CostFuncPoisson.h

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2019 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#pragma once
 
#include "MantidAPI/FunctionDomain.h"
#include "MantidAPI/FunctionValues.h"
#include "MantidCurveFitting/CostFunctions/CostFuncFitting.h"
 
namespace Mantid {
namespace CurveFitting {
namespace CostFunctions {
 
namespace PoissonLossLM {
double MANTID_CURVEFITTING_DLL calculatePoissonLossLM(double observedCounts, double predicted);
double MANTID_CURVEFITTING_DLL calculateJacobianScaleFactor(double observedCounts, double predicted);
template <typename T> int sgn(T val) { return (T(0) < val) - (val < T(0)); }
} // namespace PoissonLossLM
 
class MANTID_CURVEFITTING_DLL CostFuncPoisson : public CostFuncFitting {
public:
  CostFuncPoisson();
  virtual std::string name() const override { return "Poisson"; }
  virtual std::string shortName() const override { return "Poisson"; };
 
  void addVal(API::FunctionDomain_sptr domain, API::FunctionValues_sptr values) const override;
  void addValDerivHessian(API::IFunction_sptr function, API::FunctionDomain_sptr domain,
                          API::FunctionValues_sptr values, bool evalDeriv = true,
                          bool evalHessian = true) const override;
 
private:
  void calculateDerivative(API::IFunction &function, const API::FunctionDomain &domain,
                           API::FunctionValues &values) const;
  void calculateHessian(API::IFunction &function, const API::FunctionDomain &domain,
                        const API::FunctionValues &values) const;
};
 
} // namespace CostFunctions
} // namespace CurveFitting
} // namespace Mantid