Re: Multi-thread and TTree

From: Fons Rademakers <Fons.Rademakers_at_cern.ch>
Date: Tue, 19 Dec 2006 20:06:51 +0100


Hi Antonio,

   have a look at this poster:

ftp://root.cern.ch/root/PROOFIntelDemo.pdf

More will come in the new year.

Cheers, Fons.

Antonio Bulgheroni wrote:
> Dear Rene,
> thanks for the prompt answer, I'm having a look to the websites
> you suggested me. Do you think that PROOF can be exploited also on a
> multi-processor PC and not on a cluster (this is actually my case)?
>
> Thanks again,
>
> Antonio
>
> --
> Antonio Bulgheroni, PhD
>
> Win98 error 009: Press any key to continue or any other key to quit.
>
> On 12/19/06, *Rene Brun* <Rene.Brun_at_cern.ch <mailto:Rene.Brun_at_cern.ch>>
> wrote:
>
> Antonio,
>
> What you describe is precisely what the PROOF system is doing. See:
> http://higweb.lns.mit.edu/twikis/proof/bin/view/Proof/WebHome
> http://higweb.lns.mit.edu/twikis/proof/bin/view/Proof/ProofDocs
> etc
>
> Rene Brun
>
> Antonio Bulgheroni wrote:
> > Dear ROOTers,
> > I have browsed the ROOT-Talk archive but I wasn't able to
> find
> > an updated answer to my question. This is what I would like to do:
> >
> > I have a TFile with a TTree containing lots of events and I want to
> > process them in parallel. Since I just have to apply the same
> > procedure to all events, I think that the easiest possible way to
> > perform parallel computing is to split the amount of events among
> > different threads each of which is doing the same things.
> >
> > Here comes the first question. I've read somewhere that ROOT I/O is
> > not (yet) thread safe. Does it mean that different threads cannot
> > GetEntry from the same TTree on one TFile? Should I
> TMutex::Lock() and
> > UnLock() each GetEntry() call?
> >
> > During the event process, I would like to fill a bunch of histograms
> > and an output TTree. Can it be done by different threads? Again,
> > should I mute every Fill() call?
> >
> > In the TThreadFactory abstract base class it is written that
> depending
> > on which factory is active one gets the Posix or Win32 implementation
> > of the TThread but I'm not able to find the TWin32Thread. Does it
> exist?
> >
> > I'm using ROOT 5.15/01 on a Fedora Core 4 linux box with gcc 4.0.2
> >
> > Thank you very much for your help,
> >
> > regards,
> >
> > Antonio
> >
> > --
> > Antonio Bulgheroni, PhD
> >
>
>

-- 
Org:    CERN, European Laboratory for Particle Physics.
Mail:   1211 Geneve 23, Switzerland
E-Mail: Fons.Rademakers_at_cern.ch              Phone: +41 22 7679248
WWW:    http://fons.rademakers.org           Fax:   +41 22 7669640
Received on Tue Dec 19 2006 - 20:06:13 MET

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