eigenvectors_symmetric() [1/2]

bool Lapack::eigenvectors_symmetric ( const DMatRR * A, DMatRR * eigenvals, DMatRR * eigenvecs )

static

Definition at line 513 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);
      eigvecs->resize(0, 0);
      return true;
    }
 
  bool ret = true;
  char doit = 'V';
  char triangle = 'U'; /* Upper triangular part makes symmetric matrix */
 
  int wsize = 3 * size - 1;
  double* workspace = new double[wsize];
  int info;
 
  std::vector<double> evecs = make_lapack_array(*A);
  std::vector<double> evals(size);
 
  dsyev_(
         &doit, &triangle, &size, evecs.data(), &size, evals.data(), workspace, &wsize, &info);
 
  if (info < 0)
    {
      ERROR("argument passed to dsyev had an illegal value");
      ret = false;
    }
  else if (info > 0)
    {
      ERROR("dsyev did not converge");
      ret = false;
    }
  else
    {
      // Copy results to eigvals, eigvecs
      eigvecs->resize(size, size);
      fill_from_lapack_array(evecs, *eigvecs);
      eigvals->resize(size, 1);
      fill_from_lapack_array(evals, *eigvals);
    }
 
  delete [] workspace;
 
  return ret;
}

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