[ROOT] TTree::MakeSelector needs unique variable names

From: Robert Feuerbach (feuerbac@jlab.org)
Date: Tue May 20 2003 - 23:41:19 MEST 

Hi ROOT-Team,

I'm noticing some odd/incorrect behavior out of 
TTree::MakeSelector, where the automatically generated code 
does not have unique names for the variables to hold the data 
for each branch and leaf. I'm currently testing this with 
ROOT 3.05-04, but similar results are from 3.02-07 as well. This 
was run on a Linux RH7.3 machine.


A simple test example is (do_1 and then do_2):

//------------------------------
void do_1 ()
{
  gSystem.Load("libPhysics");
  TFile *testf = new TFile("test.root","RECREATE");
  TTree *myT = new TTree("myT","test tree");

  TVector3 *dirAp = new TVector3(0.,0.,1);
  TVector3 *dirBp = new TVector3(0.,0.,2);

  myT->Branch("dirA","TVector3",&dirAp);
  myT->Branch("dirB","TVector3",&dirBp);

  myT->Fill();

  dirAp->SetXYZ(1.,0.,0.);
  dirBp->SetXYZ(2.,0.,0.);
  myT->Fill();
  myT->Write();
  testf->Close();
}

void do_2 ()
{
  TFile *testf = new TFile("test.root");
  TTree *myT = (TTree*)gDirectory->Get("myT");
  myT->Print();
  myT->MakeSelector("my_test");
}
//------------------------------

The resulting TSelector class looks something like:

// part of my_test.h, created by TTree::MakeSelector
--------------------------------------------
class my_test : public TSelector {
   public :
   TTree          *fChain;   //!pointer to the analyzed TTree or 
TChain
//Declaration of leaves types
   TVector3        *dirA;
   UInt_t          fUniqueID;   // <-- NOT UNIQUE
   UInt_t          fBits;       
   Double_t        fX;          
   Double_t        fY;          
   Double_t        fZ;
   TVector3        *dirB;
   UInt_t          fUniqueID;
   UInt_t          fBits;
   Double_t        fX;
   Double_t        fY;
   Double_t        fZ;

//List of branches
   TBranch        *b_TObject_fUniqueID;   //!
   TBranch        *b_TObject_fBits;   //!
   TBranch        *b_dirA_fX;   //!
   TBranch        *b_dirA_fY;   //!
   TBranch        *b_dirA_fZ;   //!
   TBranch        *b_TObject_fUniqueID;   //!
   TBranch        *b_TObject_fBits;   //!
   TBranch        *b_dirB_fX;   //!
   TBranch        *b_dirB_fY;   //!
   TBranch        *b_dirB_fZ;   //!
...
---------------------------------------------


So, this is different from what I expected. What I would expect 
to happen is:

  BEST CASE:  The dirA and dirB branches are directly 
     connected to TVector3 objects.
  
  WORKABLE:   The TBranch's are read into unique variables 
     dirA_fX, dirA_fY, dirB_fX, etc...


While I can generate the correct code for a small case like this, 
the automatic code generation is invaluable for processing large 
trees. Am I doing something wrong?

I think the problem is in the name generation in
TTree::MakeClass, but the code seems to build the names for
TBranch's and the temporary variables in many places. Perhaps 
one should use a single 'MakeUniqueLeafName' method, and then 
just stick a 'b_' in front for a TBranch?

Thanks for your help,
Rob

-- 
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 * Robert Feuerbach              feuerbac@jlab.org *
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