TGraph2D::SetMaximum seems to hang forever

ROOT
1

root-config --version
6.22/06

const Int_t N = 4;

TGraph2D graph;

graph.Set(N);

for (Int_t i = 0; i != N; ++i) {
graph.SetPoint(i, (Double_t) i, 0.0, 0.0);
}

graph.SetMaximum(1.0); // hangs forever

2

Hi and welcome on forum,

It is problem in Math/Delaunay2D class.
@moneta or @couet should check it.

As temporary solution you could call graph.GetHistogram("old"); before setting maximum.
It will use old interpolation method, which does not hang with such data.

3

TGraph2D algorithm is based on triangles. The points you define are aligned.
It is not possible to find a triangle. That’s why it hangs.

4

Hi,
We should add a protection against this case and probably use a simple 1D interpolation if the points are aligned.
I will open a GitHub issue for this.

Lorenzo

5

Wouldn’t it be better to set the limit of the associated histogram only when it already exists but not create a histogram when it doesn’t exist?
It is a bit weird that a function to set a limit can lead to the creation of an internal histogram with the additional complexity.

6

I will look closer at it.