3 #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
4 #define CDSLIB_INTRUSIVE_MICHAEL_SET_RCU_H
6 #include <cds/intrusive/details/michael_set_base.h>
7 #include <cds/details/allocator.h>
9 namespace cds { namespace intrusive {
11 /// Michael's hash set, \ref cds_urcu_desc "RCU" specialization
12 /** @ingroup cds_intrusive_map
13 \anchor cds_intrusive_MichaelHashSet_rcu
16 - [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"
18 Michael's hash table algorithm is based on lock-free ordered list and it is very simple.
19 The main structure is an array \p T of size \p M. Each element in \p T is basically a pointer
20 to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded.
21 However, each bucket may contain unbounded number of items.
23 Template parameters are:
24 - \p RCU - one of \ref cds_urcu_gc "RCU type"
25 - \p OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList.
26 The intrusive ordered list implementation specifies the type \p T stored in the hash-set, the reclamation
27 schema \p GC used by hash-set, the comparison functor for the type \p T and other features specific for
29 - \p Traits - type traits, default is \p michael_set::traits.
30 Instead of defining \p Traits struct you can use option-based syntax with \p michael_set::make_traits metafunction.
33 Before including <tt><cds/intrusive/michael_set_rcu.h></tt> you should include appropriate RCU header file,
34 see \ref cds_urcu_gc "RCU type" for list of existing RCU class and corresponding header files.
35 For example, for \ref cds_urcu_general_buffered_gc "general-purpose buffered RCU" you should include:
37 #include <cds/urcu/general_buffered.h>
38 #include <cds/intrusive/michael_list_rcu.h>
39 #include <cds/intrusive/michael_set_rcu.h>
42 // Hash functor for struct Foo
44 size_t operator()( Foo const& foo ) const { return ... }
47 // Now, you can declare Michael's list for type Foo and default traits:
48 typedef cds::intrusive::MichaelList<cds::urcu::gc< general_buffered<> >, Foo > rcu_michael_list;
50 // Declare Michael's set with MichaelList as bucket type
51 typedef cds::intrusive::MichaelSet<
52 cds::urcu::gc< general_buffered<> >,
54 cds::intrusive::michael_set::make_traits<
55 cds::opt::::hash< foo_hash >
59 // Declares hash set for 1000000 items with load factor 2
60 rcu_michael_set theSet( 1000000, 2 );
62 // Now you can use theSet object in many threads without any synchronization.
68 #ifdef CDS_DOXYGEN_INVOKED
69 class Traits = michael_set::traits
74 class MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >
77 typedef cds::urcu::gc< RCU > gc; ///< RCU schema
78 typedef OrderedList bucket_type; ///< type of ordered list used as a bucket implementation
79 typedef Traits traits; ///< Set traits
81 typedef typename bucket_type::value_type value_type ; ///< type of value stored in the list
82 typedef typename bucket_type::key_comparator key_comparator ; ///< key comparing functor
83 typedef typename bucket_type::disposer disposer ; ///< Node disposer functor
85 /// Hash functor for \ref value_type and all its derivatives that you use
86 typedef typename cds::opt::v::hash_selector< typename traits::hash >::type hash;
87 typedef typename traits::item_counter item_counter; ///< Item counter type
89 /// Bucket table allocator
90 typedef cds::details::Allocator< bucket_type, typename traits::allocator > bucket_table_allocator;
92 typedef typename bucket_type::rcu_lock rcu_lock; ///< RCU scoped lock
93 typedef typename bucket_type::exempt_ptr exempt_ptr; ///< pointer to extracted node
94 /// Group of \p extract_xxx functions require external locking if underlying ordered list requires that
95 static CDS_CONSTEXPR const bool c_bExtractLockExternal = bucket_type::c_bExtractLockExternal;
98 typedef cds::intrusive::michael_set::implementation_tag implementation_tag;
102 item_counter m_ItemCounter; ///< Item counter
103 hash m_HashFunctor; ///< Hash functor
104 bucket_type * m_Buckets; ///< bucket table
108 const size_t m_nHashBitmask;
113 /// Calculates hash value of \p key
114 template <typename Q>
115 size_t hash_value( Q const& key ) const
117 return m_HashFunctor( key ) & m_nHashBitmask;
120 /// Returns the bucket (ordered list) for \p key
121 template <typename Q>
122 bucket_type& bucket( Q const& key )
124 return m_Buckets[ hash_value( key ) ];
126 template <typename Q>
127 bucket_type const& bucket( Q const& key ) const
129 return m_Buckets[ hash_value( key ) ];
136 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
137 - it has no post-increment operator
138 - it iterates items in unordered fashion
140 typedef michael_set::details::iterator< bucket_type, false > iterator;
142 /// Const forward iterator
144 For iterator's features and requirements see \ref iterator
146 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
148 /// Returns a forward iterator addressing the first element in a set
150 For empty set \code begin() == end() \endcode
154 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
157 /// Returns an iterator that addresses the location succeeding the last element in a set
159 Do not use the value returned by <tt>end</tt> function to access any item.
160 The returned value can be used only to control reaching the end of the set.
161 For empty set \code begin() == end() \endcode
165 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
168 /// Returns a forward const iterator addressing the first element in a set
170 const_iterator begin() const
174 const_iterator cbegin() const
176 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
180 /// Returns an const iterator that addresses the location succeeding the last element in a set
182 const_iterator end() const
186 const_iterator cend() const
188 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
193 /// Initialize hash set
195 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
196 At construction time you should pass estimated maximum item count and a load factor.
197 The load factor is average size of one bucket - a small number between 1 and 10.
198 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
199 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
202 size_t nMaxItemCount, ///< estimation of max item count in the hash set
203 size_t nLoadFactor ///< load factor: average size of the bucket
204 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
206 // GC and OrderedList::gc must be the same
207 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
209 // atomicity::empty_item_counter is not allowed as a item counter
210 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
211 "atomicity::empty_item_counter is not allowed as a item counter");
213 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
216 /// Clear hash set and destroy it
220 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
225 The function inserts \p val in the set if it does not contain
226 an item with key equal to \p val.
228 Returns \p true if \p val is placed into the set, \p false otherwise.
230 bool insert( value_type& val )
232 bool bRet = bucket( val ).insert( val );
240 This function is intended for derived non-intrusive containers.
242 The function allows to split creating of new item into two part:
243 - create item with key only
244 - insert new item into the set
245 - if inserting is success, calls \p f functor to initialize value-field of \p val.
247 The functor signature is:
249 void func( value_type& val );
251 where \p val is the item inserted.
252 The user-defined functor is called only if the inserting is success.
254 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
255 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
258 template <typename Func>
259 bool insert( value_type& val, Func f )
261 bool bRet = bucket( val ).insert( val, f );
267 /// Ensures that the \p item exists in the set
269 The operation performs inserting or changing data with lock-free manner.
271 If the item \p val not found in the set, then \p val is inserted into the set.
272 Otherwise, the functor \p func is called with item found.
273 The functor signature is:
275 void func( bool bNew, value_type& item, value_type& val );
278 - \p bNew - \p true if the item has been inserted, \p false otherwise
279 - \p item - item of the set
280 - \p val - argument \p val passed into the \p ensure function
281 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
282 refers to the same thing.
284 The functor can change non-key fields of the \p item.
286 Returns std::pair<bool, bool> where \p first is \p true if operation is successfull,
287 \p second is \p true if new item has been added or \p false if the item with \p key
288 already is in the set.
290 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
291 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
294 template <typename Func>
295 std::pair<bool, bool> ensure( value_type& val, Func func )
297 std::pair<bool, bool> bRet = bucket( val ).ensure( val, func );
298 if ( bRet.first && bRet.second )
303 /// Unlinks the item \p val from the set
305 The function searches the item \p val in the set and unlink it from the set
306 if it is found and is equal to \p val.
308 The function returns \p true if success and \p false otherwise.
310 bool unlink( value_type& val )
312 bool bRet = bucket( val ).unlink( val );
318 /// Deletes the item from the set
319 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
320 The function searches an item with key equal to \p key in the set,
321 unlinks it from the set, and returns \p true.
322 If the item with key equal to \p key is not found the function return \p false.
324 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
326 template <typename Q>
327 bool erase( Q const& key )
329 if ( bucket( key ).erase( key )) {
336 /// Deletes the item from the set using \p pred predicate for searching
338 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
339 but \p pred is used for key comparing.
340 \p Less functor has the interface like \p std::less.
341 \p pred must imply the same element order as the comparator used for building the set.
343 template <typename Q, typename Less>
344 bool erase_with( Q const& key, Less pred )
346 if ( bucket( key ).erase_with( key, pred )) {
353 /// Deletes the item from the set
354 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
355 The function searches an item with key equal to \p key in the set,
356 call \p f functor with item found, and unlinks it from the set.
357 The \ref disposer specified in \p OrderedList class template parameter is called
358 by garbage collector \p GC asynchronously.
360 The \p Func interface is
363 void operator()( value_type const& item );
367 If the item with key equal to \p key is not found the function return \p false.
369 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
371 template <typename Q, typename Func>
372 bool erase( const Q& key, Func f )
374 if ( bucket( key ).erase( key, f )) {
381 /// Deletes the item from the set using \p pred predicate for searching
383 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
384 but \p pred is used for key comparing.
385 \p Less functor has the interface like \p std::less.
386 \p pred must imply the same element order as the comparator used for building the set.
388 template <typename Q, typename Less, typename Func>
389 bool erase_with( const Q& key, Less pred, Func f )
391 if ( bucket( key ).erase_with( key, pred, f )) {
398 /// Extracts an item from the set
399 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
400 The function searches an item with key equal to \p key in the set,
401 unlinks it from the set, and returns \ref cds::urcu::exempt_ptr "exempt_ptr" pointer to the item found.
402 If the item with the key equal to \p key is not found the function returns an empty \p exempt_ptr.
404 @note The function does NOT call RCU read-side lock or synchronization,
405 and does NOT dispose the item found. It just excludes the item from the set
406 and returns a pointer to item found.
407 You should lock RCU before calling of the function, and you should synchronize RCU
408 outside the RCU lock before reusing returned pointer.
411 #include <cds/urcu/general_buffered.h>
412 #include <cds/intrusive/michael_list_rcu.h>
413 #include <cds/intrusive/michael_set_rcu.h>
415 typedef cds::urcu::gc< general_buffered<> > rcu;
416 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
417 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
419 rcu_michael_set theSet;
422 typename rcu_michael_set::exempt_ptr p;
424 // first, we should lock RCU
425 typename rcu_michael_set::rcu_lock lock;
427 // Now, you can apply extract function
428 // Note that you must not delete the item found inside the RCU lock
429 p = theSet.extract( 10 )
431 // do something with p
436 // We may safely release p here
437 // release() passes the pointer to RCU reclamation cycle:
438 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
442 template <typename Q>
443 exempt_ptr extract( Q const& key )
445 exempt_ptr p( bucket( key ).extract( key ) );
451 /// Extracts an item from the set using \p pred predicate for searching
453 The function is an analog of \p extract(Q const&) but \p pred is used for key comparing.
454 \p Less functor has the interface like \p std::less.
455 \p pred must imply the same element order as the comparator used for building the set.
457 template <typename Q, typename Less>
458 exempt_ptr extract_with( Q const& key, Less pred )
460 exempt_ptr p( bucket( key ).extract_with( key, pred ) );
466 /// Finds the key \p key
467 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_val
468 The function searches the item with key equal to \p key
469 and returns \p true if \p key found or \p false otherwise.
471 template <typename Q>
472 bool find( Q const& key ) const
474 return bucket( key ).find( key );
477 /// Finds the key \p key using \p pred predicate for searching
479 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_val "find(Q const&)"
480 but \p pred is used for key comparing.
481 \p Less functor has the interface like \p std::less.
482 \p pred must imply the same element order as the comparator used for building the set.
484 template <typename Q, typename Less>
485 bool find_with( Q const& key, Less pred ) const
487 return bucket( key ).find_with( key, pred );
490 /// Find the key \p key
491 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
492 The function searches the item with key equal to \p key and calls the functor \p f for item found.
493 The interface of \p Func functor is:
496 void operator()( value_type& item, Q& key );
499 where \p item is the item found, \p key is the <tt>find</tt> function argument.
501 The functor can change non-key fields of \p item.
502 The functor does not serialize simultaneous access to the set \p item. If such access is
503 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
505 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
506 can modify both arguments.
508 Note the hash functor specified for class \p Traits template parameter
509 should accept a parameter of type \p Q that can be not the same as \p value_type.
511 The function returns \p true if \p key is found, \p false otherwise.
513 template <typename Q, typename Func>
514 bool find( Q& key, Func f ) const
516 return bucket( key ).find( key, f );
519 template <typename Q, typename Func>
520 bool find( Q const& key, Func f ) const
522 return bucket( key ).find( key, f );
526 /// Finds the key \p key using \p pred predicate for searching
528 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
529 but \p pred is used for key comparing.
530 \p Less functor has the interface like \p std::less.
531 \p pred must imply the same element order as the comparator used for building the set.
533 template <typename Q, typename Less, typename Func>
534 bool find_with( Q& key, Less pred, Func f ) const
536 return bucket( key ).find_with( key, pred, f );
539 template <typename Q, typename Less, typename Func>
540 bool find_with( Q const& key, Less pred, Func f ) const
542 return bucket( key ).find_with( key, pred, f );
546 /// Finds the key \p key and return the item found
547 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
548 The function searches the item with key equal to \p key and returns the pointer to item found.
549 If \p key is not found it returns \p nullptr.
551 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
553 RCU should be locked before call of this function.
554 Returned item is valid only while RCU is locked:
556 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
561 hash_set::rcu_lock lock;
563 foo * pVal = theSet.get( 5 );
568 // Unlock RCU by rcu_lock destructor
569 // pVal can be retired by disposer at any time after RCU has been unlocked
573 template <typename Q>
574 value_type * get( Q const& key ) const
576 return bucket( key ).get( key );
579 /// Finds the key \p key and return the item found
581 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
582 but \p pred is used for comparing the keys.
584 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
586 \p pred must imply the same element order as the comparator used for building the set.
588 template <typename Q, typename Less>
589 value_type * get_with( Q const& key, Less pred ) const
591 return bucket( key ).get_with( key, pred );
594 /// Clears the set (non-atomic)
596 The function unlink all items from the set.
597 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
598 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
599 <tt> empty() </tt> may return \p true but the set may contain item(s).
600 Therefore, \p clear may be used only for debugging purposes.
602 For each item the \p disposer is called after unlinking.
606 for ( size_t i = 0; i < bucket_count(); ++i )
607 m_Buckets[i].clear();
608 m_ItemCounter.reset();
612 /// Checks if the set is empty
614 Emptiness is checked by item counting: if item count is zero then the set is empty.
615 Thus, the correct item counting feature is an important part of Michael's set implementation.
622 /// Returns item count in the set
625 return m_ItemCounter;
628 /// Returns the size of hash table
630 Since %MichaelHashSet cannot dynamically extend the hash table size,
631 the value returned is an constant depending on object initialization parameters;
632 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
634 size_t bucket_count() const
636 return m_nHashBitmask + 1;
641 }} // namespace cds::intrusive
643 #endif // #ifndef CDSLIB_INTRUSIVE_MICHAEL_SET_NOGC_H