Re: Minuit2

Thank.
>
> You have sent one message "Minuit2 IsFixed" that was answered

I did not see it, anyway, I found the answer by myself.

> 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.
In fact for this application, I want to avoid to have to implement root expecting that I can do every thing with Minuit2
>
>> 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.
>

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  Patrick DUPRÉ                      |   |
  Department of Chemistry            |   |    Phone: (44)-(0)-1904-434384
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