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Subject: Re: [OMPI users] Need Performance estimation of MPI_Bcast
From: anas trad (tradat84_at_[hidden])
Date: 2012-04-04 12:12:10


OK Jeffrey thanks a lot, the answer was very helpful to me, at least I got to know the complexity of this issue. 

--- On Wed, 4/4/12, Jeffrey Squyres <jsquyres_at_[hidden]> wrote:

From: Jeffrey Squyres <jsquyres_at_[hidden]>
Subject: Re: [OMPI users] Need Performance estimation of MPI_Bcast
To: "Open MPI Users" <users_at_[hidden]>
Date: Wednesday, April 4, 2012, 5:43 PM

On Apr 4, 2012, at 9:56 AM, anas trad wrote:

> Thanks Jeffrey, I understand, can you please guide me to such paper that give more accurate estimation for the MPI_Bcast.

I can't cite any specific papers (collectives are not my focus area, and I left academia several years ago); you'll need to do some literature searches.  I know that there have been quite a few papers and research projects over the past 15+ years about algorithms for MPI collective operations (including bcast).  A good starting place would probably be proceedings from Euro MPI (and its predecessor, Euro PVM/MPI).

I'm guessing that there are probably also some papers/projects that do modeling of collective algorithms in heterogeneous latency environments (e.g., shared memory + network), but this is even farther off my focus area, so I don't even have any general areas to point to.  Sorry!

>
>
> --- On Wed, 4/4/12, Jeffrey Squyres <jsquyres_at_[hidden]> wrote:
>
> From: Jeffrey Squyres <jsquyres_at_[hidden]>
> Subject: Re: [OMPI users] Need Performance estimation of MPI_Bcast
> To: "Open MPI Users" <users_at_[hidden]>
> Date: Wednesday, April 4, 2012, 4:35 PM
>
> 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]
> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
>
>
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-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
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