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diff --git a/Eigen/Core/Product.h b/Eigen/Core/Product.h
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+++ b/Eigen/Core/Product.h
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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra. Eigen itself is part of the KDE project.
+//
+// Copyright (C) 2006-2007 Benoit Jacob <jacob@math.jussieu.fr>
+//
+// Eigen is free software; 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 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 General Public License for more
+// details.
+//
+// You should have received a copy of the GNU General Public License along
+// with Eigen; if not, write to the Free Software Foundation, Inc., 51
+// Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+//
+// As a special exception, if other files instantiate templates or use macros
+// or functions from this file, or you compile this file and link it
+// with other works to produce a work based on this file, this file does not
+// by itself cause the resulting work to be covered by the GNU General Public
+// License. This exception does not invalidate any other reasons why a work
+// based on this file might be covered by the GNU General Public License.
+
+#ifndef EIGEN_PRODUCT_H
+#define EIGEN_PRODUCT_H
+
+template<int Index, int Size, typename Lhs, typename Rhs>
+struct ProductUnroller
+{
+  static void run(int row, int col, const Lhs& lhs, const Rhs& rhs,
+                  typename Lhs::Scalar &res)
+  {
+    ProductUnroller<Index-1, Size, Lhs, Rhs>::run(row, col, lhs, rhs, res);
+    res += lhs.coeff(row, Index) * rhs.coeff(Index, col);
+  }
+};
+
+template<int Size, typename Lhs, typename Rhs>
+struct ProductUnroller<0, Size, Lhs, Rhs>
+{
+  static void run(int row, int col, const Lhs& lhs, const Rhs& rhs,
+                  typename Lhs::Scalar &res)
+  {
+    res = lhs.coeff(row, 0) * rhs.coeff(0, col);
+  }
+};
+
+template<int Index, typename Lhs, typename Rhs>
+struct ProductUnroller<Index, Dynamic, Lhs, Rhs>
+{
+  static void run(int, int, const Lhs&, const Rhs&, typename Lhs::Scalar&) {}
+};
+
+// prevent buggy user code from causing an infinite recursion
+template<int Index, typename Lhs, typename Rhs>
+struct ProductUnroller<Index, 0, Lhs, Rhs>
+{
+  static void run(int, int, const Lhs&, const Rhs&, typename Lhs::Scalar&) {}
+};
+
+template<typename Lhs, typename Rhs> class Product : NoOperatorEquals,
+  public MatrixBase<typename Lhs::Scalar, Product<Lhs, Rhs> >
+{
+  public:
+    typedef typename Lhs::Scalar Scalar;
+    typedef typename Lhs::Ref LhsRef;
+    typedef typename Rhs::Ref RhsRef;
+    friend class MatrixBase<Scalar, Product>;
+    
+    Product(const LhsRef& lhs, const RhsRef& rhs)
+      : m_lhs(lhs), m_rhs(rhs) 
+    {
+      assert(lhs.cols() == rhs.rows());
+    }
+    
+    Product(const Product& other)
+      : m_lhs(other.m_lhs), m_rhs(other.m_rhs) {}
+    
+  private:
+    static const int _RowsAtCompileTime = Lhs::RowsAtCompileTime,
+                     _ColsAtCompileTime = Rhs::ColsAtCompileTime;
+
+    const Product& _ref() const { return *this; }
+    int _rows() const { return m_lhs.rows(); }
+    int _cols() const { return m_rhs.cols(); }
+    
+    Scalar _coeff(int row, int col) const
+    {
+      Scalar res;
+      if(EIGEN_UNROLLED_LOOPS
+      && Lhs::ColsAtCompileTime != Dynamic && Lhs::ColsAtCompileTime <= 16)
+        ProductUnroller<Lhs::ColsAtCompileTime-1, Lhs::ColsAtCompileTime, LhsRef, RhsRef>
+          ::run(row, col, m_lhs, m_rhs, res);
+      else
+      {
+        res = m_lhs.coeff(row, 0) * m_rhs.coeff(0, col);
+        for(int i = 1; i < m_lhs.cols(); i++)
+          res += m_lhs.coeff(row, i) * m_rhs.coeff(i, col);
+      }
+      return res;
+    }
+    
+  protected:
+    const LhsRef m_lhs;
+    const RhsRef m_rhs;
+};
+
+template<typename Scalar, typename Derived>
+template<typename OtherDerived>
+const Product<Derived, OtherDerived>
+MatrixBase<Scalar, Derived>::lazyProduct(const MatrixBase<Scalar, OtherDerived> &other) const
+{
+  return Product<Derived, OtherDerived>(ref(), other.ref());
+}
+
+template<typename Scalar, typename Derived1, typename Derived2>
+Eval<Product<Derived1, Derived2> >
+operator*(const MatrixBase<Scalar, Derived1> &mat1, const MatrixBase<Scalar, Derived2> &mat2)
+{
+  return mat1.lazyProduct(mat2).eval();
+}
+
+template<typename Scalar, typename Derived>
+template<typename OtherDerived>
+Derived &
+MatrixBase<Scalar, Derived>::operator*=(const MatrixBase<Scalar, OtherDerived> &other)
+{
+  return *this = *this * other;
+}
+
+#endif // EIGEN_PRODUCT_H