TMinuit warning

Hi all,
I fit an histogram with “pol1”. everything is fine, though I am receiving a warning (error?) message right at the first fit:

The relevant part of the code is this one:

  if ( fit ) {
    TF1 *f1 = new TF1("f1","pol1",0.,500.);

Again: everything is perfect with the fit.
I googled a bit and had a look at TMinuit::Command, but I didn’t find any reasonable clue… Do you have one? :slight_smile:

Many thanks in advance,

I cannot reproduce this message. Can you please send me the simples program reproducing this and tell me which ROOT version are you using,

Thank you


Dear Lorenzo,
In attachment you can find a root file and the source of the program
This is the usage:


ROOT version is 5.18.

I tried to reduce as much as I can the code, but this seems to be the minimum amount you have to put togheter to see the problem.

Many thanks in advance,
FSSRDummy.cpp (11.1 KB)
HistosFSSRCalib_0001556-ErfData.root (45 KB)


there is a problem loading the TLinearFitter class via the plug-in manager.
If you don’t care about using the linear fitter you can use the option “F”,
force to use Minuit, and that should work,


otherwise do before running the first fit you can do


or add “-lMinuit” in the list of linking libraries of your application.

Thank you for reporting this. We will fix this problem in the next release
Best Regards

Dear Lorenzo,
thanks for looking into this!

I went for ‘-lMinuit’ option.