decompose_Hessenberg_Cmplx.h

Go to the documentation of this file.

 
#ifndef DECOMPOSE_HESSENBERG_CMPLX_INCLUDED
#define DECOMPOSE_HESSENBERG_CMPLX_INCLUDED
 
#include <cmath>
#include <cfloat>
#include <valarray>
 
/*
  Class for Hessenberg decomposition with Householder transformation
  A -> H = Q^\dag A Q
  The notation of Householder transformation is the same as that of GSL.
  H = I - tau vv^\dag
  H^\dag x = - |x| sign(Re(x_1)) e_1
 */
 
class Decompose_Hessenberg_Cmplx {
 public:
  Decompose_Hessenberg_Cmplx(const size_t& Nin) : N(Nin), N2(2 * N), size(N * N2),
    m_H(size), m_tau(N2)
  {
  }
 
  void set_matrix(const double *mat);
  void get_Hessenberg(double *mat);
  void get_Q(double *mat);
  void mult_Q(double *mat);
 
 private:
  size_t N;
  size_t N2;
  size_t size;
 
  // store R and householder vector
  std::valarray<double> m_H;
  std::valarray<double> m_tau;
 
  // matrix index [i,j]
  inline size_t re(const size_t i, const size_t j)
  {
    return N2 * i + 2 * j;
  }
 
  inline size_t im(const size_t i, const size_t j)
  {
    return N2 * i + 2 * j + 1;
  }
 
  // vector index [i]
  inline size_t re(const size_t i)
  {
    return 2 * i;
  }
 
  inline size_t im(const size_t i)
  {
    return 2 * i + 1;
  }
};
#endif