cds  2.2.0
cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits > Class Template Reference

Michael's hash set (template specialization for gc::nogc) More...

#include <cds/intrusive/michael_set_nogc.h>

Public Types

typedef cds::gc::nogc gc
 Garbage collector.
 
typedef OrderedList ordered_list
 type of ordered list used as a bucket implementation
 
typedef Traits traits
 Set traits.
 
typedef ordered_list::value_type value_type
 type of value to be stored in the set
 
typedef ordered_list::key_comparator key_comparator
 key comparing functor
 
typedef ordered_list::disposer disposer
 Node disposer functor.
 
typedef ordered_list::stat stat
 Internal statistics.
 
typedef cds::opt::v::hash_selector< typename traits::hash >::type hash
 Hash functor for value_type and all its derivatives that you use.
 
typedef traits::item_counter item_counter
 Item counter type.
 
typedef traits::allocator allocator
 Bucket table allocator.
 

Public Member Functions

 MichaelHashSet (size_t nMaxItemCount, size_t nLoadFactor)
 Initializes hash set. More...
 
 ~MichaelHashSet ()
 Clears hash set object and destroys it.
 
bool insert (value_type &val)
 Inserts new node. More...
 
template<typename Func >
std::pair< bool, bool > update (value_type &val, Func func, bool bAllowInsert=true)
 Updates the element. More...
 
template<typename Q >
value_typecontains (Q const &key)
 Checks whether the set contains key. More...
 
template<typename Q , typename Less >
value_typecontains (Q const &key, Less pred)
 Checks whether the set contains key using pred predicate for searching. More...
 
template<typename Q , typename Func >
bool find (Q &key, Func f)
 Finds the key key. More...
 
template<typename Q , typename Less , typename Func >
bool find_with (Q &key, Less pred, Func f)
 Finds the key key using pred predicate for searching. More...
 
void clear ()
 Clears the set (non-atomic) More...
 
bool empty () const
 Checks if the set is empty. More...
 
size_t size () const
 Returns item count in the set.
 
size_t bucket_count () const
 Returns the size of hash table. More...
 
stat const & statistics () const
 Returns const reference to internal statistics.
 

Forward iterators

typedef michael_set::details::iterator< internal_bucket_type, false > iterator
 Forward iterator. More...
 
typedef michael_set::details::iterator< internal_bucket_type, true > const_iterator
 Const forward iterator. More...
 
iterator begin ()
 Returns a forward iterator addressing the first element in a set. More...
 
iterator end ()
 Returns an iterator that addresses the location succeeding the last element in a set. More...
 
const_iterator begin () const
 Returns a forward const iterator addressing the first element in a set.
 
const_iterator cbegin () const
 Returns a forward const iterator addressing the first element in a set.
 
const_iterator end () const
 Returns an const iterator that addresses the location succeeding the last element in a set.
 
const_iterator cend () const
 Returns an const iterator that addresses the location succeeding the last element in a set.
 

Detailed Description

template<class OrderedList, class Traits = michael_set::traits>
class cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >

Michael's hash set (template specialization for gc::nogc)

This specialization is so-called append-only when no item reclamation may be performed. The set does not support deleting of list item.

See MichaelHashSet for description of template parameters. The template parameter OrderedList should be any cds::gc::nogc -derived ordered list, for example, append-only MichaelList.

Member Typedef Documentation

§ const_iterator

template<class OrderedList , class Traits = michael_set::traits>
typedef michael_set::details::iterator< internal_bucket_type, true > cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::const_iterator

Const forward iterator.

For iterator's features and requirements see iterator

§ iterator

template<class OrderedList , class Traits = michael_set::traits>
typedef michael_set::details::iterator< internal_bucket_type, false > cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::iterator

Forward iterator.

The forward iterator for Michael's set is based on OrderedList forward iterator and has some features:

  • it has no post-increment operator
  • it iterates items in unordered fashion

The iterator interface:

class iterator {
public:
// Default constructor
// Copy construtor
iterator( iterator const& src );
// Dereference operator
value_type * operator ->() const;
// Dereference operator
value_type& operator *() const;
// Preincrement operator
iterator& operator ++();
// Assignment operator
iterator& operator = (iterator const& src);
// Equality operators
bool operator ==(iterator const& i ) const;
bool operator !=(iterator const& i ) const;
};

Constructor & Destructor Documentation

§ MichaelHashSet()

template<class OrderedList , class Traits = michael_set::traits>
cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::MichaelHashSet ( size_t  nMaxItemCount,
size_t  nLoadFactor 
)
inline

Initializes hash set.

The Michael's hash set is an unbounded container, but its hash table is non-expandable. At construction time you should pass estimated maximum item count and a load factor. The load factor is average size of one bucket - a small number between 1 and 10. The bucket is an ordered single-linked list, searching in the bucket has linear complexity O(nLoadFactor). The constructor defines hash table size as rounding nMaxItemCount / nLoadFactor up to nearest power of two.

Parameters
nMaxItemCountestimation of max item count in the hash set
nLoadFactorload factor: estimation of max number of items in the bucket

Member Function Documentation

§ begin()

template<class OrderedList , class Traits = michael_set::traits>
iterator cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::begin ( )
inline

Returns a forward iterator addressing the first element in a set.

For empty set

begin() == end()

§ bucket_count()

template<class OrderedList , class Traits = michael_set::traits>
size_t cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::bucket_count ( ) const
inline

Returns the size of hash table.

Since MichaelHashSet cannot dynamically extend the hash table size, the value returned is an constant depending on object initialization parameters; see MichaelHashSet::MichaelHashSet for explanation.

§ clear()

template<class OrderedList , class Traits = michael_set::traits>
void cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::clear ( )
inline

Clears the set (non-atomic)

The function unlink all items from the set. The function is not atomic. It cleans up each bucket and then resets the item counter to zero. If there are a thread that performs insertion while clear() is working the result is undefined in general case: empty() may return true but the set may contain item(s). Therefore, clear() may be used only for debugging purposes.

For each item the disposer is called after unlinking.

§ contains() [1/2]

template<class OrderedList , class Traits = michael_set::traits>
template<typename Q >
value_type* cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::contains ( Q const &  key)
inline

Checks whether the set contains key.

The function searches the item with key equal to key and returns the pointer to an element found or nullptr.

Note the hash functor specified for class Traits template parameter should accept a parameter of type Q that can be not the same as value_type.

§ contains() [2/2]

template<class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less >
value_type* cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::contains ( Q const &  key,
Less  pred 
)
inline

Checks whether the set contains key using pred predicate for searching.

The function is an analog of contains( key ) but pred is used for key comparing. Less functor has the interface like std::less. Less must imply the same element order as the comparator used for building the set.

§ empty()

template<class OrderedList , class Traits = michael_set::traits>
bool cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::empty ( ) const
inline

Checks if the set is empty.

Emptiness is checked by item counting: if item count is zero then the set is empty. Thus, the correct item counting feature is an important part of Michael's set implementation.

§ end()

template<class OrderedList , class Traits = michael_set::traits>
iterator cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::end ( )
inline

Returns an iterator that addresses the location succeeding the last element in a set.

Do not use the value returned by end function to access any item. The returned value can be used only to control reaching the end of the set. For empty set

begin() == end()

§ find()

template<class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Func >
bool cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::find ( Q &  key,
Func  f 
)
inline

Finds the key key.

The function searches the item with key equal to key and calls the functor f for item found. The interface of Func functor is:

struct functor {
void operator()( value_type& item, Q& key );
};

where item is the item found, key is the find function argument.

The functor can change non-key fields of item. The functor does not serialize simultaneous access to the set item. If such access is possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.

The key argument is non-const since it can be used as f functor destination i.e., the functor can modify both arguments.

Note the hash functor specified for class Traits template parameter should accept a parameter of type Q that can be not the same as value_type.

The function returns true if key is found, false otherwise.

§ find_with()

template<class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less , typename Func >
bool cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::find_with ( Q &  key,
Less  pred,
Func  f 
)
inline

Finds the key key using pred predicate for searching.

The function is an analog of find(Q&, Func) but pred is used for key comparing. Less functor has the interface like std::less. pred must imply the same element order as the comparator used for building the set.

§ insert()

template<class OrderedList , class Traits = michael_set::traits>
bool cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::insert ( value_type val)
inline

Inserts new node.

The function inserts val in the set if it does not contain an item with key equal to val.

Returns true if val is placed into the set, false otherwise.

§ update()

template<class OrderedList , class Traits = michael_set::traits>
template<typename Func >
std::pair<bool, bool> cds::intrusive::MichaelHashSet< cds::gc::nogc, OrderedList, Traits >::update ( value_type val,
Func  func,
bool  bAllowInsert = true 
)
inline

Updates the element.

The operation performs inserting or changing data with lock-free manner.

If the item val not found in the set, then val is inserted iff bAllowInsert is true. Otherwise, the functor func is called with item found. The functor signature is:

struct functor {
void operator()( bool bNew, value_type& item, value_type& val );
};

with arguments:

  • bNew - true if the item has been inserted, false otherwise
  • item - item of the set
  • val - argument val passed into the update() function If new item has been inserted (i.e. bNew is true) then item and val arguments refers to the same thing.

The functor may change non-key fields of the item.

Returns std::pair<bool, bool> where first is true if operation is successful, second is true if new item has been added or false if the item with key already is in the set.

Warning
For MichaelList as the bucket see insert item troubleshooting. LazyList provides exclusive access to inserted item and does not require any node-level synchronization.

The documentation for this class was generated from the following file:

cds 2.2.0 Developed by Maxim Khizhinsky aka khizmax 2007 - 2017
Autogenerated Wed Jan 4 2017 08:49:51 by Doxygen 1.8.12