DDC 0.4.1
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constant_extrapolation_rule.hpp
1// Copyright (C) The DDC development team, see COPYRIGHT.md file
2//
3// SPDX-License-Identifier: MIT
4
5#pragma once
6
7#include <array>
8#include <cstddef>
9#include <type_traits>
10
11#include <ddc/ddc.hpp>
12
13#include <Kokkos_Core.hpp>
14
15namespace ddc {
16
17template <class DimI, class... Dim>
19{
20};
21
22/**
23 * @brief A functor for describing a spline boundary value by a constant extrapolation for 1D evaluator.
24 *
25 * To define the value of a function on B-splines out of the domain, we here use a constant
26 * extrapolation on the edge.
27 */
28template <class DimI>
30{
31private:
32 ddc::Coordinate<DimI> m_eval_pos;
33
34public:
35 /**
36 * @brief Instantiate a ConstantExtrapolationRule.
37 *
38 * The boundary value will be the same as at the coordinate eval_pos given.
39 *
40 * @param[in] eval_pos Coordinate inside the domain where we will evaluate each points outside the domain.
41 */
42 explicit ConstantExtrapolationRule(ddc::Coordinate<DimI> eval_pos) : m_eval_pos(eval_pos) {}
43
44 /**
45 * @brief Get the value of the function on B-splines at a coordinate outside the domain.
46 *
47 * @param[in] pos The coordinate where we want to evaluate the function on B-splines.
48 * @param[in] spline_coef The coefficients of the function on B-splines.
49 *
50 * @return A double with the value of the function on B-splines evaluated at the coordinate.
51 */
52 template <class CoordType, class BSplines, class Layout, class MemorySpace>
54 [[maybe_unused]] CoordType pos,
55 ddc::ChunkSpan<double const, ddc::DiscreteDomain<BSplines>, Layout, MemorySpace> const
56 spline_coef) const
57 {
58 static_assert(in_tags_v<DimI, to_type_seq_t<CoordType>>);
59
60 std::array<double, BSplines::degree() + 1> vals_ptr;
61 Kokkos::mdspan<double, Kokkos::extents<std::size_t, BSplines::degree() + 1>> const vals(
62 vals_ptr.data());
63
64 ddc::DiscreteElement<BSplines> const idx
65 = ddc::discrete_space<BSplines>().eval_basis(vals, m_eval_pos);
66
67 double y = 0.0;
68 for (std::size_t i = 0; i < BSplines::degree() + 1; ++i) {
69 y += spline_coef(idx + i) * vals[i];
70 }
71 return y;
72 }
73};
74
75/**
76 * @brief A functor for describing a spline boundary value by a constant extrapolation for 2D evaluator.
77 *
78 * To define the value of a function on B-splines out of the domain, we here use a constant
79 * extrapolation on the edge.
80 */
81template <class DimI, class DimNI>
82struct ConstantExtrapolationRule<DimI, DimNI>
83{
84private:
85 ddc::Coordinate<DimI> m_eval_pos;
86 ddc::Coordinate<DimNI> m_eval_pos_not_interest_min;
87 ddc::Coordinate<DimNI> m_eval_pos_not_interest_max;
88
89public:
90 /**
91 * @brief Instantiate a ConstantExtrapolationRule.
92 *
93 * The boundary value will be the same as at the coordinate given in a dimension given.
94 * The dimension of the input defines the dimension of the boundary condition.
95 * The second and the third parameters are needed in case of non-periodic splines on the
96 * dimension off-interest (the complementary dimension of the boundary condition),
97 * because the evaluator can receive coordinates outside the domain in both dimension.
98 *
99 * @param[in] eval_pos Coordinate in the dimension given inside the domain where we will evaluate each points outside the domain.
100 * @param[in] eval_pos_not_interest_min The minimum coordinate inside the domain on the complementary dimension of the boundary condition.
101 * @param[in] eval_pos_not_interest_max The maximum coordinate inside the domain on the complementary dimension of the boundary condition.
102 */
104 ddc::Coordinate<DimI> eval_pos,
105 ddc::Coordinate<DimNI> eval_pos_not_interest_min,
106 ddc::Coordinate<DimNI> eval_pos_not_interest_max)
107 : m_eval_pos(eval_pos)
108 , m_eval_pos_not_interest_min(eval_pos_not_interest_min)
109 , m_eval_pos_not_interest_max(eval_pos_not_interest_max)
110 {
111 }
112
113 /**
114 * @brief Instantiate a ConstantExtrapolationRule.
115 *
116 * The boundary value will be the same as at the coordinate given in a dimension given.
117 * The dimension of the input defines the dimension of the boundary condition.
118 * No second and third parameters are needed in case of periodic splines on the
119 * dimension off-interest (the complementary dimension of the boundary condition).
120 *
121 * @param[in] eval_pos Coordinate in the dimension given inside the domain where we will evaluate each points outside the domain.
122 */
123 template <class DimNI_sfinae = DimNI, std::enable_if_t<DimNI_sfinae::PERIODIC, int> = 0>
124 explicit ConstantExtrapolationRule(ddc::Coordinate<DimI> eval_pos)
125 : m_eval_pos(eval_pos)
126 , m_eval_pos_not_interest_min(0.)
127 , m_eval_pos_not_interest_max(0.)
128 {
129 }
130
131 /**
132 * @brief Get the value of the function on B-splines at a coordinate outside the domain.
133 *
134 * In the dimension defined in the constructor Dim1 (or Dim2), it sets the coordinate pos_1 (or pos_2)
135 * given at the m_eval_pos coordinate if it is outside the domain.
136 * If the coordinate on the complementary dimension of the boundary condition dimension ddc::Coordinate<DimNI>(coord_extrap) is
137 * outside the domain, then it also sets the coordinate at eval_pos_not_interest_min
138 * (if ddc::Coordinate<DimNI>(coord_extrap) @f$ < @f$ eval_pos_not_interest_min) or
139 * at eval_pos_not_interest_max (if ddc::Coordinate<DimNI>(coord_extrap) @f$ > @f$ eval_pos_not_interest_max).
140 *
141 * @param[in] coord_extrap The coordinates where we want to evaluate the function on B-splines
142 * @param[in] spline_coef The coefficients of the function on B-splines.
143 *
144 *@return A double with the value of the function on B-splines evaluated at the coordinate.
145 */
146 template <class CoordType, class BSplines1, class BSplines2, class Layout, class MemorySpace>
147 KOKKOS_FUNCTION double operator()(
148 CoordType coord_extrap,
149 ddc::ChunkSpan<
150 double const,
151 ddc::DiscreteDomain<BSplines1, BSplines2>,
152 Layout,
153 MemorySpace> const spline_coef) const
154 {
155 static_assert(
156 in_tags_v<DimI, to_type_seq_t<CoordType>>
157 && in_tags_v<DimNI, to_type_seq_t<CoordType>>);
158
159 ddc::Coordinate<DimI, DimNI> eval_pos;
160 if constexpr (DimNI::PERIODIC) {
161 eval_pos = ddc::
162 Coordinate<DimI, DimNI>(m_eval_pos, ddc::Coordinate<DimNI>(coord_extrap));
163 } else {
164 eval_pos = ddc::Coordinate<DimI, DimNI>(
165 m_eval_pos,
166 Kokkos::
167 clamp(ddc::Coordinate<DimNI>(coord_extrap),
168 m_eval_pos_not_interest_min,
169 m_eval_pos_not_interest_max));
170 }
171
172 std::array<double, BSplines1::degree() + 1> vals1_ptr;
173 Kokkos::mdspan<double, Kokkos::extents<std::size_t, BSplines1::degree() + 1>> const vals1(
174 vals1_ptr.data());
175 std::array<double, BSplines2::degree() + 1> vals2_ptr;
176 Kokkos::mdspan<double, Kokkos::extents<std::size_t, BSplines2::degree() + 1>> const vals2(
177 vals2_ptr.data());
178
179 ddc::DiscreteElement<BSplines1> const idx1 = ddc::discrete_space<BSplines1>().eval_basis(
180 vals1,
181 ddc::Coordinate<typename BSplines1::continuous_dimension_type>(eval_pos));
182 ddc::DiscreteElement<BSplines2> const idx2 = ddc::discrete_space<BSplines2>().eval_basis(
183 vals2,
184 ddc::Coordinate<typename BSplines2::continuous_dimension_type>(eval_pos));
185
186 double y = 0.0;
187 for (std::size_t i = 0; i < BSplines1::degree() + 1; ++i) {
188 for (std::size_t j = 0; j < BSplines2::degree() + 1; ++j) {
189 y += spline_coef(idx1 + i, idx2 + j) * vals1[i] * vals2[j];
190 }
191 }
192
193 return y;
194 }
195};
196
197} // namespace ddc
friend class DiscreteDomain
The top-level namespace of DDC.
ConstantExtrapolationRule(ddc::Coordinate< DimI > eval_pos, ddc::Coordinate< DimNI > eval_pos_not_interest_min, ddc::Coordinate< DimNI > eval_pos_not_interest_max)
Instantiate a ConstantExtrapolationRule.
KOKKOS_FUNCTION double operator()(CoordType coord_extrap, ddc::ChunkSpan< double const, ddc::DiscreteDomain< BSplines1, BSplines2 >, Layout, MemorySpace > const spline_coef) const
Get the value of the function on B-splines at a coordinate outside the domain.
ConstantExtrapolationRule(ddc::Coordinate< DimI > eval_pos)
Instantiate a ConstantExtrapolationRule.
KOKKOS_FUNCTION double operator()(CoordType pos, ddc::ChunkSpan< double const, ddc::DiscreteDomain< BSplines >, Layout, MemorySpace > const spline_coef) const
Get the value of the function on B-splines at a coordinate outside the domain.
ConstantExtrapolationRule(ddc::Coordinate< DimI > eval_pos)
Instantiate a ConstantExtrapolationRule.