I think this issue was discussed recently
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Due the popular demand I wrote an example. It works under ROOT 5.12 and 5.22 (I did not convert it to the TVirtualFitter due lack of time ). See attachments.
To execute this example one has to apply ACliC
root.exe fit.C++[code]root.exe [0]
Processing fit.C++…
Info in TUnixSystem::ACLiC: creating shared library /direct/star+data08/users/fine/QTROOT/expert/./fit_C.so
In file included from /direct/star+data08/users/fine/QTROOT/expert/./fileK3oINo.h:32,
from /direct/star+data08/users/fine/QTROOT/expert/./fileK3oINo.cxx:16:
** 1 **SET ERR 1
PARAMETER DEFINITIONS:
NO. NAME VALUE STEP SIZE LIMITS
1 a0 7.00000e-01 1.00000e-01 no limits
2 a1 1.50000e+00 1.00000e-01 no limits
3 a2 0.00000e+00 1.00000e-01 no limits
** 2 **MIGRAD 500 1
FIRST CALL TO USER FUNCTION AT NEW START POINT, WITH IFLAG=4.
START MIGRAD MINIMIZATION. STRATEGY 1. CONVERGENCE WHEN EDM .LT. 1.00e-03
FCN=1260.75 FROM MIGRAD STATUS=INITIATE 12 CALLS 13 TOTAL
EDM= unknown STRATEGY= 1 NO ERROR MATRIX
EXT PARAMETER CURRENT GUESS STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 a0 7.00000e-01 1.00000e-01 1.00000e-01 1.60400e+03
2 a1 1.50000e+00 1.00000e-01 1.00000e-01 2.94600e+03
3 a2 0.00000e+00 1.00000e-01 1.00000e-01 7.95875e+02
MIGRAD MINIMIZATION HAS CONVERGED.
MIGRAD WILL VERIFY CONVERGENCE AND ERROR MATRIX.
COVARIANCE MATRIX CALCULATED SUCCESSFULLY
FCN=36.3293 FROM MIGRAD STATUS=CONVERGED 54 CALLS 55 TOTAL
EDM=2.53371e-20 STRATEGY= 1 ERROR MATRIX ACCURATE
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 a0 -4.55139e-01 1.10395e-01 1.05475e-04 -1.68415e-10
2 a1 1.16792e+00 5.69235e-02 5.86482e-05 -1.21153e-09
3 a2 4.80354e-01 2.48330e-02 5.12514e-05 8.66492e-09
EXTERNAL ERROR MATRIX. NDIM= 25 NPAR= 3 ERR DEF=1
1.219e-02 -5.572e-03 -1.034e-03
-5.572e-03 3.240e-03 7.008e-05
-1.034e-03 7.008e-05 6.167e-04
PARAMETER CORRELATION COEFFICIENTS
NO. GLOBAL 1 2 3
1 0.94733 1.000 -0.887 -0.377
2 0.93847 -0.887 1.000 0.050
3 0.72209 -0.377 0.050 1.000
root.exe [1][/code]
fit.C (7.37 KB)