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mathcoreVectorCollection.C File Reference

Detailed Description

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Example showing how to write and read a std vector of ROOT::Math LorentzVector in a ROOT tree.

In the write() function a variable number of track Vectors is generated according to a Poisson distribution with random momentum uniformly distributed in phi and eta. In the read() the vectors are read back and the content analysed and some information such as number of tracks per event or the track pt distributions are displayed in a canvas.

To execute the macro type in:

root[0]: .x mathcoreVectorCollection.C
Time for new Vector 0.20615 0.21
******************************************************************************
*Tree :t1 : Tree with new LorentzVector *
*Entries : 10000 : Total = 1854288 bytes File Size = 1667857 *
* : : Tree compression factor = 1.11 *
******************************************************************************
*Br 0 :tracks : Int_t tracks_ *
*Entries : 10000 : Total Size= 84910 bytes File Size = 24060 *
*Baskets : 4 : Basket Size= 32000 bytes Compression= 3.34 *
*............................................................................*
*Br 1 :tracks.fCoordinates.fX : Double_t fX[tracks_] *
*Entries : 10000 : Total Size= 443177 bytes File Size = 412928 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.07 *
*............................................................................*
*Br 2 :tracks.fCoordinates.fY : Double_t fY[tracks_] *
*Entries : 10000 : Total Size= 443177 bytes File Size = 412937 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.07 *
*............................................................................*
*Br 3 :tracks.fCoordinates.fZ : Double_t fZ[tracks_] *
*Entries : 10000 : Total Size= 443177 bytes File Size = 411390 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.08 *
*............................................................................*
*Br 4 :tracks.fCoordinates.fT : Double_t fT[tracks_] *
*Entries : 10000 : Total Size= 443177 bytes File Size = 405161 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.09 *
*............................................................................*
Tree Entries 10000
Time for new Vector 0.031595 0.03
(int) 0
#include "TRandom.h"
#include "TStopwatch.h"
#include "TSystem.h"
#include "TFile.h"
#include "TTree.h"
#include "TH1D.h"
#include "TCanvas.h"
#include "TMath.h"
#include <iostream>
// CLING does not understand some files included by LorentzVector
#include "Math/Vector3D.h"
#include "Math/Vector4D.h"
using namespace ROOT::Math;
double write(int n) {
TStopwatch timer;
TFile f1("mathcoreLV.root","RECREATE");
// create tree
TTree t1("t1","Tree with new LorentzVector");
std::vector<ROOT::Math::XYZTVector> tracks;
std::vector<ROOT::Math::XYZTVector> * pTracks = &tracks;
t1.Branch("tracks","std::vector<ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D<double> > >",&pTracks);
double M = 0.13957; // set pi+ mass
timer.Start();
double sum = 0;
for (int i = 0; i < n; ++i) {
int nPart = R.Poisson(5);
pTracks->clear();
pTracks->reserve(nPart);
for (int j = 0; j < nPart; ++j) {
double px = R.Gaus(0,10);
double py = R.Gaus(0,10);
double pt = sqrt(px*px +py*py);
double eta = R.Uniform(-3,3);
double phi = R.Uniform(0.0 , 2*TMath::Pi() );
RhoEtaPhiVector vcyl( pt, eta, phi);
// set energy
double E = sqrt( vcyl.R()*vcyl.R() + M*M);
XYZTVector q( vcyl.X(), vcyl.Y(), vcyl.Z(), E);
// fill track vector
pTracks->push_back(q);
// evaluate sum of components to check
sum += q.x()+q.y()+q.z()+q.t();
}
t1.Fill();
}
f1.Write();
timer.Stop();
std::cout << " Time for new Vector " << timer.RealTime() << " " << timer.CpuTime() << std::endl;
t1.Print();
return sum;
}
double read() {
TStopwatch timer;
TH1D * h1 = new TH1D("h1","total event energy ",100,0,1000.);
TH1D * h2 = new TH1D("h2","Number of track per event",21,-0.5,20.5);
TH1D * h3 = new TH1D("h3","Track Energy",100,0,200);
TH1D * h4 = new TH1D("h4","Track Pt",100,0,100);
TH1D * h5 = new TH1D("h5","Track Eta",100,-5,5);
TH1D * h6 = new TH1D("h6","Track Cos(theta)",100,-1,1);
TFile f1("mathcoreLV.root");
// create tree
TTree *t1 = (TTree*)f1.Get("t1");
std::vector<ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D<double> > > * pTracks = nullptr;
t1->SetBranchAddress("tracks",&pTracks);
timer.Start();
int n = (int) t1->GetEntries();
std::cout << " Tree Entries " << n << std::endl;
double sum=0;
for (int i = 0; i < n; ++i) {
t1->GetEntry(i);
int ntrk = pTracks->size();
h3->Fill(ntrk);
for (int j = 0; j < ntrk; ++j) {
XYZTVector v = (*pTracks)[j];
q += v;
h3->Fill(v.E());
h4->Fill(v.Pt());
h5->Fill(v.Eta());
h6->Fill(cos(v.Theta()));
sum += v.x() + v.y() + v.z() + v.t();
}
h1->Fill(q.E() );
h2->Fill(ntrk);
}
timer.Stop();
std::cout << " Time for new Vector " << timer.RealTime() << " " << timer.CpuTime() << std::endl;
TCanvas *c1 = new TCanvas("c1","demo of Trees",10,10,600,800);
c1->Divide(2,3);
c1->cd(1);
h1->Draw();
c1->cd(2);
h2->Draw();
c1->cd(3);
h3->Draw();
c1->cd(3);
h3->Draw();
c1->cd(4);
h4->Draw();
c1->cd(5);
h5->Draw();
c1->cd(6);
h6->Draw();
return sum;
}
int mathcoreVectorCollection() {
int nEvents = 10000;
double s1 = write(nEvents);
double s2 = read();
if (fabs(s1-s2) > s1*1.E-15 ) {
std::cout << "ERROR: Found difference in Vector when reading ( " << s1 << " != " << s2 << " diff = " << fabs(s1-s2) << " ) " << std::endl;
return -1;
}
return 0;
}
int main() {
return mathcoreVectorCollection();
}
int main()
Definition Prototype.cxx:12
#define s1(x)
Definition RSha256.hxx:91
#define R(a, b, c, d, e, f, g, h, i)
Definition RSha256.hxx:110
float * q
Class describing a generic displacement vector in 3 dimensions.
Class describing a generic LorentzVector in the 4D space-time, using the specified coordinate system ...
The Canvas class.
Definition TCanvas.h:23
A ROOT file is an on-disk file, usually with extension .root, that stores objects in a file-system-li...
Definition TFile.h:53
1-D histogram with a double per channel (see TH1 documentation)
Definition TH1.h:670
virtual Int_t Fill(Double_t x)
Increment bin with abscissa X by 1.
Definition TH1.cxx:3344
void Draw(Option_t *option="") override
Draw this histogram with options.
Definition TH1.cxx:3066
virtual Int_t Write(const char *name=nullptr, Int_t option=0, Int_t bufsize=0)
Write this object to the current directory.
Definition TObject.cxx:898
This is the base class for the ROOT Random number generators.
Definition TRandom.h:27
Stopwatch class.
Definition TStopwatch.h:28
Double_t RealTime()
Stop the stopwatch (if it is running) and return the realtime (in seconds) passed between the start a...
void Start(Bool_t reset=kTRUE)
Start the stopwatch.
Double_t CpuTime()
Stop the stopwatch (if it is running) and return the cputime (in seconds) passed between the start an...
void Stop()
Stop the stopwatch.
A TTree represents a columnar dataset.
Definition TTree.h:79
TPaveText * pt
RVec< PromoteType< T > > cos(const RVec< T > &v)
Definition RVec.hxx:1852
return c1
Definition legend1.C:41
const Int_t n
Definition legend1.C:16
TH1F * h1
Definition legend1.C:5
TF1 * f1
Definition legend1.C:11
VecExpr< UnaryOp< Fabs< T >, VecExpr< A, T, D >, T >, T, D > fabs(const VecExpr< A, T, D > &rhs)
constexpr Double_t Pi()
Definition TMath.h:37
auto * t1
Definition textangle.C:20
static uint64_t sum(uint64_t i)
Definition Factory.cxx:2345
void tracks()
Definition tracks.C:49
Author
Andras Zsenei

Definition in file mathcoreVectorCollection.C.