2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
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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>
35 #include <cds/details/allocator.h>
37 namespace cds { namespace intrusive {
39 /// Michael's hash set, \ref cds_urcu_desc "RCU" specialization
40 /** @ingroup cds_intrusive_map
41 \anchor cds_intrusive_MichaelHashSet_rcu
44 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
46 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
47 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
48 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
49 However, each bucket may contain unbounded number of items.
51 Template parameters are:
52 - \p RCU - one of \ref cds_urcu_gc "RCU type"
53 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList.
54 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
55 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
57 - \p Traits - type traits, default is \p michael_set::traits.
58 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
61 Before including <tt><cds/intrusive/michael_set_rcu.h></tt> you should include appropriate RCU header file,
62 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
63 For example, for \ref cds_urcu_general_buffered_gc "general-purpose buffered RCU" you should include:
65 #include <cds/urcu/general_buffered.h>
66 #include <cds/intrusive/michael_list_rcu.h>
67 #include <cds/intrusive/michael_set_rcu.h>
70 // Hash functor for struct Foo
72 size_t operator()( Foo const& foo ) const { return ... }
75 // Now, you can declare Michael's list for type Foo and default traits:
76 typedef cds::intrusive::MichaelList<cds::urcu::gc< general_buffered<> >, Foo > rcu_michael_list;
78 // Declare Michael's set with MichaelList as bucket type
79 typedef cds::intrusive::MichaelSet<
80 cds::urcu::gc< general_buffered<> >,
82 cds::intrusive::michael_set::make_traits<
83 cds::opt::::hash< foo_hash >
87 // Declares hash set for 1000000 items with load factor 2
88 rcu_michael_set theSet( 1000000, 2 );
90 // Now you can use theSet object in many threads without any synchronization.
96 #ifdef CDS_DOXYGEN_INVOKED
97 class Traits = michael_set::traits
102 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
105 typedef cds::urcu::gc< RCU > gc; ///< RCU schema
106 typedef OrderedList bucket_type; ///< type of ordered list used as a bucket implementation
107 typedef Traits traits; ///< Set traits
109 typedef typename bucket_type::value_type value_type ; ///< type of value stored in the list
110 typedef typename bucket_type::key_comparator key_comparator ; ///< key comparing functor
111 typedef typename bucket_type::disposer disposer ; ///< Node disposer functor
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
117 /// Bucket table allocator
118 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
120 typedef typename bucket_type::rcu_lock rcu_lock; ///< RCU scoped lock
121 typedef typename bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
122 typedef typename bucket_type::raw_ptr raw_ptr; ///< Return type of \p get() member function and its derivatives
123 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
124 static CDS_CONSTEXPR const bool c_bExtractLockExternal = bucket_type::c_bExtractLockExternal;
127 item_counter m_ItemCounter; ///< Item counter
128 hash m_HashFunctor; ///< Hash functor
129 bucket_type * m_Buckets; ///< bucket table
133 const size_t m_nHashBitmask;
138 /// Calculates hash value of \p key
139 template <typename Q>
140 size_t hash_value( Q const& key ) const
142 return m_HashFunctor( key ) & m_nHashBitmask;
145 /// Returns the bucket (ordered list) for \p key
146 template <typename Q>
147 bucket_type& bucket( Q const& key )
149 return m_Buckets[ hash_value( key ) ];
151 template <typename Q>
152 bucket_type const& bucket( Q const& key ) const
154 return m_Buckets[ hash_value( key ) ];
159 ///@name Forward iterators (only for debugging purpose)
163 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
164 - it has no post-increment operator
165 - it iterates items in unordered fashion
167 @warning Use this iterator on the concurrent container for debugging purpose only.
169 typedef michael_set::details::iterator< bucket_type, false > iterator;
171 /// Const forward iterator
173 For iterator's features and requirements see \ref iterator
175 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
177 /// Returns a forward iterator addressing the first element in a set
179 For empty set \code begin() == end() \endcode
183 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
186 /// Returns an iterator that addresses the location succeeding the last element in a set
188 Do not use the value returned by <tt>end</tt> function to access any item.
189 The returned value can be used only to control reaching the end of the set.
190 For empty set \code begin() == end() \endcode
194 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
197 /// Returns a forward const iterator addressing the first element in a set
198 const_iterator begin() const
203 /// Returns a forward const iterator addressing the first element in a set
204 const_iterator cbegin() const
206 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
209 /// Returns an const iterator that addresses the location succeeding the last element in a set
210 const_iterator end() const
215 /// Returns an const iterator that addresses the location succeeding the last element in a set
216 const_iterator cend() const
218 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
223 /// Initialize hash set
225 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
226 At construction time you should pass estimated maximum item count and a load factor.
227 The load factor is average size of one bucket - a small number between 1 and 10.
228 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
229 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
232 size_t nMaxItemCount, ///< estimation of max item count in the hash set
233 size_t nLoadFactor ///< load factor: average size of the bucket
234 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
236 // GC and OrderedList::gc must be the same
237 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
239 // atomicity::empty_item_counter is not allowed as a item counter
240 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
241 "atomicity::empty_item_counter is not allowed as a item counter");
243 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
246 /// Clear hash set and destroy it
250 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
255 The function inserts \p val in the set if it does not contain
256 an item with key equal to \p val.
258 Returns \p true if \p val is placed into the set, \p false otherwise.
260 bool insert( value_type& val )
262 bool bRet = bucket( val ).insert( val );
270 This function is intended for derived non-intrusive containers.
272 The function allows to split creating of new item into two part:
273 - create item with key only
274 - insert new item into the set
275 - if inserting is success, calls \p f functor to initialize value-field of \p val.
277 The functor signature is:
279 void func( value_type& val );
281 where \p val is the item inserted.
282 The user-defined functor is called only if the inserting is success.
284 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
285 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
288 template <typename Func>
289 bool insert( value_type& val, Func f )
291 bool bRet = bucket( val ).insert( val, f );
297 /// Updates the element
299 The operation performs inserting or changing data with lock-free manner.
301 If the item \p val not found in the set, then \p val is inserted iff \p bAllowInsert is \p true.
302 Otherwise, the functor \p func is called with item found.
303 The functor signature is:
306 void operator()( bool bNew, value_type& item, value_type& val );
310 - \p bNew - \p true if the item has been inserted, \p false otherwise
311 - \p item - item of the set
312 - \p val - argument \p val passed into the \p %update() function
313 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
314 refers to the same thing.
316 The functor may change non-key fields of the \p item.
318 Returns <tt> std::pair<bool, bool> </tt> where \p first is \p true if operation is successfull,
319 \p second is \p true if new item has been added or \p false if the item with \p key
320 already is in the set.
322 @warning For \ref cds_intrusive_MichaelList_hp "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
323 \ref cds_intrusive_LazyList_hp "LazyList" provides exclusive access to inserted item and does not require any node-level
326 template <typename Func>
327 std::pair<bool, bool> update( value_type& val, Func func, bool bAllowInsert = true )
329 std::pair<bool, bool> bRet = bucket( val ).update( val, func, bAllowInsert );
335 template <typename Func>
336 CDS_DEPRECATED("ensure() is deprecated, use update()")
337 std::pair<bool, bool> ensure( value_type& val, Func func )
339 return update( val, func, true );
343 /// Unlinks the item \p val from the set
345 The function searches the item \p val in the set and unlink it from the set
346 if it is found and is equal to \p val.
348 The function returns \p true if success and \p false otherwise.
350 bool unlink( value_type& val )
352 bool bRet = bucket( val ).unlink( val );
358 /// Deletes the item from the set
359 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
360 The function searches an item with key equal to \p key in the set,
361 unlinks it from the set, and returns \p true.
362 If the item with key equal to \p key is not found the function return \p false.
364 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
366 template <typename Q>
367 bool erase( Q const& key )
369 if ( bucket( key ).erase( key )) {
376 /// Deletes the item from the set using \p pred predicate for searching
378 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
379 but \p pred is used for key comparing.
380 \p Less functor has the interface like \p std::less.
381 \p pred must imply the same element order as the comparator used for building the set.
383 template <typename Q, typename Less>
384 bool erase_with( Q const& key, Less pred )
386 if ( bucket( key ).erase_with( key, pred )) {
393 /// Deletes the item from the set
394 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
395 The function searches an item with key equal to \p key in the set,
396 call \p f functor with item found, and unlinks it from the set.
397 The \ref disposer specified in \p OrderedList class template parameter is called
398 by garbage collector \p GC asynchronously.
400 The \p Func interface is
403 void operator()( value_type const& item );
407 If the item with key equal to \p key is not found the function return \p false.
409 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
411 template <typename Q, typename Func>
412 bool erase( const Q& key, Func f )
414 if ( bucket( key ).erase( key, f )) {
421 /// Deletes the item from the set using \p pred predicate for searching
423 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
424 but \p pred is used for key comparing.
425 \p Less functor has the interface like \p std::less.
426 \p pred must imply the same element order as the comparator used for building the set.
428 template <typename Q, typename Less, typename Func>
429 bool erase_with( const Q& key, Less pred, Func f )
431 if ( bucket( key ).erase_with( key, pred, f )) {
438 /// Extracts an item from the set
439 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
440 The function searches an item with key equal to \p key in the set,
441 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
442 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
444 Depends on \p bucket_type you should or should not lock RCU before calling of this function:
445 - for the set based on \ref cds_intrusive_MichaelList_rcu "MichaelList" RCU should not be locked
446 - for the set based on \ref cds_intrusive_LazyList_rcu "LazyList" RCU should be locked
448 See ordered list implementation for details.
451 #include <cds/urcu/general_buffered.h>
452 #include <cds/intrusive/michael_list_rcu.h>
453 #include <cds/intrusive/michael_set_rcu.h>
455 typedef cds::urcu::gc< general_buffered<> > rcu;
456 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
457 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
459 rcu_michael_set theSet;
462 typename rcu_michael_set::exempt_ptr p;
464 // For MichaelList we should not lock RCU
466 // Now, you can apply extract function
467 // Note that you must not delete the item found inside the RCU lock
468 p = theSet.extract( 10 )
470 // do something with p
474 // We may safely release p here
475 // release() passes the pointer to RCU reclamation cycle:
476 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
480 template <typename Q>
481 exempt_ptr extract( Q const& key )
483 exempt_ptr p( bucket( key ).extract( key ) );
489 /// Extracts an item from the set using \p pred predicate for searching
491 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
492 \p Less functor has the interface like \p std::less.
493 \p pred must imply the same element order as the comparator used for building the set.
495 template <typename Q, typename Less>
496 exempt_ptr extract_with( Q const& key, Less pred )
498 exempt_ptr p( bucket( key ).extract_with( key, pred ) );
504 /// Checks whether the set contains \p key
507 The function searches the item with key equal to \p key
508 and returns \p true if the key is found, and \p false otherwise.
510 Note the hash functor specified for class \p Traits template parameter
511 should accept a parameter of type \p Q that can be not the same as \p value_type.
513 template <typename Q>
514 bool contains( Q const& key )
516 return bucket( key ).contains( key );
519 template <typename Q>
520 CDS_DEPRECATED("use contains()")
521 bool find( Q const& key )
523 return contains( key );
527 /// Checks whether the set contains \p key using \p pred predicate for searching
529 The function is an analog of <tt>contains( key )</tt> but \p pred is used for key comparing.
530 \p Less functor has the interface like \p std::less.
531 \p Less must imply the same element order as the comparator used for building the set.
533 template <typename Q, typename Less>
534 bool contains( Q const& key, Less pred )
536 return bucket( key ).contains( key, pred );
539 template <typename Q, typename Less>
540 CDS_DEPRECATED("use contains()")
541 bool find_with( Q const& key, Less pred )
543 return contains( key, pred );
547 /// Find the key \p key
548 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
549 The function searches the item with key equal to \p key and calls the functor \p f for item found.
550 The interface of \p Func functor is:
553 void operator()( value_type& item, Q& key );
556 where \p item is the item found, \p key is the <tt>find</tt> function argument.
558 The functor can change non-key fields of \p item.
559 The functor does not serialize simultaneous access to the set \p item. If such access is
560 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
562 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
563 can modify both arguments.
565 Note the hash functor specified for class \p Traits template parameter
566 should accept a parameter of type \p Q that can be not the same as \p value_type.
568 The function returns \p true if \p key is found, \p false otherwise.
570 template <typename Q, typename Func>
571 bool find( Q& key, Func f )
573 return bucket( key ).find( key, f );
576 template <typename Q, typename Func>
577 bool find( Q const& key, Func f )
579 return bucket( key ).find( key, f );
583 /// Finds the key \p key using \p pred predicate for searching
585 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
586 but \p pred is used for key comparing.
587 \p Less functor has the interface like \p std::less.
588 \p pred must imply the same element order as the comparator used for building the set.
590 template <typename Q, typename Less, typename Func>
591 bool find_with( Q& key, Less pred, Func f )
593 return bucket( key ).find_with( key, pred, f );
596 template <typename Q, typename Less, typename Func>
597 bool find_with( Q const& key, Less pred, Func f )
599 return bucket( key ).find_with( key, pred, f );
603 /// Finds the key \p key and return the item found
604 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
605 The function searches the item with key equal to \p key and returns the pointer to item found.
606 If \p key is not found it returns \p nullptr.
607 Note the type of returned value depends on underlying \p bucket_type.
608 For details, see documentation of ordered list you use.
610 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
612 RCU should be locked before call of this function.
613 Returned item is valid only while RCU is locked:
615 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
618 // Result of get() call
619 typename hash_set::raw_ptr ptr;
622 hash_set::rcu_lock lock;
624 ptr = theSet.get( 5 );
629 // Unlock RCU by rcu_lock destructor
630 // ptr can be reclaimed by disposer at any time after RCU has been unlocked
634 template <typename Q>
635 raw_ptr get( Q const& key )
637 return bucket( key ).get( key );
640 /// Finds the key \p key and return the item found
642 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
643 but \p pred is used for comparing the keys.
645 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
647 \p pred must imply the same element order as the comparator used for building the set.
649 template <typename Q, typename Less>
650 raw_ptr get_with( Q const& key, Less pred )
652 return bucket( key ).get_with( key, pred );
655 /// Clears the set (non-atomic)
657 The function unlink all items from the set.
658 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
659 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
660 <tt> empty() </tt> may return \p true but the set may contain item(s).
661 Therefore, \p clear may be used only for debugging purposes.
663 For each item the \p disposer is called after unlinking.
667 for ( size_t i = 0; i < bucket_count(); ++i )
668 m_Buckets[i].clear();
669 m_ItemCounter.reset();
673 /// Checks if the set is empty
675 Emptiness is checked by item counting: if item count is zero then the set is empty.
676 Thus, the correct item counting feature is an important part of Michael's set implementation.
683 /// Returns item count in the set
686 return m_ItemCounter;
689 /// Returns the size of hash table
691 Since %MichaelHashSet cannot dynamically extend the hash table size,
692 the value returned is an constant depending on object initialization parameters;
693 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
695 size_t bucket_count() const
697 return m_nHashBitmask + 1;
702 }} // namespace cds::intrusive
704 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H