Logo ROOT   6.21/01
Reference Guide
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;
T.Branch("tcl",&arr,256000,split);
//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++) {
ar.Clear();
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);
}
T.Fill();
}
T.Print();
T.Write();
}
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");
T->GetBranch("tcl")->SetAutoDelete(kFALSE);
T->SetBranchAddress("tcl",&arr);
Long64_t nentries = T->GetEntries();
for (Long64_t ev=0;ev<nentries;ev++) {
arr->Clear();
T->GetEntry(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()));
}
}
h2->Draw("lego");
}
void tcl(Int_t split=0)
{
gBenchmark->Start("tcl");
tclwrite(split);
tclread();
gBenchmark->Show("tcl");
}
Author
Rene Brun

Definition in file tcl.C.