Re: Minuit2

> I sent already 2 messages about Minuit, but I did not get
> any feedback !!

You have sent one message "Minuit2 IsFixed" that was answered by Lorenzo and you have sent a message with this title 5 hours ago that went not answered yet . I am sending you this answer at 2:27 am in England and do not expect a response in the next 5 hours .....

> Now I am experiencing several problems.
> 1) Minuit2 has a lot less option than TFitter has, Why I
> cannot
> manage the max number of iterations, etc.. how can
> ROOT:TFitter can
> ne based on minuit2 and offer more options ? Am I wrong ?
> arglist
> offers those options !

Why don't you use TVirtualFitter , see $ROOTSYS/test/stressFit.C . It will give you access to all TFitter methods and you can easily switch between TMinuit, TMinuit2 and TFumili.

> 2) Minuit does not congerve at all in some circunstancies.
> I
> notice for example having to fit a big number : 5e12.
> the fitter change the value of the parameter, calculate the
> chi2,
> finds that it is lower, but finally keep the original
> value:
> example:
> Density: 4.90049e+12
> chi2 1.01073e-05
> Density: 4.89951e+12
> chi2 1.03073e-05
> Density: 4.9049e+12
> chi2 9.23127e-06
> Density: 4.8951e+12
> chi2 1.12318e-05
> Density: 4.949e+12
> chi2 2.65485e-06
> Density: 4.851e+12
> chi2 2.26607e-05
> Density: 4.9e+12
> chi2 1.02068e-05
> Density: 4.9e+12
> chi2 1.02073e-05
>

You will have to give more information to see if it should/could converge . Generally speaking, it is good numerical practice to define your problem such that the fitting parameters are in the [-1;1] range and the objective function [0;1] range .

> 3) When I user Strategy, 2, it crash after a couple of
> iterations !
> ../inc/Minuit2/LASymMatrix.h:226: double&
> ROOT::Minuit2::LASymMatrix::operator()(unsigned int,
> unsigned int):
> Assertion `row<fNRow && col < fNRow'
> failed.
>
> Should I keep using this package ?

As I point out above, if you go through TVirtualFitter, you can easily switch between the different minimizers.

Eddy Received on Wed Sep 03 2008 - 03:36:05 CEST