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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2012 Chen-Pang He <jdh8@ms63.hinet.net>
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#ifndef EIGEN_RANK2UPDATE_H
+#define EIGEN_RANK2UPDATE_H
+
+namespace Eigen {
+namespace internal {
+
+/* Optimized selfadjoint matrix += alpha * uv' + conj(alpha)*vu'
+ * This is the low-level version of SelfadjointRank2Update.h
+ */
+template <typename Scalar, typename Index, int UpLo>
+struct rank2_update_selector {
+  static void run(Index size, Scalar* mat, Index stride, const Scalar* u, const Scalar* v, Scalar alpha) {
+    typedef Map<const Matrix<Scalar, Dynamic, 1> > OtherMap;
+    for (Index i = 0; i < size; ++i) {
+      Map<Matrix<Scalar, Dynamic, 1> >(mat + stride * i + (UpLo == Lower ? i : 0),
+                                       UpLo == Lower ? size - i : (i + 1)) +=
+          numext::conj(alpha) * numext::conj(u[i]) *
+              OtherMap(v + (UpLo == Lower ? i : 0), UpLo == Lower ? size - i : (i + 1)) +
+          alpha * numext::conj(v[i]) * OtherMap(u + (UpLo == Lower ? i : 0), UpLo == Lower ? size - i : (i + 1));
+    }
+  }
+};
+
+/* Optimized selfadjoint matrix += alpha * uv' + conj(alpha)*vu'
+ * The matrix is in packed form.
+ */
+template <typename Scalar, typename Index, int UpLo>
+struct packed_rank2_update_selector {
+  static void run(Index size, Scalar* mat, const Scalar* u, const Scalar* v, Scalar alpha) {
+    typedef Map<const Matrix<Scalar, Dynamic, 1> > OtherMap;
+    Index offset = 0;
+    for (Index i = 0; i < size; ++i) {
+      Map<Matrix<Scalar, Dynamic, 1> >(mat + offset, UpLo == Lower ? size - i : (i + 1)) +=
+          numext::conj(alpha) * numext::conj(u[i]) *
+              OtherMap(v + (UpLo == Lower ? i : 0), UpLo == Lower ? size - i : (i + 1)) +
+          alpha * numext::conj(v[i]) * OtherMap(u + (UpLo == Lower ? i : 0), UpLo == Lower ? size - i : (i + 1));
+      // FIXME This should be handled outside.
+      mat[offset + (UpLo == Lower ? 0 : i)] = numext::real(mat[offset + (UpLo == Lower ? 0 : i)]);
+      offset += UpLo == Lower ? size - i : (i + 1);
+    }
+  }
+};
+
+}  // namespace internal
+}  // namespace Eigen
+
+#endif  // EIGEN_RANK2UPDATE_H