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| 1 | /* | ||
| 2 | * Copyright (c) 2000-2022 Inria | ||
| 3 | * All rights reserved. | ||
| 4 | * | ||
| 5 | * Redistribution and use in source and binary forms, with or without | ||
| 6 | * modification, are permitted provided that the following conditions are met: | ||
| 7 | * | ||
| 8 | * * Redistributions of source code must retain the above copyright notice, | ||
| 9 | * this list of conditions and the following disclaimer. | ||
| 10 | * * Redistributions in binary form must reproduce the above copyright notice, | ||
| 11 | * this list of conditions and the following disclaimer in the documentation | ||
| 12 | * and/or other materials provided with the distribution. | ||
| 13 | * * Neither the name of the ALICE Project-Team nor the names of its | ||
| 14 | * contributors may be used to endorse or promote products derived from this | ||
| 15 | * software without specific prior written permission. | ||
| 16 | * | ||
| 17 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" | ||
| 18 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | ||
| 19 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | ||
| 20 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE | ||
| 21 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR | ||
| 22 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF | ||
| 23 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS | ||
| 24 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN | ||
| 25 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | ||
| 26 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE | ||
| 27 | * POSSIBILITY OF SUCH DAMAGE. | ||
| 28 | * | ||
| 29 | * Contact: Bruno Levy | ||
| 30 | * | ||
| 31 | * https://www.inria.fr/fr/bruno-levy | ||
| 32 | * | ||
| 33 | * Inria, | ||
| 34 | * Domaine de Voluceau, | ||
| 35 | * 78150 Le Chesnay - Rocquencourt | ||
| 36 | * FRANCE | ||
| 37 | * | ||
| 38 | */ | ||
| 39 | |||
| 40 | #ifndef GEOGRAM_BASIC_PERMUTATION | ||
| 41 | #define GEOGRAM_BASIC_PERMUTATION | ||
| 42 | |||
| 43 | #include <geogram/basic/common.h> | ||
| 44 | #include <geogram/basic/numeric.h> | ||
| 45 | #include <geogram/basic/memory.h> | ||
| 46 | |||
| 47 | /** | ||
| 48 | * \file geogram/basic/permutation.h | ||
| 49 | * \brief Functions to manipulate permutations | ||
| 50 | */ | ||
| 51 | |||
| 52 | namespace GEO { | ||
| 53 | |||
| 54 | /** | ||
| 55 | * \brief Utilities for manipulating permutations | ||
| 56 | */ | ||
| 57 | namespace Permutation { | ||
| 58 | |||
| 59 | /** | ||
| 60 | * \brief Mark used to mark elements for in-place permutation | ||
| 61 | */ | ||
| 62 | constexpr index_t MARKED_BIT = index_t(1) << (sizeof(index_t)*8 - 1); | ||
| 63 | |||
| 64 | /** | ||
| 65 | * \brief Maximum size of a permutation that can be applied in-place | ||
| 66 | */ | ||
| 67 | constexpr index_t MAX_SIZE = MARKED_BIT; | ||
| 68 | |||
| 69 | /** | ||
| 70 | * \brief Checks whether a vector is a valid permutation. | ||
| 71 | * \details The vector \p permutation is a valid permutation if there | ||
| 72 | * is a bijection between the range [0..N-1] and the range | ||
| 73 | * [permutation[0]..permutation[N-1]] where N is the number of | ||
| 74 | * elements in the vector. An empty vector is considered as a valid | ||
| 75 | * permutation. | ||
| 76 | * \param[in] permutation a vector of integers | ||
| 77 | * \retval true if \p permutation is a valid permutation | ||
| 78 | * \retval false otherwise | ||
| 79 | */ | ||
| 80 | 66 | inline bool is_valid(const vector<index_t>& permutation) { | |
| 81 |
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66 | std::vector<bool> visited(permutation.size(), false); |
| 82 |
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52406 | for(index_t i = 0; i < permutation.size(); i++) { |
| 83 |
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52340 | if(permutation[i] >= permutation.size()) { |
| 84 | ✗ | return false; | |
| 85 | } | ||
| 86 |
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52340 | if(visited[permutation[i]]) { |
| 87 | ✗ | return false; | |
| 88 | } | ||
| 89 |
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52340 | visited[permutation[i]] = true; |
| 90 | } | ||
| 91 | 66 | return true; | |
| 92 | 66 | } | |
| 93 | |||
| 94 | /** | ||
| 95 | * \brief Marks a permutation element as visited | ||
| 96 | * \details Sets a \e visited mark for element at index \p i. | ||
| 97 | * in \p permutation. The element must \b not have been already marked. | ||
| 98 | * The mark can be checked with is_marked() and removed with unmark(). | ||
| 99 | * \param[in,out] permutation a valid permutation | ||
| 100 | * \param[in] i the index of the element in \p permutation | ||
| 101 | * \note Used internally by apply(). | ||
| 102 | * Implementation note: marking an element modifies the value in such | ||
| 103 | * a way that the initial value of the element can be restored. | ||
| 104 | */ | ||
| 105 | 52340 | inline void mark(vector<index_t>& permutation, index_t i) { | |
| 106 |
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52340 | geo_debug_assert(i < permutation.size()); |
| 107 | 52340 | permutation[i] |= MARKED_BIT; | |
| 108 | 52340 | } | |
| 109 | |||
| 110 | /** | ||
| 111 | * \brief Checks if a permutation element has been visited | ||
| 112 | * \param[in] permutation a valid permutation | ||
| 113 | * \param[in] i the index of the element in \p permutation | ||
| 114 | * \note Used internally by apply() | ||
| 115 | */ | ||
| 116 | 104680 | inline bool is_marked(const vector<index_t>& permutation, index_t i) { | |
| 117 |
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104680 | geo_debug_assert(i < permutation.size()); |
| 118 | 104680 | return ((permutation[i] & MARKED_BIT) != 0); | |
| 119 | } | ||
| 120 | |||
| 121 | /** | ||
| 122 | * \brief Unmarks a permutation element | ||
| 123 | * \details This restores the initial value of element at index \p i | ||
| 124 | * in \p permutation | ||
| 125 | * \param[in,out] permutation a valid permutation | ||
| 126 | * \param[in] i the index of the element in \p permutation | ||
| 127 | * \note Used internally by apply() | ||
| 128 | */ | ||
| 129 | 52340 | inline void unmark(vector<index_t>& permutation, index_t i) { | |
| 130 |
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52340 | geo_debug_assert(is_marked(permutation, i)); |
| 131 | 52340 | permutation[i] &= ~MARKED_BIT; | |
| 132 | 52340 | } | |
| 133 | |||
| 134 | /** | ||
| 135 | * \brief Applies a permutation in-place. | ||
| 136 | * Permutes the first \p N elements of size \p elemsize in array \p | ||
| 137 | * data using permutation \p permutation where \p N is the number | ||
| 138 | * of elements in \p permutation. The result of the permutation is | ||
| 139 | * left in \p data. | ||
| 140 | * The array \p data must contain at least \c permutation.size() | ||
| 141 | * elements otherwise memory corruption will happen. | ||
| 142 | * | ||
| 143 | * Applying permutation \p permutation is equivalent to: | ||
| 144 | * \code | ||
| 145 | * for(i=0; i<permutation.size(); i++) { | ||
| 146 | * data2[i] = data[permutation[i]] | ||
| 147 | * } | ||
| 148 | * data = data2 ; | ||
| 149 | * \endcode | ||
| 150 | * \param[in,out] data an array of \c permutation.size() elements to | ||
| 151 | * permute | ||
| 152 | * \param[in] permutation_in the permutation. | ||
| 153 | * It is temporarily changed during execution of the | ||
| 154 | * function, but identical to the input on exit. | ||
| 155 | * \param[in] elemsize size of the vector elements | ||
| 156 | */ | ||
| 157 | 42 | inline void apply( | |
| 158 | void* data, const vector<index_t>& permutation_in, | ||
| 159 | size_t elemsize | ||
| 160 | ) { | ||
| 161 |
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42 | geo_debug_assert(permutation_in.size() <= MAX_SIZE); |
| 162 | 42 | Memory::pointer pdata = (Memory::pointer) (data); | |
| 163 | 42 | vector<index_t>& permutation = | |
| 164 | const_cast<vector<index_t>&>(permutation_in); | ||
| 165 |
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42 | geo_debug_assert(is_valid(permutation)); |
| 166 | 42 | Memory::byte* temp = static_cast<Memory::byte*>(alloca(elemsize)); | |
| 167 |
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37791 | for(index_t k = 0; k < permutation.size(); k++) { |
| 168 |
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37749 | if(is_marked(permutation, k)) { |
| 169 | 37444 | continue; | |
| 170 | } | ||
| 171 | 305 | index_t i = k; | |
| 172 | 305 | index_t j = permutation[k]; | |
| 173 | 305 | Memory::copy(temp, pdata + i * elemsize, elemsize); | |
| 174 | 305 | mark(permutation, k); | |
| 175 |
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37749 | while(j != k) { |
| 176 | 37444 | Memory::copy( | |
| 177 | 37444 | pdata + i * elemsize, pdata + j * elemsize, elemsize | |
| 178 | ); | ||
| 179 | 37444 | index_t nj = permutation[j]; | |
| 180 | 37444 | mark(permutation, j); | |
| 181 | 37444 | i = j; | |
| 182 | 37444 | j = nj; | |
| 183 | } | ||
| 184 | 305 | Memory::copy(pdata + i * elemsize, temp, elemsize); | |
| 185 | } | ||
| 186 |
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37791 | for(index_t k = 0; k < permutation.size(); k++) { |
| 187 | 37749 | unmark(permutation, k); | |
| 188 | } | ||
| 189 | 42 | } | |
| 190 | |||
| 191 | /** | ||
| 192 | * \brief Applies a permutation in-place. | ||
| 193 | * Permutes the first \p N elements of vector \p data using | ||
| 194 | * permutation \p permutation where \p N is the number of elements in | ||
| 195 | * \p permutation. The result of the permutation is left in \p data. | ||
| 196 | * The array \p data must contain at least \c permutation.size() | ||
| 197 | * elements otherwise the function throws an out_of_range exception. | ||
| 198 | * | ||
| 199 | * Applying permutation \p permutation is equivalent to: | ||
| 200 | * \code | ||
| 201 | * for(i=0; i<permutation.size(); i++) { | ||
| 202 | * data2[i] = data[permutation[i]] | ||
| 203 | * } | ||
| 204 | * data = data2 ; | ||
| 205 | * \endcode | ||
| 206 | * \param[in,out] data the vector to permute | ||
| 207 | * \param[in] permutation_in the permutation. | ||
| 208 | * It is temporarily changed during execution of the | ||
| 209 | * function, but identical to the input on exit. | ||
| 210 | */ | ||
| 211 | template <class T> | ||
| 212 | inline void apply( | ||
| 213 | vector<T>& data, const vector<index_t>& permutation_in | ||
| 214 | ) { | ||
| 215 | geo_debug_assert(permutation_in.size() <= MAX_SIZE); | ||
| 216 | vector<index_t>& permutation = | ||
| 217 | const_cast<vector<index_t>&>(permutation_in); | ||
| 218 | geo_debug_assert(is_valid(permutation)); | ||
| 219 | T temp; | ||
| 220 | for(index_t k = 0; k < permutation.size(); k++) { | ||
| 221 | if(is_marked(permutation, k)) { | ||
| 222 | continue; | ||
| 223 | } | ||
| 224 | index_t i = k; | ||
| 225 | temp = data[i]; | ||
| 226 | index_t j = permutation[k]; | ||
| 227 | mark(permutation, k); | ||
| 228 | while(j != k) { | ||
| 229 | data[i] = data[j]; | ||
| 230 | index_t nj = permutation[j]; | ||
| 231 | mark(permutation, j); | ||
| 232 | i = j; | ||
| 233 | j = nj; | ||
| 234 | } | ||
| 235 | data[i] = temp; | ||
| 236 | } | ||
| 237 | for(index_t k = 0; k < permutation.size(); k++) { | ||
| 238 | unmark(permutation, k); | ||
| 239 | } | ||
| 240 | } | ||
| 241 | |||
| 242 | /** | ||
| 243 | * \brief Inverts a permutation in-place. | ||
| 244 | * \details Inverses the given \p permutation in place, the | ||
| 245 | * result of the inversion is left in \p permutation. | ||
| 246 | * | ||
| 247 | * The inversion is equivalent to: | ||
| 248 | * \code | ||
| 249 | * vector<index_t> inverse; | ||
| 250 | * Permutation::invert(permutation, inverse); | ||
| 251 | * permutation = inverse; | ||
| 252 | * \endcode | ||
| 253 | * \param[in,out] permutation to inverse. | ||
| 254 | */ | ||
| 255 | 24 | inline void invert(vector<index_t>& permutation) { | |
| 256 |
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24 | geo_debug_assert(permutation.size() < MAX_SIZE); |
| 257 |
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24 | geo_debug_assert(is_valid(permutation)); |
| 258 |
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14615 | for(index_t k = 0; k < permutation.size(); k++) { |
| 259 |
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14591 | if(is_marked(permutation, k)) { |
| 260 | 14445 | continue; | |
| 261 | } | ||
| 262 | 146 | index_t i = k; | |
| 263 | 146 | index_t j = permutation[i]; | |
| 264 |
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14591 | while(j != k) { |
| 265 | 14445 | index_t temp = permutation[j]; | |
| 266 | 14445 | permutation[j] = i; | |
| 267 | 14445 | mark(permutation, j); | |
| 268 | 14445 | i = j; | |
| 269 | 14445 | j = temp; | |
| 270 | } | ||
| 271 | 146 | permutation[j] = i; | |
| 272 | 146 | mark(permutation, j); | |
| 273 | } | ||
| 274 |
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14615 | for(index_t k = 0; k < permutation.size(); k++) { |
| 275 | 14591 | unmark(permutation, k); | |
| 276 | } | ||
| 277 | 24 | } | |
| 278 | |||
| 279 | /** | ||
| 280 | * \brief Inverts a permutation. | ||
| 281 | * \details Computes the inverse of a given \p permutation and | ||
| 282 | * stores the result in another one. | ||
| 283 | * \param[in] permutation the permutation to invert | ||
| 284 | * \param[out] invert the computed inverse of \p permutation | ||
| 285 | * \note there is also a variant of invert() that computes the | ||
| 286 | * permutation in-place. | ||
| 287 | */ | ||
| 288 | inline void invert( | ||
| 289 | const vector<index_t>& permutation, vector<index_t>& invert | ||
| 290 | ) { | ||
| 291 | geo_debug_assert(is_valid(permutation)); | ||
| 292 | invert.resize(permutation.size()); | ||
| 293 | for(index_t i=0; i<permutation.size(); ++i) { | ||
| 294 | invert[permutation[i]] = i; | ||
| 295 | } | ||
| 296 | } | ||
| 297 | } | ||
| 298 | } | ||
| 299 | |||
| 300 | #endif | ||
| 301 |