CorrelatedNoisifier.h

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#ifndef SimAlgos_CorrelatedNoisifier_h
#define SimAlgos_CorrelatedNoisifier_h

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

template<class M> 
class CorrelatedNoisifier
{
   public:

      typedef std::vector<double> VecDou ;

      CorrelatedNoisifier( const M&                symCorMat , //correlation matrix
               CLHEP::HepRandomEngine* engine      = 0 ) ;

      CorrelatedNoisifier( CLHEP::HepRandomEngine* engine    ,
               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
            const VecDou* rangau = 0 ) 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 ;

      CLHEP::RandGaussQ* m_rangau ;

      bool m_isDiagonal ;
      bool m_isIdentity ;

      M m_H ;
};


#endif