ExternalInternalGradientCalculator.h

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// @(#)root/minuit2:$Id$
// Authors: M. Winkler, F. James, L. Moneta, A. Zsenei, E.G.P. Bos   2003-2017
 
/**********************************************************************
 *                                                                    *
 * Copyright (c) 2005 LCG ROOT Math team,  CERN/PH-SFT                *
 *                                                                    *
 **********************************************************************/
 
#ifndef ROOT_Minuit2_ExternalInternalGradientCalculator
#define ROOT_Minuit2_ExternalInternalGradientCalculator
 
#include "Minuit2/AnalyticalGradientCalculator.h"
 
namespace ROOT {
 
namespace Minuit2 {
 
class FCNGradientBase;
class MnUserTransformation;
 
/// Similar to the AnalyticalGradientCalculator, the ExternalInternalGradientCalculator
/// supplies Minuit with an externally calculated gradient. The main difference is that
/// ExternalInternalGradientCalculator expects that the external gradient calculator does
/// things in Minuit2-internal parameter space, which means many int2ext and ext2int
/// transformation steps are not necessary. This avoids loss of precision in some cases,
/// where trigonometrically transforming parameters back and forth can lose a few bits of
/// floating point precision on every pass.
 
class ExternalInternalGradientCalculator : public AnalyticalGradientCalculator {
 
public:
   ExternalInternalGradientCalculator(const FCNGradientBase &fcn, const MnUserTransformation &state)
      : AnalyticalGradientCalculator(fcn, state)
   {
   }
 
   ~ExternalInternalGradientCalculator() {}
 
   virtual FunctionGradient operator()(const MinimumParameters &) const;
 
   virtual FunctionGradient operator()(const MinimumParameters &, const FunctionGradient &) const;
};
 
} // namespace Minuit2
 
} // namespace ROOT
 
#endif // ROOT_Minuit2_ExternalInternalGradientCalculator