NumCpp  2.7.0
A Templatized Header Only C++ Implementation of the Python NumPy Library
cross.hpp
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1 #pragma once
29 
32 #include "NumCpp/Core/Shape.hpp"
33 #include "NumCpp/Core/Types.hpp"
34 #include "NumCpp/NdArray.hpp"
35 
36 #include <string>
37 
38 namespace nc
39 {
40  //============================================================================
41  // Method Description:
51  template<typename dtype>
52  NdArray<dtype> cross(const NdArray<dtype>& inArray1, const NdArray<dtype>& inArray2, Axis inAxis = Axis::NONE)
53  {
55 
56  if (inArray1.shape() != inArray2.shape())
57  {
58  THROW_INVALID_ARGUMENT_ERROR("the input array dimensions are not consistant.");
59  }
60 
61  switch (inAxis)
62  {
63  case Axis::NONE:
64  {
65  const uint32 arraySize = inArray1.size();
66  if (arraySize != inArray2.size() || arraySize < 2 || arraySize > 3)
67  {
68  THROW_INVALID_ARGUMENT_ERROR("incompatible dimensions for cross product (dimension must be 2 or 3)");
69  }
70 
71  NdArray<dtype> in1 = inArray1.flatten();
72  NdArray<dtype> in2 = inArray2.flatten();
73 
74  switch (arraySize)
75  {
76  case 2:
77  {
78  NdArray<dtype> returnArray = { in1[0] * in2[1] - in1[1] * in2[0] };
79  return returnArray;
80  }
81  case 3:
82  {
83  dtype i = in1[1] * in2[2] - in1[2] * in2[1];
84  dtype j = -(in1[0] * in2[2] - in1[2] * in2[0]);
85  dtype k = in1[0] * in2[1] - in1[1] * in2[0];
86 
87  NdArray<dtype> returnArray = { i, j, k };
88  return returnArray;
89  }
90  default:
91  {
92  THROW_INVALID_ARGUMENT_ERROR("Unimplemented array size.");
93  return {}; // get rid of compiler warning
94  }
95  }
96  }
97  case Axis::ROW:
98  {
99  const Shape arrayShape = inArray1.shape();
100  if (arrayShape != inArray2.shape() || arrayShape.rows < 2 || arrayShape.rows > 3)
101  {
102  THROW_INVALID_ARGUMENT_ERROR("incompatible dimensions for cross product (dimension must be 2 or 3)");
103  }
104 
105  Shape returnArrayShape;
106  returnArrayShape.cols = arrayShape.cols;
107  if (arrayShape.rows == 2)
108  {
109  returnArrayShape.rows = 1;
110  }
111  else
112  {
113  returnArrayShape.rows = 3;
114  }
115 
116  NdArray<dtype> returnArray(returnArrayShape);
117  for (uint32 col = 0; col < arrayShape.cols; ++col)
118  {
119  const auto theCol = static_cast<int32>(col);
120  NdArray<dtype> vec1 = inArray1(inArray1.rSlice(), { theCol, theCol + 1 });
121  NdArray<dtype> vec2 = inArray2(inArray2.rSlice(), { theCol, theCol + 1 });
122  NdArray<dtype> vecCross = cross(vec1, vec2, Axis::NONE);
123 
124  returnArray.put({ 0, static_cast<int32>(returnArrayShape.rows) }, { theCol, theCol + 1 }, vecCross);
125  }
126 
127  return returnArray;
128  }
129  case Axis::COL:
130  {
131  const Shape arrayShape = inArray1.shape();
132  if (arrayShape != inArray2.shape() || arrayShape.cols < 2 || arrayShape.cols > 3)
133  {
134  THROW_INVALID_ARGUMENT_ERROR("incompatible dimensions for cross product (dimension must be 2 or 3)");
135  }
136 
137  Shape returnArrayShape;
138  returnArrayShape.rows = arrayShape.rows;
139  if (arrayShape.cols == 2)
140  {
141  returnArrayShape.cols = 1;
142  }
143  else
144  {
145  returnArrayShape.cols = 3;
146  }
147 
148  NdArray<dtype> returnArray(returnArrayShape);
149  for (uint32 row = 0; row < arrayShape.rows; ++row)
150  {
151  const auto theRow = static_cast<int32>(row);
152  NdArray<dtype> vec1 = inArray1({ theRow, theRow + 1 }, inArray1.cSlice());
153  NdArray<dtype> vec2 = inArray2({ theRow, theRow + 1 }, inArray2.cSlice());
154  NdArray<dtype> vecCross = cross(vec1, vec2, Axis::NONE);
155 
156  returnArray.put({ theRow, theRow + 1 }, { 0, static_cast<int32>(returnArrayShape.cols) }, vecCross);
157  }
158 
159  return returnArray;
160  }
161  default:
162  {
163  THROW_INVALID_ARGUMENT_ERROR("Unimplemented axis type.");
164  return {}; // get rid of compiler warning
165  }
166  }
167  }
168 } // namespace nc
#define THROW_INVALID_ARGUMENT_ERROR(msg)
Definition: Error.hpp:36
#define STATIC_ASSERT_ARITHMETIC_OR_COMPLEX(dtype)
Definition: StaticAsserts.hpp:50
Holds 1D and 2D arrays, the main work horse of the NumCpp library.
Definition: NdArrayCore.hpp:72
NdArray< dtype > & put(int32 inIndex, value_type inValue)
Definition: NdArrayCore.hpp:3666
size_type size() const noexcept
Definition: NdArrayCore.hpp:4296
NdArray< dtype > flatten() const
Definition: NdArrayCore.hpp:2759
Slice cSlice(int32 inStartIdx=0, uint32 inStepSize=1) const noexcept
Definition: NdArrayCore.hpp:964
Shape shape() const noexcept
Definition: NdArrayCore.hpp:4283
Slice rSlice(int32 inStartIdx=0, uint32 inStepSize=1) const noexcept
Definition: NdArrayCore.hpp:978
A Shape Class for NdArrays.
Definition: Core/Shape.hpp:41
uint32 rows
Definition: Core/Shape.hpp:44
uint32 cols
Definition: Core/Shape.hpp:45
constexpr auto j
Definition: Constants.hpp:45
Definition: Coordinate.hpp:45
NdArray< dtype > cross(const NdArray< dtype > &inArray1, const NdArray< dtype > &inArray2, Axis inAxis=Axis::NONE)
Definition: cross.hpp:52
Axis
Enum To describe an axis.
Definition: Types.hpp:46
std::int32_t int32
Definition: Types.hpp:36
std::uint32_t uint32
Definition: Types.hpp:40