Minuit problem

Dear Roottalk,

I use a chi square minimization routin minuit. I call it in the following way:

TGraph2DErrors *dte = new TGraph2DErrors(data_length);

for(int i=0;i<file_length;i++){
dte->SetPoint(i,x_b[i],Q2[i],F2[i]);
dte->SetPointError(i,er_x[i],er_y[i],er_z[i]); };

TF2 *func = new TF2("fit", fitted_function, 0,0.013, 0,150, 3);

func->SetParName(0,"mu0");
func->SetParName(1,"A");
func->SetParName(2,"Omega_0");

func->SetParameters(param);
dte->Fit("fit");

where "fitted_function" is my function with three parameters and two variables (x_b,Q2)

The problem is: the result of minuit or a value of chi square depends on the initial values of my parameters, i.e. a little change in the initial values affects considerably on the result of minimization (a value of chi squre). I think that the reason for this is that my function has many local minima and one global minimum, but I can not achieve it.

Can I do something with it?

-- 
Sincerely,

                      Andrey K.

   *************************************************************


   * Andrey Kormilitsin    *                                   *

   *                       *                                   *

   * Department  of        *                                   *

   * Particle Physics      *                                   *

   * School of Physics     *  Tel: ++ 972- 3 - 640 7954 (o)    *

   * Tel Aviv University   *                                   *

   * Ramat Aviv,Tel Aviv   *  E-mail: andreyk1_at_post.tau.ac.il  *

   * 69978, ISRAEL         *                                   *

   *                       *                                   *

   *************************************************************


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