Event/RootEventData/include/RootEventData/SimMatr.h

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#ifndef SimMatr_h
#define SimMatr_h
 
namespace SimMat {
 
  // packing of symmetric matrices 'sm' in one-dimensional array 'pac_sm'
  // 'pac_sm' MUST be large enough to receive n*(n+1)/2 elements
  template <class T> inline void pack2d( int n, const T* sm, T* pac_sm ) {
    for ( int i = 0; i < n; i++ )
    {
      for ( int j = 0; j <= i; j++ )
      {
        int k     = i * ( i + 1 ) / 2 + j;
        pac_sm[k] = sm[i * n + j];
      }
    }
  }
 
  // for a given i and j in 'sm' returns the index in 'pac_sm'
  inline int get_idx( int i, int j ) {
    return ( i > j ) ? i * ( i + 1 ) / 2 + j : j * ( j + 1 ) / 2 + i;
  }
 
  // for a given i and j return 'sm[i][j]'
  template <class T> inline T get_element( const T* pac_sm, int i, int j ) {
    return pac_sm[get_idx( i, j )];
  }
 
  // unpacks the 'pac_sm' in the symmetric matrix 'sm'
  // 'sm' MUST be large enough to receive n*n elements
  template <class T> inline void unpack2d( int n, T* sm, const T* pac_sm ) {
    for ( int i = 0; i < n; i++ )
    {
      for ( int j = 0; j <= i; j++ )
      {
        int k         = i * ( i + 1 ) / 2 + j;
        sm[i * n + j] = sm[i + j * n] = pac_sm[k];
      }
    }
  }
 
} // namespace SimMat
#endif