Problem with CopyTree and writing to file

From: Ola Kristoffer Oye <oye_at_ift.uib.no>
Date: Thu, 27 Jan 2005 15:31:06 +0100

Hi,
I have a TChain from which I want to select certain entries, copy them to a new TTree, and write the new TTree to a file.

My problem is that when I copy more than a certain number of entries to the new tree, the original tree also gets written to the file.

My macro:

#include "Analysis_split.C"

void WriteEtMiss(Long64_t nbrEntries)
{
  Analysis_split *a = new Analysis_split(0); //made with MakeClass on

the TChain I                                            //I want to copy 

from.
  TFile *output = new TFile("EtMissCut.root","RECREATE");   TTree *EtMiss;
  EtMiss = a->fChain->CopyTree("ETmiss>500","",nbrEntries,0);

  EtMiss->SetName("EtMiss");
  EtMiss->SetTitle("EtMissTitle");
  EtMiss->Write();

}

The output from root when scanning 5336 events or less from the original tree:

     root [5] WriteEtMiss(5336)
     root [6] .ls
     TFile**         EtMissCut.root
      TFile*         EtMissCut.root
       OBJ: TTree    EtMiss  EtMissTitle : 0 at: 0xcc5ced8
       KEY: TTree    EtMiss;1        EtMissTitle
     root [7] EtMiss->GetEntries()


     (long long)2291

     root [8]

This works as I meant it to. The tree EtMiss gets written to the file. However, if I try to scan more than 5336 entries, the tree/chain that I copy from (t3333) also gets written to the file:

     root [1] WriteEtMiss(5337)
     root [2] .ls
     TFile**         EtMissCut.root
      TFile*         EtMissCut.root
       OBJ: TTree    EtMiss  EtMissTitle : 0 at: 0xbb4e260
       KEY: TTree    t3333;1 Combined Ntuple
       KEY: TTree    EtMiss;1        EtMissTitle
     root [3] t3333->GetEntries()


     (long long)2292

     root [4] EtMiss->GetEntries()


     (long long)2292

The chain that I run on has 25256 events. Each file in the chain has 400 entries (except for the last). If I run on more events, for instance 20000, t3333;1 is replaced by t3333;4.

If I run on another dataset, the number for entries where this happens is different.
The phenomenon then occurs at 23384 entries. But the number of entries copied to EtMiss is now 2107, which is of the same order as in the first example (the second data sample has fewer entries that satisfies the selection criteria).

I have never used CopyTree before, so I might be doing something the wrong way here.

I use root version 4.02/00 on SLC3. I downloaded binaries from the root homepage.

Thanks in advance!

cheers,
Ola Received on Thu Jan 27 2005 - 15:32:49 MET