ScanBuilder.cxx

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei   2003-2005
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
#include "Minuit2/ScanBuilder.h"
#include "Minuit2/MnParameterScan.h"
#include "Minuit2/FunctionMinimum.h"
#include "Minuit2/MinimumSeed.h"
#include "Minuit2/MinimumState.h"
#include "Minuit2/MnFcn.h"
#include <cmath>
 
namespace ROOT {
 
namespace Minuit2 {
 
FunctionMinimum ScanBuilder::Minimum(const MnFcn &mfcn, const GradientCalculator &, const MinimumSeed &seed,
                                     const MnStrategy &, unsigned int, double) const
{
   // find the function minimum performing a parameter scan (using MnParameterScan class)
   // function gradient is not used
   MnAlgebraicVector x = seed.Parameters().Vec();
   MnUserParameterState upst(seed.State(), mfcn.Up(), seed.Trafo());
   MnParameterScan scan(mfcn.Fcn(), upst.Parameters(), seed.Fval());
   double amin = scan.Fval();
   unsigned int n = seed.Trafo().VariableParameters();
   MnAlgebraicVector dirin(n);
   for (unsigned int i = 0; i < n; i++) {
      unsigned int ext = seed.Trafo().ExtOfInt(i);
      scan(ext);
      if (scan.Fval() < amin) {
         amin = scan.Fval();
         x(i) = seed.Trafo().Ext2int(ext, scan.Parameters().Value(ext));
      }
      dirin(i) = std::sqrt(2. * mfcn.Up() * seed.Error().InvHessian()(i, i));
   }
 
   MinimumParameters mp(x, dirin, amin);
   MinimumState st(mp, 0., mfcn.NumOfCalls());
 
   return FunctionMinimum(seed, {&st, 1}, mfcn.Up());
}
 
} // namespace Minuit2
 
} // namespace ROOT