Yes, easy to find the problem.
Change the 2 lines
root [2] tree->Branch("x",&x,"x");
root [3] tree->Branch("y",&y,"y");
to
root [2] tree->Branch("x",&x,"x/I");
root [3] tree->Branch("y",&y,"y/I");
When defining a branch with basic types, one must specify the data type.
By default Root assumes float. The type of your variable is not
accessible to TTree::Branch for a cross-check unfortunately.
(see TTree class comments for definition of branches)
Rene Brun
On Fri, 28 Aug 1998, Ye Shuwei wrote:
>
> Hi, ROOTers,
>
> I found strange behavior of TTreeFormula for ROOT2.00/09 under IBM/AIX and
> DEC-Alpha/OSF1.
>
> If I get TTree object from a ROOT file and feed into TTreeFormula, its
> function EvalInstance() works as expected. But if I create TTree object
> myself, then strange behavior came.
>
> Under interactive ROOT, I enter the sequence commands below
>
> root [0] TTree *tree = new TTree("t1","an example");
> root [1] int x,y;
> root [2] tree->Branch("x",&x,"x");
> root [3] tree->Branch("y",&y,"y");
> root [4] x=19981; y=10;
> root [5] char *cut1 = "x>1998";
> root [6] TTreeFormula *f_cut1=new TTreeFormula("cut1",cut1,t1);
> root [7] .p f_cut1->EvalInstance(0);
> (Double_t)0.000000000000e+00 // under IBM/AIX
> *** Break *** floating point exception // under Alpha/OSF1
>
> if change x and y into type of float, then everything works. So, what is
> the difference for TTree object created by myself and read from a file ?
> How can different type variable make TTreeFormula::EvalInstance behaves
> differently ?
>
> And hints ? Thanks.
>
> --Shuwei
>
>
>
>
>
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