Re: minimization different in ROOT4 and ROOT5

Hi Luca,

There are several improvements (well I hope!) from ROOT4 to ROOT5. Could you tell us exactly which version 4 you were using and which version 5?
It would be good too if you could provide a simple script and a data file with your histogram
showing the problem.

Rene

Luca Grandi wrote:
> Hi all,
>
> I have got a problem with minimization using ROOT. I get slightly diffrenet
> results from ROOT 4 and ROOT 5.
>
> I wrote a script in which I define a histogram
>
> hf = new TH1F("hf", "Photoelectrons Spectrum", 200, 0., 1000.);
>
> I fill it
>
> hf->Fill(data[ev_count]);
>
> and then fit it with a function called "Linear"
>
> TF1 *f1 = new TF1("f1", Linear, 0., 1000., 2);
> f1->SetParameter(0, 1.);
> f1->SetParName(0, "Rho");
> f1->SetParameter(1, 1.);
> f1->SetParName(1, "L.Y. (p.e./keV)");
> c1->cd(1);
> hf->Fit("f1", "L", "", threshold, 1000.);
> hf->Draw("e");
>
> and "Linear" is
>
> Double_t Linear(Double_t *x, Double_t *par)
> {
> Double_t arg = 0;
> if (par[1] != 0) arg = x[0]/par[1];
> Double_t fitval = par[0]*dNdE(x[0]/par[1])/par[1];
> return fitval;
> }
>
> If I run it on ROOT 4 I get
>
> FCN=134.135 FROM MIGRAD STATUS=CONVERGED 65 CALLS 66
> TOTAL
> EDM=2.13358e-10 STRATEGY= 1 ERROR
> MATRIX ACCURATE
> EXT PARAMETER STEP FIRST
> NO. NAME VALUE ERROR SIZE DERIVATIVE
> 1 Rho 1.78512e+00 6.83244e-02 4.69665e-04 -2.69615e-04
> 2 L.Y. (p.e./keV) 1.12079e+00 4.27042e-02 2.93564e-04
> 6.41165e-05
>
> while if i run ROOT 5 I get
>
> FCN=493.398 FROM MIGRAD STATUS=CONVERGED 53 CALLS 54 TOTAL
> EDM=5.30182e-08 STRATEGY= 1 ERROR MATRIX
> ACCURATE
> EXT PARAMETER STEP FIRST
> NO. NAME VALUE ERROR SIZE DERIVATIVE
> 1 Rho 1.72045e+00 6.75899e-02 4.36268e-04 4.58320e-03
> 2 L.Y. (p.e./keV) 1.19107e+00 5.01150e-02 3.24074e-04
> 1.03245e-02
>
> The results are different as the FCN values. Any suggestion?
>
>
Received on Thu Sep 14 2006 - 15:42:11 MEST