ParametricFunction.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/ParametricFunction.h"
#include "Minuit2/MnFcn.h"
#include "Minuit2/MnStrategy.h"
#include "Minuit2/MnUserParameterState.h"
#include "Minuit2/Numerical2PGradientCalculator.h"
#include "Minuit2/FunctionGradient.h"
#include "Minuit2/MinimumParameters.h"
 
namespace ROOT {
 
namespace Minuit2 {
 
std::vector<double> ParametricFunction::GetGradient(std::vector<double> const &x) const
{
   // calculate the numerical gradient (using Numerical2PGradientCalculator)
 
   // LM:  this I believe is not very efficient
   MnFcn mfcn(*this);
 
   MnStrategy strategy(1);
 
   // ????????? how does it know the transformation????????
   std::vector<double> err(x.size());
   err.assign(x.size(), 0.1);
   // need to use parameters
   MnUserParameterState st(x, err);
 
   Numerical2PGradientCalculator gc(mfcn, st.Trafo(), strategy);
   MnAlgebraicVector xVec{x};
   FunctionGradient g = gc(MinimumParameters{xVec, MnFcnCaller{mfcn}(xVec)});
   const MnAlgebraicVector &grad = g.Vec();
   assert(grad.size() == x.size());
   //  std::cout << "Param Function Gradient " << grad << std::endl;
   return {grad.Data(), grad.Data() + grad.size()};
}
 
} // namespace Minuit2
 
} // namespace ROOT