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Subject: Re: [OMPI users] Multicast?
From: Brock Palen (brockp_at_[hidden])
Date: 2008-12-10 13:52:45


Thanks I will pass that on to the person asking. And it answers my
own questions of observed behavior with IMB and other tools.

Brock Palen
www.umich.edu/~brockp
Center for Advanced Computing
brockp_at_[hidden]
(734)936-1985

On Dec 10, 2008, at 10:37 AM, George Bosilca wrote:

> Brock,
>
> Open MPI has a very fancy collective implementation. While we don't
> use multicast, we dynamically change the algorithm used for the
> collective based on the number of nodes, the size and type of the
> message, and eventually the operation involved if any. Moreover, we
> detect hierarchies, and we can potentially change the algorithms to
> take advantage of this knowledge.
>
> If you want more information, please refer to this paper (Flexible
> collective communication tuning architecture applied to Open MPI)
> for more information, http://www.netlib.org/netlib/utk/people/
> JackDongarra/PAPERS/Flex-collective-euro-pvmmpi-2006.pdf..
>
> Thanks,
> george.
>
> On Dec 9, 2008, at 21:49 , Brock Palen wrote:
>
>> Is OpenMPI using Multicast for things like MPI_Bcast() ?
>>
>> Some simple tests of really old versions (1.0.2) showed binary
>> tree type performance, while latter versions gave me the same run
>> time no matter how many CPU's I used.
>>
>> Thus this lead me to believe that something like multicast is in
>> use. Is it?
>>
>>
>> Brock Palen
>> www.umich.edu/~brockp
>> Center for Advanced Computing
>> brockp_at_[hidden]
>> (734)936-1985
>>
>>
>>
>>
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>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
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