cds  2.3.1
cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits > Class Template Reference

Michael's hash set, RCU specialization. More...

#include <cds/intrusive/michael_set_rcu.h>

Public Types

typedef cds::urcu::gc< RCU > gc
 RCU schema.
 
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 stored in the list
 
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.
 
typedef ordered_list::rcu_lock rcu_lock
 
typedef internal_bucket_type::exempt_ptr exempt_ptr
 pointer to extracted node
 
typedef internal_bucket_type::raw_ptr raw_ptr
 Return type of get() member function and its derivatives.
 

Public Member Functions

 MichaelHashSet (size_t nMaxItemCount, size_t nLoadFactor)
 Initialize hash set. More...
 
 ~MichaelHashSet ()
 Clear hash set and destroy it.
 
bool insert (value_type &val)
 Inserts new node. More...
 
template<typename Func >
bool insert (value_type &val, Func f)
 Inserts new node. More...
 
template<typename Func >
std::pair< bool, bool > update (value_type &val, Func func, bool bAllowInsert=true)
 Updates the element. More...
 
bool unlink (value_type &val)
 Unlinks the item val from the set. More...
 
template<typename Q >
bool erase (Q const &key)
 Deletes the item from the set. More...
 
template<typename Q , typename Less >
bool erase_with (Q const &key, Less pred)
 Deletes the item from the set using pred predicate for searching. More...
 
template<typename Q , typename Func >
bool erase (const Q &key, Func f)
 Deletes the item from the set. More...
 
template<typename Q , typename Less , typename Func >
bool erase_with (const Q &key, Less pred, Func f)
 Deletes the item from the set using pred predicate for searching. More...
 
template<typename Q >
exempt_ptr extract (Q const &key)
 Extracts an item from the set. More...
 
template<typename Q , typename Less >
exempt_ptr extract_with (Q const &key, Less pred)
 Extracts an item from the set using pred predicate for searching. More...
 
template<typename Q >
bool contains (Q const &key)
 Checks whether the set contains key. More...
 
template<typename Q , typename Less >
bool contains (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)
 Find 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...
 
template<typename Q >
raw_ptr get (Q const &key)
 Finds the key key and return the item found. More...
 
template<typename Q , typename Less >
raw_ptr get_with (Q const &key, Less pred)
 Finds the key key and return the item found. 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. More...
 
size_t bucket_count () const
 Returns the size of hash table. More...
 
stat const & statistics () const
 Returns const reference to internal statistics.
 

Static Public Attributes

static constexpr const bool c_bExtractLockExternal = ordered_list::c_bExtractLockExternal
 Group of extract_xxx functions require external locking if underlying ordered list requires that.
 

Forward iterators (thread-safe under RCU lock)

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 RCU, class OrderedList, class Traits = michael_set::traits>
class cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >

Michael's hash set, RCU specialization.

Source:

  • [2002] Maged Michael "High performance dynamic lock-free hash tables and list-based sets"

Michael's hash table algorithm is based on lock-free ordered list and it is very simple. The main structure is an array T of size M. Each element in T is basically a pointer to a hash bucket, implemented as a singly linked list. The array of buckets cannot be dynamically expanded. However, each bucket may contain unbounded number of items.

Template parameters are:

  • RCU - one of RCU type
  • OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList. The intrusive ordered list implementation specifies the type T stored in the hash-set, the reclamation schema GC used by hash-set, the comparison functor for the type T and other features specific for the ordered list.
  • Traits - type traits, default is michael_set::traits. Instead of defining Traits struct you can use option-based syntax with michael_set::make_traits metafunction.
Usage
Before including <cds/intrusive/michael_set_rcu.h> you should include appropriate RCU header file, see RCU type for list of existing RCU class and corresponding header files. For example, for general-purpose buffered RCU you should include:
#include <cds/urcu/general_buffered.h>
#include <cds/intrusive/michael_list_rcu.h>
#include <cds/intrusive/michael_set_rcu.h>
struct Foo { ... };
// Hash functor for struct Foo
struct foo_hash {
size_t operator()( Foo const& foo ) const { return ... }
};
// Now, you can declare Michael's list for type Foo and default traits:
// Declare Michael's set with MichaelList as bucket type
typedef cds::intrusive::MichaelSet<
cds::urcu::gc< general_buffered<> >,
rcu_michael_list,
cds::opt::::hash< foo_hash >
>::type
> rcu_michael_set;
// Declares hash set for 1000000 items with load factor 2
rcu_michael_set theSet( 1000000, 2 );
// Now you can use theSet object in many threads without any synchronization.

Member Typedef Documentation

◆ const_iterator

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

Const forward iterator.

For iterator's features and requirements see iterator

◆ iterator

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

You may safely use iterators in multi-threaded environment only under RCU lock. Otherwise, a crash is possible if another thread deletes the element the iterator points to.

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;
};

◆ rcu_lock

template<class RCU , class OrderedList , class Traits = michael_set::traits>
typedef ordered_list::rcu_lock cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::rcu_lock

RCU scoped lock

Constructor & Destructor Documentation

◆ MichaelHashSet()

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

Initialize 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, the complexity of searching in the bucket is linear 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: average size of the bucket

Member Function Documentation

◆ begin()

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

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

For empty set

begin() == end()

◆ bucket_count()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
size_t cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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 for explanation.

◆ clear()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
void cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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 RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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 true if the key is found, and false otherwise.

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 RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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 RCU , class OrderedList , class Traits = michael_set::traits>
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::empty ( ) const
inline

Checks if the set is empty.

Warning
If you use atomicity::empty_item_counter in traits::item_counter, the function always returns true.

◆ end()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
iterator cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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()

◆ erase() [1/2]

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::erase ( Q const &  key)
inline

Deletes the item from the set.

The function searches an item with key equal to key in the set, unlinks it from the set, and returns true. If the item with key equal to key is not found the function return false.

Note the hash functor should accept a parameter of type Q that may be not the same as value_type.

◆ erase() [2/2]

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

Deletes the item from the set.

The function searches an item with key equal to key in the set, call f functor with item found, and unlinks it from the set. The disposer specified in OrderedList class template parameter is called by garbage collector GC asynchronously.

The Func interface is

struct functor {
void operator()( value_type const& item );
};

If the item with key equal to key is not found the function return false.

Note the hash functor should accept a parameter of type Q that can be not the same as value_type.

◆ erase_with() [1/2]

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::erase_with ( Q const &  key,
Less  pred 
)
inline

Deletes the item from the set using pred predicate for searching.

The function is an analog of erase(Q const&) 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.

◆ erase_with() [2/2]

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

Deletes the item from the set using pred predicate for searching.

The function is an analog of erase(Q const&) 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.

◆ extract()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q >
exempt_ptr cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::extract ( Q const &  key)
inline

Extracts an item from the set.

The function searches an item with key equal to key in the set, unlinks it from the set, and returns exempt_ptr pointer to the item found. If the item with the key equal to key is not found the function returns an empty exempt_ptr.

Depends on ordered_list you should or should not lock RCU before calling of this function:

  • for the set based on MichaelList RCU should not be locked
  • for the set based on LazyList RCU should be locked

See ordered list implementation for details.

#include <cds/urcu/general_buffered.h>
#include <cds/intrusive/michael_list_rcu.h>
#include <cds/intrusive/michael_set_rcu.h>
typedef cds::urcu::gc< general_buffered<> > rcu;
typedef cds::intrusive::MichaelList< rcu, Foo > rcu_michael_list;
rcu_michael_set theSet;
// ...
typename rcu_michael_set::exempt_ptr p;
// For MichaelList we should not lock RCU
// Now, you can apply extract function
// Note that you must not delete the item found inside the RCU lock
p = theSet.extract( 10 )
if ( p ) {
// do something with p
...
}
// We may safely release p here
// release() passes the pointer to RCU reclamation cycle:
// it invokes RCU retire_ptr function with the disposer you provided for rcu_michael_list.
p.release();

◆ extract_with()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less >
exempt_ptr cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::extract_with ( Q const &  key,
Less  pred 
)
inline

Extracts an item from the set using pred predicate for searching.

The function is an analog of extract(Q const&) 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.

◆ find()

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

Find 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 RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less , typename Func >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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.

◆ get()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q >
raw_ptr cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::get ( Q const &  key)
inline

Finds the key key and return the item found.

The function searches the item with key equal to key and returns the pointer to item found. If key is not found it returns nullptr. Note the type of returned value depends on underlying ordered_list. For details, see documentation of ordered list you use.

Note the compare functor should accept a parameter of type Q that can be not the same as value_type.

RCU should be locked before call of this function. Returned item is valid only while RCU is locked:

hash_set theSet;
// ...
// Result of get() call
typename hash_set::raw_ptr ptr;
{
// Lock RCU
hash_set::rcu_lock lock;
ptr = theSet.get( 5 );
if ( ptr ) {
// Deal with ptr
//...
}
// Unlock RCU by rcu_lock destructor
// ptr can be reclaimed by disposer at any time after RCU has been unlocked
}

◆ get_with()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Q , typename Less >
raw_ptr cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::get_with ( Q const &  key,
Less  pred 
)
inline

Finds the key key and return the item found.

The function is an analog of get(Q const&) but pred is used for comparing the keys.

Less functor has the semantics like std::less but should take arguments of type value_type and Q in any order. pred must imply the same element order as the comparator used for building the set.

◆ insert() [1/2]

template<class RCU , class OrderedList , class Traits = michael_set::traits>
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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.

◆ insert() [2/2]

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Func >
bool cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, OrderedList, Traits >::insert ( value_type val,
Func  f 
)
inline

Inserts new node.

This function is intended for derived non-intrusive containers.

The function allows to split creating of new item into two part:

  • create item with key only
  • insert new item into the set
  • if inserting is success, calls f functor to initialize value-field of val.

The functor signature is:

void func( value_type& val );

where val is the item inserted. The user-defined functor is called only if the inserting is success.

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.

◆ size()

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

Returns item count in the set.

If you use atomicity::empty_item_counter in traits::item_counter, the function always returns 0.

◆ unlink()

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

Unlinks the item val from the set.

The function searches the item val in the set and unlink it from the set if it is found and is equal to val.

The function returns true if success and false otherwise.

◆ update()

template<class RCU , class OrderedList , class Traits = michael_set::traits>
template<typename Func >
std::pair<bool, bool> cds::intrusive::MichaelHashSet< cds::urcu::gc< RCU >, 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 2.3.1 Developed by Maxim Khizhinsky aka khizmax 2007 - 2017
Autogenerated Fri Sep 1 2017 08:47:22 by Doxygen 1.8.13