CorrelatedNoisifier.h

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#ifndef SimAlgos_CorrelatedNoisifier_h
#define SimAlgos_CorrelatedNoisifier_h

#include "DataFormats/Math/interface/Error.h"
#include <vector>

namespace CLHEP {
  class HepRandomEngine;
}

template <class M>
class CorrelatedNoisifier {
public:
  typedef std::vector<double> VecDou;

  CorrelatedNoisifier(const M &symCorMat);  // correlation matrix

  CorrelatedNoisifier(int *dummy, const M &cholDecMat);  // decomposition matrix

  virtual ~CorrelatedNoisifier();

  void resetCorrelationMatrix(const M &symCorMat);

  void resetCholDecompMatrix(const M &cholMat);

  template <class T>
  void noisify(T &frame,  // applies random noise to frame
               CLHEP::HepRandomEngine *,
               const VecDou *rangau = nullptr) const;  // use these

  const M &cholMat() const;  // return decomposition

  const VecDou &vecgau() const;

private:
  static const double k_precision;  // precision to which 0 & 1 are compared

  void init(const M &symCorMat);

  void initChol();

  bool computeDecomposition(const M &symCorMat);

  bool checkDecomposition(const M &symCorMat, M &HHtDiff) const;

  void checkOffDiagonal(const M &symCorMat);

  mutable VecDou m_vecgau;

  bool m_isDiagonal;
  bool m_isIdentity;

  M m_H;
};

#endif