ScanBuilder.cxx

Go to the documentation of this file.

// @(#)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"

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) = sqrt(2.*mfcn.Up()*seed.Error().InvHessian()(i,i));
   }

   MinimumParameters mp(x, dirin, amin);
   MinimumState st(mp, 0., mfcn.NumOfCalls());

   return FunctionMinimum(seed, std::vector<MinimumState>(1, st), mfcn.Up());
}

   }  // namespace Minuit2

}  // namespace ROOT