Alexandria  2.22.0
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Piecewise.cpp
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1 /*
2  * Copyright (C) 2012-2021 Euclid Science Ground Segment
3  *
4  * This library is free software; you can redistribute it and/or modify it under
5  * the terms of the GNU Lesser General Public License as published by the Free
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9  * This library is distributed in the hope that it will be useful, but WITHOUT
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11  * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
12  * details.
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16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
28 #include <algorithm>
29 
30 namespace Euclid {
31 namespace MathUtils {
32 
34  : PiecewiseBase(std::move(knots)) {
35  if (m_knots.size() - functions.size() != 1) {
36  throw Elements::Exception() << "Invalid number of knots(" << m_knots.size() << ")-functions(" << m_functions.size()
37  << ")";
38  }
39 
40  m_functions.reserve(functions.size());
41  std::transform(functions.begin(), functions.end(), std::back_inserter(m_functions),
42  [](std::shared_ptr<Function>& f) { return f->clone(); });
43 
44  auto knotsIter = m_knots.begin();
45  while (++knotsIter != m_knots.end()) {
46  if (*knotsIter < *(knotsIter - 1)) {
47  throw Elements::Exception("knots must be increasing");
48  }
49  }
50 }
51 
53  : PiecewiseBase(std::move(knots)), m_functions{std::move(functions)} {
54  if (m_knots.size() - m_functions.size() != 1) {
55  throw Elements::Exception() << "Invalid number of knots(" << m_knots.size() << ")-functions(" << m_functions.size()
56  << ")";
57  }
58  auto knotsIter = m_knots.begin();
59  while (++knotsIter != m_knots.end()) {
60  if (*knotsIter < *(knotsIter - 1)) {
61  throw Elements::Exception("knots must be increasing");
62  }
63  }
64 }
65 
67  return m_functions;
68 }
69 
70 double Piecewise::operator()(const double x) const {
71  auto i = findKnot(x);
72  if (i < 0 || i >= static_cast<ssize_t>(m_knots.size())) {
73  return 0.;
74  }
75  if (i == 0) {
76  return (*m_functions[0])(x);
77  }
78  return (*m_functions[i - 1])(x);
79 }
80 
82  out.resize(xs.size());
83  std::transform(xs.begin(), xs.end(), out.begin(), std::cref(*this));
84 }
85 
87  std::vector<std::unique_ptr<Function>> cloned_functions;
88  cloned_functions.reserve(m_functions.size());
89  for (auto& f : m_functions) {
90  cloned_functions.emplace_back(f->clone());
91  }
92  return std::unique_ptr<Function>{new Piecewise(m_knots, std::move(cloned_functions))};
93 }
94 
95 double Piecewise::integrate(const double x1, const double x2) const {
96  if (x1 == x2) {
97  return 0;
98  }
99  int direction = 1;
100  double min = x1;
101  double max = x2;
102  if (min > max) {
103  direction = -1;
104  min = x2;
105  max = x1;
106  }
107  double result = 0;
108  auto knotIter = std::upper_bound(m_knots.begin(), m_knots.end(), min);
109  if (knotIter != m_knots.begin()) {
110  --knotIter;
111  }
112  auto functionIter = m_functions.begin() + (knotIter - m_knots.begin());
113  while (++knotIter != m_knots.end()) {
114  auto prevKnotIter = knotIter - 1;
115  if (max <= *prevKnotIter) {
116  break;
117  }
118  if (min < *knotIter) {
119  double down = (min > *prevKnotIter) ? min : *prevKnotIter;
120  double up = (max < *knotIter) ? max : *knotIter;
121  result += Euclid::MathUtils::integrate(**functionIter, down, up);
122  }
123  ++functionIter;
124  }
125  return direction * result;
126 }
127 
128 } // namespace MathUtils
129 } // end of namespace Euclid
T back_inserter(T... args)
T begin(T... args)
Represents a piecewise function.
Definition: Piecewise.h:48
ssize_t findKnot(double x) const
Definition: Piecewise.h:60
std::vector< double > m_knots
A vector where the knots are kept.
Definition: Piecewise.h:74
double integrate(const double x1, const double x2) const override
Definition: Piecewise.cpp:95
double operator()(const double) const override
Definition: Piecewise.cpp:70
std::vector< std::unique_ptr< Function > > m_functions
A vector where the sub-functions are kept.
Definition: Piecewise.h:136
Piecewise(std::vector< double > knots, std::vector< std::shared_ptr< Function >> functions)
Definition: Piecewise.cpp:33
const std::vector< std::unique_ptr< Function > > & getFunctions() const
Returns the functions in the ranges between the knots.
Definition: Piecewise.cpp:66
std::unique_ptr< Function > clone() const override
Definition: Piecewise.cpp:86
T emplace_back(T... args)
T end(T... args)
T move(T... args)
ELEMENTS_API double integrate(const Function &function, const double min, const double max, std::unique_ptr< NumericalIntegrationScheme > numericalIntegrationScheme=nullptr)
STL namespace.
T cref(T... args)
T reserve(T... args)
T resize(T... args)
T size(T... args)
T transform(T... args)
T upper_bound(T... args)