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

   1 // -*- C++ -*-
   2
   3 // Copyright (C) 2007, 2008, 2009 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 <functional>
  36 #include <omp.h>
  37 #include <parallel/features.h>
  38 #include <parallel/basic_iterator.h>
  39 #include <parallel/parallel.h>
  40
  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
  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::__norm;
  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 int
  85   get_max_threads()
  86   {
  87     int __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   // XXX remove std::duplicates from here if possible,
  97   // XXX but keep minimal dependencies.
  98
  99 /** @brief Calculates the rounded-down logarithm of @c n for base 2.
 100   *  @param n Argument.
 101   *  @return Returns 0 for any argument <1.
 102   */
 103 template<typename Size>
 104   inline Size
 105   __log2(Size n)
 106     {
 107       Size k;
 108       for (k = 0; n > 1; n >>= 1)
 109         ++k;
 110       return k;
 111     }
 112
 113 /** @brief Encode two integers into one __gnu_parallel::lcas_t.
 114   *  @param a First integer, to be encoded in the most-significant @c
 115   *  lcas_t_bits/2 bits.
 116   *  @param b Second integer, to be encoded in the least-significant
 117   *  @c lcas_t_bits/2 bits.
 118   *  @return __gnu_parallel::lcas_t value encoding @c a and @c b.
 119   *  @see decode2
 120   */
 121 inline lcas_t
 122 encode2(int a, int b)   //must all be non-negative, actually
 123 {
 124   return (((lcas_t)a) << (lcas_t_bits / 2)) | (((lcas_t)b) << 0);
 125 }
 126
 127 /** @brief Decode two integers from one __gnu_parallel::lcas_t.
 128   *  @param x __gnu_parallel::lcas_t to decode integers from.
 129   *  @param a First integer, to be decoded from the most-significant
 130   *  @c lcas_t_bits/2 bits of @c x.
 131   *  @param b Second integer, to be encoded in the least-significant
 132   *  @c lcas_t_bits/2 bits of @c x.
 133   *  @see encode2
 134   */
 135 inline void
 136 decode2(lcas_t x, int& a, int& b)
 137 {
 138   a = (int)((x >> (lcas_t_bits / 2)) & lcas_t_mask);
 139   b = (int)((x >>               0 ) & lcas_t_mask);
 140 }
 141
 142 /** @brief Equivalent to std::min. */
 143 template<typename T>
 144   const T&
 145   min(const T& a, const T& b)
 146   { return (a < b) ? a : b; }
 147
 148 /** @brief Equivalent to std::max. */
 149 template<typename T>
 150   const T&
 151   max(const T& a, const T& b)
 152   { return (a > b) ? a : b; }
 153
 154 /** @brief Constructs predicate for equality from strict weak
 155   *  ordering predicate
 156   */
 157 // XXX comparator at the end, as per others
 158 template<typename Comparator, typename T1, typename T2>
 159   class equal_from_less : public std::binary_function<T1, T2, bool>
 160   {
 161   private:
 162     Comparator& comp;
 163
 164   public:
 165     equal_from_less(Comparator& _comp) : comp(_comp) { }
 166
 167     bool operator()(const T1& a, const T2& b)
 168     {
 169       return !comp(a, b) && !comp(b, a);
 170     }
 171   };
 172
 173
 174 /** @brief Similar to std::binder1st,
 175   *  but giving the argument types explicitly. */
 176 template<typename _Predicate, typename argument_type>
 177   class unary_negate
 178   : public std::unary_function<argument_type, bool>
 179   {
 180   protected:
 181     _Predicate _M_pred;
 182
 183   public:
 184     explicit
 185     unary_negate(const _Predicate& __x) : _M_pred(__x) { }
 186
 187     bool
 188     operator()(const argument_type& __x)
 189     { return !_M_pred(__x); }
 190   };
 191
 192 /** @brief Similar to std::binder1st,
 193   *  but giving the argument types explicitly. */
 194 template<typename _Operation, typename first_argument_type,
 195          typename second_argument_type, typename result_type>
 196   class binder1st
 197   : public std::unary_function<second_argument_type, result_type>
 198   {
 199   protected:
 200     _Operation op;
 201     first_argument_type value;
 202
 203   public:
 204     binder1st(const _Operation& __x,
 205               const first_argument_type& __y)
 206     : op(__x), value(__y) { }
 207
 208     result_type
 209     operator()(const second_argument_type& __x)
 210     { return op(value, __x); }
 211
 212     // _GLIBCXX_RESOLVE_LIB_DEFECTS
 213     // 109.  Missing binders for non-const sequence elements
 214     result_type
 215     operator()(second_argument_type& __x) const
 216     { return op(value, __x); }
 217   };
 218
 219 /**
 220   *  @brief Similar to std::binder2nd, but giving the argument types
 221   *  explicitly.
 222   */
 223 template<typename _Operation, typename first_argument_type,
 224          typename second_argument_type, typename result_type>
 225   class binder2nd
 226   : public std::unary_function<first_argument_type, result_type>
 227   {
 228   protected:
 229     _Operation op;
 230     second_argument_type value;
 231
 232   public:
 233     binder2nd(const _Operation& __x,
 234               const second_argument_type& __y)
 235     : op(__x), value(__y) { }
 236
 237     result_type
 238     operator()(const first_argument_type& __x) const
 239     { return op(__x, value); }
 240
 241     // _GLIBCXX_RESOLVE_LIB_DEFECTS
 242     // 109.  Missing binders for non-const sequence elements
 243     result_type
 244     operator()(first_argument_type& __x)
 245     { return op(__x, value); }
 246   };
 247
 248 /** @brief Similar to std::equal_to, but allows two different types. */
 249 template<typename T1, typename T2>
 250   struct equal_to : std::binary_function<T1, T2, bool>
 251   {
 252     bool operator()(const T1& t1, const T2& t2) const
 253     { return t1 == t2; }
 254   };
 255
 256 /** @brief Similar to std::less, but allows two different types. */
 257 template<typename T1, typename T2>
 258   struct less : std::binary_function<T1, T2, bool>
 259   {
 260     bool
 261     operator()(const T1& t1, const T2& t2) const
 262     { return t1 < t2; }
 263
 264     bool
 265     operator()(const T2& t2, const T1& t1) const
 266     { return t2 < t1; }
 267   };
 268
 269 // Partial specialization for one type. Same as std::less.
 270 template<typename _Tp>
 271 struct less<_Tp, _Tp> : public std::binary_function<_Tp, _Tp, bool>
 272   {
 273     bool
 274     operator()(const _Tp& __x, const _Tp& __y) const
 275     { return __x < __y; }
 276   };
 277
 278
 279   /** @brief Similar to std::plus, but allows two different types. */
 280 template<typename _Tp1, typename _Tp2>
 281   struct plus : public std::binary_function<_Tp1, _Tp2, _Tp1>
 282   {
 283     typedef __typeof__(*static_cast<_Tp1*>(NULL)
 284                        + *static_cast<_Tp2*>(NULL)) result;
 285
 286     result
 287     operator()(const _Tp1& __x, const _Tp2& __y) const
 288     { return __x + __y; }
 289   };
 290
 291 // Partial specialization for one type. Same as std::plus.
 292 template<typename _Tp>
 293   struct plus<_Tp, _Tp> : public std::binary_function<_Tp, _Tp, _Tp>
 294   {
 295     typedef __typeof__(*static_cast<_Tp*>(NULL)
 296                        + *static_cast<_Tp*>(NULL)) result;
 297
 298     result
 299     operator()(const _Tp& __x, const _Tp& __y) const
 300     { return __x + __y; }
 301   };
 302
 303
 304 /** @brief Similar to std::multiplies, but allows two different types. */
 305 template<typename _Tp1, typename _Tp2>
 306   struct multiplies : public std::binary_function<_Tp1, _Tp2, _Tp1>
 307   {
 308     typedef __typeof__(*static_cast<_Tp1*>(NULL)
 309                        * *static_cast<_Tp2*>(NULL)) result;
 310
 311     result
 312     operator()(const _Tp1& __x, const _Tp2& __y) const
 313     { return __x * __y; }
 314   };
 315
 316 // Partial specialization for one type. Same as std::multiplies.
 317 template<typename _Tp>
 318   struct multiplies<_Tp, _Tp> : public std::binary_function<_Tp, _Tp, _Tp>
 319   {
 320     typedef __typeof__(*static_cast<_Tp*>(NULL)
 321                        * *static_cast<_Tp*>(NULL)) result;
 322
 323     result
 324     operator()(const _Tp& __x, const _Tp& __y) const
 325     { return __x * __y; }
 326   };
 327
 328
 329 template<typename T, typename _DifferenceTp>
 330   class pseudo_sequence;
 331
 332 /** @brief Iterator associated with __gnu_parallel::pseudo_sequence.
 333   *  If features the usual random-access iterator functionality.
 334   *  @param T Sequence value type.
 335   *  @param difference_type Sequence difference type.
 336   */
 337 template<typename T, typename _DifferenceTp>
 338   class pseudo_sequence_iterator
 339   {
 340   public:
 341     typedef _DifferenceTp difference_type;
 342
 343   private:
 344     typedef pseudo_sequence_iterator<T, _DifferenceTp> type;
 345
 346     const T& val;
 347     difference_type pos;
 348
 349   public:
 350     pseudo_sequence_iterator(const T& val, difference_type pos)
 351     : val(val), pos(pos) { }
 352
 353     // Pre-increment operator.
 354     type&
 355     operator++()
 356     {
 357       ++pos;
 358       return *this;
 359     }
 360
 361     // Post-increment operator.
 362     const type
 363     operator++(int)
 364     { return type(pos++); }
 365
 366     const T&
 367     operator*() const
 368     { return val; }
 369
 370     const T&
 371     operator[](difference_type) const
 372     { return val; }
 373
 374     bool
 375     operator==(const type& i2)
 376     { return pos == i2.pos; }
 377
 378     difference_type
 379     operator!=(const type& i2)
 380     { return pos != i2.pos; }
 381
 382     difference_type
 383     operator-(const type& i2)
 384     { return pos - i2.pos; }
 385   };
 386
 387 /** @brief Sequence that conceptually consists of multiple copies of
 388     the same element.
 389   *  The copies are not stored explicitly, of course.
 390   *  @param T Sequence value type.
 391   *  @param difference_type Sequence difference type.
 392   */
 393 template<typename T, typename _DifferenceTp>
 394   class pseudo_sequence
 395   {
 396     typedef pseudo_sequence<T, _DifferenceTp> type;
 397
 398   public:
 399     typedef _DifferenceTp difference_type;
 400
 401     // Better case down to uint64, than up to _DifferenceTp.
 402     typedef pseudo_sequence_iterator<T, uint64> iterator;
 403
 404     /** @brief Constructor.
 405       *  @param val Element of the sequence.
 406       *  @param count Number of (virtual) copies.
 407       */
 408     pseudo_sequence(const T& val, difference_type count)
 409     : val(val), count(count)  { }
 410
 411     /** @brief Begin iterator. */
 412     iterator
 413     begin() const
 414     { return iterator(val, 0); }
 415
 416     /** @brief End iterator. */
 417     iterator
 418     end() const
 419     { return iterator(val, count); }
 420
 421   private:
 422     const T& val;
 423     difference_type count;
 424   };
 425
 426 /** @brief Functor that does nothing */
 427 template<typename _ValueTp>
 428   class void_functor
 429   {
 430     inline void
 431     operator()(const _ValueTp& v) const { }
 432   };
 433
 434 /** @brief Compute the median of three referenced elements,
 435     according to @c comp.
 436   *  @param a First iterator.
 437   *  @param b Second iterator.
 438   *  @param c Third iterator.
 439   *  @param comp Comparator.
 440   */
 441 template<typename RandomAccessIterator, typename Comparator>
 442   RandomAccessIterator
 443   median_of_three_iterators(RandomAccessIterator a, RandomAccessIterator b,
 444                             RandomAccessIterator c, Comparator& comp)
 445   {
 446     if (comp(*a, *b))
 447       if (comp(*b, *c))
 448         return b;
 449       else
 450         if (comp(*a, *c))
 451           return c;
 452         else
 453           return a;
 454     else
 455       {
 456         // Just swap a and b.
 457         if (comp(*a, *c))
 458           return a;
 459         else
 460           if (comp(*b, *c))
 461             return c;
 462           else
 463             return b;
 464       }
 465   }
 466
 467 #define _GLIBCXX_PARALLEL_ASSERT(_Condition) __glibcxx_assert(_Condition)
 468
 469 } //namespace __gnu_parallel
 470
 471 #endif /* _GLIBCXX_PARALLEL_BASE_H */