Re: [ROOT] write a big Tree in a TFile

From: Matthieu Lechowski (lechowsk@lal.in2p3.fr)
Date: Mon Sep 29 2003 - 11:42:37 MEST


Hello,

It's not easy to have a simplified version of my code, but if it's
necessary I will provide you.

I understand why the 2nd solution did not work: actually, I have to
open a second file where I get data to fill my Tree.

So I have this order of instructions:

 TTree *TREE = new TTree(...)
 TFile *data_file = new TFile(name_data_file);
 //..fill tree
 data_file->Close();

 TFile *myfile=new TFile(name_ntuple, "RECREATE");
 TREE->Write();
 myfile->Close(); //"delete myfile;" doesn't work

I just have changed the place of data_file->Close(). Indeed it was at
the end, so when I tried to put "TFile *myfile=new ..." at the top as you
said, of course the TREE->Write() wanted write in "data_file" instead of
"myfile" (that's why I had the message "... not writable", I did not see
that the message concerned "data_file" and not "myfile", sorry).

But even placing data_file->Close() before writing the tree, it does not
work when I put "TFile *myfile=new ..." at the top.

----
In conclusion, I have to manage 2 files, and I want write a Tree in one
of them. The instructions above work for small files, but not for big
ones.
Do you see where could be the problem ?

Matthieu.

On Mon, 29 Sep 2003, Rene Brun wrote:

> I am afraid that we will not make any progress without looking at a simplified
> version of your code reproducing this problem.
>
> Rene Brun
>
> Matthieu Lechowski wrote:
> >
> > Hello,
> > Thanks, but unfortunately it doesn't work.
> > The first solution doesn't change anything, and with the second ROOT
> > tells me my file is not writable (Error in <TTree::Write>: File ... is
> > not writable).
> > Have you others ideas ?
> > Thank you.
> >
> > Matthieu.
> >
> > On Fri, 26 Sep 2003, Rene Brun wrote:
> >
> > > Matthieu,
> > >
> > > This seems to be a problem with the destructor of your TTree when
> > > you close the file.
> > > You can try two solutions:
> > >  1- after TREE.Write(); add the statement
> > >     TREE.SetFile(0);
> > >
> > >  2- Do not create your Tree in the stack, but in the heap with
> > >    TFile *myfile=new TFile(name_ntuple, "RECREATE");
> > >    TTree *TREE = new TTRee(...
> > >    //..fill tree
> > >    TREE->Write();
> > >    delete myfile; //do not delete TREE
> > >
> > > Rene Brun
> > >
> > > Matthieu Lechowski wrote:
> > > >
> > > > Hello,
> > > >
> > > > ROOT leaves without saying anything when I try to write a TTree in a
> > > > TFile, and the file has only few bytes (and can not be opened of
> > > > course).
> > > >
> > > > I have a global tree: TTree TREE("T","TREE");
> > > > In a function, I fill it, then:
> > > >  TFile *myfile=new TFile(name_ntuple, "RECREATE");
> > > >  TREE.Write();
> > > >  myfile->Close();
> > > >
> > > > This is the way I always used, and it always worked, but this time I
> > > > have a big Tree and this doesn't work, I don't know why.
> > > > Its size is less than the limit 2Gb, I think it should be around 80Mb
> > > > with 100.000 entries (I have already a similar file of 8Mb with 10.000
> > > > entries that I succeeded to write).
> > > >
> > > > Have you an idea of what goes wrong ?
> > > > Thank you.
> > > >
> > > >         Matthieu Lechowski
> > > >         LAL Orsay
> > > >
> > > > lxplus
> > > > ROOTSYS=/afs/cern.ch/sw/root/v3.05.05/rh73_gcc2952/root
> > >
>



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