libstdc++-v3/include/parallel/base.h

   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/base.h
  26  *  @brief Sequential helper functions.
  27  *  This file is a GNU parallel extension to the Standard C++ Library.
  28  */
  29
  30 // Written by Johannes Singler.
  31
  32 #ifndef _GLIBCXX_PARALLEL_BASE_H
  33 #define _GLIBCXX_PARALLEL_BASE_H 1
  34
  35 #include <bits/c++config.h>
  36 #include <bits/stl_function.h>
  37 #include <omp.h>
  38 #include <parallel/features.h>
  39 #include <parallel/basic_iterator.h>
  40 #include <parallel/parallel.h>
  41
  42 // Parallel mode namespaces.
  43
  44 /**
  45  * @namespace std::__parallel
  46  * @brief GNU parallel code, replaces standard behavior with parallel behavior.
  47  */
  48 namespace std _GLIBCXX_VISIBILITY(default)
  49 {
  50   namespace __parallel { }
  51 }
  52
  53 /**
  54  * @namespace __gnu_parallel
  55  * @brief GNU parallel code for public use.
  56  */
  57 namespace __gnu_parallel
  58 {
  59   // Import all the parallel versions of components in namespace std.
  60   using namespace std::__parallel;
  61 }
  62
  63 /**
  64  * @namespace __gnu_sequential
  65  * @brief GNU sequential classes for public use.
  66  */
  67 namespace __gnu_sequential
  68 {
  69   // Import whatever is the serial version.
  70 #ifdef _GLIBCXX_PARALLEL
  71   using namespace std::_GLIBCXX_STD_A;
  72 #else
  73   using namespace std;
  74 #endif
  75 }
  76
  77
  78 namespace __gnu_parallel
  79 {
  80   // NB: Including this file cannot produce (unresolved) symbols from
  81   // the OpenMP runtime unless the parallel mode is actually invoked
  82   // and active, which imples that the OpenMP runtime is actually
  83   // going to be linked in.
  84   inline _ThreadIndex
  85   __get_max_threads()
  86   {
  87     _ThreadIndex __i = omp_get_max_threads();
  88     return __i > 1 ? __i : 1;
  89   }
  90
  91
  92   inline bool
  93   __is_parallel(const _Parallelism __p) { return __p != sequential; }
  94
  95
  96   /** @brief Calculates the rounded-down logarithm of @c __n for base 2.
  97    *  @param __n Argument.
  98    *  @return Returns 0 for any argument <1.
  99    */
 100   template<typename _Size>
 101     inline _Size
 102     __rd_log2(_Size __n)
 103     {
 104       _Size __k;
 105       for (__k = 0; __n > 1; __n >>= 1)
 106         ++__k;
 107       return __k;
 108     }
 109
 110   /** @brief Encode two integers into one gnu_parallel::_CASable.
 111    *  @param __a First integer, to be encoded in the most-significant @c
 112    *  _CASable_bits/2 bits.
 113    *  @param __b Second integer, to be encoded in the least-significant
 114    *  @c _CASable_bits/2 bits.
 115    *  @return value encoding @c __a and @c __b.
 116    *  @see __decode2
 117    */
 118   inline _CASable
 119   __encode2(int __a, int __b)     //must all be non-negative, actually
 120   {
 121     return (((_CASable)__a) << (_CASable_bits / 2)) | (((_CASable)__b) << 0);
 122   }
 123
 124   /** @brief Decode two integers from one gnu_parallel::_CASable.
 125    *  @param __x __gnu_parallel::_CASable to decode integers from.
 126    *  @param __a First integer, to be decoded from the most-significant
 127    *  @c _CASable_bits/2 bits of @c __x.
 128    *  @param __b Second integer, to be encoded in the least-significant
 129    *  @c _CASable_bits/2 bits of @c __x.
 130    *  @see __encode2
 131    */
 132   inline void
 133   __decode2(_CASable __x, int& __a, int& __b)
 134   {
 135     __a = (int)((__x >> (_CASable_bits / 2)) & _CASable_mask);
 136     __b = (int)((__x >>               0 ) & _CASable_mask);
 137   }
 138
 139   //needed for parallel "numeric", even if "algorithm" not included
 140
 141   /** @brief Equivalent to std::min. */
 142   template<typename _Tp>
 143     inline const _Tp&
 144     min(const _Tp& __a, const _Tp& __b)
 145     { return (__a < __b) ? __a : __b; }
 146
 147   /** @brief Equivalent to std::max. */
 148   template<typename _Tp>
 149     inline const _Tp&
 150     max(const _Tp& __a, const _Tp& __b)
 151     { return (__a > __b) ? __a : __b; }
 152
 153 #pragma GCC diagnostic push
 154 #pragma GCC diagnostic ignored "-Wdeprecated-declarations" // *nary_function
 155
 156   /** @brief Constructs predicate for equality from strict weak
 157    *  ordering predicate
 158    */
 159   template<typename _T1, typename _T2, typename _Compare>
 160     class _EqualFromLess : public std::binary_function<_T1, _T2, bool>
 161     {
 162     private:
 163       _Compare& _M_comp;
 164
 165     public:
 166       _EqualFromLess(_Compare& __comp) : _M_comp(__comp) { }
 167
 168       bool operator()(const _T1& __a, const _T2& __b)
 169       { return !_M_comp(__a, __b) && !_M_comp(__b, __a); }
 170     };
 171
 172   /** @brief Similar to std::unary_negate,
 173    *  but giving the argument types explicitly. */
 174   template<typename _Predicate, typename argument_type>
 175     class __unary_negate
 176     : public std::unary_function<argument_type, bool>
 177     {
 178     protected:
 179       _Predicate _M_pred;
 180
 181     public:
 182       explicit
 183       __unary_negate(const _Predicate& __x) : _M_pred(__x) { }
 184
 185       bool
 186       operator()(const argument_type& __x)
 187       { return !_M_pred(__x); }
 188     };
 189
 190   /** @brief Similar to std::binder1st,
 191    *  but giving the argument types explicitly. */
 192   template<typename _Operation, typename _FirstArgumentType,
 193            typename _SecondArgumentType, typename _ResultType>
 194     class __binder1st
 195     : public std::unary_function<_SecondArgumentType, _ResultType>
 196     {
 197     protected:
 198       _Operation _M_op;
 199       _FirstArgumentType _M_value;
 200
 201     public:
 202       __binder1st(const _Operation& __x, const _FirstArgumentType& __y)
 203       : _M_op(__x), _M_value(__y) { }
 204
 205       _ResultType
 206       operator()(const _SecondArgumentType& __x)
 207       { return _M_op(_M_value, __x); }
 208
 209       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 210       // 109.  Missing binders for non-const sequence elements
 211       _ResultType
 212       operator()(_SecondArgumentType& __x) const
 213       { return _M_op(_M_value, __x); }
 214     };
 215
 216   /**
 217    *  @brief Similar to std::binder2nd, but giving the argument types
 218    *  explicitly.
 219    */
 220   template<typename _Operation, typename _FirstArgumentType,
 221            typename _SecondArgumentType, typename _ResultType>
 222     class __binder2nd
 223     : public std::unary_function<_FirstArgumentType, _ResultType>
 224     {
 225     protected:
 226       _Operation _M_op;
 227       _SecondArgumentType _M_value;
 228
 229     public:
 230       __binder2nd(const _Operation& __x, const _SecondArgumentType& __y)
 231       : _M_op(__x), _M_value(__y) { }
 232
 233       _ResultType
 234       operator()(const _FirstArgumentType& __x) const
 235       { return _M_op(__x, _M_value); }
 236
 237       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 238       // 109.  Missing binders for non-const sequence elements
 239       _ResultType
 240       operator()(_FirstArgumentType& __x)
 241       { return _M_op(__x, _M_value); }
 242     };
 243
 244   /** @brief Similar to std::equal_to, but allows two different types. */
 245   template<typename _T1, typename _T2>
 246     struct _EqualTo : std::binary_function<_T1, _T2, bool>
 247     {
 248       bool operator()(const _T1& __t1, const _T2& __t2) const
 249       { return __t1 == __t2; }
 250     };
 251
 252   /** @brief Similar to std::less, but allows two different types. */
 253   template<typename _T1, typename _T2>
 254     struct _Less : std::binary_function<_T1, _T2, bool>
 255     {
 256       bool
 257       operator()(const _T1& __t1, const _T2& __t2) const
 258       { return __t1 < __t2; }
 259
 260       bool
 261       operator()(const _T2& __t2, const _T1& __t1) const
 262       { return __t2 < __t1; }
 263     };
 264
 265   // Partial specialization for one type. Same as std::less.
 266   template<typename _Tp>
 267     struct _Less<_Tp, _Tp>
 268     : public std::less<_Tp> { };
 269
 270   /** @brief Similar to std::plus, but allows two different types. */
 271   template<typename _Tp1, typename _Tp2, typename _Result
 272            = __typeof__(*static_cast<_Tp1*>(0)
 273                         + *static_cast<_Tp2*>(0))>
 274     struct _Plus : public std::binary_function<_Tp1, _Tp2, _Result>
 275     {
 276       _Result
 277       operator()(const _Tp1& __x, const _Tp2& __y) const
 278       { return __x + __y; }
 279     };
 280
 281   // Partial specialization for one type. Same as std::plus.
 282   template<typename _Tp>
 283     struct _Plus<_Tp, _Tp, _Tp>
 284     : public std::plus<_Tp> { };
 285
 286   /** @brief Similar to std::multiplies, but allows two different types. */
 287   template<typename _Tp1, typename _Tp2, typename _Result
 288            = __typeof__(*static_cast<_Tp1*>(0)
 289                         * *static_cast<_Tp2*>(0))>
 290     struct _Multiplies : public std::binary_function<_Tp1, _Tp2, _Result>
 291     {
 292       _Result
 293       operator()(const _Tp1& __x, const _Tp2& __y) const
 294       { return __x * __y; }
 295     };
 296
 297   // Partial specialization for one type. Same as std::multiplies.
 298   template<typename _Tp>
 299     struct _Multiplies<_Tp, _Tp, _Tp>
 300     : public std::multiplies<_Tp> { };
 301
 302 #pragma GCC diagnostic pop // -Wdeprecated-declarations
 303
 304   /** @brief _Iterator associated with __gnu_parallel::_PseudoSequence.
 305    *  If features the usual random-access iterator functionality.
 306    *  @param _Tp Sequence _M_value type.
 307    *  @param _DifferenceTp Sequence difference type.
 308    */
 309   template<typename _Tp, typename _DifferenceTp>
 310     class _PseudoSequenceIterator
 311     {
 312     public:
 313       typedef _DifferenceTp _DifferenceType;
 314
 315       _PseudoSequenceIterator(const _Tp& __val, _DifferenceType __pos)
 316       : _M_val(__val), _M_pos(__pos) { }
 317
 318       // Pre-increment operator.
 319       _PseudoSequenceIterator&
 320       operator++()
 321       {
 322         ++_M_pos;
 323         return *this;
 324       }
 325
 326       // Post-increment operator.
 327       _PseudoSequenceIterator
 328       operator++(int)
 329       { return _PseudoSequenceIterator(_M_pos++); }
 330
 331       const _Tp&
 332       operator*() const
 333       { return _M_val; }
 334
 335       const _Tp&
 336       operator[](_DifferenceType) const
 337       { return _M_val; }
 338
 339       bool
 340       operator==(const _PseudoSequenceIterator& __i2)
 341       { return _M_pos == __i2._M_pos; }
 342
 343       bool
 344       operator!=(const _PseudoSequenceIterator& __i2)
 345       { return _M_pos != __i2._M_pos; }
 346
 347       _DifferenceType
 348       operator-(const _PseudoSequenceIterator& __i2)
 349       { return _M_pos - __i2._M_pos; }
 350
 351     private:
 352       const _Tp& _M_val;
 353       _DifferenceType _M_pos;
 354     };
 355
 356   /** @brief Sequence that conceptually consists of multiple copies of
 357       the same element.
 358       *  The copies are not stored explicitly, of course.
 359       *  @param _Tp Sequence _M_value type.
 360       *  @param _DifferenceTp Sequence difference type.
 361       */
 362   template<typename _Tp, typename _DifferenceTp>
 363     class _PseudoSequence
 364     {
 365     public:
 366       typedef _DifferenceTp _DifferenceType;
 367
 368       // Better cast down to uint64_t, than up to _DifferenceTp.
 369       typedef _PseudoSequenceIterator<_Tp, uint64_t> iterator;
 370
 371       /** @brief Constructor.
 372        *  @param __val Element of the sequence.
 373        *  @param __count Number of (virtual) copies.
 374        */
 375       _PseudoSequence(const _Tp& __val, _DifferenceType __count)
 376       : _M_val(__val), _M_count(__count)  { }
 377
 378       /** @brief Begin iterator. */
 379       iterator
 380       begin() const
 381       { return iterator(_M_val, 0); }
 382
 383       /** @brief End iterator. */
 384       iterator
 385       end() const
 386       { return iterator(_M_val, _M_count); }
 387
 388     private:
 389       const _Tp& _M_val;
 390       _DifferenceType _M_count;
 391     };
 392
 393   /** @brief Compute the median of three referenced elements,
 394       according to @c __comp.
 395       *  @param __a First iterator.
 396       *  @param __b Second iterator.
 397       *  @param __c Third iterator.
 398       *  @param __comp Comparator.
 399       */
 400   template<typename _RAIter, typename _Compare>
 401     _RAIter
 402     __median_of_three_iterators(_RAIter __a, _RAIter __b,
 403                                 _RAIter __c, _Compare __comp)
 404     {
 405       if (__comp(*__a, *__b))
 406         if (__comp(*__b, *__c))
 407           return __b;
 408         else
 409           if (__comp(*__a, *__c))
 410             return __c;
 411           else
 412             return __a;
 413       else
 414         {
 415           // Just swap __a and __b.
 416           if (__comp(*__a, *__c))
 417             return __a;
 418           else
 419             if (__comp(*__b, *__c))
 420               return __c;
 421             else
 422               return __b;
 423         }
 424     }
 425
 426 #if _GLIBCXX_PARALLEL_ASSERTIONS && defined(__glibcxx_assert_impl)
 427 # define _GLIBCXX_PARALLEL_ASSERT(_Condition) \
 428   do { __glibcxx_assert_impl(_Condition); } while (false)
 429 #else
 430 # define _GLIBCXX_PARALLEL_ASSERT(_Condition) do { } while (false)
 431 #endif
 432
 433 } //namespace __gnu_parallel
 434
 435 #endif /* _GLIBCXX_PARALLEL_BASE_H */