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The C and C++ Include Header Files
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1 // -*- C++ -*- 2 3 // Copyright (C) 2007-2025 Free Software Foundation, Inc. 4 // 5 // This file is part of the GNU ISO C++ Library. This library is free 6 // software; you can redistribute it and/or modify it under the terms 7 // of the GNU General Public License as published by the Free Software 8 // Foundation; either version 3, or (at your option) any later 9 // version. 10 11 // This library is distributed in the hope that it will be useful, but 12 // WITHOUT ANY WARRANTY; without even the implied warranty of 13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 // General Public License for more details. 15 16 // Under Section 7 of GPL version 3, you are granted additional 17 // permissions described in the GCC Runtime Library Exception, version 18 // 3.1, as published by the Free Software Foundation. 19 20 // You should have received a copy of the GNU General Public License and 21 // a copy of the GCC Runtime Library Exception along with this program; 22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23 // <http://www.gnu.org/licenses/>. 24 25 /** @file parallel/find.h 26 * @brief Parallel implementation base for std::find(), std::equal() 27 * and related functions. 28 * This file is a GNU parallel extension to the Standard C++ Library. 29 */ 30 31 // Written by Felix Putze and Johannes Singler. 32 33 #ifndef _GLIBCXX_PARALLEL_FIND_H 34 #define _GLIBCXX_PARALLEL_FIND_H 1 35 36 #include <bits/stl_algobase.h> 37 38 #include <parallel/features.h> 39 #include <parallel/parallel.h> 40 #include <parallel/compatibility.h> 41 #include <parallel/equally_split.h> 42 43 namespace __gnu_parallel 44 { 45 /** 46 * @brief Parallel std::find, switch for different algorithms. 47 * @param __begin1 Begin iterator of first sequence. 48 * @param __end1 End iterator of first sequence. 49 * @param __begin2 Begin iterator of second sequence. Must have same 50 * length as first sequence. 51 * @param __pred Find predicate. 52 * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) 53 * @return Place of finding in both sequences. 54 */ 55 template<typename _RAIter1, 56 typename _RAIter2, 57 typename _Pred, 58 typename _Selector> 59 inline std::pair<_RAIter1, _RAIter2> 60 __find_template(_RAIter1 __begin1, _RAIter1 __end1, 61 _RAIter2 __begin2, _Pred __pred, _Selector __selector) 62 { 63 switch (_Settings::get().find_algorithm) 64 { 65 case GROWING_BLOCKS: 66 return __find_template(__begin1, __end1, __begin2, __pred, 67 __selector, growing_blocks_tag()); 68 case CONSTANT_SIZE_BLOCKS: 69 return __find_template(__begin1, __end1, __begin2, __pred, 70 __selector, constant_size_blocks_tag()); 71 case EQUAL_SPLIT: 72 return __find_template(__begin1, __end1, __begin2, __pred, 73 __selector, equal_split_tag()); 74 default: 75 _GLIBCXX_PARALLEL_ASSERT(false); 76 return std::make_pair(__begin1, __begin2); 77 } 78 } 79 80 #if _GLIBCXX_FIND_EQUAL_SPLIT 81 82 /** 83 * @brief Parallel std::find, equal splitting variant. 84 * @param __begin1 Begin iterator of first sequence. 85 * @param __end1 End iterator of first sequence. 86 * @param __begin2 Begin iterator of second sequence. Second __sequence 87 * must have same length as first sequence. 88 * @param __pred Find predicate. 89 * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) 90 * @return Place of finding in both sequences. 91 */ 92 template<typename _RAIter1, 93 typename _RAIter2, 94 typename _Pred, 95 typename _Selector> 96 std::pair<_RAIter1, _RAIter2> 97 __find_template(_RAIter1 __begin1, _RAIter1 __end1, 98 _RAIter2 __begin2, _Pred __pred, 99 _Selector __selector, equal_split_tag) 100 { 101 _GLIBCXX_CALL(__end1 - __begin1) 102 103 typedef std::iterator_traits<_RAIter1> _TraitsType; 104 typedef typename _TraitsType::difference_type _DifferenceType; 105 typedef typename _TraitsType::value_type _ValueType; 106 107 _DifferenceType __length = __end1 - __begin1; 108 _DifferenceType __result = __length; 109 _DifferenceType* __borders; 110 111 omp_lock_t __result_lock; 112 omp_init_lock(&__result_lock); 113 114 _ThreadIndex __num_threads = __get_max_threads(); 115 # pragma omp parallel num_threads(__num_threads) 116 { 117 # pragma omp single 118 { 119 __num_threads = omp_get_num_threads(); 120 __borders = new _DifferenceType[__num_threads + 1]; 121 __equally_split(__length, __num_threads, __borders); 122 } //single 123 124 _ThreadIndex __iam = omp_get_thread_num(); 125 _DifferenceType __start = __borders[__iam], 126 __stop = __borders[__iam + 1]; 127 128 _RAIter1 __i1 = __begin1 + __start; 129 _RAIter2 __i2 = __begin2 + __start; 130 for (_DifferenceType __pos = __start; __pos < __stop; ++__pos) 131 { 132 # pragma omp flush(__result) 133 // Result has been set to something lower. 134 if (__result < __pos) 135 break; 136 137 if (__selector(__i1, __i2, __pred)) 138 { 139 omp_set_lock(&__result_lock); 140 if (__pos < __result) 141 __result = __pos; 142 omp_unset_lock(&__result_lock); 143 break; 144 } 145 ++__i1; 146 ++__i2; 147 } 148 } //parallel 149 150 omp_destroy_lock(&__result_lock); 151 delete[] __borders; 152 153 return std::pair<_RAIter1, _RAIter2>(__begin1 + __result, 154 __begin2 + __result); 155 } 156 157 #endif 158 159 #if _GLIBCXX_FIND_GROWING_BLOCKS 160 161 /** 162 * @brief Parallel std::find, growing block size variant. 163 * @param __begin1 Begin iterator of first sequence. 164 * @param __end1 End iterator of first sequence. 165 * @param __begin2 Begin iterator of second sequence. Second __sequence 166 * must have same length as first sequence. 167 * @param __pred Find predicate. 168 * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) 169 * @return Place of finding in both sequences. 170 * @see __gnu_parallel::_Settings::find_sequential_search_size 171 * @see __gnu_parallel::_Settings::find_scale_factor 172 * 173 * There are two main differences between the growing blocks and 174 * the constant-size blocks variants. 175 * 1. For GB, the block size grows; for CSB, the block size is fixed. 176 * 2. For GB, the blocks are allocated dynamically; 177 * for CSB, the blocks are allocated in a predetermined manner, 178 * namely spacial round-robin. 179 */ 180 template<typename _RAIter1, 181 typename _RAIter2, 182 typename _Pred, 183 typename _Selector> 184 std::pair<_RAIter1, _RAIter2> 185 __find_template(_RAIter1 __begin1, _RAIter1 __end1, 186 _RAIter2 __begin2, _Pred __pred, _Selector __selector, 187 growing_blocks_tag) 188 { 189 _GLIBCXX_CALL(__end1 - __begin1) 190 191 typedef std::iterator_traits<_RAIter1> _TraitsType; 192 typedef typename _TraitsType::difference_type _DifferenceType; 193 typedef typename _TraitsType::value_type _ValueType; 194 195 const _Settings& __s = _Settings::get(); 196 197 _DifferenceType __length = __end1 - __begin1; 198 199 _DifferenceType 200 __sequential_search_size = std::min<_DifferenceType> 201 (__length, __s.find_sequential_search_size); 202 203 // Try it sequentially first. 204 std::pair<_RAIter1, _RAIter2> 205 __find_seq_result = __selector._M_sequential_algorithm 206 (__begin1, __begin1 + __sequential_search_size, 207 __begin2, __pred); 208 209 if (__find_seq_result.first != (__begin1 + __sequential_search_size)) 210 return __find_seq_result; 211 212 // Index of beginning of next free block (after sequential find). 213 _DifferenceType __next_block_start = __sequential_search_size; 214 _DifferenceType __result = __length; 215 216 omp_lock_t __result_lock; 217 omp_init_lock(&__result_lock); 218 219 const float __scale_factor = __s.find_scale_factor; 220 221 _ThreadIndex __num_threads = __get_max_threads(); 222 # pragma omp parallel shared(__result) num_threads(__num_threads) 223 { 224 # pragma omp single 225 __num_threads = omp_get_num_threads(); 226 227 // Not within first __k elements -> start parallel. 228 _ThreadIndex __iam = omp_get_thread_num(); 229 230 _DifferenceType __block_size = 231 std::max<_DifferenceType>(1, __scale_factor * __next_block_start); 232 _DifferenceType __start = __fetch_and_add<_DifferenceType> 233 (&__next_block_start, __block_size); 234 235 // Get new block, update pointer to next block. 236 _DifferenceType __stop = 237 std::min<_DifferenceType>(__length, __start + __block_size); 238 239 std::pair<_RAIter1, _RAIter2> __local_result; 240 241 while (__start < __length) 242 { 243 # pragma omp flush(__result) 244 // Get new value of result. 245 if (__result < __start) 246 { 247 // No chance to find first element. 248 break; 249 } 250 251 __local_result = __selector._M_sequential_algorithm 252 (__begin1 + __start, __begin1 + __stop, 253 __begin2 + __start, __pred); 254 255 if (__local_result.first != (__begin1 + __stop)) 256 { 257 omp_set_lock(&__result_lock); 258 if ((__local_result.first - __begin1) < __result) 259 { 260 __result = __local_result.first - __begin1; 261 262 // Result cannot be in future blocks, stop algorithm. 263 __fetch_and_add<_DifferenceType>(&__next_block_start, 264 __length); 265 } 266 omp_unset_lock(&__result_lock); 267 } 268 269 _DifferenceType __block_size = 270 std::max<_DifferenceType>(1, __scale_factor * __next_block_start); 271 272 // Get new block, update pointer to next block. 273 __start = __fetch_and_add<_DifferenceType>(&__next_block_start, 274 __block_size); 275 __stop = 276 std::min<_DifferenceType>(__length, __start + __block_size); 277 } 278 } //parallel 279 280 omp_destroy_lock(&__result_lock); 281 282 // Return iterator on found element. 283 return 284 std::pair<_RAIter1, _RAIter2>(__begin1 + __result, 285 __begin2 + __result); 286 } 287 288 #endif 289 290 #if _GLIBCXX_FIND_CONSTANT_SIZE_BLOCKS 291 292 /** 293 * @brief Parallel std::find, constant block size variant. 294 * @param __begin1 Begin iterator of first sequence. 295 * @param __end1 End iterator of first sequence. 296 * @param __begin2 Begin iterator of second sequence. Second __sequence 297 * must have same length as first sequence. 298 * @param __pred Find predicate. 299 * @param __selector _Functionality (e. g. std::find_if(), std::equal(),...) 300 * @return Place of finding in both sequences. 301 * @see __gnu_parallel::_Settings::find_sequential_search_size 302 * @see __gnu_parallel::_Settings::find_block_size 303 * There are two main differences between the growing blocks and the 304 * constant-size blocks variants. 305 * 1. For GB, the block size grows; for CSB, the block size is fixed. 306 * 2. For GB, the blocks are allocated dynamically; for CSB, the 307 * blocks are allocated in a predetermined manner, namely spacial 308 * round-robin. 309 */ 310 template<typename _RAIter1, 311 typename _RAIter2, 312 typename _Pred, 313 typename _Selector> 314 std::pair<_RAIter1, _RAIter2> 315 __find_template(_RAIter1 __begin1, _RAIter1 __end1, 316 _RAIter2 __begin2, _Pred __pred, _Selector __selector, 317 constant_size_blocks_tag) 318 { 319 _GLIBCXX_CALL(__end1 - __begin1) 320 typedef std::iterator_traits<_RAIter1> _TraitsType; 321 typedef typename _TraitsType::difference_type _DifferenceType; 322 typedef typename _TraitsType::value_type _ValueType; 323 324 const _Settings& __s = _Settings::get(); 325 326 _DifferenceType __length = __end1 - __begin1; 327 328 _DifferenceType __sequential_search_size = std::min<_DifferenceType> 329 (__length, __s.find_sequential_search_size); 330 331 // Try it sequentially first. 332 std::pair<_RAIter1, _RAIter2> 333 __find_seq_result = __selector._M_sequential_algorithm 334 (__begin1, __begin1 + __sequential_search_size, __begin2, __pred); 335 336 if (__find_seq_result.first != (__begin1 + __sequential_search_size)) 337 return __find_seq_result; 338 339 _DifferenceType __result = __length; 340 omp_lock_t __result_lock; 341 omp_init_lock(&__result_lock); 342 343 // Not within first __sequential_search_size elements -> start parallel. 344 345 _ThreadIndex __num_threads = __get_max_threads(); 346 # pragma omp parallel shared(__result) num_threads(__num_threads) 347 { 348 # pragma omp single 349 __num_threads = omp_get_num_threads(); 350 351 _ThreadIndex __iam = omp_get_thread_num(); 352 _DifferenceType __block_size = __s.find_initial_block_size; 353 354 // First element of thread's current iteration. 355 _DifferenceType __iteration_start = __sequential_search_size; 356 357 // Where to work (initialization). 358 _DifferenceType __start = __iteration_start + __iam * __block_size; 359 _DifferenceType __stop = std::min<_DifferenceType>(__length, 360 __start 361 + __block_size); 362 363 std::pair<_RAIter1, _RAIter2> __local_result; 364 365 while (__start < __length) 366 { 367 // Get new value of result. 368 # pragma omp flush(__result) 369 // No chance to find first element. 370 if (__result < __start) 371 break; 372 373 __local_result = __selector._M_sequential_algorithm 374 (__begin1 + __start, __begin1 + __stop, 375 __begin2 + __start, __pred); 376 377 if (__local_result.first != (__begin1 + __stop)) 378 { 379 omp_set_lock(&__result_lock); 380 if ((__local_result.first - __begin1) < __result) 381 __result = __local_result.first - __begin1; 382 omp_unset_lock(&__result_lock); 383 // Will not find better value in its interval. 384 break; 385 } 386 387 __iteration_start += __num_threads * __block_size; 388 389 // Where to work. 390 __start = __iteration_start + __iam * __block_size; 391 __stop = std::min<_DifferenceType>(__length, 392 __start + __block_size); 393 } 394 } //parallel 395 396 omp_destroy_lock(&__result_lock); 397 398 // Return iterator on found element. 399 return std::pair<_RAIter1, _RAIter2>(__begin1 + __result, 400 __begin2 + __result); 401 } 402 #endif 403 } // end namespace 404 405 #endif /* _GLIBCXX_PARALLEL_FIND_H */
