Writing Trees from Geant 3.21

From: Norbert Danneberg (norbert.danneberg@psi.ch)
Date: Mon Mar 22 1999 - 19:02:44 MET 

Hi rooters,

we use GEANT 3.21 for our monte carlo and ROOT for analysis. We solved
the problem of
writing the same root-trees as we use in the experiment from GEANT 3.21
the following way:

At the start of GEANT we call initroot_ which initalizes the ROOT
environment.
After each GEANT Trigger we call a function calle filltree_ which
receives the pointers to the TTREE
and our Eventstructure created by initroot_ as ordianry integers.
At the end we Write the TTree usin writetree_ again passing pointers as
integers.

Attached you will find the code. In our case it seams to work well,

any comments?



extern "C" void initroot_(UInt_t* pRawEv, UInt_t* pOutTree){
  static  TROOT api("Test","Test");

  TApplication theApp("App", 0, 0);

  Int_t bsize =64000;
  Int_t split = 1;

  static MTEventRaw* RawEv = new MTEventRaw();

  TFile* OutFile = new TFile("Test.root","RECREATE","Test");

  TTree* OutTree = new TTree("Events","Events");

  OutTree->Branch("MTEventRaw","MTEventRaw", &RawEv, bsize, split);

  OutTree->SetAutoSave(1000000);

  *pRawEv = (UInt_t)RawEv;
  *pOutTree = (UInt_t)OutTree;
}

extern "C" void filltree_(UInt_t* pRawEv, UInt_t* pOutTree, Int_t*
data){

  MTEventRaw* RawEv;
  TTree* OutTree;

  RawEv = (MTEventRaw*)*pRawEv;
  OutTree = (TTree*)*pOutTree;

  Int_t* BGO_energy;
  BGO_energy = data;

  // Fill Raw Data Structure
  RawEv->Clear();
  for (Int_t i=0;i < 127;i++){
    if (BGO_energy[i]>0){
      MTDetectorRaw* MyBgo = RawEv->AddBgo(i);
      MyBgo->SetAdc(BGO_energy[i]);
    }
  }

  //Fill Raw Data Structure into Tree
  OutTree->Fill();

}


#include <stdio.h>
#include <iostream.h>
#include "TTree.h"

extern "C" void writetree_(UInt_t* pOutTree){

  TTree* OutTree;

  OutTree = (TTree*)*pOutTree;
  OutTree->Write();

}

--

Norbert Danneberg

ETH Zurich - Institute for Particle Physics
  Laboratory for Nuclear Physics          Phone.: +41-1-633-2034
  Hoenggerberg                            Fax.:   +41-1-633-1067
  CH-8093 Zurich


ETH Zurich - Institute for Particle Physics
  Paul Scherrer Institute                 Phone.: +41-56-310-3284
  CH-5232 Villigen PSI                    Fax.:   +41-56-310-4362

email: Norbert.Danneberg@psi.ch

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