[Fwd: Re: A lot of root files]
From: Rene Brun (Rene.Brun@cern.ch)
Date: Tue Feb 10 1998 - 10:42:09 MET
attached mail follows:
Tadeusz Pytlos wrote:
> Hello RootPeople,
> At first best wishes for the ROOT team. I'm very happy to change PAW
> on ROOT, but in case each new system there are some new problems.
> I've got a lot of root files (circe 160), which I converted from Hbook's
> ntuples. Everyone is the same and looks
>
> root [0] f=new TFile("dst001.root")
> (class TFile*)0x0
> root [1] f.ls()
> TFile** dst001.root
> TFile* dst001.root
> KEY: TTree h10;1
>
> I would like to analyse about 150 files together, but I couldn't
> find anywhere corresponding example.
> I tried to read it in this way
>
> TChain bas("h10");
> bas.Add("/home/root/dst001.root");
> bas.Add("/home/root/dst002.root");
> bas.Add("/home/root/dst003.root");
> bas.Add("/home/root/dst004.root");
> bas.Add("/home/root/dst005.root");
> .....
> but I received the error:
>
> Error in <TChain::Add>: Too many chain elements
> Error in <TChain::Add>: Too many chain elements
> Error in <TChain::Add>: Too many chain elements
> ...
The current implementation of TChain has a stupid limitationof 100 files
maximum. I have modified the dev version
to support an unlimited number of files.
>
>
> and created histogram only for partly data.
> Everthing is good if I take less root files. But I prefer to have
> everything in one macro, so in that case I wanted to divide root
> files in chains,because in the TChain.Add description there is
> "An element can be the name of another chain or the name of a file
> containing a tree".
>
> TChain bas("h10");
> TChain bas1("h10");
> TChain bas2("h10");
> bas1.Add("/home/root/dst001.root");
> ....
> bas2.Add("/home/root/dst070.root");
> ....
> bas.Add("bas1")
> bas.Add("bas2")
> ....
>
> But it doesnt work because root require .root extension
> and looks for files, not for chains.
> Would you help me to solve this problem?
TChain supports only files, not chains.Following my recent discussions at
FNAL with the D0 and CDF
collaborations to support branches of a Tree going to different files,
I want to prototype an extension of TTree and TChain to support
a hierarchy of files and chains in TChain.
> I've also problem with how to limit histrogram in the direction of
> y axis (something like 'max 1 1000' in PAW).
Use TH1::SetMaximum or/and TH1::SetMinimum
Rene Brun
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: Tue Jan 04 2000 - 00:34:29 MET