libstdc++
parallel/base.h
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00001 // -*- C++ -*-
00002 
00003 // Copyright (C) 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the terms
00007 // of the GNU General Public License as published by the Free Software
00008 // Foundation; either version 3, or (at your option) any later
00009 // version.
00010 
00011 // This library is distributed in the hope that it will be useful, but
00012 // WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014 // General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file parallel/base.h
00026  *  @brief Sequential helper functions.
00027  *  This file is a GNU parallel extension to the Standard C++ Library.
00028  */
00029 
00030 // Written by Johannes Singler.
00031 
00032 #ifndef _GLIBCXX_PARALLEL_BASE_H
00033 #define _GLIBCXX_PARALLEL_BASE_H 1
00034 
00035 #include <bits/c++config.h>
00036 #include <bits/stl_function.h>
00037 #include <omp.h>
00038 #include <parallel/features.h>
00039 #include <parallel/basic_iterator.h>
00040 #include <parallel/parallel.h>
00041 
00042 // Parallel mode namespaces.
00043 
00044 /**
00045  * @namespace std::__parallel
00046  * @brief GNU parallel code, replaces standard behavior with parallel behavior.
00047  */
00048 namespace std _GLIBCXX_VISIBILITY(default) 
00049 { 
00050   namespace __parallel { } 
00051 }
00052 
00053 /**
00054  * @namespace __gnu_parallel
00055  * @brief GNU parallel code for public use.
00056  */
00057 namespace __gnu_parallel
00058 {
00059   // Import all the parallel versions of components in namespace std.
00060   using namespace std::__parallel;
00061 }
00062 
00063 /**
00064  * @namespace __gnu_sequential
00065  * @brief GNU sequential classes for public use.
00066  */
00067 namespace __gnu_sequential 
00068 { 
00069   // Import whatever is the serial version.
00070 #ifdef _GLIBCXX_PARALLEL
00071   using namespace std::_GLIBCXX_STD_A;
00072 #else
00073   using namespace std;
00074 #endif   
00075 }
00076 
00077 
00078 namespace __gnu_parallel
00079 {
00080   // NB: Including this file cannot produce (unresolved) symbols from
00081   // the OpenMP runtime unless the parallel mode is actually invoked
00082   // and active, which imples that the OpenMP runtime is actually
00083   // going to be linked in.
00084   inline _ThreadIndex
00085   __get_max_threads() 
00086   { 
00087     _ThreadIndex __i = omp_get_max_threads();
00088     return __i > 1 ? __i : 1; 
00089   }
00090 
00091 
00092   inline bool 
00093   __is_parallel(const _Parallelism __p) { return __p != sequential; }
00094 
00095 
00096   /** @brief Calculates the rounded-down logarithm of @c __n for base 2.
00097    *  @param __n Argument.
00098    *  @return Returns 0 for any argument <1.
00099    */
00100   template<typename _Size>
00101     inline _Size
00102     __rd_log2(_Size __n)
00103     {
00104       _Size __k;
00105       for (__k = 0; __n > 1; __n >>= 1)
00106         ++__k;
00107       return __k;
00108     }
00109 
00110   /** @brief Encode two integers into one gnu_parallel::_CASable.
00111    *  @param __a First integer, to be encoded in the most-significant @c
00112    *  _CASable_bits/2 bits.
00113    *  @param __b Second integer, to be encoded in the least-significant
00114    *  @c _CASable_bits/2 bits.
00115    *  @return value encoding @c __a and @c __b.
00116    *  @see __decode2
00117    */
00118   inline _CASable
00119   __encode2(int __a, int __b)     //must all be non-negative, actually
00120   {
00121     return (((_CASable)__a) << (_CASable_bits / 2)) | (((_CASable)__b) << 0);
00122   }
00123 
00124   /** @brief Decode two integers from one gnu_parallel::_CASable.
00125    *  @param __x __gnu_parallel::_CASable to decode integers from.
00126    *  @param __a First integer, to be decoded from the most-significant
00127    *  @c _CASable_bits/2 bits of @c __x.
00128    *  @param __b Second integer, to be encoded in the least-significant
00129    *  @c _CASable_bits/2 bits of @c __x.
00130    *  @see __encode2
00131    */
00132   inline void
00133   __decode2(_CASable __x, int& __a, int& __b)
00134   {
00135     __a = (int)((__x >> (_CASable_bits / 2)) & _CASable_mask);
00136     __b = (int)((__x >>               0 ) & _CASable_mask);
00137   }
00138 
00139   //needed for parallel "numeric", even if "algorithm" not included
00140 
00141   /** @brief Equivalent to std::min. */
00142   template<typename _Tp>
00143     inline const _Tp&
00144     min(const _Tp& __a, const _Tp& __b)
00145     { return (__a < __b) ? __a : __b; }
00146 
00147   /** @brief Equivalent to std::max. */
00148   template<typename _Tp>
00149     inline const _Tp&
00150     max(const _Tp& __a, const _Tp& __b)
00151     { return (__a > __b) ? __a : __b; }
00152 
00153   /** @brief Constructs predicate for equality from strict weak
00154    *  ordering predicate
00155    */
00156   template<typename _T1, typename _T2, typename _Compare>
00157     class _EqualFromLess : public std::binary_function<_T1, _T2, bool>
00158     {
00159     private:
00160       _Compare& _M_comp;
00161 
00162     public:
00163       _EqualFromLess(_Compare& __comp) : _M_comp(__comp) { }
00164 
00165       bool operator()(const _T1& __a, const _T2& __b)
00166       { return !_M_comp(__a, __b) && !_M_comp(__b, __a); }
00167     };
00168 
00169 
00170   /** @brief Similar to std::unary_negate,
00171    *  but giving the argument types explicitly. */
00172   template<typename _Predicate, typename argument_type>
00173     class __unary_negate
00174     : public std::unary_function<argument_type, bool>
00175     {
00176     protected:
00177       _Predicate _M_pred;
00178 
00179     public:
00180       explicit
00181       __unary_negate(const _Predicate& __x) : _M_pred(__x) { }
00182 
00183       bool
00184       operator()(const argument_type& __x)
00185       { return !_M_pred(__x); }
00186     };
00187 
00188   /** @brief Similar to std::binder1st,
00189    *  but giving the argument types explicitly. */
00190   template<typename _Operation, typename _FirstArgumentType,
00191        typename _SecondArgumentType, typename _ResultType>
00192     class __binder1st
00193     : public std::unary_function<_SecondArgumentType, _ResultType>
00194     {
00195     protected:
00196       _Operation _M_op;
00197       _FirstArgumentType _M_value;
00198 
00199     public:
00200       __binder1st(const _Operation& __x, const _FirstArgumentType& __y)
00201       : _M_op(__x), _M_value(__y) { }
00202 
00203       _ResultType
00204       operator()(const _SecondArgumentType& __x)
00205       { return _M_op(_M_value, __x); }
00206 
00207       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00208       // 109.  Missing binders for non-const sequence elements
00209       _ResultType
00210       operator()(_SecondArgumentType& __x) const
00211       { return _M_op(_M_value, __x); }
00212     };
00213 
00214   /**
00215    *  @brief Similar to std::binder2nd, but giving the argument types
00216    *  explicitly.
00217    */
00218   template<typename _Operation, typename _FirstArgumentType,
00219        typename _SecondArgumentType, typename _ResultType>
00220     class __binder2nd
00221     : public std::unary_function<_FirstArgumentType, _ResultType>
00222     {
00223     protected:
00224       _Operation _M_op;
00225       _SecondArgumentType _M_value;
00226 
00227     public:
00228       __binder2nd(const _Operation& __x, const _SecondArgumentType& __y)
00229       : _M_op(__x), _M_value(__y) { }
00230 
00231       _ResultType
00232       operator()(const _FirstArgumentType& __x) const
00233       { return _M_op(__x, _M_value); }
00234 
00235       // _GLIBCXX_RESOLVE_LIB_DEFECTS
00236       // 109.  Missing binders for non-const sequence elements
00237       _ResultType
00238       operator()(_FirstArgumentType& __x)
00239       { return _M_op(__x, _M_value); }
00240     };
00241 
00242   /** @brief Similar to std::equal_to, but allows two different types. */
00243   template<typename _T1, typename _T2>
00244     struct _EqualTo : std::binary_function<_T1, _T2, bool>
00245     {
00246       bool operator()(const _T1& __t1, const _T2& __t2) const
00247       { return __t1 == __t2; }
00248     };
00249 
00250   /** @brief Similar to std::less, but allows two different types. */
00251   template<typename _T1, typename _T2>
00252     struct _Less : std::binary_function<_T1, _T2, bool>
00253     {
00254       bool
00255       operator()(const _T1& __t1, const _T2& __t2) const
00256       { return __t1 < __t2; }
00257 
00258       bool
00259       operator()(const _T2& __t2, const _T1& __t1) const
00260       { return __t2 < __t1; }
00261     };
00262 
00263   // Partial specialization for one type. Same as std::less.
00264   template<typename _Tp>
00265     struct _Less<_Tp, _Tp>
00266     : public std::less<_Tp> { };
00267 
00268   /** @brief Similar to std::plus, but allows two different types. */
00269   template<typename _Tp1, typename _Tp2, typename _Result
00270        = __typeof__(*static_cast<_Tp1*>(0)
00271             + *static_cast<_Tp2*>(0))>
00272     struct _Plus : public std::binary_function<_Tp1, _Tp2, _Result>
00273     {
00274       _Result
00275       operator()(const _Tp1& __x, const _Tp2& __y) const
00276       { return __x + __y; }
00277     };
00278 
00279   // Partial specialization for one type. Same as std::plus.
00280   template<typename _Tp>
00281     struct _Plus<_Tp, _Tp, _Tp>
00282     : public std::plus<_Tp> { };
00283 
00284   /** @brief Similar to std::multiplies, but allows two different types. */
00285   template<typename _Tp1, typename _Tp2, typename _Result
00286        = __typeof__(*static_cast<_Tp1*>(0)
00287             * *static_cast<_Tp2*>(0))>
00288     struct _Multiplies : public std::binary_function<_Tp1, _Tp2, _Result>
00289     {
00290       _Result
00291       operator()(const _Tp1& __x, const _Tp2& __y) const
00292       { return __x * __y; }
00293     };
00294 
00295   // Partial specialization for one type. Same as std::multiplies.
00296   template<typename _Tp>
00297     struct _Multiplies<_Tp, _Tp, _Tp>
00298     : public std::multiplies<_Tp> { };
00299 
00300   /** @brief _Iterator associated with __gnu_parallel::_PseudoSequence.
00301    *  If features the usual random-access iterator functionality.
00302    *  @param _Tp Sequence _M_value type.
00303    *  @param _DifferenceTp Sequence difference type.
00304    */
00305   template<typename _Tp, typename _DifferenceTp>
00306     class _PseudoSequenceIterator
00307     {
00308     public:
00309       typedef _DifferenceTp _DifferenceType;
00310 
00311       _PseudoSequenceIterator(const _Tp& __val, _DifferenceType __pos)
00312       : _M_val(__val), _M_pos(__pos) { }
00313 
00314       // Pre-increment operator.
00315       _PseudoSequenceIterator&
00316       operator++()
00317       {
00318     ++_M_pos;
00319     return *this;
00320       }
00321 
00322       // Post-increment operator.
00323       _PseudoSequenceIterator
00324       operator++(int)
00325       { return _PseudoSequenceIterator(_M_pos++); }
00326 
00327       const _Tp&
00328       operator*() const
00329       { return _M_val; }
00330 
00331       const _Tp&
00332       operator[](_DifferenceType) const
00333       { return _M_val; }
00334 
00335       bool
00336       operator==(const _PseudoSequenceIterator& __i2)
00337       { return _M_pos == __i2._M_pos; }
00338 
00339       bool
00340       operator!=(const _PseudoSequenceIterator& __i2)
00341       { return _M_pos != __i2._M_pos; }
00342 
00343       _DifferenceType
00344       operator-(const _PseudoSequenceIterator& __i2)
00345       { return _M_pos - __i2._M_pos; }
00346 
00347     private:
00348       const _Tp& _M_val;
00349       _DifferenceType _M_pos;
00350     };
00351 
00352   /** @brief Sequence that conceptually consists of multiple copies of
00353       the same element.
00354       *  The copies are not stored explicitly, of course.
00355       *  @param _Tp Sequence _M_value type.
00356       *  @param _DifferenceTp Sequence difference type.
00357       */
00358   template<typename _Tp, typename _DifferenceTp>
00359     class _PseudoSequence
00360     {
00361     public:
00362       typedef _DifferenceTp _DifferenceType;
00363 
00364       // Better cast down to uint64_t, than up to _DifferenceTp.
00365       typedef _PseudoSequenceIterator<_Tp, uint64_t> iterator;
00366 
00367       /** @brief Constructor.
00368        *  @param _M_val Element of the sequence.
00369        *  @param __count Number of (virtual) copies.
00370        */
00371       _PseudoSequence(const _Tp& __val, _DifferenceType __count)
00372       : _M_val(__val), _M_count(__count)  { }
00373 
00374       /** @brief Begin iterator. */
00375       iterator
00376       begin() const
00377       { return iterator(_M_val, 0); }
00378 
00379       /** @brief End iterator. */
00380       iterator
00381       end() const
00382       { return iterator(_M_val, _M_count); }
00383 
00384     private:
00385       const _Tp& _M_val;
00386       _DifferenceType _M_count;
00387     };
00388 
00389   /** @brief Compute the median of three referenced elements,
00390       according to @c __comp.
00391       *  @param __a First iterator.
00392       *  @param __b Second iterator.
00393       *  @param __c Third iterator.
00394       *  @param __comp Comparator.
00395       */
00396   template<typename _RAIter, typename _Compare>
00397     _RAIter
00398     __median_of_three_iterators(_RAIter __a, _RAIter __b,
00399                 _RAIter __c, _Compare __comp)
00400     {
00401       if (__comp(*__a, *__b))
00402     if (__comp(*__b, *__c))
00403       return __b;
00404     else
00405       if (__comp(*__a, *__c))
00406         return __c;
00407       else
00408         return __a;
00409       else
00410     {
00411       // Just swap __a and __b.
00412       if (__comp(*__a, *__c))
00413         return __a;
00414       else
00415         if (__comp(*__b, *__c))
00416           return __c;
00417         else
00418           return __b;
00419     }
00420     }
00421 
00422 #define _GLIBCXX_PARALLEL_ASSERT(_Condition) __glibcxx_assert(_Condition)
00423 
00424 } //namespace __gnu_parallel
00425 
00426 #endif /* _GLIBCXX_PARALLEL_BASE_H */