general, the only MPI collective operation that *forces* an explicit, global synchronization is MPI_Barrier. Specifically: no process can exit the barrier until all processes have entered the barrier.

In you example (MPI_Bcast), none of the non-root processes can exit the bcast before the root enters the bcast. This is a much weaker synchronization than barrier.

On Nov 18, 2012, at 10:18 PM, George Bosilca wrote:

> In this case the MPI_Bcast will act as a synchronization point, the slaves will be blocked in the call until the master do the operation.
>
> george.
>
> On Nov 18, 2012, at 15:54 , Sandra Guija <sguija_at_[hidden]> wrote:
>
>> Hello,
>> Could someone be kind and explain me the MPI_Bcast when is call by all the other processes?
>> I am having some difficulties in fully understanding it.
>> The reason I asked, it is because in my code there are some slaves calling the MPI_Bcast function prior the master calls it.
>> Thanks,
>> Sandra Guija
>>
>> > From: jsquyres_at_[hidden]
>> > Date: Wed, 14 Nov 2012 08:02:13 -0700
>> > To: devel_at_[hidden]
>> > Subject: [OMPI devel] topics for Dec. developer's meeting
>> >
>> > A few people have approached me with topics for the Dec meeting. I put the ones that I could remember on the wiki. Please go fill in whatever topics you want to discuss:
>> >
>> > https://svn.open-mpi.org/trac/ompi/wiki/Dec12Meeting
>> >
>> > --
>> > Jeff Squyres
>> > jsquyres_at_[hidden]
>> > For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
>> >
>> >
>> > _______________________________________________
>> > devel mailing list
>> > devel_at_[hidden]
>> > http://www.open-mpi.org/mailman/listinfo.cgi/devel
>> _______________________________________________
>> devel mailing list
>> devel_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>
> _______________________________________________
> devel mailing list
> devel_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/devel

-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/