cds::container::LazyList< GC, T, Traits > Class Template Reference

Lazy ordered list. More...

#include <cds/container/lazy_list_impl.h>

Inheritance diagram for cds::container::LazyList< GC, T, Traits >:

Public Types
typedef T	value_type
	Type of value stored in the list.
typedef base_class::gc	gc
	Garbage collector used.
typedef base_class::back_off	back_off
	Back-off strategy used.
typedef options::allocator_type	allocator_type
	Allocator type used for allocate/deallocate the nodes.
typedef base_class::item_counter	item_counter
	Item counting policy used.
typedef options::key_comparator	key_comparator
	key comparision functor
typedef base_class::memory_model	memory_model
	Memory ordering. See cds::opt::memory_model option.
typedef iterator_type< false >	iterator
	Forward iterator.
typedef iterator_type< true >	const_iterator
	Const forward iterator.

Public Member Functions
iterator	begin ()
	Returns a forward iterator addressing the first element in a list.
iterator	end ()
	Returns an iterator that addresses the location succeeding the last element in a list.
const_iterator	begin () const
	Returns a forward const iterator addressing the first element in a list.
const_iterator	end () const
	Returns an const iterator that addresses the location succeeding the last element in a list.
	LazyList ()
	Default constructor.
	~LazyList ()
	List desctructor.
template<typename Q >
bool	insert (Q const &val)
	Inserts new node.
template<typename Q , typename Func >
bool	insert (Q const &key, Func func)
	Inserts new node.
template<typename... Args>
bool	emplace (Args &&...args)
	Inserts data of type value_type constructed with std::forward<Args>(args)...
template<typename Q , typename Func >
std::pair< bool, bool >	ensure (Q const &key, Func f)
	Ensures that the key exists in the list.
template<typename Q >
bool	erase (const Q &key)
	Delete key from the list.
template<typename Q , typename Func >
bool	erase (const Q &key, Func f)
	Get value of item with key by a functor and delete it.
template<typename Q >
bool	find (const Q &key)
	Find the key key.
template<typename Q , typename Func >
bool	find (Q &val, Func f)
	Find the key val and perform an action with it.
template<typename Q , typename Func >
bool	find (Q const &val, Func f)
	Find the key val and perform an action with it.
bool	empty () const
	Check if the list is empty.
size_t	size () const
	Returns list's item count.
void	clear ()
	Clears the list.

Additional Inherited Members
Protected Types inherited from cds::intrusive::LazyList< GC, T, Traits >
typedef T	value_type
	type of value stored in the list
typedef Traits	options
	Traits template parameter.
typedef options::hook	hook
	hook type
typedef hook::node_type	node_type
	node type
typedef implementation_defined	key_comparator
	key comparision functor based on opt::compare and opt::less option setter.
typedef options::disposer	disposer
	disposer used
typedef get_node_traits < value_type, node_type, hook > ::type	node_traits
	node traits
typedef lazy_list::get_link_checker < node_type, options::link_checker >::type	link_checker
	link checker
typedef GC	gc
	Garbage collector.
typedef options::back_off	back_off
	back-off strategy
typedef options::item_counter	item_counter
	Item counting policy used.
typedef options::memory_model	memory_model
	C++ memory ordering (see lazy_list::type_traits::memory_model)
typedef iterator_type< false >	iterator
	Forward iterator.
typedef iterator_type< true >	const_iterator
	Const forward iterator.
typedef node_type::marked_ptr	marked_node_ptr
	Node marked pointer.
typedef node_type *	auxiliary_head
	Auxiliary head type (for split-list support)
Protected Member Functions inherited from cds::intrusive::LazyList< GC, T, Traits >
iterator	begin ()
	Returns a forward iterator addressing the first element in a list.
iterator	end ()
	Returns an iterator that addresses the location succeeding the last element in a list.
const_iterator	begin () const
	Returns a forward const iterator addressing the first element in a list.
const_iterator	end () const
	Returns an const iterator that addresses the location succeeding the last element in a list.
	LazyList ()
	Default constructor initializes empty list.
	~LazyList ()
	Destroy list.
bool	insert (value_type &val)
	Inserts new node.
template<typename Func >
bool	insert (value_type &val, Func f)
	Inserts new node.
template<typename Func >
std::pair< bool, bool >	ensure (value_type &val, Func func)
	Ensures that the item exists in the list.
bool	unlink (value_type &val)
	Unlink the item val from the list.
template<typename Q >
bool	erase (const Q &val)
	Delete the item from the list.
template<typename Q , typename Func >
bool	erase (const Q &val, Func func)
	Delete the item from the list.
template<typename Q , typename Func >
bool	find (Q &val, Func f)
	Find the key val.
template<typename Q , typename Func >
bool	find (Q const &val, Func f)
	Find the key val.
template<typename Q >
bool	find (Q const &val)
	Find the key val.
void	clear ()
	Clears the list.
bool	empty () const
	Check if the list is empty.
size_t	size () const
	Returns list's item count.

Detailed Description

template<typename GC, typename T, typename Traits = lazy_list::type_traits>
class cds::container::LazyList< GC, T, Traits >

Lazy ordered list.

Usually, ordered single-linked list is used as a building block for the hash table implementation.

Source:

• [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit "A Lazy Concurrent List-Based Set Algorithm"

The lazy list is based on an optimistic locking scheme for inserts and removes, eliminating the need to use the equivalent of an atomically markable reference. It also has a novel wait-free membership find operation that does not need to perform cleanup operations and is more efficient.

It is non-intrusive version of cds::intrusive::LazyList class

Template arguments:

• GC - garbage collector used
• T - type stored in the list. The type must be default- and copy-constructible.
• Traits - type traits, default is lazy_list::type_traits

Unlike standard container, this implementation does not divide type T into key and value part and may be used as main building block for hash set algorithms.

The key is a function (or a part) of type T, and this function is specified by Traits::compare functor or Traits::less predicate

LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.

It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of Traits template argument. For example, the following traits-based declaration of gc::HP lazy list

#include <cds/container/lazy_list_hp.h>
// Declare comparator for the item
struct my_compare {
    int operator ()( int i1, int i2 )
    {
        return i1 - i2  ;
    }
};

// Declare type_traits
struct my_traits: public cds::container::lazy_list::type_traits
{
    typedef my_compare compare ;
};

// Declare traits-based list
typedef cds::container::LazyList< cds::gc::HP, int, my_traits >     traits_based_list   ;

is equivalent for the following option-based list

#include <cds/container/lazy_list_hp.h>

// my_compare is the same

// Declare option-based list
typedef cds::container::LazyList< cds::gc::HP, int,
    typename cds::container::lazy_list::make_traits<
        cds::container::opt::compare< my_compare >     // item comparator option
    >::type
>     option_based_list   ;

Template argument list Options of cds::container::lazy_list::make_traits metafunction are:

• opt::lock_type - lock type for per-node locking. Default is cds::lock::Spin. Note that each node of the list has member of type lock_type, therefore, heavy-weighted locking primitive is not acceptable as candidate for lock_type.
• opt::compare - key comparison functor. No default functor is provided. If the option is not specified, the opt::less is used.
• opt::less - specifies binary predicate used for key comparision. Default is std::less<T>.
• opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::empty is used.
• opt::item_counter - the type of item counting feature. Default is atomicity::empty_item_counter that is no item counting.
• opt::allocator - the allocator used for creating and freeing list's item. Default is CDS_DEFAULT_ALLOCATOR macro.
• opt::memory_model - C++ memory ordering model. Can be opt::v::relaxed_ordering (relaxed memory model, the default) or opt::v::sequential_consistent (sequentially consisnent memory model).

Usage

There are different specializations of this template for each garbage collecting schema used. You should include appropriate .h-file depending on GC you are using:

• for gc::HP:

  #include <cds/container/lazy_list_hp.h> 

• for gc::PTB:

  #include <cds/container/lazy_list_ptb.h> 

• for gc::HRC:

  #include <cds/container/lazy_list_hrc.h> 

• for gc::nogc:

  #include <cds/container/lazy_list_nogc.h> 

Member Typedef Documentation

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

typedef iterator_type<true> cds::container::LazyList< GC, T, Traits >::const_iterator

Const forward iterator.

For iterator's features and requirements see iterator

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

typedef iterator_type<false> cds::container::LazyList< GC, T, Traits >::iterator

Forward iterator.

The forward iterator for lazy list has some features:

• it has no post-increment operator
• to protect the value, the iterator contains a GC-specific guard + another guard is required locally for increment operator. For some GC (gc::HP, gc::HRC), a guard is limited resource per thread, so an exception (or assertion) "no free guard" may be thrown if a limit of guard count per thread is exceeded.
• The iterator cannot be moved across thread boundary since it contains GC's guard that is thread-private GC data.
• Iterator ensures thread-safety even if you delete the item that iterator points to. However, in case of concurrent deleting operations it is no guarantee that you iterate all item in the list.

Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container for debug purpose only.

Constructor & Destructor Documentation

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

cds::container::LazyList< GC, T, Traits >::LazyList ( )

inline

Default constructor.

Initialize empty list

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

cds::container::LazyList< GC, T, Traits >::~LazyList ( )

inline

List desctructor.

Clears the list

Member Function Documentation

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

iterator cds::container::LazyList< GC, T, Traits >::begin ( )

inline

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

For empty list

begin() == end() 

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

void cds::container::LazyList< GC, T, Traits >::clear ( )

inline

Clears the list.

Post-condition: the list is empty

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename... Args>

bool cds::container::LazyList< GC, T, Traits >::emplace ( Args &&...  args )

inline

Inserts data of type value_type constructed with std::forward<Args>(args)...

Returns true if inserting successful, false otherwise.

This function is available only for compiler that supports variadic template and move semantics

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

iterator cds::container::LazyList< GC, T, Traits >::end ( )

inline

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

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 list. For empty list

begin() == end() 

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q , typename Func >

std::pair<bool, bool> cds::container::LazyList< GC, T, Traits >::ensure ( Q const &  key, Func  f  )

inline

Ensures that the key exists in the list.

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

If the key not found in the list, then the new item created from key is inserted into the list. Otherwise, the functor func is called with the item found. The functor Func should be a function with signature:

void func( bool bNew, value_type& item, const Q& val ) ;

or a functor:

struct my_functor {
    void operator()( bool bNew, value_type& item, const Q& val ) ;
};

with arguments:

• bNew - true if the item has been inserted, false otherwise
• item - item of the list
• val - argument key passed into the ensure function

The functor may change non-key fields of the item; however, func must guarantee that during changing no any other modifications could be made on this item by concurrent threads.

You may pass func argument by reference using boost::ref.

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

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q >

bool cds::container::LazyList< GC, T, Traits >::erase ( const Q &  key )

inline

Delete key from the list.

Since the key of LazyList's item type T is not explicitly specified, template parameter Q defines the key type searching in the list. The list item comparator should be able to compare the type T of list item and the type Q.

Return true if key is found and deleted, false otherwise

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q , typename Func >

bool cds::container::LazyList< GC, T, Traits >::erase ( const Q &  key, Func  f  )

inline

Get value of item with key by a functor and delete it.

The function searches an item with key key, calls f functor and deletes the item. If key is not found, the functor is not called.

The functor Func interface:

struct extractor {
    void operator()(const value_type& val) { ... }
};

The functor may be passed by reference with boost:ref

Since the key of LazyList's item type T is not explicitly specified, template parameter Q defines the key type searching in the list. The list item comparator should be able to compare the type T of list item and the type Q.

Return true if key is found and deleted, false otherwise

See also: erase

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q >

bool cds::container::LazyList< GC, T, Traits >::find ( const Q &  key )

inline

Find the key key.

The function searches the item with key equal to key and returns true if it is found, and false otherwise

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q , typename Func >

bool cds::container::LazyList< GC, T, Traits >::find ( Q &  val, Func  f  )

inline

Find the key val and perform an action with it.

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

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

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

You may pass f argument by reference using boost::ref or cds::ref.

The functor may change non-key fields of item. Note that the function is only guarantee that item cannot be deleted during functor is executing. The function does not serialize simultaneous access to the list item. If such access is possible you must provide your own synchronization schema to exclude unsafe item modifications.

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

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

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q , typename Func >

bool cds::container::LazyList< GC, T, Traits >::find ( Q const &  val, Func  f  )

inline

Find the key val and perform an action with it.

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

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

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

You may pass f argument by reference using boost::ref or cds::ref.

The functor may change non-key fields of item. Note that the function is only guarantee that item cannot be deleted during functor is executing. The function does not serialize simultaneous access to the list item. If such access is possible you must provide your own synchronization schema to exclude unsafe item modifications.

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

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q >

bool cds::container::LazyList< GC, T, Traits >::insert ( Q const &  val )

inline

Inserts new node.

The function creates a node with copy of val value and then inserts the node created into the list.

The type Q should contain as minimum the complete key of the node. The object of value_type should be constructible from val of type Q. In trivial case, Q is equal to value_type.

Returns true if inserting successful, false otherwise.

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

template<typename Q , typename Func >

bool cds::container::LazyList< GC, T, Traits >::insert ( Q const &  key, Func  func  )

inline

Inserts new node.

This function inserts new node with default-constructed value and then it calls func functor with signature

void func( value_type& itemValue ) ;

The argument itemValue of user-defined functor func is the reference to the list's item inserted. User-defined functor func should guarantee that during changing item's value no any other changes could be made on this list's item by concurrent threads. The user-defined functor can be passed by reference using boost::ref and it is called only if the inserting is success.

The type Q should contain the complete key of the node. The object of value_type should be constructible from key of type Q.

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

• create item from key with initializing key-fields only;
• insert new item into the list;
• if inserting is successful, initialize non-key fields of item by calling f functor

This can be useful if complete initialization of object of value_type is heavyweight and it is preferable that the initialization should be completed only if inserting is successful.

template<typename GC , typename T , typename Traits = lazy_list::type_traits>

size_t cds::container::LazyList< GC, T, Traits >::size ( ) const

inline

Returns list's item count.

The value returned depends on opt::item_counter option. For atomicity::empty_item_counter, this function always returns 0.

Warning: even if you use real item counter and it returns 0, this fact is not mean that the list is empty. To check list emptyness use empty() method.

---

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

• cds/container/lazy_list_impl.h