3 #ifndef __CDS_INTRUSIVE_MICHAEL_SET_RCU_H
4 #define __CDS_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 item_counter m_ItemCounter; ///< Item counter
99 hash m_HashFunctor; ///< Hash functor
100 bucket_type * m_Buckets; ///< bucket table
104 const size_t m_nHashBitmask;
109 /// Calculates hash value of \p key
110 template <typename Q>
111 size_t hash_value( Q const& key ) const
113 return m_HashFunctor( key ) & m_nHashBitmask;
116 /// Returns the bucket (ordered list) for \p key
117 template <typename Q>
118 bucket_type& bucket( Q const& key )
120 return m_Buckets[ hash_value( key ) ];
122 template <typename Q>
123 bucket_type const& bucket( Q const& key ) const
125 return m_Buckets[ hash_value( key ) ];
132 The forward iterator for Michael's set is based on \p OrderedList forward iterator and has some features:
133 - it has no post-increment operator
134 - it iterates items in unordered fashion
136 typedef michael_set::details::iterator< bucket_type, false > iterator;
138 /// Const forward iterator
140 For iterator's features and requirements see \ref iterator
142 typedef michael_set::details::iterator< bucket_type, true > const_iterator;
144 /// Returns a forward iterator addressing the first element in a set
146 For empty set \code begin() == end() \endcode
150 return iterator( m_Buckets[0].begin(), m_Buckets, m_Buckets + bucket_count() );
153 /// Returns an iterator that addresses the location succeeding the last element in a set
155 Do not use the value returned by <tt>end</tt> function to access any item.
156 The returned value can be used only to control reaching the end of the set.
157 For empty set \code begin() == end() \endcode
161 return iterator( m_Buckets[bucket_count() - 1].end(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
164 /// Returns a forward const iterator addressing the first element in a set
166 const_iterator begin() const
170 const_iterator cbegin() const
172 return const_iterator( m_Buckets[0].cbegin(), m_Buckets, m_Buckets + bucket_count() );
176 /// Returns an const iterator that addresses the location succeeding the last element in a set
178 const_iterator end() const
182 const_iterator cend() const
184 return const_iterator( m_Buckets[bucket_count() - 1].cend(), m_Buckets + bucket_count() - 1, m_Buckets + bucket_count() );
189 /// Initialize hash set
191 The Michael's hash set is an unbounded container, but its hash table is non-expandable.
192 At construction time you should pass estimated maximum item count and a load factor.
193 The load factor is average size of one bucket - a small number between 1 and 10.
194 The bucket is an ordered single-linked list, the complexity of searching in the bucket is linear <tt>O(nLoadFactor)</tt>.
195 The constructor defines hash table size as rounding <tt>nMaxItemCount / nLoadFactor</tt> up to nearest power of two.
198 size_t nMaxItemCount, ///< estimation of max item count in the hash set
199 size_t nLoadFactor ///< load factor: average size of the bucket
200 ) : m_nHashBitmask( michael_set::details::init_hash_bitmask( nMaxItemCount, nLoadFactor ))
202 // GC and OrderedList::gc must be the same
203 static_assert( std::is_same<gc, typename bucket_type::gc>::value, "GC and OrderedList::gc must be the same");
205 // atomicity::empty_item_counter is not allowed as a item counter
206 static_assert( !std::is_same<item_counter, atomicity::empty_item_counter>::value,
207 "atomicity::empty_item_counter is not allowed as a item counter");
209 m_Buckets = bucket_table_allocator().NewArray( bucket_count() );
212 /// Clear hash set and destroy it
216 bucket_table_allocator().Delete( m_Buckets, bucket_count() );
221 The function inserts \p val in the set if it does not contain
222 an item with key equal to \p val.
224 Returns \p true if \p val is placed into the set, \p false otherwise.
226 bool insert( value_type& val )
228 bool bRet = bucket( val ).insert( val );
236 This function is intended for derived non-intrusive containers.
238 The function allows to split creating of new item into two part:
239 - create item with key only
240 - insert new item into the set
241 - if inserting is success, calls \p f functor to initialize value-field of \p val.
243 The functor signature is:
245 void func( value_type& val );
247 where \p val is the item inserted.
248 The user-defined functor is called only if the inserting is success.
250 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
251 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
254 template <typename Func>
255 bool insert( value_type& val, Func f )
257 bool bRet = bucket( val ).insert( val, f );
263 /// Ensures that the \p item exists in the set
265 The operation performs inserting or changing data with lock-free manner.
267 If the item \p val not found in the set, then \p val is inserted into the set.
268 Otherwise, the functor \p func is called with item found.
269 The functor signature is:
271 void func( bool bNew, value_type& item, value_type& val );
274 - \p bNew - \p true if the item has been inserted, \p false otherwise
275 - \p item - item of the set
276 - \p val - argument \p val passed into the \p ensure function
277 If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
278 refers to the same thing.
280 The functor can change non-key fields of the \p item.
282 Returns std::pair<bool, bool> where \p first is \p true if operation is successfull,
283 \p second is \p true if new item has been added or \p false if the item with \p key
284 already is in the set.
286 @warning For \ref cds_intrusive_MichaelList_rcu "MichaelList" as the bucket see \ref cds_intrusive_item_creating "insert item troubleshooting".
287 \ref cds_intrusive_LazyList_rcu "LazyList" provides exclusive access to inserted item and does not require any node-level
290 template <typename Func>
291 std::pair<bool, bool> ensure( value_type& val, Func func )
293 std::pair<bool, bool> bRet = bucket( val ).ensure( val, func );
294 if ( bRet.first && bRet.second )
299 /// Unlinks the item \p val from the set
301 The function searches the item \p val in the set and unlink it from the set
302 if it is found and is equal to \p val.
304 The function returns \p true if success and \p false otherwise.
306 bool unlink( value_type& val )
308 bool bRet = bucket( val ).unlink( val );
314 /// Deletes the item from the set
315 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase
316 The function searches an item with key equal to \p key in the set,
317 unlinks it from the set, and returns \p true.
318 If the item with key equal to \p key is not found the function return \p false.
320 Note the hash functor should accept a parameter of type \p Q that may be not the same as \p value_type.
322 template <typename Q>
323 bool erase( Q const& key )
325 if ( bucket( key ).erase( key )) {
332 /// Deletes the item from the set using \p pred predicate for searching
334 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase "erase(Q const&)"
335 but \p pred is used for key comparing.
336 \p Less functor has the interface like \p std::less.
337 \p pred must imply the same element order as the comparator used for building the set.
339 template <typename Q, typename Less>
340 bool erase_with( Q const& key, Less pred )
342 if ( bucket( key ).erase_with( key, pred )) {
349 /// Deletes the item from the set
350 /** \anchor cds_intrusive_MichaelHashSet_rcu_erase_func
351 The function searches an item with key equal to \p key in the set,
352 call \p f functor with item found, and unlinks it from the set.
353 The \ref disposer specified in \p OrderedList class template parameter is called
354 by garbage collector \p GC asynchronously.
356 The \p Func interface is
359 void operator()( value_type const& item );
363 If the item with key equal to \p key is not found the function return \p false.
365 Note the hash functor should accept a parameter of type \p Q that can be not the same as \p value_type.
367 template <typename Q, typename Func>
368 bool erase( const Q& key, Func f )
370 if ( bucket( key ).erase( key, f )) {
377 /// Deletes the item from the set using \p pred predicate for searching
379 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_erase_func "erase(Q const&)"
380 but \p pred is used for key comparing.
381 \p Less functor has the interface like \p std::less.
382 \p pred must imply the same element order as the comparator used for building the set.
384 template <typename Q, typename Less, typename Func>
385 bool erase_with( const Q& key, Less pred, Func f )
387 if ( bucket( key ).erase_with( key, pred, f )) {
394 /// Extracts an item from the set
395 /** \anchor cds_intrusive_MichaelHashSet_rcu_extract
396 The function searches an item with key equal to \p key in the set,
397 unlinks it from the set, places item pointer into \p dest argument, and returns \p true.
398 If the item with the key equal to \p key is not found the function return \p false.
400 @note The function does NOT call RCU read-side lock or synchronization,
401 and does NOT dispose the item found. It just excludes the item from the set
402 and returns a pointer to item found.
403 You should lock RCU before calling of the function, and you should synchronize RCU
404 outside the RCU lock before reusing returned pointer.
407 #include <cds/urcu/general_buffered.h>
408 #include <cds/intrusive/michael_list_rcu.h>
409 #include <cds/intrusive/michael_set_rcu.h>
411 typedef cds::urcu::gc< general_buffered<> > rcu;
412 typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
413 typedef cds::intrusive::MichaelHashSet< rcu, rcu_michael_list, foo_traits > rcu_michael_set;
415 rcu_michael_set theSet;
418 rcu_michael_set::exempt_ptr p;
420 // first, we should lock RCU
421 rcu_michael_set::rcu_lock lock;
423 // Now, you can apply extract function
424 // Note that you must not delete the item found inside the RCU lock
425 if ( theSet.extract( p, 10 )) {
426 // do something with p
431 // We may safely release p here
432 // release() passes the pointer to RCU reclamation cycle:
433 // it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
437 template <typename Q>
438 bool extract( exempt_ptr& dest, Q const& key )
440 if ( bucket( key ).extract( dest, key )) {
447 /// Extracts an item from the set using \p pred predicate for searching
449 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_extract "extract(exempt_ptr&, Q const&)"
450 but \p pred is used for key comparing.
451 \p Less functor has the interface like \p std::less.
452 \p pred must imply the same element order as the comparator used for building the set.
454 template <typename Q, typename Less>
455 bool extract_with( exempt_ptr& dest, Q const& key, Less pred )
457 if ( bucket( key ).extract_with( dest, key, pred )) {
464 /// Finds the key \p key
465 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_val
466 The function searches the item with key equal to \p key
467 and returns \p true if \p key found or \p false otherwise.
469 template <typename Q>
470 bool find( Q const& key ) const
472 return bucket( key ).find( key );
475 /// Finds the key \p key using \p pred predicate for searching
477 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_val "find(Q const&)"
478 but \p pred is used for key comparing.
479 \p Less functor has the interface like \p std::less.
480 \p pred must imply the same element order as the comparator used for building the set.
482 template <typename Q, typename Less>
483 bool find_with( Q const& key, Less pred ) const
485 return bucket( key ).find_with( key, pred );
488 /// Find the key \p key
489 /** \anchor cds_intrusive_MichaelHashSet_rcu_find_func
490 The function searches the item with key equal to \p key and calls the functor \p f for item found.
491 The interface of \p Func functor is:
494 void operator()( value_type& item, Q& key );
497 where \p item is the item found, \p key is the <tt>find</tt> function argument.
499 The functor can change non-key fields of \p item.
500 The functor does not serialize simultaneous access to the set \p item. If such access is
501 possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
503 The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
504 can modify both arguments.
506 Note the hash functor specified for class \p Traits template parameter
507 should accept a parameter of type \p Q that can be not the same as \p value_type.
509 The function returns \p true if \p key is found, \p false otherwise.
511 template <typename Q, typename Func>
512 bool find( Q& key, Func f ) const
514 return bucket( key ).find( key, f );
517 /// Finds the key \p key using \p pred predicate for searching
519 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_find_func "find(Q&, Func)"
520 but \p pred is used for key comparing.
521 \p Less functor has the interface like \p std::less.
522 \p pred must imply the same element order as the comparator used for building the set.
524 template <typename Q, typename Less, typename Func>
525 bool find_with( Q& key, Less pred, Func f ) const
527 return bucket( key ).find_with( key, pred, f );
530 /// Finds the key \p key and return the item found
531 /** \anchor cds_intrusive_MichaelHashSet_rcu_get
532 The function searches the item with key equal to \p key and returns the pointer to item found.
533 If \p key is not found it returns \p nullptr.
535 Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
537 RCU should be locked before call of this function.
538 Returned item is valid only while RCU is locked:
540 typedef cds::intrusive::MichaelHashSet< your_template_parameters > hash_set;
545 hash_set::rcu_lock lock;
547 foo * pVal = theSet.get( 5 );
552 // Unlock RCU by rcu_lock destructor
553 // pVal can be retired by disposer at any time after RCU has been unlocked
557 template <typename Q>
558 value_type * get( Q const& key ) const
560 return bucket( key ).get( key );
563 /// Finds the key \p key and return the item found
565 The function is an analog of \ref cds_intrusive_MichaelHashSet_rcu_get "get(Q const&)"
566 but \p pred is used for comparing the keys.
568 \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
570 \p pred must imply the same element order as the comparator used for building the set.
572 template <typename Q, typename Less>
573 value_type * get_with( Q const& key, Less pred ) const
575 return bucket( key ).get_with( key, pred );
578 /// Clears the set (non-atomic)
580 The function unlink all items from the set.
581 The function is not atomic. It cleans up each bucket and then resets the item counter to zero.
582 If there are a thread that performs insertion while \p clear is working the result is undefined in general case:
583 <tt> empty() </tt> may return \p true but the set may contain item(s).
584 Therefore, \p clear may be used only for debugging purposes.
586 For each item the \p disposer is called after unlinking.
590 for ( size_t i = 0; i < bucket_count(); ++i )
591 m_Buckets[i].clear();
592 m_ItemCounter.reset();
596 /// Checks if the set is empty
598 Emptiness is checked by item counting: if item count is zero then the set is empty.
599 Thus, the correct item counting feature is an important part of Michael's set implementation.
606 /// Returns item count in the set
609 return m_ItemCounter;
612 /// Returns the size of hash table
614 Since %MichaelHashSet cannot dynamically extend the hash table size,
615 the value returned is an constant depending on object initialization parameters;
616 see \ref cds_intrusive_MichaelHashSet_hp "MichaelHashSet" for explanation.
618 size_t bucket_count() const
620 return m_nHashBitmask + 1;
625 }} // namespace cds::intrusive
627 #endif // #ifndef __CDS_INTRUSIVE_MICHAEL_SET_NOGC_H