eigenvalues() [1/4]

bool Lapack::eigenvalues ( const DMatCC * A, DMatCC * eigenvals )

static

Definition at line 1233 of file lapack.cpp.

{
  int size = static_cast<int>(A->numRows());
  if (size != static_cast<int>(A->numColumns()))
    {
      ERROR("expected a square matrix");
      return false;
    }
 
  if (size == 0)
    {
      eigvals->resize(0, 1);
      return true;
    }
 
  bool ret = true;
  char dont = 'N';
  int info;
  int wsize = 2 * size;
  int rsize = 2 * size;
  double *workspace = new double[2*wsize]; 
  double *rwork = new double[rsize];
 
  std::vector<double> copyA = make_lapack_array(*A);
  std::vector<double> evals(2 * size); // TODO: set to 0?
 
  zgeev_(&dont,
         &dont,
         &size,
         copyA.data(),
         &size,
         evals.data(),
         static_cast<double *>(nullptr),
         &size, /* left eigenvectors */
         static_cast<double *>(nullptr),
         &size, /* right eigenvectors */
         workspace,
         &wsize,
         rwork,
         &info);
 
  if (info < 0)
    {
      ERROR("argument passed to zgeev had an illegal value");
      ret = false;
    }
  else if (info > 0)
    {
      ERROR("the QR algorithm in zgeev failed to compute all eigvals");
      ret = false;
    }
  else
    {
      eigvals->resize(size, 1);
      fill_from_lapack_array(evals, *eigvals);
    }
 
  delete[] workspace;
  delete[] rwork;
 
  return ret;
}

References ERROR, fill_from_lapack_array(), make_lapack_array(), DMat< ACoeffRing >::numColumns(), DMat< ACoeffRing >::numRows(), DMat< ACoeffRing >::resize(), and zgeev_().