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tcl.C File Reference

Detailed Description

View in nbviewer Open in SWAN How to write a TClonesArray to a TTree

The following tests can be run Interactive tests

Root > .x tcl.C //no-split interpreted
Root > .x tcl.C(1) //split interpreted
Root > .x tcl.C++ //no-split compiled
Root > .x tcl.C++(1) //split compiled

Batch tests: same as above but with no graphics

root -b -q tcl.C
root -b -q tcl.C++
root -b -q "tcl.C(1)"
root -b -q "tcl.C++(1)"
#include "TFile.h"
#include "TClonesArray.h"
#include "TH2.h"
#include "TLine.h"
#include "TTree.h"
#include "TBenchmark.h"
#include "TRandom.h"
void tclwrite(Int_t split)
// Generate a Tree with a TClonesArray
// The array can be split or not
TFile f("tcl.root","recreate");
f.SetCompressionLevel(1); //try level 2 also
TTree T("T","test tcl");
TClonesArray *arr = new TClonesArray("TLine");
TClonesArray &ar = *arr;
//By default a TClonesArray is created with its BypassStreamer bit set.
//However, because TLine has a custom Streamer, this bit was reset
//by TTree::Branch above. We set again this bit because the current
//version of TLine uses the automatic Streamer.
//BypassingStreamer saves space and time.
for (Int_t ev=0;ev<10000;ev++) {
Int_t nlines = Int_t(gRandom->Gaus(50,10));
if(nlines < 0) nlines = 1;
for (Int_t i=0;i<nlines;i++) {
Float_t y1 = gRandom->Rndm();
Float_t y2 = gRandom->Rndm();
new(ar[i]) TLine(x1,y1,x2,y2);
void tclread()
// read file generated by tclwrite
// loop on all entries.
// histogram center of lines
TFile *f = new TFile("tcl.root");
TTree *T = (TTree*)f->Get("T");
TH2F *h2 = new TH2F("h2","center of lines",40,0,1,40,0,1);
TClonesArray *arr = new TClonesArray("TLine");
Long64_t nentries = T->GetEntries();
for (Long64_t ev=0;ev<nentries;ev++) {
Int_t nlines = arr->GetEntriesFast();
for (Int_t i=0;i<nlines;i++) {
TLine *line = (TLine*)arr->At(i);
h2->Fill(0.5*(line->GetX1()+line->GetX2()), 0.5*(line->GetY1()+line->GetY2()));
void tcl(Int_t split=0)
#define f(i)
Definition RSha256.hxx:104
static const double x2[5]
static const double x1[5]
int Int_t
Definition RtypesCore.h:45
const Bool_t kFALSE
Definition RtypesCore.h:92
long long Long64_t
Definition RtypesCore.h:73
float Float_t
Definition RtypesCore.h:57
R__EXTERN TBenchmark * gBenchmark
Definition TBenchmark.h:59
int nentries
R__EXTERN TRandom * gRandom
Definition TRandom.h:62
virtual void Start(const char *name)
Starts Benchmark with the specified name.
virtual void Show(const char *name)
Stops Benchmark name and Prints results.
An array of clone (identical) objects.
void BypassStreamer(Bool_t bypass=kTRUE)
When the kBypassStreamer bit is set, the automatically generated Streamer can call directly TClass::W...
virtual void Clear(Option_t *option="")
Clear the clones array.
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition TFile.h:54
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition TH1.cxx:3073
2-D histogram with a float per channel (see TH1 documentation)}
Definition TH2.h:251
Int_t Fill(Double_t)
Invalid Fill method.
Definition TH2.cxx:294
A simple line.
Definition TLine.h:22
Double_t GetY1() const
Definition TLine.h:52
Double_t GetX2() const
Definition TLine.h:51
Double_t GetX1() const
Definition TLine.h:50
Double_t GetY2() const
Definition TLine.h:53
Int_t GetEntriesFast() const
Definition TObjArray.h:64
TObject * At(Int_t idx) const
Definition TObjArray.h:166
virtual Double_t Gaus(Double_t mean=0, Double_t sigma=1)
Samples a random number from the standard Normal (Gaussian) Distribution with the given mean and sigm...
Definition TRandom.cxx:274
virtual Double_t Rndm()
Machine independent random number generator.
Definition TRandom.cxx:552
A TTree represents a columnar dataset.
Definition TTree.h:79
TLine * line
double T(double x)
Rene Brun

Definition in file tcl.C.