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Subject: Re: [OMPI users] Need Performance estimation of MPI_Bcast
From: Jeffrey Squyres (jsquyres_at_[hidden])
Date: 2012-04-04 09:35:56


It's a bit more complicated than that; there are many factors involved:

- how many peer MPI processes are involved in the broadcast
- how many of those peers are local (and will likely communicate via shared memory, not a network device) and how many are remote
- what broadcast algorithm is used (there are many)

So the simplistic logp model won't help you here -- you'll need to be more complicated, and/or dig into the academic papers on these kinds of things.

On Apr 4, 2012, at 9:11 AM, anas trad wrote:

> Hi Envoyé ,
>
> Thanks for the reply but I want to estimate the time of executing MPI_Bcast function by mathmatics. I found that we can achieve this by using LogGP model with this equation:
>
> T = ceil(log2p) . (L + 2 · o + (n − 1) · G
>
> but that does not give good accuracy for time evaluation.
>
>
>
> --- On Wed, 4/4/12, Aurélien Bouteiller <bouteill_at_[hidden]> wrote:
>
> From: Aurélien Bouteiller <bouteill_at_[hidden]>
> Subject: Re: [OMPI users] Need Performance estimation of MPI_Bcast
> To: "Open MPI Users" <users_at_[hidden]>
> Cc: "users_at_[hidden]" <users_at_[hidden]>
> Date: Wednesday, April 4, 2012, 3:50 PM
>
> You can use the intel mpi benchmark, or skampi. These two programs are designed to evaluate Moi performance.
>
> Envoyé de mon iPad
>
> Le 2012-04-04 à 08:46, anas trad <tradat84_at_[hidden]> a écrit :
>
>> Hi all,
>>
>> I need to know the time estimation of executing MPI_Bcast function on Neolith Cluster. Please, can anyone show me how to achieve that.
>>
>> Thanks,
>> Anas
>>
>> _______________________________________________
>> users mailing list
>> users_at_[hidden]
>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>
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-- 
Jeff Squyres
jsquyres_at_[hidden]
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