Source:
- [2005] Steve Heller, Maurice Herlihy, Victor Luchangco, Mark Moir, William N. Scherer III, and Nir Shavit
- "A Lazy Concurrent List-Based Set Algorithm"
+ "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 \p find operation
+ reference. It also has a novel wait-free membership \p find() operation
that does not need to perform cleanup operations and is more efficient.
- It is non-intrusive version of cds::intrusive::LazyList class.
+ It is non-intrusive version of \p cds::intrusive::LazyList class.
Template arguments:
- - \p GC - garbage collector used
- - \p T - type stored in the list. The type must be default- and copy-constructible.
- - \p Traits - type traits, default is lazy_list::type_traits
+ - \p GC - garbage collector: \p gc::HP, \p gp::DHP
+ - \p T - type to be stored in the list.
+ - \p Traits - type traits, default is \p lazy_list::traits.
+ It is possible to declare option-based list with \p lazy_list::make_traits metafunction istead of \p Traits template
+ argument. For example, the following traits-based declaration of \p gc::HP lazy list
+ \code
+ #include <cds/container/lazy_list_hp.h>
+ // Declare comparator for the item
+ struct my_compare {
+ int operator ()( int i1, int i2 )
+ {
+ return i1 - i2;
+ }
+ };
- Unlike standard container, this implementation does not divide type \p T into key and value part and
- may be used as main building block for hash set algorithms.
+ // Declare type_traits
+ struct my_traits: public cds::container::lazy_list::traits
+ {
+ typedef my_compare compare;
+ };
- The key is a function (or a part) of type \p T, and this function is specified by <tt> Traits::compare </tt> functor
- or <tt> Traits::less </tt> predicate.
+ // Declare traits-based list
+ typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
+ \endcode
+ is equal to the following option-based list:
+ \code
+ #include <cds/container/lazy_list_hp.h>
- You don't need to include <tt><cds/container/impl/lazy_list.h></tt>. Instead, you should do:
- - <tt><cds/container/lazy_list_hp.h></tt> - for gc::HP-based lazy list
- - <tt><cds/container/lazy_list_ptb.h></tt> - for gc::PTB-based lazy list
- - <tt><cds/container/lazy_list_rcu.h></tt> - for @ref cds_urcu_desc "RCU" based lazy list
+ // my_compare is the same
- LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
+ // 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;
+ \endcode
- It is possible to declare option-based list with cds::container::lazy_list::make_traits metafunction istead of \p Traits template
- argument. For example, the following traits-based declaration of gc::HP lazy list
- \code
- #include <cds/container/lazy_list_hp.h>
- // Declare comparator for the item
- struct my_compare {
- int operator ()( int i1, int i2 )
- {
- return i1 - i2;
- }
- };
+ Unlike standard container, this implementation does not divide type \p T into key and value part and
+ may be used as main building block for hash set algorithms.
- // Declare type_traits
- struct my_traits: public cds::container::lazy_list::type_traits
- {
- typedef my_compare compare;
- };
+ The key is a function (or a part) of type \p T, and the comparing function is specified by \p Traits::compare functor
+ or \p Traits::less predicate.
- // Declare traits-based list
- typedef cds::container::LazyList< cds::gc::HP, int, my_traits > traits_based_list;
- \endcode
-
- is equivalent for the following option-based list
- \code
- #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;
- \endcode
-
- Template argument list \p 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 <b>each</b> node
- of the list has member of type \p lock_type, therefore, heavy-weighted locking primitive is not
- acceptable as candidate for \p lock_type.
- - opt::compare - key compare 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 compare. Default is \p 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 \ref atomicity::empty_item_counter that is no item counting.
- - opt::allocator - the allocator used for creating and freeing list's item. Default is \ref 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).
+ \p LazyKVList is a key-value version of lazy non-intrusive list that is closer to the C++ std library approach.
\par 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: \code #include <cds/container/lazy_list_hp.h> \endcode
- - for gc::PTB: \code #include <cds/container/lazy_list_ptb.h> \endcode
- - for gc::HRC: \code #include <cds/container/lazy_list_hrc.h> \endcode
- - for \ref cds_urcu_desc "RCU": \code #include <cds/container/lazy_list_rcu.h> \endcode
- - for gc::nogc: \code #include <cds/container/lazy_list_nogc.h> \endcode
+ - for gc::HP: <tt> <cds/container/lazy_list_hp.h> </tt>
+ - for gc::DHP: <tt> <cds/container/lazy_list_dhp.h> </tt>
+ - for \ref cds_urcu_desc "RCU": <tt> <cds/container/lazy_list_rcu.h> </tt>
+ - for gc::nogc: <tt> <cds/container/lazy_list_nogc.h> </tt>
*/
template <
typename GC,
typename T,
#ifdef CDS_DOXYGEN_INVOKED
- typename Traits = lazy_list::type_traits
+ typename Traits = lazy_list::traits
#else
typename Traits
#endif
#endif
{
//@cond
- typedef details::make_lazy_list< GC, T, Traits > options;
- typedef typename options::type base_class;
+ typedef details::make_lazy_list< GC, T, Traits > maker;
+ typedef typename maker::type base_class;
//@endcond
public:
- typedef T value_type ; ///< Type of value stored in the list
- typedef typename base_class::gc gc ; ///< Garbage collector used
- typedef typename base_class::back_off back_off ; ///< Back-off strategy used
- typedef typename options::allocator_type allocator_type ; ///< Allocator type used for allocate/deallocate the nodes
- typedef typename base_class::item_counter item_counter ; ///< Item counting policy used
- typedef typename options::key_comparator key_comparator ; ///< key comparison functor
- typedef typename base_class::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
+ typedef GC gc; ///< Garbage collector used
+ typedef T value_type; ///< Type of value stored in the list
+ typedef Traits traits; ///< List traits
+
+ typedef typename base_class::back_off back_off; ///< Back-off strategy used
+ typedef typename maker::allocator_type allocator_type; ///< Allocator type used for allocate/deallocate the nodes
+ typedef typename base_class::item_counter item_counter; ///< Item counting policy used
+ typedef typename maker::key_comparator key_comparator; ///< key comparison functor
+ typedef typename base_class::memory_model memory_model; ///< Memory ordering. See cds::opt::memory_model option
protected:
//@cond
- typedef typename base_class::value_type node_type;
- typedef typename options::cxx_allocator cxx_allocator;
- typedef typename options::node_deallocator node_deallocator;
- typedef typename options::type_traits::compare intrusive_key_comparator;
+ typedef typename base_class::value_type node_type;
+ typedef typename maker::cxx_allocator cxx_allocator;
+ typedef typename maker::node_deallocator node_deallocator;
+ typedef typename maker::intrusive_traits::compare intrusive_key_comparator;
- typedef typename base_class::node_type head_type;
+ typedef typename base_class::node_type head_type;
//@endcond
public:
head_type& head()
{
- return *base_class::head();
+ return base_class::m_Head;
}
head_type const& head() const
{
- return *base_class::head();
+ return base_class::m_Head;
}
head_type& tail()
{
- return *base_class::tail();
+ return base_class::m_Tail;
}
head_type const& tail() const
{
- return *base_class::tail();
+ return base_class::m_Tail;
}
//@endcond
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"
+ For some GC (\p gc::HP), 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
++it ; // skip dummy head node
return it;
}
- const_iterator cbegin()
+ const_iterator cbegin() const
{
const_iterator it( head() );
++it ; // skip dummy head node
{
return const_iterator( tail() );
}
- const_iterator cend()
+ const_iterator cend() const
{
return const_iterator( tail() );
}
public:
/// Default constructor
- /**
- Initializes empty list
- */
LazyList()
{}
- /// List desctructor
- /**
- Clears the list
- */
+ /// Destructor clears the list
~LazyList()
{
clear();
/**
This function inserts new node with default-constructed value and then it calls
\p func functor with signature
- \code void func( value_type& itemValue ) ;\endcode
+ \code void func( value_type& item ) ;\endcode
- The argument \p itemValue of user-defined functor \p func is the reference
- to the list's item inserted. User-defined functor \p 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 <tt>boost::ref</tt>
- and it is called only if the inserting is success.
+ The argument \p item of user-defined functor \p func is the reference
+ to the list's item inserted.
+ When \p func is called it has exclusive access to the item.
+ The user-defined functor is called only if the inserting is success.
The type \p Q should contain the complete key of the node.
- The object of \ref value_type should be constructible from \p key of type \p Q.
+ The object of \p value_type should be constructible from \p key of type \p Q.
The function allows to split creating of new item into two part:
- create item from \p key with initializing key-fields only;
- insert new item into the list;
- - if inserting is successful, initialize non-key fields of item by calling \p f functor
+ - if inserting is successful, initialize non-key fields of item by calling \p func functor
This can be useful if complete initialization of object of \p value_type is heavyweight and
it is preferable that the initialization should be completed only if inserting is successful.
return insert_at( head(), key, func );
}
- /// Inserts data of type \ref value_type constructed with <tt>std::forward<Args>(args)...</tt>
+ /// Inserts data of type \p value_type constructed from \p args
/**
Returns \p true if inserting successful, \p false otherwise.
*/
The operation performs inserting or changing data with lock-free manner.
If the \p key not found in the list, then the new item created from \p key
- is inserted into the list. Otherwise, the functor \p func is called with the item found.
- The functor \p Func should be a function with signature:
- \code
- void func( bool bNew, value_type& item, const Q& val );
- \endcode
- or a functor:
+ is inserted into the list. Otherwise, the functor \p f is called with the item found.
+ \p Func signature is:
\code
struct my_functor {
- void operator()( bool bNew, value_type& item, const Q& val );
+ void operator()( bool bNew, value_type& item, const Q& key );
};
\endcode
with arguments:
- \p bNew - \p true if the item has been inserted, \p false otherwise
- - \p item - item of the list
- - \p val - argument \p key passed into the \p ensure function
+ - \p item - an item of the list
+ - \p key - argument \p key passed into the \p %ensure() function
- The functor may change non-key fields of the \p item; however, \p func must guarantee
- that during changing no any other modifications could be made on this item by concurrent threads.
-
- You may pass \p func argument by reference using <tt>boost::ref</tt>.
+ The functor may change non-key fields of the \p item.
+ When \p func is called it has exclusive access to the item.
Returns <tt> std::pair<bool, bool> </tt> where \p first is true if operation is successfull,
\p second is true if new item has been added or \p false if the item with \p key
template <typename Q, typename Less>
bool erase_with( Q const& key, Less pred )
{
- return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), [](value_type const&){} );
+ return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), [](value_type const&){} );
}
/// Deletes \p key from the list
void operator()(const value_type& val) { ... }
};
\endcode
- The functor may be passed by reference with <tt>boost:ref</tt>
Since the key of LazyList's item type \p T is not explicitly specified,
template parameter \p Q defines the key type searching in the list.
template <typename Q, typename Less, typename Func>
bool erase_with( Q const& key, Less pred, Func f )
{
- return erase_at( head(), key, typename options::template less_wrapper<Less>::type(), f );
+ return erase_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
}
/// Extracts the item from the list with specified \p key
template <typename Q, typename Less>
bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
{
- return extract_at( head(), dest.guard(), key, typename options::template less_wrapper<Less>::type() );
+ return extract_at( head(), dest.guard(), key, typename maker::template less_wrapper<Less>::type() );
}
/// Finds the key \p key
return find_at( head(), key, intrusive_key_comparator() );
}
- /// Finds the key \p val using \p pred predicate for searching
+ /// Finds the key \p key using \p pred predicate for searching
/**
The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_val "find(Q const&)"
but \p pred is used for key comparing.
template <typename Q, typename Less>
bool find_with( Q const& key, Less pred )
{
- return find_at( head(), key, typename options::template less_wrapper<Less>::type() );
+ return find_at( head(), key, typename maker::template less_wrapper<Less>::type() );
}
- /// Finds the key \p val and performs an action with it
+ /// Finds the key \p key and performs an action with it
/** \anchor cds_nonintrusive_LazyList_hp_find_func
- The function searches an item with key equal to \p val and calls the functor \p f for the item found.
+ The function searches an item with key equal to \p key and calls the functor \p f for the item found.
The interface of \p Func functor is:
\code
struct functor {
- void operator()( value_type& item, Q& val );
+ void operator()( value_type& item, Q& key );
};
\endcode
- where \p item is the item found, \p val is the <tt>find</tt> function argument.
-
- You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
+ where \p item is the item found, \p key is the <tt>find</tt> function argument.
The functor may change non-key fields of \p item. Note that the function is only guarantee
that \p item cannot be deleted during functor is executing.
The function does not serialize simultaneous access to the list \p item. If such access is
possible you must provide your own synchronization schema to exclude unsafe item modifications.
- The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
+ The \p key argument is non-const since it can be used as \p f functor destination i.e., the functor
may modify both arguments.
- The function returns \p true if \p val is found, \p false otherwise.
+ The function returns \p true if \p key is found, \p false otherwise.
*/
template <typename Q, typename Func>
- bool find( Q& val, Func f )
+ bool find( Q& key, Func f )
{
- return find_at( head(), val, intrusive_key_comparator(), f );
+ return find_at( head(), key, intrusive_key_comparator(), f );
}
- /// Finds the key \p val using \p pred predicate for searching
+ /// Finds the key \p key using \p pred predicate for searching
/**
The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_func "find(Q&, Func)"
but \p pred is used for key comparing.
\p pred must imply the same element order as the comparator used for building the list.
*/
template <typename Q, typename Less, typename Func>
- bool find_with( Q& val, Less pred, Func f )
+ bool find_with( Q& key, Less pred, Func f )
{
- return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
+ return find_at( head(), key, typename maker::template less_wrapper<Less>::type(), f );
}
- /// Finds the key \p val and performs an action with it
- /** \anchor cds_nonintrusive_LazyList_hp_find_cfunc
- The function searches an item with key equal to \p val and calls the functor \p f for the item found.
- The interface of \p Func functor is:
- \code
- struct functor {
- void operator()( value_type& item, Q const& val );
- };
- \endcode
- where \p item is the item found, \p val is the <tt>find</tt> function argument.
-
- You may pass \p f argument by reference using <tt>boost::ref</tt> or cds::ref.
-
- The function does not serialize simultaneous access to the list \p item. If such access is
- possible you must provide your own synchronization schema to exclude unsafe item modifications.
-
- The function returns \p true if \p val is found, \p false otherwise.
- */
- template <typename Q, typename Func>
- bool find( Q const& val, Func f )
- {
- return find_at( head(), val, intrusive_key_comparator(), f );
- }
-
- /// Finds the key \p val using \p pred predicate for searching
- /**
- The function is an analog of \ref cds_nonintrusive_LazyList_hp_find_cfunc "find(Q&, Func)"
- but \p pred is used for key comparing.
- \p Less functor has the interface like \p std::less.
- \p pred must imply the same element order as the comparator used for building the list.
- */
- template <typename Q, typename Less, typename Func>
- bool find_with( Q const& val, Less pred, Func f )
- {
- return find_at( head(), val, typename options::template less_wrapper<Less>::type(), f );
- }
-
- /// Finds the key \p val and return the item found
+ /// Finds the key \p key and return the item found
/** \anchor cds_nonintrusive_LazyList_hp_get
- The function searches the item with key equal to \p val
+ The function searches the item with key equal to \p key
and assigns the item found to guarded pointer \p ptr.
- The function returns \p true if \p val is found, and \p false otherwise.
- If \p val is not found the \p ptr parameter is not changed.
+ The function returns \p true if \p key is found, and \p false otherwise.
+ If \p key is not found the \p ptr parameter is not changed.
@note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
should accept a parameter of type \p Q that can be not the same as \p value_type.
*/
template <typename Q>
- bool get( guarded_ptr& ptr, Q const& val )
+ bool get( guarded_ptr& ptr, Q const& key )
{
- return get_at( head(), ptr.guard(), val, intrusive_key_comparator() );
+ return get_at( head(), ptr.guard(), key, intrusive_key_comparator() );
}
- /// Finds the key \p val and return the item found
+ /// Finds the key \p key and return the item found
/**
The function is an analog of \ref cds_nonintrusive_LazyList_hp_get "get( guarded_ptr& ptr, Q const&)"
but \p pred is used for comparing the keys.
\p pred must imply the same element order as the comparator used for building the list.
*/
template <typename Q, typename Less>
- bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
+ bool get_with( guarded_ptr& ptr, Q const& key, Less pred )
{
- return get_at( head(), ptr.guard(), val, typename options::template less_wrapper<Less>::type() );
+ return get_at( head(), ptr.guard(), key, typename maker::template less_wrapper<Less>::type() );
}
- /// Checks if the list is empty
+ /// Checks whether the list is empty
bool empty() const
{
return base_class::empty();
/// Returns list's item count
/**
- The value returned depends on opt::item_counter option. For atomicity::empty_item_counter,
+ The value returned depends on \p Traits::item_counter type. For \p atomicity::empty_item_counter,
this function always returns 0.
- <b>Warning</b>: even if you use real item counter and it returns 0, this fact is not mean that the list
+ @note 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 \ref empty() method.
*/
size_t size() const
}
/// Clears the list
- /**
- Post-condition: the list is empty
- */
void clear()
{
base_class::clear();
{
scoped_node_ptr pNode( alloc_node( key ));
- if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ cds::unref(f)( node_to_value(node) ); } )) {
+ if ( base_class::insert_at( &refHead, *pNode, [&f](node_type& node){ f( node_to_value(node) ); } )) {
pNode.release();
return true;
}
template <typename Q, typename Compare, typename Func>
bool erase_at( head_type& refHead, const Q& key, Compare cmp, Func f )
{
- return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ cds::unref(f)( node_to_value(node) ); } );
+ return base_class::erase_at( &refHead, key, cmp, [&f](node_type const& node){ f( node_to_value(node) ); } );
}
template <typename Q, typename Compare>
scoped_node_ptr pNode( alloc_node( key ));
std::pair<bool, bool> ret = base_class::ensure_at( &refHead, *pNode,
- [&f, &key](bool bNew, node_type& node, node_type&){cds::unref(f)( bNew, node_to_value(node), key ); });
+ [&f, &key](bool bNew, node_type& node, node_type&){f( bNew, node_to_value(node), key ); });
if ( ret.first && ret.second )
pNode.release();
template <typename Q, typename Compare, typename Func>
bool find_at( head_type& refHead, Q& val, Compare cmp, Func f )
{
- return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ cds::unref(f)( node_to_value(node), val ); });
+ return base_class::find_at( &refHead, val, cmp, [&f](node_type& node, Q& val){ f( node_to_value(node), val ); });
}
template <typename Q, typename Compare>
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