Stride.h revision c981c48f5bc9aefeffc0bcb0cc3934c2fae179dd 
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  *  \param _OuterStrideAtCompileTime the outer stride, or Dynamic if you want to specify it at runtime.
35  *  \param _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 DenseIndex Index;
48    enum {
49      InnerStrideAtCompileTime = _InnerStrideAtCompileTime,
50      OuterStrideAtCompileTime = _OuterStrideAtCompileTime
51    };
52
53    /** Default constructor, for use when strides are fixed at compile time */
54    Stride()
55      : m_outer(OuterStrideAtCompileTime), m_inner(InnerStrideAtCompileTime)
56    {
57      eigen_assert(InnerStrideAtCompileTime != Dynamic && OuterStrideAtCompileTime != Dynamic);
58    }
59
60    /** Constructor allowing to pass the strides at runtime */
61    Stride(Index outerStride, Index innerStride)
62      : m_outer(outerStride), m_inner(innerStride)
63    {
64      eigen_assert(innerStride>=0 && outerStride>=0);
65    }
66
67    /** Copy constructor */
68    Stride(const Stride& other)
69      : m_outer(other.outer()), m_inner(other.inner())
70    {}
71
72    /** \returns the outer stride */
73    inline Index outer() const { return m_outer.value(); }
74    /** \returns the inner stride */
75    inline Index inner() const { return m_inner.value(); }
76
77  protected:
78    internal::variable_if_dynamic<Index, OuterStrideAtCompileTime> m_outer;
79    internal::variable_if_dynamic<Index, InnerStrideAtCompileTime> m_inner;
80};
81
82/** \brief Convenience specialization of Stride to specify only an inner stride
83  * See class Map for some examples */
84template<int Value = Dynamic>
85class InnerStride : public Stride<0, Value>
86{
87    typedef Stride<0, Value> Base;
88  public:
89    typedef DenseIndex Index;
90    InnerStride() : Base() {}
91    InnerStride(Index v) : Base(0, v) {}
92};
93
94/** \brief Convenience specialization of Stride to specify only an outer stride
95  * See class Map for some examples */
96template<int Value = Dynamic>
97class OuterStride : public Stride<Value, 0>
98{
99    typedef Stride<Value, 0> Base;
100  public:
101    typedef DenseIndex Index;
102    OuterStride() : Base() {}
103    OuterStride(Index v) : Base(v,0) {}
104};
105
106} // end namespace Eigen
107
108#endif // EIGEN_STRIDE_H
109