[ROOT] TChain with TCutG

From: LEE, KERRY T. (JSC-SR) (UHCL) (kerry.t.lee1@jsc.nasa.gov)
Date: Wed Oct 02 2002 - 21:34:45 MEST


Hi,

I am using ROOT from CVS on September 30, 2002, running on Red Hat 7.1.

I have run into what appears to be a bug in TChain when using a graphical
cut (TCutG).  To see if it was a problem just in my code, I went back to the
Event example provided in ROOT.  I ran the Event example and produced the
Event.root file, I then made a copy of Event.root and called it Event2.root
so that I could make a TChain with more than one file.

I then ran an interactive session of ROOT.

root [0] .L libEvent.so
root [1] TChain f("T")
root [2] f.Add("Event.root")
(Int_t)1
root [3] f.Add("Event2.root")
(Int_t)1
root [4] f.StartViewer()
tv__tree = (TTree *) gROOT->FindObject("T");
tv__tree_list->Add(tv__tree);
File name : Event2.root

After I started the tree viewer I plotted fNtrack:fNseg.  I then made a
graphical cut using the editor from the Edit menu, and renamed it cut1.

root [5] tv__tree->Draw("fNtrack:fNseg","","", 800, 0);
<TCanvas::MakeDefCanvas>: created default TCanvas with name c1
 
root [5] f.Draw("fNtrack:fNseg","cut1")
(Int_t)424
root [6] f.Draw("fNtrack:fNseg","cut1 && fNseg<6000")
 
 *** Break *** segmentation violation

Notice that when doing f.Draw() with only the graphical cut things work
fine, but when an additional selection requirement is added it breaks.  I
noticed that it seems to break after it has iterated through the first file
and breaks when reading the second file.

Is this a bug or am I missing something?

Thanks
Kerry



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