[ROOT] ROOT hangs while fitting histograms

From: Robert Feuerbach (feuerbac@ernest.phys.cmu.edu)
Date: Thu Sep 27 2001 - 18:48:20 MEST


Hi,

I'm using ROOT version 3.01/06 on a LinuxRH7.1 machine, and am having
problems using TH1::Fit when using a user-defined function. We were able
to create a short program that has the same problems:

/*---------------------------------------------------------*/
#include <TF1.h>
#include <TMath.h>
#include <TH1.h>
// #include <TROOT.h>     /* needed for ROOT 2.25 */

Double_t fitf(Double_t *x, Double_t *par) {
  Double_t arg=0;
  Double_t result=0.;
  arg = (x[0]-par[1])/par[2];
  result = par[0]*TMath::Exp(-0.5*arg*arg)+par[3];
  return result;
}

void main(int argc, char *argv[]) {
  
  //  TROOT root("myroot","stuff"); /* needed for ROOT 2.25 */
  TF1 *myfunc = new TF1("myfunc",fitf,-2.,2.,4);
  //TF1 *myfunc = new TF1("myfunc","gaus",-2.,2.); /* doesn't hang up */
  myfunc->SetParameters(1000.,0.,.4,10.);
  
  TH1F *hist = new TH1F("hist1","test",100,-4.,4.);
  hist->FillRandom("myfunc",1000);

  myfunc->SetParameters(200.,-1.,.5,100.);
  hist->Fit("myfunc","R0");
  //  hist->Fit("myfunc","R0N");  /* doesn't seg-fault/hang up */

}
/*---------------------------------------------------------*/

After the actual fit is done (and the results printed to the screen), the
program just hangs, and never exits from the hist->Fit line. If we tell
ROOT NOT to store the function (with the 'N' option), it exits just
fine. This works if we use a pre-defined function (such as "gaus") or
run it under ROOT 2.25.

Would you please look into this?

Thank you,
Rob Feuerbach

-- 
/***************************************************
 * Robert Feuerbach   feuerbac@ernest.phys.cmu.edu *
 * CMU Physics Department           (412) 268-2772 *
 * Pittsburgh, PA 15213        FAX: (412) 681-0648 *
 ***************************************************/



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