TensorFlow: Initial commit of TensorFlow library.

TensorFlow is an open source software library for numerical computation
using data flow graphs.

Base CL: 107276108

1 files changed, 547 insertions, 0 deletions

diff --git a/third_party/eigen3/Eigen/src/SparseCore/SparseBlock.h b/third_party/eigen3/Eigen/src/SparseCore/SparseBlock.h
new file mode 100644
index 0000000000..3a6d8a275c
--- /dev/null
+++ b/third_party/eigen3/Eigen/src/SparseCore/SparseBlock.h
@@ -0,0 +1,547 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008-2009 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_SPARSE_BLOCK_H
+#define EIGEN_SPARSE_BLOCK_H
+
+namespace Eigen {
+
+template<typename XprType, int BlockRows, int BlockCols>
+class BlockImpl<XprType,BlockRows,BlockCols,true,Sparse>
+  : public SparseMatrixBase<Block<XprType,BlockRows,BlockCols,true> >
+{
+    typedef typename internal::remove_all<typename XprType::Nested>::type _MatrixTypeNested;
+    typedef Block<XprType, BlockRows, BlockCols, true> BlockType;
+public:
+    enum { IsRowMajor = internal::traits<BlockType>::IsRowMajor };
+protected:
+    enum { OuterSize = IsRowMajor ? BlockRows : BlockCols };
+public:
+    EIGEN_SPARSE_PUBLIC_INTERFACE(BlockType)
+
+    class InnerIterator: public XprType::InnerIterator
+    {
+        typedef typename BlockImpl::Index Index;
+      public:
+        inline InnerIterator(const BlockType& xpr, Index outer)
+          : XprType::InnerIterator(xpr.m_matrix, xpr.m_outerStart + outer), m_outer(outer)
+        {}
+        inline Index row() const { return IsRowMajor ? m_outer : this->index(); }
+        inline Index col() const { return IsRowMajor ? this->index() : m_outer; }
+      protected:
+        Index m_outer;
+    };
+    class ReverseInnerIterator: public XprType::ReverseInnerIterator
+    {
+        typedef typename BlockImpl::Index Index;
+      public:
+        inline ReverseInnerIterator(const BlockType& xpr, Index outer)
+          : XprType::ReverseInnerIterator(xpr.m_matrix, xpr.m_outerStart + outer), m_outer(outer)
+        {}
+        inline Index row() const { return IsRowMajor ? m_outer : this->index(); }
+        inline Index col() const { return IsRowMajor ? this->index() : m_outer; }
+      protected:
+        Index m_outer;
+    };
+
+    inline BlockImpl(const XprType& xpr, int i)
+      : m_matrix(xpr), m_outerStart(i), m_outerSize(OuterSize)
+    {}
+
+    inline BlockImpl(const XprType& xpr, int startRow, int startCol, int blockRows, int blockCols)
+      : m_matrix(xpr), m_outerStart(IsRowMajor ? startRow : startCol), m_outerSize(IsRowMajor ? blockRows : blockCols)
+    {}
+
+    EIGEN_STRONG_INLINE Index rows() const { return IsRowMajor ? m_outerSize.value() : m_matrix.rows(); }
+    EIGEN_STRONG_INLINE Index cols() const { return IsRowMajor ? m_matrix.cols() : m_outerSize.value(); }
+
+    Index nonZeros() const
+    {
+      Index nnz = 0;
+      Index end = m_outerStart + m_outerSize.value();
+      for(int j=m_outerStart; j<end; ++j)
+        for(typename XprType::InnerIterator it(m_matrix, j); it; ++it)
+          ++nnz;
+      return nnz;
+    }
+
+  protected:
+
+    typename XprType::Nested m_matrix;
+    Index m_outerStart;
+    const internal::variable_if_dynamic<Index, OuterSize> m_outerSize;
+
+  public:
+    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(BlockImpl)
+};
+
+
+/***************************************************************************
+* specialization for SparseMatrix
+***************************************************************************/
+
+namespace internal {
+
+template<typename SparseMatrixType, int BlockRows, int BlockCols>
+class sparse_matrix_block_impl
+  : public SparseMatrixBase<Block<SparseMatrixType,BlockRows,BlockCols,true> >
+{
+    typedef typename internal::remove_all<typename SparseMatrixType::Nested>::type _MatrixTypeNested;
+    typedef Block<SparseMatrixType, BlockRows, BlockCols, true> BlockType;
+public:
+    enum { IsRowMajor = internal::traits<BlockType>::IsRowMajor };
+    EIGEN_SPARSE_PUBLIC_INTERFACE(BlockType)
+protected:
+    enum { OuterSize = IsRowMajor ? BlockRows : BlockCols };
+public:
+
+    class InnerIterator: public SparseMatrixType::InnerIterator
+    {
+      public:
+        inline InnerIterator(const BlockType& xpr, Index outer)
+          : SparseMatrixType::InnerIterator(xpr.m_matrix, xpr.m_outerStart + outer), m_outer(outer)
+        {}
+        inline Index row() const { return IsRowMajor ? m_outer : this->index(); }
+        inline Index col() const { return IsRowMajor ? this->index() : m_outer; }
+      protected:
+        Index m_outer;
+    };
+    class ReverseInnerIterator: public SparseMatrixType::ReverseInnerIterator
+    {
+      public:
+        inline ReverseInnerIterator(const BlockType& xpr, Index outer)
+          : SparseMatrixType::ReverseInnerIterator(xpr.m_matrix, xpr.m_outerStart + outer), m_outer(outer)
+        {}
+        inline Index row() const { return IsRowMajor ? m_outer : this->index(); }
+        inline Index col() const { return IsRowMajor ? this->index() : m_outer; }
+      protected:
+        Index m_outer;
+    };
+
+    inline sparse_matrix_block_impl(const SparseMatrixType& xpr, int i)
+      : m_matrix(xpr), m_outerStart(i), m_outerSize(OuterSize)
+    {}
+
+    inline sparse_matrix_block_impl(const SparseMatrixType& xpr, int startRow, int startCol, int blockRows, int blockCols)
+      : m_matrix(xpr), m_outerStart(IsRowMajor ? startRow : startCol), m_outerSize(IsRowMajor ? blockRows : blockCols)
+    {}
+
+    template<typename OtherDerived>
+    inline BlockType& operator=(const SparseMatrixBase<OtherDerived>& other)
+    {
+      typedef typename internal::remove_all<typename SparseMatrixType::Nested>::type _NestedMatrixType;
+      _NestedMatrixType& matrix = const_cast<_NestedMatrixType&>(m_matrix);;
+      // This assignment is slow if this vector set is not empty
+      // and/or it is not at the end of the nonzeros of the underlying matrix.
+
+      // 1 - eval to a temporary to avoid transposition and/or aliasing issues
+      SparseMatrix<Scalar, IsRowMajor ? RowMajor : ColMajor, Index> tmp(other);
+
+      // 2 - let's check whether there is enough allocated memory
+      Index nnz           = tmp.nonZeros();
+      Index start         = m_outerStart==0 ? 0 : matrix.outerIndexPtr()[m_outerStart]; // starting position of the current block
+      Index end           = m_matrix.outerIndexPtr()[m_outerStart+m_outerSize.value()]; // ending position of the current block
+      Index block_size    = end - start;                                                // available room in the current block
+      Index tail_size     = m_matrix.outerIndexPtr()[m_matrix.outerSize()] - end;
+
+      Index free_size     = m_matrix.isCompressed()
+                          ? Index(matrix.data().allocatedSize()) + block_size
+                          : block_size;
+
+      if(nnz>free_size)
+      {
+        // realloc manually to reduce copies
+        typename SparseMatrixType::Storage newdata(m_matrix.data().allocatedSize() - block_size + nnz);
+
+        internal::smart_copy(&m_matrix.data().value(0),  &m_matrix.data().value(0) + start, &newdata.value(0));
+        internal::smart_copy(&m_matrix.data().index(0),  &m_matrix.data().index(0) + start, &newdata.index(0));
+
+        internal::smart_copy(&tmp.data().value(0),  &tmp.data().value(0) + nnz, &newdata.value(start));
+        internal::smart_copy(&tmp.data().index(0),  &tmp.data().index(0) + nnz, &newdata.index(start));
+
+        internal::smart_copy(&matrix.data().value(end),  &matrix.data().value(end) + tail_size, &newdata.value(start+nnz));
+        internal::smart_copy(&matrix.data().index(end),  &matrix.data().index(end) + tail_size, &newdata.index(start+nnz));
+
+        newdata.resize(m_matrix.outerIndexPtr()[m_matrix.outerSize()] - block_size + nnz);
+
+        matrix.data().swap(newdata);
+      }
+      else
+      {
+        // no need to realloc, simply copy the tail at its respective position and insert tmp
+        matrix.data().resize(start + nnz + tail_size);
+
+        internal::smart_memmove(&matrix.data().value(end),  &matrix.data().value(end) + tail_size, &matrix.data().value(start + nnz));
+        internal::smart_memmove(&matrix.data().index(end),  &matrix.data().index(end) + tail_size, &matrix.data().index(start + nnz));
+
+        internal::smart_copy(&tmp.data().value(0),  &tmp.data().value(0) + nnz, &matrix.data().value(start));
+        internal::smart_copy(&tmp.data().index(0),  &tmp.data().index(0) + nnz, &matrix.data().index(start));
+      }
+
+      // update innerNonZeros
+      if(!m_matrix.isCompressed())
+        for(Index j=0; j<m_outerSize.value(); ++j)
+          matrix.innerNonZeroPtr()[m_outerStart+j] = tmp.innerVector(j).nonZeros();
+
+      // update outer index pointers
+      Index p = start;
+      for(Index k=0; k<m_outerSize.value(); ++k)
+      {
+        matrix.outerIndexPtr()[m_outerStart+k] = p;
+        p += tmp.innerVector(k).nonZeros();
+      }
+      std::ptrdiff_t offset = nnz - block_size;
+      for(Index k = m_outerStart + m_outerSize.value(); k<=matrix.outerSize(); ++k)
+      {
+        matrix.outerIndexPtr()[k] += offset;
+      }
+
+      return derived();
+    }
+
+    inline BlockType& operator=(const BlockType& other)
+    {
+      return operator=<BlockType>(other);
+    }
+
+    inline const Scalar* valuePtr() const
+    { return m_matrix.valuePtr() + m_matrix.outerIndexPtr()[m_outerStart]; }
+    inline Scalar* valuePtr()
+    { return m_matrix.const_cast_derived().valuePtr() + m_matrix.outerIndexPtr()[m_outerStart]; }
+
+    inline const Index* innerIndexPtr() const
+    { return m_matrix.innerIndexPtr() + m_matrix.outerIndexPtr()[m_outerStart]; }
+    inline Index* innerIndexPtr()
+    { return m_matrix.const_cast_derived().innerIndexPtr() + m_matrix.outerIndexPtr()[m_outerStart]; }
+
+    inline const Index* outerIndexPtr() const
+    { return m_matrix.outerIndexPtr() + m_outerStart; }
+    inline Index* outerIndexPtr()
+    { return m_matrix.const_cast_derived().outerIndexPtr() + m_outerStart; }
+
+    Index nonZeros() const
+    {
+      if(m_matrix.isCompressed())
+        return  std::size_t(m_matrix.outerIndexPtr()[m_outerStart+m_outerSize.value()])
+              - std::size_t(m_matrix.outerIndexPtr()[m_outerStart]);
+      else if(m_outerSize.value()==0)
+        return 0;
+      else
+        return Map<const Matrix<Index,OuterSize,1> >(m_matrix.innerNonZeroPtr()+m_outerStart, m_outerSize.value()).sum();
+    }
+
+    const Scalar& lastCoeff() const
+    {
+      EIGEN_STATIC_ASSERT_VECTOR_ONLY(sparse_matrix_block_impl);
+      eigen_assert(nonZeros()>0);
+      if(m_matrix.isCompressed())
+        return m_matrix.valuePtr()[m_matrix.outerIndexPtr()[m_outerStart+1]-1];
+      else
+        return m_matrix.valuePtr()[m_matrix.outerIndexPtr()[m_outerStart]+m_matrix.innerNonZeroPtr()[m_outerStart]-1];
+    }
+
+    EIGEN_STRONG_INLINE Index rows() const { return IsRowMajor ? m_outerSize.value() : m_matrix.rows(); }
+    EIGEN_STRONG_INLINE Index cols() const { return IsRowMajor ? m_matrix.cols() : m_outerSize.value(); }
+
+  protected:
+
+    typename SparseMatrixType::Nested m_matrix;
+    Index m_outerStart;
+    const internal::variable_if_dynamic<Index, OuterSize> m_outerSize;
+
+};
+
+} // namespace internal
+
+template<typename _Scalar, int _Options, typename _Index, int BlockRows, int BlockCols>
+class BlockImpl<SparseMatrix<_Scalar, _Options, _Index>,BlockRows,BlockCols,true,Sparse>
+  : public internal::sparse_matrix_block_impl<SparseMatrix<_Scalar, _Options, _Index>,BlockRows,BlockCols>
+{
+public:
+  typedef SparseMatrix<_Scalar, _Options, _Index> SparseMatrixType;
+  typedef internal::sparse_matrix_block_impl<SparseMatrixType,BlockRows,BlockCols> Base;
+  inline BlockImpl(SparseMatrixType& xpr, int i)
+    : Base(xpr, i)
+  {}
+
+  inline BlockImpl(SparseMatrixType& xpr, int startRow, int startCol, int blockRows, int blockCols)
+    : Base(xpr, startRow, startCol, blockRows, blockCols)
+  {}
+
+  using Base::operator=;
+};
+
+template<typename _Scalar, int _Options, typename _Index, int BlockRows, int BlockCols>
+class BlockImpl<const SparseMatrix<_Scalar, _Options, _Index>,BlockRows,BlockCols,true,Sparse>
+  : public internal::sparse_matrix_block_impl<const SparseMatrix<_Scalar, _Options, _Index>,BlockRows,BlockCols>
+{
+public:
+  typedef const SparseMatrix<_Scalar, _Options, _Index> SparseMatrixType;
+  typedef internal::sparse_matrix_block_impl<SparseMatrixType,BlockRows,BlockCols> Base;
+  inline BlockImpl(SparseMatrixType& xpr, int i)
+    : Base(xpr, i)
+  {}
+
+  inline BlockImpl(SparseMatrixType& xpr, int startRow, int startCol, int blockRows, int blockCols)
+    : Base(xpr, startRow, startCol, blockRows, blockCols)
+  {}
+
+  using Base::operator=;
+};
+
+//----------
+
+/** \returns the \a outer -th column (resp. row) of the matrix \c *this if \c *this
+  * is col-major (resp. row-major).
+  */
+template<typename Derived>
+typename SparseMatrixBase<Derived>::InnerVectorReturnType SparseMatrixBase<Derived>::innerVector(Index outer)
+{ return InnerVectorReturnType(derived(), outer); }
+
+/** \returns the \a outer -th column (resp. row) of the matrix \c *this if \c *this
+  * is col-major (resp. row-major). Read-only.
+  */
+template<typename Derived>
+const typename SparseMatrixBase<Derived>::ConstInnerVectorReturnType SparseMatrixBase<Derived>::innerVector(Index outer) const
+{ return ConstInnerVectorReturnType(derived(), outer); }
+
+/** \returns the \a outer -th column (resp. row) of the matrix \c *this if \c *this
+  * is col-major (resp. row-major).
+  */
+template<typename Derived>
+Block<Derived,Dynamic,Dynamic,true> SparseMatrixBase<Derived>::innerVectors(Index outerStart, Index outerSize)
+{
+  return Block<Derived,Dynamic,Dynamic,true>(derived(),
+                                             IsRowMajor ? outerStart : 0, IsRowMajor ? 0 : outerStart,
+                                             IsRowMajor ? outerSize : rows(), IsRowMajor ? cols() : outerSize);
+
+}
+
+/** \returns the \a outer -th column (resp. row) of the matrix \c *this if \c *this
+  * is col-major (resp. row-major). Read-only.
+  */
+template<typename Derived>
+const Block<const Derived,Dynamic,Dynamic,true> SparseMatrixBase<Derived>::innerVectors(Index outerStart, Index outerSize) const
+{
+  return Block<const Derived,Dynamic,Dynamic,true>(derived(),
+                                                  IsRowMajor ? outerStart : 0, IsRowMajor ? 0 : outerStart,
+                                                  IsRowMajor ? outerSize : rows(), IsRowMajor ? cols() : outerSize);
+
+}
+
+namespace internal {
+
+template< typename XprType, int BlockRows, int BlockCols, bool InnerPanel,
+          bool OuterVector =  (BlockCols==1 && XprType::IsRowMajor)
+                               | // FIXME | instead of || to please GCC 4.4.0 stupid warning "suggest parentheses around &&".
+                                 // revert to || as soon as not needed anymore.
+                              (BlockRows==1 && !XprType::IsRowMajor)>
+class GenericSparseBlockInnerIteratorImpl;
+
+}
+
+/** Generic implementation of sparse Block expression.
+  * Real-only.
+  */
+template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel>
+class BlockImpl<XprType,BlockRows,BlockCols,InnerPanel,Sparse>
+  : public SparseMatrixBase<Block<XprType,BlockRows,BlockCols,InnerPanel> >, internal::no_assignment_operator
+{
+  typedef Block<XprType, BlockRows, BlockCols, InnerPanel> BlockType;
+public:
+    enum { IsRowMajor = internal::traits<BlockType>::IsRowMajor };
+    EIGEN_SPARSE_PUBLIC_INTERFACE(BlockType)
+
+    typedef typename internal::remove_all<typename XprType::Nested>::type _MatrixTypeNested;
+
+    /** Column or Row constructor
+      */
+    inline BlockImpl(const XprType& xpr, int i)
+      : m_matrix(xpr),
+        m_startRow( (BlockRows==1) && (BlockCols==XprType::ColsAtCompileTime) ? i : 0),
+        m_startCol( (BlockRows==XprType::RowsAtCompileTime) && (BlockCols==1) ? i : 0),
+        m_blockRows(BlockRows==1 ? 1 : xpr.rows()),
+        m_blockCols(BlockCols==1 ? 1 : xpr.cols())
+    {}
+
+    /** Dynamic-size constructor
+      */
+    inline BlockImpl(const XprType& xpr, int startRow, int startCol, int blockRows, int blockCols)
+      : m_matrix(xpr), m_startRow(startRow), m_startCol(startCol), m_blockRows(blockRows), m_blockCols(blockCols)
+    {}
+
+    inline int rows() const { return m_blockRows.value(); }
+    inline int cols() const { return m_blockCols.value(); }
+
+    inline Scalar& coeffRef(int row, int col)
+    {
+      return m_matrix.const_cast_derived()
+               .coeffRef(row + m_startRow.value(), col + m_startCol.value());
+    }
+
+    inline const Scalar coeff(int row, int col) const
+    {
+      return m_matrix.coeff(row + m_startRow.value(), col + m_startCol.value());
+    }
+
+    inline Scalar& coeffRef(int index)
+    {
+      return m_matrix.const_cast_derived()
+             .coeffRef(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
+                       m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
+    }
+
+    inline const Scalar coeff(int index) const
+    {
+      return m_matrix
+             .coeff(m_startRow.value() + (RowsAtCompileTime == 1 ? 0 : index),
+                    m_startCol.value() + (RowsAtCompileTime == 1 ? index : 0));
+    }
+
+    inline const _MatrixTypeNested& nestedExpression() const { return m_matrix; }
+
+    typedef internal::GenericSparseBlockInnerIteratorImpl<XprType,BlockRows,BlockCols,InnerPanel> InnerIterator;
+
+    class ReverseInnerIterator : public _MatrixTypeNested::ReverseInnerIterator
+    {
+      typedef typename _MatrixTypeNested::ReverseInnerIterator Base;
+      const BlockType& m_block;
+      Index m_begin;
+    public:
+
+      EIGEN_STRONG_INLINE ReverseInnerIterator(const BlockType& block, Index outer)
+        : Base(block.derived().nestedExpression(), outer + (IsRowMajor ? block.m_startRow.value() : block.m_startCol.value())),
+          m_block(block),
+          m_begin(IsRowMajor ? block.m_startCol.value() : block.m_startRow.value())
+      {
+        while( (Base::operator bool()) && (Base::index() >= (IsRowMajor ? m_block.m_startCol.value()+block.m_blockCols.value() : m_block.m_startRow.value()+block.m_blockRows.value())) )
+          Base::operator--();
+      }
+
+      inline Index index()  const { return Base::index() - (IsRowMajor ? m_block.m_startCol.value() : m_block.m_startRow.value()); }
+      inline Index outer()  const { return Base::outer() - (IsRowMajor ? m_block.m_startRow.value() : m_block.m_startCol.value()); }
+      inline Index row()    const { return Base::row()   - m_block.m_startRow.value(); }
+      inline Index col()    const { return Base::col()   - m_block.m_startCol.value(); }
+
+      inline operator bool() const { return Base::operator bool() && Base::index() >= m_begin; }
+    };
+  protected:
+    friend class internal::GenericSparseBlockInnerIteratorImpl<XprType,BlockRows,BlockCols,InnerPanel>;
+    friend class ReverseInnerIterator;
+
+    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(BlockImpl)
+
+    typename XprType::Nested m_matrix;
+    const internal::variable_if_dynamic<Index, XprType::RowsAtCompileTime == 1 ? 0 : Dynamic> m_startRow;
+    const internal::variable_if_dynamic<Index, XprType::ColsAtCompileTime == 1 ? 0 : Dynamic> m_startCol;
+    const internal::variable_if_dynamic<Index, RowsAtCompileTime> m_blockRows;
+    const internal::variable_if_dynamic<Index, ColsAtCompileTime> m_blockCols;
+
+};
+
+namespace internal {
+  template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel>
+  class GenericSparseBlockInnerIteratorImpl<XprType,BlockRows,BlockCols,InnerPanel,false> : public Block<XprType, BlockRows, BlockCols, InnerPanel>::_MatrixTypeNested::InnerIterator
+  {
+    typedef Block<XprType, BlockRows, BlockCols, InnerPanel> BlockType;
+    enum {
+      IsRowMajor = BlockType::IsRowMajor
+    };
+    typedef typename BlockType::_MatrixTypeNested _MatrixTypeNested;
+    typedef typename BlockType::Index Index;
+    typedef typename _MatrixTypeNested::InnerIterator Base;
+    const BlockType& m_block;
+    Index m_end;
+  public:
+
+    EIGEN_STRONG_INLINE GenericSparseBlockInnerIteratorImpl(const BlockType& block, Index outer)
+      : Base(block.derived().nestedExpression(), outer + (IsRowMajor ? block.m_startRow.value() : block.m_startCol.value())),
+        m_block(block),
+        m_end(IsRowMajor ? block.m_startCol.value()+block.m_blockCols.value() : block.m_startRow.value()+block.m_blockRows.value())
+    {
+      while( (Base::operator bool()) && (Base::index() < (IsRowMajor ? m_block.m_startCol.value() : m_block.m_startRow.value())) )
+        Base::operator++();
+    }
+
+    inline Index index()  const { return Base::index() - (IsRowMajor ? m_block.m_startCol.value() : m_block.m_startRow.value()); }
+    inline Index outer()  const { return Base::outer() - (IsRowMajor ? m_block.m_startRow.value() : m_block.m_startCol.value()); }
+    inline Index row()    const { return Base::row()   - m_block.m_startRow.value(); }
+    inline Index col()    const { return Base::col()   - m_block.m_startCol.value(); }
+
+    inline operator bool() const { return Base::operator bool() && Base::index() < m_end; }
+  };
+
+  // Row vector of a column-major sparse matrix or column of a row-major one.
+  template<typename XprType, int BlockRows, int BlockCols, bool InnerPanel>
+  class GenericSparseBlockInnerIteratorImpl<XprType,BlockRows,BlockCols,InnerPanel,true>
+  {
+    typedef Block<XprType, BlockRows, BlockCols, InnerPanel> BlockType;
+    enum {
+      IsRowMajor = BlockType::IsRowMajor
+    };
+    typedef typename BlockType::_MatrixTypeNested _MatrixTypeNested;
+    typedef typename BlockType::Index Index;
+    typedef typename BlockType::Scalar Scalar;
+    const BlockType& m_block;
+    Index m_outerPos;
+    Index m_innerIndex;
+    Scalar m_value;
+    Index m_end;
+  public:
+
+    EIGEN_STRONG_INLINE GenericSparseBlockInnerIteratorImpl(const BlockType& block, Index outer = 0)
+      :
+        m_block(block),
+        m_outerPos( (IsRowMajor ? block.m_startCol.value() : block.m_startRow.value()) - 1), // -1 so that operator++ finds the first non-zero entry
+        m_innerIndex(IsRowMajor ? block.m_startRow.value() : block.m_startCol.value()),
+        m_end(IsRowMajor ? block.m_startCol.value()+block.m_blockCols.value() : block.m_startRow.value()+block.m_blockRows.value())
+    {
+      EIGEN_UNUSED_VARIABLE(outer);
+      eigen_assert(outer==0);
+
+      ++(*this);
+    }
+
+    inline Index index()  const { return m_outerPos - (IsRowMajor ? m_block.m_startCol.value() : m_block.m_startRow.value()); }
+    inline Index outer()  const { return 0; }
+    inline Index row()    const { return IsRowMajor ? 0 : index(); }
+    inline Index col()    const { return IsRowMajor ? index() : 0; }
+
+    inline Scalar value() const { return m_value; }
+
+    inline GenericSparseBlockInnerIteratorImpl& operator++()
+    {
+      // At end already?
+      if (m_outerPos >= m_end)
+        return *this;
+
+      // search next non-zero entry.
+      while(++m_outerPos<m_end)
+      {
+        typename XprType::InnerIterator it(m_block.m_matrix, m_outerPos);
+        // search for the key m_innerIndex in the current outer-vector
+        while(it && it.index() < m_innerIndex) ++it;
+        if(it && it.index()==m_innerIndex)
+        {
+          m_value = it.value();
+          break;
+        }
+      }
+      return *this;
+    }
+
+    inline operator bool() const { return m_outerPos < m_end; }
+  };
+
+} // end namespace internal
+
+
+} // end namespace Eigen
+
+#endif // EIGEN_SPARSE_BLOCK_H