[ROOT] TH1::Fit() never ends

From: Miroslav Helbich (helbich@mail.desy.de)
Date: Tue Nov 20 2001 - 13:12:07 MET


 Hi all,

 when I fit the histogram, it happens sometimes that the fit procedure
never ends. The only way to end the program is to interrupt it and of
course all the results are lost. This is very troublesome. Is there
anything I can do about it? Is it possible to handle this by some
exception? Thanks for advice.

 I use root 3.02/02 on SuSE Linux 6.3 (i386) - Kernel 2.2.16 (pts/7).

					Miro Helbich

root [7] fMassSpectrum->Fit(func->GetName(),"RIV","E");

 **********
 **  129 **SET ERR           1
 **********
 PARAMETER DEFINITIONS:
    NO.   NAME         VALUE      STEP SIZE      LIMITS
     1 p0           2.00000e+01  6.00000e+00     no limits
     2 p1           1.02000e+00  3.06000e-01     no limits
     3 p2           9.99999e-03  3.00000e-03     no limits
     4 p3           5.00000e+00  1.50000e+00     no limits
     5 p4           5.00000e-01  1.50000e-01     no limits
     6 p5           9.86000e-01  2.95800e-01     no limits
 **********
 **  130 **FIX           6
 **********
 **********
 **  131 **SET PRINT           0
 **********
 **********
 **  132 **MIGRAD        5000     0.00026
 **********
 MINUIT WARNING IN MIGRAD  
 ============== Negative diagonal element 1 in Error Matrix
 MINUIT WARNING IN MIGRAD  
 ============== Negative diagonal element 2 in Error Matrix
 MINUIT WARNING IN MIGRAD  
 ============== Negative diagonal element 3 in Error Matrix
 MINUIT WARNING IN MIGRAD  
 ============== Negative diagonal element 4 in Error Matrix
 MINUIT WARNING IN MIGRAD  
 ============== Negative diagonal element 5 in Error Matrix
 MINUIT WARNING IN MIGRAD  
 ============== 1469.61 added to diagonal of error matrix
 EIGENVALUES OF SECOND-DERIVATIVE MATRIX:
        -2.0594e+01  1.0000e+00  1.0001e+00  1.0048e+00  2.2589e+01
 MINUIT WARNING IN MIGRAD  
 ============== MATRIX FORCED POS-DEF BY ADDING 20.616870 TO DIAGONAL.



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