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
Processing /mnt/build/workspace/root-makedoc-v608/rootspi/rdoc/src/v6-08-00-patches/tutorials/math/mathcoreVectorCollection.C...
Time for new Vector 0.166092 0.15
******************************************************************************
*Tree :t1 : Tree with new LorentzVector *
*Entries : 10000 : Total = 1854222 bytes File Size = 1667864 *
* : : Tree compression factor = 1.11 *
******************************************************************************
*Br 0 :tracks : Int_t tracks_ *
*Entries : 10000 : Total Size= 84844 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= 443166 bytes File Size = 412927 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.07 *
*............................................................................*
*Br 2 :tracks.fCoordinates.fY : Double_t fY[tracks_] *
*Entries : 10000 : Total Size= 443166 bytes File Size = 412940 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.07 *
*............................................................................*
*Br 3 :tracks.fCoordinates.fZ : Double_t fZ[tracks_] *
*Entries : 10000 : Total Size= 443166 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= 443166 bytes File Size = 405166 *
*Baskets : 16 : Basket Size= 32000 bytes Compression= 1.09 *
*............................................................................*
Tree Entries 10000
Time for new Vector 0.134437 0.14
(int) 0
#include <iostream>
TFile
f1(
"mathcoreLV.root",
"RECREATE");
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;
double sum = 0;
for (
int i = 0; i <
n; ++i) {
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 E =
sqrt( vcyl.R()*vcyl.R() + M*M);
pTracks->push_back(q);
sum += q.x()+q.y()+q.z()+q.t();
}
t1.Fill();
}
std::cout <<
" Time for new Vector " << timer.
RealTime() <<
" " << timer.
CpuTime() << std::endl;
}
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");
TTree *t1 = (TTree*)f1.Get("t1");
std::vector<ROOT::Math::LorentzVector<ROOT::Math::PxPyPzE4D<double> > > * pTracks = 0;
t1->SetBranchAddress("tracks",&pTracks);
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();
for (int j = 0; j < ntrk; ++j) {
sum += v.
x() + v.
y() + v.
z() + v.
t();
}
}
std::cout <<
" Time for new Vector " << timer.
RealTime() <<
" " << timer.
CpuTime() << std::endl;
}
int mathcoreVectorCollection() {
double s1 =
write(nEvents);
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;
}
return mathcoreVectorCollection();
}
- Author
- Andras Zsenei
Definition in file mathcoreVectorCollection.C.