eigen/Eigen/src/Core/IndexedView.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2017 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_INDEXED_VIEW_H
#define EIGEN_INDEXED_VIEW_H

namespace Eigen {

namespace internal {

template<typename XprType, typename RowIndices, typename ColIndices>
struct traits<IndexedView<XprType, RowIndices, ColIndices> >
 : traits<XprType>
{
  enum {
    RowsAtCompileTime = get_compile_time_size<RowIndices,traits<XprType>::RowsAtCompileTime>::value,
    ColsAtCompileTime = get_compile_time_size<ColIndices,traits<XprType>::ColsAtCompileTime>::value,
    MaxRowsAtCompileTime = RowsAtCompileTime != Dynamic ? int(RowsAtCompileTime) : int(traits<XprType>::MaxRowsAtCompileTime),
    MaxColsAtCompileTime = ColsAtCompileTime != Dynamic ? int(ColsAtCompileTime) : int(traits<XprType>::MaxColsAtCompileTime),

    XprTypeIsRowMajor = (int(traits<XprType>::Flags)&RowMajorBit) != 0,
    IsRowMajor = (MaxRowsAtCompileTime==1&&MaxColsAtCompileTime!=1) ? 1
               : (MaxColsAtCompileTime==1&&MaxRowsAtCompileTime!=1) ? 0
               : XprTypeIsRowMajor,

    RowIncr = get_compile_time_incr<RowIndices>::value,
    ColIncr = get_compile_time_incr<ColIndices>::value,
    InnerIncr = IsRowMajor ? ColIncr : RowIncr,
    OuterIncr = IsRowMajor ? RowIncr : ColIncr,

    HasSameStorageOrderAsXprType = (IsRowMajor == XprTypeIsRowMajor),
    XprInnerStride = HasSameStorageOrderAsXprType ? int(inner_stride_at_compile_time<XprType>::ret) : int(outer_stride_at_compile_time<XprType>::ret),
    XprOuterstride = HasSameStorageOrderAsXprType ? int(outer_stride_at_compile_time<XprType>::ret) : int(inner_stride_at_compile_time<XprType>::ret),

    InnerStrideAtCompileTime = InnerIncr<0 || InnerIncr==DynamicIndex || XprInnerStride==Dynamic ? Dynamic : XprInnerStride * InnerIncr,
    OuterStrideAtCompileTime = OuterIncr<0 || OuterIncr==DynamicIndex || XprOuterstride==Dynamic ? Dynamic : XprOuterstride * OuterIncr,

    // FIXME we deal with compile-time strides if and only if we have DirectAccessBit flag,
    // but this is too strict regarding negative strides...
    DirectAccessMask = (InnerIncr!=UndefinedIncr && OuterIncr!=UndefinedIncr && InnerIncr>=0 && OuterIncr>=0) ? DirectAccessBit : 0,
    FlagsRowMajorBit = IsRowMajor ? RowMajorBit : 0,
    FlagsLvalueBit = is_lvalue<XprType>::value ? LvalueBit : 0,
    Flags = (traits<XprType>::Flags & (HereditaryBits | DirectAccessMask)) | FlagsLvalueBit | FlagsRowMajorBit
  };
};

}

template<typename XprType, typename RowIndices, typename ColIndices, typename StorageKind>
class IndexedViewImpl;

// Expression of a generic slice
template<typename XprType, typename RowIndices, typename ColIndices>
class IndexedView : public IndexedViewImpl<XprType, RowIndices, ColIndices, typename internal::traits<XprType>::StorageKind>
{
public:
  typedef typename IndexedViewImpl<XprType, RowIndices, ColIndices, typename internal::traits<XprType>::StorageKind>::Base Base;
  EIGEN_GENERIC_PUBLIC_INTERFACE(IndexedView)

  typedef typename internal::ref_selector<XprType>::non_const_type MatrixTypeNested;
  typedef typename internal::remove_all<XprType>::type NestedExpression;

  template<typename T0, typename T1>
  IndexedView(XprType& xpr, const T0& rowIndices, const T1& colIndices)
    : m_xpr(xpr), m_rowIndices(rowIndices), m_colIndices(colIndices)
  {}
  Index rows() const { return internal::size(m_rowIndices); }
  Index cols() const { return internal::size(m_colIndices); }

  /** \returns the nested expression */
  const typename internal::remove_all<XprType>::type&
  nestedExpression() const { return m_xpr; }

  /** \returns the nested expression */
  typename internal::remove_reference<XprType>::type&
  nestedExpression() { return m_xpr.const_cast_derived(); }

  const RowIndices& rowIndices() const { return m_rowIndices; }
  const ColIndices& colIndices() const { return m_colIndices; }

protected:
  MatrixTypeNested m_xpr;
  RowIndices m_rowIndices;
  ColIndices m_colIndices;
};


// Generic API dispatcher
template<typename XprType, typename RowIndices, typename ColIndices, typename StorageKind>
class IndexedViewImpl
  : public internal::generic_xpr_base<IndexedView<XprType, RowIndices, ColIndices> >::type
{
public:
  typedef typename internal::generic_xpr_base<IndexedView<XprType, RowIndices, ColIndices> >::type Base;
};

namespace internal {


template<typename ArgType, typename RowIndices, typename ColIndices>
struct unary_evaluator<IndexedView<ArgType, RowIndices, ColIndices>, IndexBased>
  : evaluator_base<IndexedView<ArgType, RowIndices, ColIndices> >
{
  typedef IndexedView<ArgType, RowIndices, ColIndices> XprType;

  enum {
    CoeffReadCost = evaluator<ArgType>::CoeffReadCost /* + cost of row/col index */,

    Flags = (evaluator<ArgType>::Flags & (HereditaryBits /*| LinearAccessBit | DirectAccessBit*/)),

    Alignment = 0
  };

  EIGEN_DEVICE_FUNC explicit unary_evaluator(const XprType& xpr) : m_argImpl(xpr.nestedExpression()), m_xpr(xpr)
  {
    EIGEN_INTERNAL_CHECK_COST_VALUE(CoeffReadCost);
  }

  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;

  EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE
  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_argImpl.coeff(m_xpr.rowIndices()[row], m_xpr.colIndices()[col]);
  }

protected:

  evaluator<ArgType> m_argImpl;
  const XprType& m_xpr;

};

} // end namespace internal

} // end namespace Eigen

#endif // EIGEN_INDEXED_VIEW_H