1// This file is part of Eigen, a lightweight C++ template library
2// for linear algebra.
3//
4// Copyright (C) 2010 Benoit Jacob <jacob.benoit.1@gmail.com>
5//
6// This Source Code Form is subject to the terms of the Mozilla
7// Public License v. 2.0. If a copy of the MPL was not distributed
8// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9
10#ifndef EIGEN_STRIDE_H
11#define EIGEN_STRIDE_H
12
13namespace Eigen {
14
15/** \class Stride
16  * \ingroup Core_Module
17  *
18  * \brief Holds strides information for Map
19  *
20  * This class holds the strides information for mapping arrays with strides with class Map.
21  *
22  * It holds two values: the inner stride and the outer stride.
23  *
24  * The inner stride is the pointer increment between two consecutive entries within a given row of a
25  * row-major matrix or within a given column of a column-major matrix.
26  *
27  * The outer stride is the pointer increment between two consecutive rows of a row-major matrix or
28  * between two consecutive columns of a column-major matrix.
29  *
30  * These two values can be passed either at compile-time as template parameters, or at runtime as
31  * arguments to the constructor.
32  *
33  * Indeed, this class takes two template parameters:
34  *  \tparam _OuterStrideAtCompileTime the outer stride, or Dynamic if you want to specify it at runtime.
35  *  \tparam _InnerStrideAtCompileTime the inner stride, or Dynamic if you want to specify it at runtime.
36  *
37  * Here is an example:
38  * \include Map_general_stride.cpp
39  * Output: \verbinclude Map_general_stride.out
40  *
41  * \sa class InnerStride, class OuterStride, \ref TopicStorageOrders
42  */
43template<int _OuterStrideAtCompileTime, int _InnerStrideAtCompileTime>
44class Stride
45{
46  public:
47    typedef Eigen::Index Index; ///< \deprecated since Eigen 3.3
48    enum {
49      InnerStrideAtCompileTime = _InnerStrideAtCompileTime,
50      OuterStrideAtCompileTime = _OuterStrideAtCompileTime
51    };
52
53    /** Default constructor, for use when strides are fixed at compile time */
54    EIGEN_DEVICE_FUNC
55    Stride()
56      : m_outer(OuterStrideAtCompileTime), m_inner(InnerStrideAtCompileTime)
57    {
58      eigen_assert(InnerStrideAtCompileTime != Dynamic && OuterStrideAtCompileTime != Dynamic);
59    }
60
61    /** Constructor allowing to pass the strides at runtime */
62    EIGEN_DEVICE_FUNC
63    Stride(Index outerStride, Index innerStride)
64      : m_outer(outerStride), m_inner(innerStride)
65    {
66      eigen_assert(innerStride>=0 && outerStride>=0);
67    }
68
69    /** Copy constructor */
70    EIGEN_DEVICE_FUNC
71    Stride(const Stride& other)
72      : m_outer(other.outer()), m_inner(other.inner())
73    {}
74
75    /** \returns the outer stride */
76    EIGEN_DEVICE_FUNC
77    inline Index outer() const { return m_outer.value(); }
78    /** \returns the inner stride */
79    EIGEN_DEVICE_FUNC
80    inline Index inner() const { return m_inner.value(); }
81
82  protected:
83    internal::variable_if_dynamic<Index, OuterStrideAtCompileTime> m_outer;
84    internal::variable_if_dynamic<Index, InnerStrideAtCompileTime> m_inner;
85};
86
87/** \brief Convenience specialization of Stride to specify only an inner stride
88  * See class Map for some examples */
89template<int Value>
90class InnerStride : public Stride<0, Value>
91{
92    typedef Stride<0, Value> Base;
93  public:
94    EIGEN_DEVICE_FUNC InnerStride() : Base() {}
95    EIGEN_DEVICE_FUNC InnerStride(Index v) : Base(0, v) {} // FIXME making this explicit could break valid code
96};
97
98/** \brief Convenience specialization of Stride to specify only an outer stride
99  * See class Map for some examples */
100template<int Value>
101class OuterStride : public Stride<Value, 0>
102{
103    typedef Stride<Value, 0> Base;
104  public:
105    EIGEN_DEVICE_FUNC OuterStride() : Base() {}
106    EIGEN_DEVICE_FUNC OuterStride(Index v) : Base(v,0) {} // FIXME making this explicit could break valid code
107};
108
109} // end namespace Eigen
110
111#endif // EIGEN_STRIDE_H
112