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diff --git a/Eigen/src/SparseCore/SparseProduct.h b/Eigen/src/SparseCore/SparseProduct.h
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+++ b/Eigen/src/SparseCore/SparseProduct.h
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+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008-2010 Gael Guennebaud <gael.guennebaud@inria.fr>
+//
+// 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_SPARSEPRODUCT_H
+#define EIGEN_SPARSEPRODUCT_H
+
+namespace Eigen { 
+
+template<typename Lhs, typename Rhs>
+struct SparseSparseProductReturnType
+{
+  typedef typename internal::traits<Lhs>::Scalar Scalar;
+  enum {
+    LhsRowMajor = internal::traits<Lhs>::Flags & RowMajorBit,
+    RhsRowMajor = internal::traits<Rhs>::Flags & RowMajorBit,
+    TransposeRhs = (!LhsRowMajor) && RhsRowMajor,
+    TransposeLhs = LhsRowMajor && (!RhsRowMajor)
+  };
+
+  typedef typename internal::conditional<TransposeLhs,
+    SparseMatrix<Scalar,0>,
+    typename internal::nested<Lhs,Rhs::RowsAtCompileTime>::type>::type LhsNested;
+
+  typedef typename internal::conditional<TransposeRhs,
+    SparseMatrix<Scalar,0>,
+    typename internal::nested<Rhs,Lhs::RowsAtCompileTime>::type>::type RhsNested;
+
+  typedef SparseSparseProduct<LhsNested, RhsNested> Type;
+};
+
+namespace internal {
+template<typename LhsNested, typename RhsNested>
+struct traits<SparseSparseProduct<LhsNested, RhsNested> >
+{
+  typedef MatrixXpr XprKind;
+  // clean the nested types:
+  typedef typename remove_all<LhsNested>::type _LhsNested;
+  typedef typename remove_all<RhsNested>::type _RhsNested;
+  typedef typename _LhsNested::Scalar Scalar;
+  typedef typename promote_index_type<typename traits<_LhsNested>::Index,
+                                         typename traits<_RhsNested>::Index>::type Index;
+
+  enum {
+    LhsCoeffReadCost = _LhsNested::CoeffReadCost,
+    RhsCoeffReadCost = _RhsNested::CoeffReadCost,
+    LhsFlags = _LhsNested::Flags,
+    RhsFlags = _RhsNested::Flags,
+
+    RowsAtCompileTime    = _LhsNested::RowsAtCompileTime,
+    ColsAtCompileTime    = _RhsNested::ColsAtCompileTime,
+    MaxRowsAtCompileTime = _LhsNested::MaxRowsAtCompileTime,
+    MaxColsAtCompileTime = _RhsNested::MaxColsAtCompileTime,
+
+    InnerSize = EIGEN_SIZE_MIN_PREFER_FIXED(_LhsNested::ColsAtCompileTime, _RhsNested::RowsAtCompileTime),
+
+    EvalToRowMajor = (RhsFlags & LhsFlags & RowMajorBit),
+
+    RemovedBits = ~(EvalToRowMajor ? 0 : RowMajorBit),
+
+    Flags = (int(LhsFlags | RhsFlags) & HereditaryBits & RemovedBits)
+          | EvalBeforeAssigningBit
+          | EvalBeforeNestingBit,
+
+    CoeffReadCost = Dynamic
+  };
+
+  typedef Sparse StorageKind;
+};
+
+} // end namespace internal
+
+template<typename LhsNested, typename RhsNested>
+class SparseSparseProduct : internal::no_assignment_operator,
+  public SparseMatrixBase<SparseSparseProduct<LhsNested, RhsNested> >
+{
+  public:
+
+    typedef SparseMatrixBase<SparseSparseProduct> Base;
+    EIGEN_DENSE_PUBLIC_INTERFACE(SparseSparseProduct)
+
+  private:
+
+    typedef typename internal::traits<SparseSparseProduct>::_LhsNested _LhsNested;
+    typedef typename internal::traits<SparseSparseProduct>::_RhsNested _RhsNested;
+
+  public:
+
+    template<typename Lhs, typename Rhs>
+    EIGEN_STRONG_INLINE SparseSparseProduct(const Lhs& lhs, const Rhs& rhs)
+      : m_lhs(lhs), m_rhs(rhs), m_tolerance(0), m_conservative(true)
+    {
+      init();
+    }
+
+    template<typename Lhs, typename Rhs>
+    EIGEN_STRONG_INLINE SparseSparseProduct(const Lhs& lhs, const Rhs& rhs, RealScalar tolerance)
+      : m_lhs(lhs), m_rhs(rhs), m_tolerance(tolerance), m_conservative(false)
+    {
+      init();
+    }
+
+    SparseSparseProduct pruned(Scalar reference = 0, RealScalar epsilon = NumTraits<RealScalar>::dummy_precision()) const
+    {
+      return SparseSparseProduct(m_lhs,m_rhs,internal::abs(reference)*epsilon);
+    }
+
+    template<typename Dest>
+    void evalTo(Dest& result) const
+    {
+      if(m_conservative)
+        internal::conservative_sparse_sparse_product_selector<_LhsNested, _RhsNested, Dest>::run(lhs(),rhs(),result);
+      else
+        internal::sparse_sparse_product_with_pruning_selector<_LhsNested, _RhsNested, Dest>::run(lhs(),rhs(),result,m_tolerance);
+    }
+
+    EIGEN_STRONG_INLINE Index rows() const { return m_lhs.rows(); }
+    EIGEN_STRONG_INLINE Index cols() const { return m_rhs.cols(); }
+
+    EIGEN_STRONG_INLINE const _LhsNested& lhs() const { return m_lhs; }
+    EIGEN_STRONG_INLINE const _RhsNested& rhs() const { return m_rhs; }
+
+  protected:
+    void init()
+    {
+      eigen_assert(m_lhs.cols() == m_rhs.rows());
+
+      enum {
+        ProductIsValid = _LhsNested::ColsAtCompileTime==Dynamic
+                      || _RhsNested::RowsAtCompileTime==Dynamic
+                      || int(_LhsNested::ColsAtCompileTime)==int(_RhsNested::RowsAtCompileTime),
+        AreVectors = _LhsNested::IsVectorAtCompileTime && _RhsNested::IsVectorAtCompileTime,
+        SameSizes = EIGEN_PREDICATE_SAME_MATRIX_SIZE(_LhsNested,_RhsNested)
+      };
+      // note to the lost user:
+      //    * for a dot product use: v1.dot(v2)
+      //    * for a coeff-wise product use: v1.cwise()*v2
+      EIGEN_STATIC_ASSERT(ProductIsValid || !(AreVectors && SameSizes),
+        INVALID_VECTOR_VECTOR_PRODUCT__IF_YOU_WANTED_A_DOT_OR_COEFF_WISE_PRODUCT_YOU_MUST_USE_THE_EXPLICIT_FUNCTIONS)
+      EIGEN_STATIC_ASSERT(ProductIsValid || !(SameSizes && !AreVectors),
+        INVALID_MATRIX_PRODUCT__IF_YOU_WANTED_A_COEFF_WISE_PRODUCT_YOU_MUST_USE_THE_EXPLICIT_FUNCTION)
+      EIGEN_STATIC_ASSERT(ProductIsValid || SameSizes, INVALID_MATRIX_PRODUCT)
+    }
+
+    LhsNested m_lhs;
+    RhsNested m_rhs;
+    RealScalar m_tolerance;
+    bool m_conservative;
+};
+
+// sparse = sparse * sparse
+template<typename Derived>
+template<typename Lhs, typename Rhs>
+inline Derived& SparseMatrixBase<Derived>::operator=(const SparseSparseProduct<Lhs,Rhs>& product)
+{
+  product.evalTo(derived());
+  return derived();
+}
+
+/** \returns an expression of the product of two sparse matrices.
+  * By default a conservative product preserving the symbolic non zeros is performed.
+  * The automatic pruning of the small values can be achieved by calling the pruned() function
+  * in which case a totally different product algorithm is employed:
+  * \code
+  * C = (A*B).pruned();             // supress numerical zeros (exact)
+  * C = (A*B).pruned(ref);
+  * C = (A*B).pruned(ref,epsilon);
+  * \endcode
+  * where \c ref is a meaningful non zero reference value.
+  * */
+template<typename Derived>
+template<typename OtherDerived>
+inline const typename SparseSparseProductReturnType<Derived,OtherDerived>::Type
+SparseMatrixBase<Derived>::operator*(const SparseMatrixBase<OtherDerived> &other) const
+{
+  return typename SparseSparseProductReturnType<Derived,OtherDerived>::Type(derived(), other.derived());
+}
+
+} // end namespace Eigen
+
+#endif // EIGEN_SPARSEPRODUCT_H