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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2007-2022 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.
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  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   /** @brief Constructs predicate for equality from strict weak
 154    *  ordering predicate
 155    */
 156   template<typename _T1, typename _T2, typename _Compare>
 157     class _EqualFromLess : public std::binary_function<_T1, _T2, bool>
 158     {
 159     private:
 160       _Compare& _M_comp;
 161
 162     public:
 163       _EqualFromLess(_Compare& __comp) : _M_comp(__comp) { }
 164
 165       bool operator()(const _T1& __a, const _T2& __b)
 166       { return !_M_comp(__a, __b) && !_M_comp(__b, __a); }
 167     };
 168
 169
 170   /** @brief Similar to std::unary_negate,
 171    *  but giving the argument types explicitly. */
 172   template<typename _Predicate, typename argument_type>
 173     class __unary_negate
 174     : public std::unary_function<argument_type, bool>
 175     {
 176     protected:
 177       _Predicate _M_pred;
 178
 179     public:
 180       explicit
 181       __unary_negate(const _Predicate& __x) : _M_pred(__x) { }
 182
 183       bool
 184       operator()(const argument_type& __x)
 185       { return !_M_pred(__x); }
 186     };
 187
 188   /** @brief Similar to std::binder1st,
 189    *  but giving the argument types explicitly. */
 190   template<typename _Operation, typename _FirstArgumentType,
 191            typename _SecondArgumentType, typename _ResultType>
 192     class __binder1st
 193     : public std::unary_function<_SecondArgumentType, _ResultType>
 194     {
 195     protected:
 196       _Operation _M_op;
 197       _FirstArgumentType _M_value;
 198
 199     public:
 200       __binder1st(const _Operation& __x, const _FirstArgumentType& __y)
 201       : _M_op(__x), _M_value(__y) { }
 202
 203       _ResultType
 204       operator()(const _SecondArgumentType& __x)
 205       { return _M_op(_M_value, __x); }
 206
 207       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 208       // 109.  Missing binders for non-const sequence elements
 209       _ResultType
 210       operator()(_SecondArgumentType& __x) const
 211       { return _M_op(_M_value, __x); }
 212     };
 213
 214   /**
 215    *  @brief Similar to std::binder2nd, but giving the argument types
 216    *  explicitly.
 217    */
 218   template<typename _Operation, typename _FirstArgumentType,
 219            typename _SecondArgumentType, typename _ResultType>
 220     class __binder2nd
 221     : public std::unary_function<_FirstArgumentType, _ResultType>
 222     {
 223     protected:
 224       _Operation _M_op;
 225       _SecondArgumentType _M_value;
 226
 227     public:
 228       __binder2nd(const _Operation& __x, const _SecondArgumentType& __y)
 229       : _M_op(__x), _M_value(__y) { }
 230
 231       _ResultType
 232       operator()(const _FirstArgumentType& __x) const
 233       { return _M_op(__x, _M_value); }
 234
 235       // _GLIBCXX_RESOLVE_LIB_DEFECTS
 236       // 109.  Missing binders for non-const sequence elements
 237       _ResultType
 238       operator()(_FirstArgumentType& __x)
 239       { return _M_op(__x, _M_value); }
 240     };
 241
 242   /** @brief Similar to std::equal_to, but allows two different types. */
 243   template<typename _T1, typename _T2>
 244     struct _EqualTo : std::binary_function<_T1, _T2, bool>
 245     {
 246       bool operator()(const _T1& __t1, const _T2& __t2) const
 247       { return __t1 == __t2; }
 248     };
 249
 250   /** @brief Similar to std::less, but allows two different types. */
 251   template<typename _T1, typename _T2>
 252     struct _Less : std::binary_function<_T1, _T2, bool>
 253     {
 254       bool
 255       operator()(const _T1& __t1, const _T2& __t2) const
 256       { return __t1 < __t2; }
 257
 258       bool
 259       operator()(const _T2& __t2, const _T1& __t1) const
 260       { return __t2 < __t1; }
 261     };
 262
 263   // Partial specialization for one type. Same as std::less.
 264   template<typename _Tp>
 265     struct _Less<_Tp, _Tp>
 266     : public std::less<_Tp> { };
 267
 268   /** @brief Similar to std::plus, but allows two different types. */
 269   template<typename _Tp1, typename _Tp2, typename _Result
 270            = __typeof__(*static_cast<_Tp1*>(0)
 271                         + *static_cast<_Tp2*>(0))>
 272     struct _Plus : public std::binary_function<_Tp1, _Tp2, _Result>
 273     {
 274       _Result
 275       operator()(const _Tp1& __x, const _Tp2& __y) const
 276       { return __x + __y; }
 277     };
 278
 279   // Partial specialization for one type. Same as std::plus.
 280   template<typename _Tp>
 281     struct _Plus<_Tp, _Tp, _Tp>
 282     : public std::plus<_Tp> { };
 283
 284   /** @brief Similar to std::multiplies, but allows two different types. */
 285   template<typename _Tp1, typename _Tp2, typename _Result
 286            = __typeof__(*static_cast<_Tp1*>(0)
 287                         * *static_cast<_Tp2*>(0))>
 288     struct _Multiplies : public std::binary_function<_Tp1, _Tp2, _Result>
 289     {
 290       _Result
 291       operator()(const _Tp1& __x, const _Tp2& __y) const
 292       { return __x * __y; }
 293     };
 294
 295   // Partial specialization for one type. Same as std::multiplies.
 296   template<typename _Tp>
 297     struct _Multiplies<_Tp, _Tp, _Tp>
 298     : public std::multiplies<_Tp> { };
 299
 300   /** @brief _Iterator associated with __gnu_parallel::_PseudoSequence.
 301    *  If features the usual random-access iterator functionality.
 302    *  @param _Tp Sequence _M_value type.
 303    *  @param _DifferenceTp Sequence difference type.
 304    */
 305   template<typename _Tp, typename _DifferenceTp>
 306     class _PseudoSequenceIterator
 307     {
 308     public:
 309       typedef _DifferenceTp _DifferenceType;
 310
 311       _PseudoSequenceIterator(const _Tp& __val, _DifferenceType __pos)
 312       : _M_val(__val), _M_pos(__pos) { }
 313
 314       // Pre-increment operator.
 315       _PseudoSequenceIterator&
 316       operator++()
 317       {
 318         ++_M_pos;
 319         return *this;
 320       }
 321
 322       // Post-increment operator.
 323       _PseudoSequenceIterator
 324       operator++(int)
 325       { return _PseudoSequenceIterator(_M_pos++); }
 326
 327       const _Tp&
 328       operator*() const
 329       { return _M_val; }
 330
 331       const _Tp&
 332       operator[](_DifferenceType) const
 333       { return _M_val; }
 334
 335       bool
 336       operator==(const _PseudoSequenceIterator& __i2)
 337       { return _M_pos == __i2._M_pos; }
 338
 339       bool
 340       operator!=(const _PseudoSequenceIterator& __i2)
 341       { return _M_pos != __i2._M_pos; }
 342
 343       _DifferenceType
 344       operator-(const _PseudoSequenceIterator& __i2)
 345       { return _M_pos - __i2._M_pos; }
 346
 347     private:
 348       const _Tp& _M_val;
 349       _DifferenceType _M_pos;
 350     };
 351
 352   /** @brief Sequence that conceptually consists of multiple copies of
 353       the same element.
 354       *  The copies are not stored explicitly, of course.
 355       *  @param _Tp Sequence _M_value type.
 356       *  @param _DifferenceTp Sequence difference type.
 357       */
 358   template<typename _Tp, typename _DifferenceTp>
 359     class _PseudoSequence
 360     {
 361     public:
 362       typedef _DifferenceTp _DifferenceType;
 363
 364       // Better cast down to uint64_t, than up to _DifferenceTp.
 365       typedef _PseudoSequenceIterator<_Tp, uint64_t> iterator;
 366
 367       /** @brief Constructor.
 368        *  @param __val Element of the sequence.
 369        *  @param __count Number of (virtual) copies.
 370        */
 371       _PseudoSequence(const _Tp& __val, _DifferenceType __count)
 372       : _M_val(__val), _M_count(__count)  { }
 373
 374       /** @brief Begin iterator. */
 375       iterator
 376       begin() const
 377       { return iterator(_M_val, 0); }
 378
 379       /** @brief End iterator. */
 380       iterator
 381       end() const
 382       { return iterator(_M_val, _M_count); }
 383
 384     private:
 385       const _Tp& _M_val;
 386       _DifferenceType _M_count;
 387     };
 388
 389   /** @brief Compute the median of three referenced elements,
 390       according to @c __comp.
 391       *  @param __a First iterator.
 392       *  @param __b Second iterator.
 393       *  @param __c Third iterator.
 394       *  @param __comp Comparator.
 395       */
 396   template<typename _RAIter, typename _Compare>
 397     _RAIter
 398     __median_of_three_iterators(_RAIter __a, _RAIter __b,
 399                                 _RAIter __c, _Compare __comp)
 400     {
 401       if (__comp(*__a, *__b))
 402         if (__comp(*__b, *__c))
 403           return __b;
 404         else
 405           if (__comp(*__a, *__c))
 406             return __c;
 407           else
 408             return __a;
 409       else
 410         {
 411           // Just swap __a and __b.
 412           if (__comp(*__a, *__c))
 413             return __a;
 414           else
 415             if (__comp(*__b, *__c))
 416               return __c;
 417             else
 418               return __b;
 419         }
 420     }
 421
 422 #if _GLIBCXX_PARALLEL_ASSERTIONS && defined(__glibcxx_assert_impl)
 423 # define _GLIBCXX_PARALLEL_ASSERT(_Condition) \
 424   do { __glibcxx_assert_impl(_Condition); } while (false)
 425 #else
 426 # define _GLIBCXX_PARALLEL_ASSERT(_Condition) do { } while (false)
 427 #endif
 428
 429 } //namespace __gnu_parallel
 430
 431 #endif /* _GLIBCXX_PARALLEL_BASE_H */