MnParameterScan.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/MnParameterScan.h"
#include "Minuit2/FCNBase.h"

namespace ROOT {

   namespace Minuit2 {


MnParameterScan::MnParameterScan(const FCNBase& fcn, const MnUserParameters& par) : fFCN(fcn), fParameters(par), fAmin(fcn(par.Params())) {}

MnParameterScan::MnParameterScan(const FCNBase& fcn, const MnUserParameters& par, double fval) : fFCN(fcn), fParameters(par), fAmin(fval) {}

std::vector<std::pair<double, double> > MnParameterScan::operator()(unsigned int par, unsigned int maxsteps, double low, double high) {
   // do the scan for parameter par between low and high values

   //if(maxsteps > 101) maxsteps = 101;
   std::vector<std::pair<double, double> > result; result.reserve(maxsteps+1);
   std::vector<double> params = fParameters.Params();
   result.push_back(std::pair<double, double>(params[par], fAmin));

   if(low > high) return result;
   if(maxsteps < 2) return result;

   if(low == 0. && high == 0.) {
      low = params[par] - 2.*fParameters.Error(par);
      high = params[par] + 2.*fParameters.Error(par);
   }

   if(low == 0. && high == 0. && fParameters.Parameter(par).HasLimits()) {
      if(fParameters.Parameter(par).HasLowerLimit())
         low = fParameters.Parameter(par).LowerLimit();
      if(fParameters.Parameter(par).HasUpperLimit())
         high = fParameters.Parameter(par).UpperLimit();
   }

   if(fParameters.Parameter(par).HasLimits()) {
      if(fParameters.Parameter(par).HasLowerLimit())
         low = std::max(low, fParameters.Parameter(par).LowerLimit());
      if(fParameters.Parameter(par).HasUpperLimit())
         high = std::min(high, fParameters.Parameter(par).UpperLimit());
   }

   double x0 = low;
   double stp = (high - low)/double(maxsteps - 1);
   for(unsigned int i = 0; i < maxsteps; i++) {
      params[par] = x0 + double(i)*stp;
      double fval = fFCN(params);
      if(fval < fAmin) {
         fParameters.SetValue(par, params[par]);
         fAmin = fval;
      }
      result.push_back(std::pair<double, double>(params[par], fval));
   }

   return result;
}

   }  // namespace Minuit2

}  // namespace ROOT