# mathcoreVectorIO¶

Example of I/O of a mathcore Lorentz Vectors in a Tree and comparison with a TLorentzVector. A ROOT tree is written and read in both using either a XYZTVector or a TLorentzVector.

To execute the macro type in:

root[0] .x  mathcoreVectorIO.C


Author: Lorenzo Moneta
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Wednesday, August 17, 2022 at 09:34 AM.

In [1]:
%%cpp -d
#include "TRandom2.h"
#include "TStopwatch.h"
#include "TSystem.h"
#include "TFile.h"
#include "TTree.h"
#include "TH1D.h"
#include "TCanvas.h"

#include <iostream>

#include "TLorentzVector.h"

#include "Math/Vector4D.h"

using namespace ROOT::Math;


Definition of a helper function:

In [2]:
%%cpp -d
void write(int n) {
TRandom2 R;
TStopwatch timer;

R.SetSeed(1);
timer.Start();
double s = 0;
for (int i = 0; i < n; ++i) {
s  += R.Gaus(0,10);
s  += R.Gaus(0,10);
s  += R.Gaus(0,10);
s  += R.Gaus(100,10);
}

timer.Stop();
std::cout << s/double(n) << std::endl;
std::cout << " Time for Random gen " << timer.RealTime() << "  " << timer.CpuTime() << std::endl;

TFile f1("mathcoreVectorIO_1.root","RECREATE");

// create tree
TTree t1("t1","Tree with new LorentzVector");

XYZTVector *v1 = new XYZTVector();
t1.Branch("LV branch","ROOT::Math::XYZTVector",&v1);

R.SetSeed(1);
timer.Start();
for (int i = 0; i < n; ++i) {
double Px = R.Gaus(0,10);
double Py = R.Gaus(0,10);
double Pz = R.Gaus(0,10);
double E  = R.Gaus(100,10);
v1->SetCoordinates(Px,Py,Pz,E);
t1.Fill();
}

f1.Write();
timer.Stop();
std::cout << " Time for new Vector " << timer.RealTime() << "  " << timer.CpuTime() << std::endl;

t1.Print();

// create tree with old LV

TFile f2("mathcoreVectorIO_2.root","RECREATE");
TTree t2("t2","Tree with TLorentzVector");

TLorentzVector * v2 = new TLorentzVector();
TLorentzVector::Class()->IgnoreTObjectStreamer();
TVector3::Class()->IgnoreTObjectStreamer();

t2.Branch("TLV branch","TLorentzVector",&v2,16000,2);

R.SetSeed(1);
timer.Start();
for (int i = 0; i < n; ++i) {
double Px = R.Gaus(0,10);
double Py = R.Gaus(0,10);
double Pz = R.Gaus(0,10);
double E  = R.Gaus(100,10);
v2->SetPxPyPzE(Px,Py,Pz,E);
t2.Fill();
}

f2.Write();
timer.Stop();
std::cout << " Time for old Vector " << timer.RealTime() << "  " << timer.CpuTime() << endl;
t2.Print();
}


Definition of a helper function:

In [3]:
%%cpp -d

TRandom R;
TStopwatch timer;

TFile f1("mathcoreVectorIO_1.root");

// create tree
TTree *t1 = (TTree*)f1.Get("t1");

XYZTVector *v1 = 0;

timer.Start();
int n = (int) t1->GetEntries();
std::cout << " Tree Entries " << n << std::endl;
double etot=0;
for (int i = 0; i < n; ++i) {
t1->GetEntry(i);
etot += v1->Px();
etot += v1->Py();
etot += v1->Pz();
etot += v1->E();
}
timer.Stop();
std::cout << " Time for new Vector " << timer.RealTime() << "  " << timer.CpuTime() << std::endl;

std::cout << " TOT average : n = " << n << "\t " << etot/double(n) << endl;

// create tree with old LV
TFile f2("mathcoreVectorIO_2.root");
TTree *t2 = (TTree*)f2.Get("t2");

TLorentzVector * v2 = 0;

timer.Start();
n = (int) t2->GetEntries();
std::cout << " Tree Entries " << n << std::endl;
etot = 0;
for (int i = 0; i < n; ++i) {
t2->GetEntry(i);
etot  += v2->Px();
etot  += v2->Py();
etot  += v2->Pz();
etot  += v2->E();
}

timer.Stop();
std::cout << " Time for old Vector " << timer.RealTime() << "  " << timer.CpuTime() << endl;
std::cout << " TOT average:\t" << etot/double(n) << endl;
}

In [4]:
int nEvents = 100000;
write(nEvents);

99.8767
Time for Random gen 0.0112448  0.02
Time for new Vector 0.275624  0.27
******************************************************************************
*Tree    :t1        : Tree with new LorentzVector                            *
*Entries :   100000 : Total =         3214176 bytes  File  Size =    2910669 *
*        :          : Tree compression factor =   1.10                       *
******************************************************************************
*Branch  :LV branch                                                          *
*Entries :   100000 : BranchElement (see below)                              *
*............................................................................*
*Br    0 :fCoordinates :                                                     *
*Entries :   100000 : Total  Size=       4720 bytes  One basket in memory    *
*............................................................................*
*Br    1 :fCoordinates.fX : Double_t                                         *
*Entries :   100000 : Total  Size=     803057 bytes  File Size  =     733353 *
*............................................................................*
*Br    2 :fCoordinates.fY : Double_t                                         *
*Entries :   100000 : Total  Size=     803057 bytes  File Size  =     733905 *
*............................................................................*
*Br    3 :fCoordinates.fZ : Double_t                                         *
*Entries :   100000 : Total  Size=     803057 bytes  File Size  =     733645 *
*............................................................................*
*Br    4 :fCoordinates.fT : Double_t                                         *
*Entries :   100000 : Total  Size=     803057 bytes  File Size  =     708062 *
*............................................................................*
Time for old Vector 0.197989  0.18
******************************************************************************
*Tree    :t2        : Tree with TLorentzVector                               *
*Entries :   100000 : Total =         4835755 bytes  File  Size =    3369959 *
*        :          : Tree compression factor =   1.43                       *
******************************************************************************
*Br    0 :TLV branch : TLorentzVector                                        *
*Entries :   100000 : Total  Size=    4835322 bytes  File Size  =    3366724 *

Warning in <TTree::Bronch>: TLorentzVector cannot be split, resetting splitlevel to 0