Re: [ROOT] chaining/efficiency query

From: Rene Brun (Rene.Brun@cern.ch)
Date: Fri Sep 12 2003 - 15:23:33 MEST


Ed,

How big are your files? 1 Mbyte, 100 MBytes, 1 GByte ?
How long does it take to process one single file?
TChain should not add any overhead.
Which version are you using?

Rene Brun

Edward Moyse wrote:
> 
> Hi guys,
> 
> A quick question: I have 3000 files on castor. At the moment I have a loop
> which chains all the files together, and then the resulting TChain is used
> for the eventloop. This is extremely, extremely slow - so far it's been 30
> mins and only 300 of the 3000 files are chained.
> 
> I'm not sure how ROOT works - does it load the files in memory to chain them?
> 
> Does the number of files make a difference? Would it be quicker to merge the
> 3000 into (say) 30 large files and chain those, or is ROOT just limited by
> network performance (i.e. there's nothing I can do)?
> 
> Cheers!
> 
> Ed Moyse



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