SparseView.h

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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2011-2014 Gael Guennebaud <gael.guennebaud@inria.fr>
// Copyright (C) 2010 Daniel Lowengrub <lowdanie@gmail.com>
//
// 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_SPARSEVIEW_H
#define EIGEN_SPARSEVIEW_H
 
// IWYU pragma: private
#include "./InternalHeaderCheck.h"
 
namespace Eigen {
 
namespace internal {
 
template <typename MatrixType>
struct traits<SparseView<MatrixType> > : traits<MatrixType> {
  typedef typename MatrixType::StorageIndex StorageIndex;
  typedef Sparse StorageKind;
  enum { Flags = int(traits<MatrixType>::Flags) & (RowMajorBit) };
};
 
}  // end namespace internal
 
template <typename MatrixType>
class SparseView : public SparseMatrixBase<SparseView<MatrixType> > {
  typedef typename MatrixType::Nested MatrixTypeNested;
  typedef internal::remove_all_t<MatrixTypeNested> MatrixTypeNested_;
  typedef SparseMatrixBase<SparseView> Base;
 
 public:
  EIGEN_SPARSE_PUBLIC_INTERFACE(SparseView)
  typedef internal::remove_all_t<MatrixType> NestedExpression;
 
  explicit SparseView(const MatrixType& mat, const Scalar& reference = Scalar(0),
                      const RealScalar& epsilon = NumTraits<Scalar>::dummy_precision())
      : m_matrix(mat), m_reference(reference), m_epsilon(epsilon) {}
 
  inline Index rows() const { return m_matrix.rows(); }
  inline Index cols() const { return m_matrix.cols(); }
 
  inline Index innerSize() const { return m_matrix.innerSize(); }
  inline Index outerSize() const { return m_matrix.outerSize(); }
 
  const internal::remove_all_t<MatrixTypeNested>& nestedExpression() const { return m_matrix; }
 
  Scalar reference() const { return m_reference; }
  RealScalar epsilon() const { return m_epsilon; }
 
 protected:
  MatrixTypeNested m_matrix;
  Scalar m_reference;
  RealScalar m_epsilon;
};
 
namespace internal {
 
// TODO find a way to unify the two following variants
// This is tricky because implementing an inner iterator on top of an IndexBased evaluator is
// not easy because the evaluators do not expose the sizes of the underlying expression.
 
template <typename ArgType>
struct unary_evaluator<SparseView<ArgType>, IteratorBased> : public evaluator_base<SparseView<ArgType> > {
  typedef typename evaluator<ArgType>::InnerIterator EvalIterator;
 
 public:
  typedef SparseView<ArgType> XprType;
 
  class InnerIterator : public EvalIterator {
   protected:
    typedef typename XprType::Scalar Scalar;
 
   public:
    EIGEN_STRONG_INLINE InnerIterator(const unary_evaluator& sve, Index outer)
        : EvalIterator(sve.m_argImpl, outer), m_view(sve.m_view) {
      incrementToNonZero();
    }
 
    EIGEN_STRONG_INLINE InnerIterator& operator++() {
      EvalIterator::operator++();
      incrementToNonZero();
      return *this;
    }
 
    using EvalIterator::value;
 
   protected:
    const XprType& m_view;
 
   private:
    void incrementToNonZero() {
      while ((bool(*this)) && internal::isMuchSmallerThan(value(), m_view.reference(), m_view.epsilon())) {
        EvalIterator::operator++();
      }
    }
  };
 
  enum { CoeffReadCost = evaluator<ArgType>::CoeffReadCost, Flags = XprType::Flags };
 
  explicit unary_evaluator(const XprType& xpr) : m_argImpl(xpr.nestedExpression()), m_view(xpr) {}
 
 protected:
  evaluator<ArgType> m_argImpl;
  const XprType& m_view;
};
 
template <typename ArgType>
struct unary_evaluator<SparseView<ArgType>, IndexBased> : public evaluator_base<SparseView<ArgType> > {
 public:
  typedef SparseView<ArgType> XprType;
 
 protected:
  enum { IsRowMajor = (XprType::Flags & RowMajorBit) == RowMajorBit };
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::StorageIndex StorageIndex;
 
 public:
  class InnerIterator {
   public:
    EIGEN_STRONG_INLINE InnerIterator(const unary_evaluator& sve, Index outer)
        : m_sve(sve), m_inner(0), m_outer(outer), m_end(sve.m_view.innerSize()) {
      incrementToNonZero();
    }
 
    EIGEN_STRONG_INLINE InnerIterator& operator++() {
      m_inner++;
      incrementToNonZero();
      return *this;
    }
 
    EIGEN_STRONG_INLINE Scalar value() const {
      return (IsRowMajor) ? m_sve.m_argImpl.coeff(m_outer, m_inner) : m_sve.m_argImpl.coeff(m_inner, m_outer);
    }
 
    EIGEN_STRONG_INLINE StorageIndex index() const { return m_inner; }
    inline Index row() const { return IsRowMajor ? m_outer : index(); }
    inline Index col() const { return IsRowMajor ? index() : m_outer; }
 
    EIGEN_STRONG_INLINE operator bool() const { return m_inner < m_end && m_inner >= 0; }
 
   protected:
    const unary_evaluator& m_sve;
    Index m_inner;
    const Index m_outer;
    const Index m_end;
 
   private:
    void incrementToNonZero() {
      while ((bool(*this)) && internal::isMuchSmallerThan(value(), m_sve.m_view.reference(), m_sve.m_view.epsilon())) {
        m_inner++;
      }
    }
  };
 
  enum { CoeffReadCost = evaluator<ArgType>::CoeffReadCost, Flags = XprType::Flags };
 
  explicit unary_evaluator(const XprType& xpr) : m_argImpl(xpr.nestedExpression()), m_view(xpr) {}
 
 protected:
  evaluator<ArgType> m_argImpl;
  const XprType& m_view;
};
 
}  // end namespace internal
 
template <typename Derived>
const SparseView<Derived> MatrixBase<Derived>::sparseView(const Scalar& reference,
                                                          const typename NumTraits<Scalar>::Real& epsilon) const {
  return SparseView<Derived>(derived(), reference, epsilon);
}
 
template <typename Derived>
const SparseView<Derived> SparseMatrixBase<Derived>::pruned(const Scalar& reference, const RealScalar& epsilon) const {
  return SparseView<Derived>(derived(), reference, epsilon);
}
 
}  // end namespace Eigen
 
#endif