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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2009 Claire Maurice
+// Copyright (C) 2009 Gael Guennebaud <g.gael@free.fr>
+//
+// Eigen is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 3 of the License, or (at your option) any later version.
+//
+// Alternatively, you can redistribute it and/or
+// modify it under the terms of the GNU General Public License as
+// published by the Free Software Foundation; either version 2 of
+// the License, or (at your option) any later version.
+//
+// Eigen is distributed in the hope that it will be useful, but WITHOUT ANY
+// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+// FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License or the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License and a copy of the GNU General Public License along with
+// Eigen. If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef EIGEN_COMPLEX_EIGEN_SOLVER_H
+#define EIGEN_COMPLEX_EIGEN_SOLVER_H
+
+/** \eigenvalues_module \ingroup Eigenvalues_Module
+  * \nonstableyet
+  *
+  * \class ComplexEigenSolver
+  *
+  * \brief Eigen values/vectors solver for general complex matrices
+  *
+  * \param MatrixType the type of the matrix of which we are computing the eigen decomposition
+  *
+  * \sa class EigenSolver, class SelfAdjointEigenSolver
+  */
+template<typename _MatrixType> class ComplexEigenSolver
+{
+  public:
+    typedef _MatrixType MatrixType;
+    typedef typename MatrixType::Scalar Scalar;
+    typedef typename NumTraits<Scalar>::Real RealScalar;
+    typedef std::complex<RealScalar> Complex;
+    typedef Matrix<Complex, MatrixType::ColsAtCompileTime,1> EigenvalueType;
+    typedef Matrix<Complex, MatrixType::RowsAtCompileTime,MatrixType::ColsAtCompileTime> EigenvectorType;
+
+    /**
+    * \brief Default Constructor.
+    *
+    * The default constructor is useful in cases in which the user intends to
+    * perform decompositions via ComplexEigenSolver::compute(const MatrixType&).
+    */
+    ComplexEigenSolver() : m_eivec(), m_eivalues(), m_isInitialized(false)
+    {}
+
+    ComplexEigenSolver(const MatrixType& matrix)
+            : m_eivec(matrix.rows(),matrix.cols()),
+              m_eivalues(matrix.cols()),
+              m_isInitialized(false)
+    {
+      compute(matrix);
+    }
+
+    EigenvectorType eigenvectors(void) const
+    {
+      ei_assert(m_isInitialized && "ComplexEigenSolver is not initialized.");
+      return m_eivec;
+    }
+
+    EigenvalueType eigenvalues() const
+    {
+      ei_assert(m_isInitialized && "ComplexEigenSolver is not initialized.");
+      return m_eivalues;
+    }
+
+    void compute(const MatrixType& matrix);
+
+  protected:
+    MatrixType m_eivec;
+    EigenvalueType m_eivalues;
+    bool m_isInitialized;
+};
+
+
+template<typename MatrixType>
+void ComplexEigenSolver<MatrixType>::compute(const MatrixType& matrix)
+{
+  // this code is inspired from Jampack
+  assert(matrix.cols() == matrix.rows());
+  int n = matrix.cols();
+  m_eivalues.resize(n,1);
+
+  RealScalar eps = epsilon<RealScalar>();
+
+  // Reduce to complex Schur form
+  ComplexSchur<MatrixType> schur(matrix);
+
+  m_eivalues = schur.matrixT().diagonal();
+
+  m_eivec.setZero();
+
+  Scalar d2, z;
+  RealScalar norm = matrix.norm();
+
+  // compute the (normalized) eigenvectors
+  for(int k=n-1 ; k>=0 ; k--)
+  {
+    d2 = schur.matrixT().coeff(k,k);
+    m_eivec.coeffRef(k,k) = Scalar(1.0,0.0);
+    for(int i=k-1 ; i>=0 ; i--)
+    {
+      m_eivec.coeffRef(i,k) = -schur.matrixT().coeff(i,k);
+      if(k-i-1>0)
+        m_eivec.coeffRef(i,k) -= (schur.matrixT().row(i).segment(i+1,k-i-1) * m_eivec.col(k).segment(i+1,k-i-1)).value();
+      z = schur.matrixT().coeff(i,i) - d2;
+      if(z==Scalar(0))
+        ei_real_ref(z) = eps * norm;
+      m_eivec.coeffRef(i,k) = m_eivec.coeff(i,k) / z;
+
+    }
+    m_eivec.col(k).normalize();
+  }
+
+  m_eivec = schur.matrixU() * m_eivec;
+  m_isInitialized = true;
+
+  // sort the eigenvalues
+  {
+    for (int i=0; i<n; i++)
+    {
+      int k;
+      m_eivalues.cwise().abs().end(n-i).minCoeff(&k);
+      if (k != 0)
+      {
+        k += i;
+        std::swap(m_eivalues[k],m_eivalues[i]);
+        m_eivec.col(i).swap(m_eivec.col(k));
+      }
+    }
+  }
+}
+
+
+
+#endif // EIGEN_COMPLEX_EIGEN_SOLVER_H