Redhat 6.0 Linux with SMP kernel with ROOT 2.22/10.
I've been having problems moving from simple TNtuples to TTrees.
I took the "simple example" from the TTree Class Description,
made it into an macro, and simplified it to:
{
TFile hfile("htree.root","RECREATE","Demo ROOT file with histograms &
trees")
typedef struct {
Int_t ntrack,nseg,nvertex;
UInt_t flag;
Float_t temperature;
// Double_t temperature;
} EVENTN;
static EVENTN eventn;
TTree *tree = new TTree("T","An example of ROOT tree with a few
branches");
tree->Branch("eventn",&eventn,"ntrack/I:nseg:nvertex:flag/i:temperature/F");
//
tree->Branch("eventn",&eventn,"ntrack/I:nseg:nvertex:flag/i:temperature/D")
for ( Int_t i=0; i<1000; i++) {
Float_t random = gRandom->Rndm(1);
eventn.ntrack = Int_t(100*random);
eventn.nseg = Int_t(2*eventn.ntrack);
eventn.nvertex = 1;
eventn.flag = Int_t(random+0.5);
eventn.temperature = Float_t(20+random);
// eventn.temperature = Double_t (20+random);
tree->Fill();
}
hfile.Write();
hfile.Close();
}
I get what looks like a good histogram with the Float_t lines,
but when I use the Double_t lines I get a histogram with a
single spike at zero.
What am I doing wrong?
Chris Stevens
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