Re: gMinuit problem ..

Thanks, Rene. Something similar must be happening with our slightly more complex fit where sometimes gMinuit apprears and other times not.

I would guess that if we move the fitting function to pre-defined function rather then a string in the TF1 function this would fix the "problem" as root would no longer be able to see if the function was simple or not and would always have to use Minuit.

Does that sound right?

-Art

A.E. Snyder, Group EC                        \!c*p?/
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On Sat, 28 Feb 2009, Rene Brun wrote:

> Art,
>
> When fitting with simple functions like polynomials, TMinuit is not used,
> only the linear fitter (TLinearFitter). The linear fitter is much faster than
> Minuit. You can force fitting of a polynomial with Minuit by specifying the
> fit option "L", see documentation of TH1::Fit
>
> Rene Brun
>
> Arthur E. Snyder wrote:
>>
>> Rene et al.,
>>
>> We are seeing strange behavior with gMinuit. It seems to come and go. I
>> expect it to be there after I do it fit.
>>
>> An example:
>>
>> I have a histogram (it doesn't matter what it is).
>>
>> root [26] h->Fit("pol4")
>> Fitting results:
>> Parameters:
>> NO. VALUE ERROR
>> 0 2.625170e+03 1.191186e+02
>> 1 -1.565262e+04 1.055977e+03
>> 2 3.861477e+04 3.327115e+03
>> 3 -4.315887e+04 4.446220e+03
>> 4 1.804345e+04 2.140152e+03
>> (Int_t)0
>> root [27] gMinuit
>> (class TMinuit*)0x0
>> root [28]
>>
>> -->gMinuit is MIA
>>
>> root [28] h->Fit("gaus")
>> FCN=687.968 FROM MIGRAD STATUS=CONVERGED 3927 CALLS 3928
>> TOTAL
>> EDM=5.19353e-06 STRATEGY= 1 ERR MATRIX NOT
>> POS-DEF
>> EXT PARAMETER APPROXIMATE STEP FIRST
>> NO. NAME VALUE ERROR SIZE DERIVATIVE
>> 1 Constant 1.93812e+09 1.54608e+08 9.24169e+02 2.24749e-10
>> 2 Mean -8.98813e+00 2.37909e-02 2.18708e-05 1.46725e+00
>> 3 Sigma 1.67356e+00 3.02321e-02 2.53915e-03** at limit **
>> (Int_t)0
>> root [29] gMinuit
>> (class TMinuit*)0x9486650
>>
>> -->gMinuit is there!
>>
>> In a more complex sitution where we construct a simple TF1 in a macro,
>> gMinuit is sometimes there and sometimes not -- seemingly w/o reason --
>>
>> -Art S.
>>
>>
>>
>> A.E. Snyder, Group EC \!c*p?/
>> SLAC Mail Stop #95 ((. .))
>> Box 4349 |
>> Stanford, Ca, USA, 94309 '\|/`
>> e-mail:snyder_at_slac.stanford.edu o
>> phone:650-926-2701 _
>> http://www.slac.stanford.edu/~snyder BaBar
>> FAX:650-926-2657 Collaboration
>>
>>
>>
>
>
Received on Mon Mar 02 2009 - 04:09:40 CET