2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
6 Source code repo: http://github.com/khizmax/libcds/
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31 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
32 #define CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
34 #include <cds/intrusive/details/michael_set_base.h>
36 namespace cds { namespace intrusive {
38 /// Michael's hash set, \ref cds_urcu_desc "RCU" specialization
39 /** @ingroup cds_intrusive_map
40 \anchor cds_intrusive_MichaelHashSet_rcu
43 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
45 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
46 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
47 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
48 However, each bucket may contain unbounded number of items.
50 Template parameters are:
51 - \p RCU - one of \ref cds_urcu_gc "RCU type"
52 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList.
53 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
54 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
56 - \p Traits - type traits, default is \p michael_set::traits.
57 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
60 Before including <tt><cds/intrusive/michael_set_rcu.h></tt> you should include appropriate RCU header file,
61 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
62 For example, for \ref cds_urcu_general_buffered_gc "general-purpose buffered RCU" you should include:
64 #include <cds/urcu/general_buffered.h>
65 #include <cds/intrusive/michael_list_rcu.h>
66 #include <cds/intrusive/michael_set_rcu.h>
69 // Hash functor for struct Foo
71 size_t operator()( Foo const& foo ) const { return ... }
74 // Now, you can declare Michael's list for type Foo and default traits:
75 typedef cds::intrusive::MichaelList<cds::urcu::gc< general_buffered<> >, Foo > rcu_michael_list;
77 // Declare Michael's set with MichaelList as bucket type
78 typedef cds::intrusive::MichaelSet<
79 cds::urcu::gc< general_buffered<> >,
81 cds::intrusive::michael_set::make_traits<
82 cds::opt::::hash< foo_hash >
86 // Declares hash set for 1000000 items with load factor 2
87 rcu_michael_set theSet( 1000000, 2 );
89 // Now you can use theSet object in many threads without any synchronization.
95 #ifdef CDS_DOXYGEN_INVOKED
96 class Traits = michael_set::traits
101 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
104 typedef cds::urcu::gc< RCU > gc; ///< RCU schema
105 typedef OrderedList ordered_list; ///< type of ordered list used as a bucket implementation
106 typedef Traits traits; ///< Set traits
108 typedef typename ordered_list::value_type value_type; ///< type of value stored in the list
109 typedef typename ordered_list::key_comparator key_comparator; ///< key comparing functor
110 typedef typename ordered_list::disposer disposer; ///< Node disposer functor
111 typedef typename ordered_list::stat stat; ///< Internal statistics
113 /// Hash functor for \ref value_type and all its derivatives that you use
114 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
115 typedef typename traits::item_counter item_counter; ///< Item counter type
116 typedef typename traits::allocator allocator; ///< Bucket table allocator
118 typedef typename ordered_list::rcu_lock rcu_lock; ///< RCU scoped lock
119 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
120 static CDS_CONSTEXPR const bool c_bExtractLockExternal = ordered_list::c_bExtractLockExternal;
122 // GC and OrderedList::gc must be the same
123 static_assert(std::is_same<gc, typename ordered_list::gc>::value, "GC and OrderedList::gc must be the same");
125 // atomicity::empty_item_counter is not allowed as a item counter
126 static_assert(!std::is_same<item_counter, atomicity::empty_item_counter>::value,
127 "atomicity::empty_item_counter is not allowed as a item counter");
131 typedef typename ordered_list::template select_stat_wrapper< typename ordered_list::stat > bucket_stat;
133 typedef typename ordered_list::template rebind_traits<
134 cds::opt::item_counter< cds::atomicity::empty_item_counter >
135 , cds::opt::stat< typename bucket_stat::wrapped_stat >
136 >::type internal_bucket_type;
138 typedef typename allocator::template rebind< internal_bucket_type >::other bucket_table_allocator;
142 typedef typename internal_bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
143 typedef typename internal_bucket_type::raw_ptr raw_ptr; ///< Return type of \p get() member function and its derivatives
147 hash m_HashFunctor; ///< Hash functor
148 size_t const m_nHashBitmask;
149 internal_bucket_type* m_Buckets; ///< bucket table
150 item_counter m_ItemCounter; ///< Item counter
151 typename bucket_stat::stat m_Stat; ///< Internal statistics
155 ///@name Forward iterators (thread-safe under RCU lock)
159 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
160 - it has no post-increment operator
161 - it iterates items in unordered fashion
163 You may safely use iterators in multi-threaded environment only under RCU lock.
164 Otherwise, a crash is possible if another thread deletes the element the iterator points to.
166 The iterator interface:
170 // Default constructor
174 iterator( iterator const& src );
176 // Dereference operator
177 value_type * operator ->() const;
179 // Dereference operator
180 value_type& operator *() const;
182 // Preincrement operator
183 iterator& operator ++();
185 // Assignment operator
186 iterator& operator = (iterator const& src);
188 // Equality operators
189 bool operator ==(iterator const& i ) const;
190 bool operator !=(iterator const& i ) const;
194 typedef michael_set::details::iterator< internal_bucket_type, false > iterator;
196 /// Const forward iterator
198 For iterator's features and requirements see \ref iterator
200 typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator;
202 /// Returns a forward iterator addressing the first element in a set
204 For empty set \code begin() == end() \endcode
208 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
211 /// Returns an iterator that addresses the location succeeding the last element in a set
213 Do not use the value returned by <tt>end</tt> function to access any item.
214 The returned value can be used only to control reaching the end of the set.
215 For empty set \code begin() == end() \endcode
219 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
222 /// Returns a forward const iterator addressing the first element in a set
223 const_iterator begin() const
228 /// Returns a forward const iterator addressing the first element in a set
229 const_iterator cbegin() const
231 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
234 /// Returns an const iterator that addresses the location succeeding the last element in a set
235 const_iterator end() const
240 /// Returns an const iterator that addresses the location succeeding the last element in a set
241 const_iterator cend() const
243 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
248 /// Initialize hash set
250 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
251 At construction time you should pass estimated maximum item count and a load factor.
252 The load factor is average size of one bucket - a small number between 1 and 10.
253 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
254 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
257 size_t nMaxItemCount, ///< estimation of max item count in the hash set
258 size_t nLoadFactor ///< load factor: average size of the bucket
259 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
260 , m_Buckets( bucket_table_allocator().allocate( bucket_count() ) )
262 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
263 construct_bucket<bucket_stat>( it );
266 /// Clear hash set and destroy it
271 for ( auto it = m_Buckets, itEnd = m_Buckets + bucket_count(); it != itEnd; ++it )
272 it->~internal_bucket_type();
273 bucket_table_allocator().deallocate( m_Buckets, bucket_count() );
278 The function inserts \p val in the set if it does not contain
279 an item with key equal to \p val.
281 Returns \p true if \p val is placed into the set, \p false otherwise.
283 bool insert( value_type& val )
285 bool bRet = bucket( val ).insert( val );
293 This function is intended for derived non-intrusive containers.
295 The function allows to split creating of new item into two part:
296 - create item with key only
297 - insert new item into the set
298 - if inserting is success, calls \p f functor to initialize value-field of \p val.
300 The functor signature is:
302 void func( value_type& val );
304 where \p val is the item inserted.
305 The user-defined functor is called only if the inserting is success.
307 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
308 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
311 template <typename Func>
312 bool insert( value_type& val, Func f )
314 bool bRet = bucket( val ).insert( val, f );
320 /// Updates the element
322 The operation performs inserting or changing data with lock-free manner.
324 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
325 Otherwise, the functor \p func is called with item found.
326 The functor signature is:
329 void operator()( bool bNew, value_type& item, value_type& val );
333 - \p bNew - \p true if the item has been inserted, \p false otherwise
334 - \p item - item of the set
335 - \p val - argument \p val passed into the \p %update() function
336 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
337 refers to the same thing.
339 The functor may change non-key fields of the \p item.
341 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successful,
342 \p second is \p true if new item has been added or \p false if the item with \p key
343 already is in the set.
345 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
346 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
349 template <typename Func>
350 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
352 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
358 template <typename Func>
359 CDS_DEPRECATED("ensure() is deprecated, use update()")
360 std::pair<bool, bool> ensure( value_type& val, Func func )
362 return update( val, func, true );
366 /// Unlinks the item \p val from the set
368 The function searches the item \p val in the set and unlink it from the set
369 if it is found and is equal to \p val.
371 The function returns \p true if success and \p false otherwise.
373 bool unlink( value_type& val )
375 bool bRet = bucket( val ).unlink( val );
381 /// Deletes the item from the set
382 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
383 The function searches an item with key equal to \p key in the set,
384 unlinks it from the set, and returns \p true.
385 If the item with key equal to \p key is not found the function return \p false.
387 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
389 template <typename Q>
390 bool erase( Q const& key )
392 if ( bucket( key ).erase( key )) {
399 /// Deletes the item from the set using \p pred predicate for searching
401 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
402 but \p pred is used for key comparing.
403 \p Less functor has the interface like \p std::less.
404 \p pred must imply the same element order as the comparator used for building the set.
406 template <typename Q, typename Less>
407 bool erase_with( Q const& key, Less pred )
409 if ( bucket( key ).erase_with( key, pred )) {
416 /// Deletes the item from the set
417 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
418 The function searches an item with key equal to \p key in the set,
419 call \p f functor with item found, and unlinks it from the set.
420 The \ref disposer specified in \p OrderedList class template parameter is called
421 by garbage collector \p GC asynchronously.
423 The \p Func interface is
426 void operator()( value_type const& item );
430 If the item with key equal to \p key is not found the function return \p false.
432 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
434 template <typename Q, typename Func>
435 bool erase( const Q& key, Func f )
437 if ( bucket( key ).erase( key, f )) {
444 /// Deletes the item from the set using \p pred predicate for searching
446 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
447 but \p pred is used for key comparing.
448 \p Less functor has the interface like \p std::less.
449 \p pred must imply the same element order as the comparator used for building the set.
451 template <typename Q, typename Less, typename Func>
452 bool erase_with( const Q& key, Less pred, Func f )
454 if ( bucket( key ).erase_with( key, pred, f )) {
461 /// Extracts an item from the set
462 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
463 The function searches an item with key equal to \p key in the set,
464 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
465 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
467 Depends on \p ordered_list you should or should not lock RCU before calling of this function:
468 - for the set based on \ref cds_intrusive_MichaelList_rcu "MichaelList" RCU should not be locked
469 - for the set based on \ref cds_intrusive_LazyList_rcu "LazyList" RCU should be locked
471 See ordered list implementation for details.
474 #include <cds/urcu/general_buffered.h>
475 #include <cds/intrusive/michael_list_rcu.h>
476 #include <cds/intrusive/michael_set_rcu.h>
478 typedef cds::urcu::gc< general_buffered<> > rcu;
479 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
480 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
482 rcu_michael_set theSet;
485 typename rcu_michael_set::exempt_ptr p;
487 // For MichaelList we should not lock RCU
489 // Now, you can apply extract function
490 // Note that you must not delete the item found inside the RCU lock
491 p = theSet.extract( 10 )
493 // do something with p
497 // We may safely release p here
498 // release() passes the pointer to RCU reclamation cycle:
499 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
503 template <typename Q>
504 exempt_ptr extract( Q const& key )
506 exempt_ptr p( bucket( key ).extract( key ) );
512 /// Extracts an item from the set using \p pred predicate for searching
514 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
515 \p Less functor has the interface like \p std::less.
516 \p pred must imply the same element order as the comparator used for building the set.
518 template <typename Q, typename Less>
519 exempt_ptr extract_with( Q const& key, Less pred )
521 exempt_ptr p( bucket( key ).extract_with( key, pred ) );
527 /// Checks whether the set contains \p key
530 The function searches the item with key equal to \p key
531 and returns \p true if the key is found, and \p false otherwise.
533 Note the hash functor specified for class \p Traits template parameter
534 should accept a parameter of type \p Q that can be not the same as \p value_type.
536 template <typename Q>
537 bool contains( Q const& key )
539 return bucket( key ).contains( key );
542 template <typename Q>
543 CDS_DEPRECATED("use contains()")
544 bool find( Q const& key )
546 return contains( key );
550 /// Checks whether the set contains \p key using \p pred predicate for searching
552 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
553 \p Less functor has the interface like \p std::less.
554 \p Less must imply the same element order as the comparator used for building the set.
556 template <typename Q, typename Less>
557 bool contains( Q const& key, Less pred )
559 return bucket( key ).contains( key, pred );
562 template <typename Q, typename Less>
563 CDS_DEPRECATED("use contains()")
564 bool find_with( Q const& key, Less pred )
566 return contains( key, pred );
570 /// Find the key \p key
571 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
572 The function searches the item with key equal to \p key and calls the functor \p f for item found.
573 The interface of \p Func functor is:
576 void operator()( value_type& item, Q& key );
579 where \p item is the item found, \p key is the <tt>find</tt> function argument.
581 The functor can change non-key fields of \p item.
582 The functor does not serialize simultaneous access to the set \p item. If such access is
583 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
585 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
586 can modify both arguments.
588 Note the hash functor specified for class \p Traits template parameter
589 should accept a parameter of type \p Q that can be not the same as \p value_type.
591 The function returns \p true if \p key is found, \p false otherwise.
593 template <typename Q, typename Func>
594 bool find( Q& key, Func f )
596 return bucket( key ).find( key, f );
599 template <typename Q, typename Func>
600 bool find( Q const& key, Func f )
602 return bucket( key ).find( key, f );
606 /// Finds the key \p key using \p pred predicate for searching
608 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
609 but \p pred is used for key comparing.
610 \p Less functor has the interface like \p std::less.
611 \p pred must imply the same element order as the comparator used for building the set.
613 template <typename Q, typename Less, typename Func>
614 bool find_with( Q& key, Less pred, Func f )
616 return bucket( key ).find_with( key, pred, f );
619 template <typename Q, typename Less, typename Func>
620 bool find_with( Q const& key, Less pred, Func f )
622 return bucket( key ).find_with( key, pred, f );
626 /// Finds the key \p key and return the item found
627 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
628 The function searches the item with key equal to \p key and returns the pointer to item found.
629 If \p key is not found it returns \p nullptr.
630 Note the type of returned value depends on underlying \p ordered_list.
631 For details, see documentation of ordered list you use.
633 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
635 RCU should be locked before call of this function.
636 Returned item is valid only while RCU is locked:
638 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
641 // Result of get() call
642 typename hash_set::raw_ptr ptr;
645 hash_set::rcu_lock lock;
647 ptr = theSet.get( 5 );
652 // Unlock RCU by rcu_lock destructor
653 // ptr can be reclaimed by disposer at any time after RCU has been unlocked
657 template <typename Q>
658 raw_ptr get( Q const& key )
660 return bucket( key ).get( key );
663 /// Finds the key \p key and return the item found
665 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
666 but \p pred is used for comparing the keys.
668 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
670 \p pred must imply the same element order as the comparator used for building the set.
672 template <typename Q, typename Less>
673 raw_ptr get_with( Q const& key, Less pred )
675 return bucket( key ).get_with( key, pred );
678 /// Clears the set (non-atomic)
680 The function unlink all items from the set.
681 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
682 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
683 <tt> empty() </tt> may return \p true but the set may contain item(s).
684 Therefore, \p clear may be used only for debugging purposes.
686 For each item the \p disposer is called after unlinking.
690 for ( size_t i = 0; i < bucket_count(); ++i )
691 m_Buckets[i].clear();
692 m_ItemCounter.reset();
696 /// Checks if the set is empty
698 Emptiness is checked by item counting: if item count is zero then the set is empty.
699 Thus, the correct item counting feature is an important part of Michael's set implementation.
706 /// Returns item count in the set
709 return m_ItemCounter;
712 /// Returns the size of hash table
714 Since %MichaelHashSet cannot dynamically extend the hash table size,
715 the value returned is an constant depending on object initialization parameters;
716 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
718 size_t bucket_count() const
720 return m_nHashBitmask + 1;
723 /// Returns const reference to internal statistics
724 stat const& statistics() const
731 template <typename Stat>
732 typename std::enable_if< Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
734 new (bucket) internal_bucket_type;
737 template <typename Stat>
738 typename std::enable_if< !Stat::empty >::type construct_bucket( internal_bucket_type * bucket )
740 new (bucket) internal_bucket_type( m_Stat );
743 /// Calculates hash value of \p key
744 template <typename Q>
745 size_t hash_value( Q const& key ) const
747 return m_HashFunctor( key ) & m_nHashBitmask;
750 /// Returns the bucket (ordered list) for \p key
751 template <typename Q>
752 internal_bucket_type& bucket( Q const& key )
754 return m_Buckets[hash_value( key )];
756 template <typename Q>
757 internal_bucket_type const& bucket( Q const& key ) const
759 return m_Buckets[hash_value( key )];
764 }} // namespace cds::intrusive
766 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H