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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