cds  2.2.0
cds::intrusive::EllenBinTree< GC, Key, T, Traits > Class Template Reference

Ellen's et al binary search tree. More...

#include <cds/intrusive/impl/ellen_bintree.h>

Inheritance diagram for cds::intrusive::EllenBinTree< GC, Key, T, Traits >:
cds::container::EllenBinTreeMap< GC, Key, T, Traits > cds::container::EllenBinTreeSet< GC, Key, T, Traits >

Public Types

typedef GC gc
 Garbage collector.
 
typedef Key key_type
 type of a key to be stored in internal nodes; key is a part of value_type
 
typedef T value_type
 type of value stored in the binary tree
 
typedef Traits traits
 Traits template parameter.
 
typedef traits::hook hook
 hook type
 
typedef hook::node_type node_type
 node type
 
typedef traits::disposer disposer
 leaf node disposer
 
typedef traits::back_off back_off
 back-off strategy
 
typedef gc::template guarded_ptr< value_typeguarded_ptr
 Guarded pointer.
 
typedef implementation_defined key_comparator
 key compare functor based on Traits::compare and Traits::less
 
typedef get_node_traits< value_type, node_type, hook >::type node_traits
 Node traits.
 
typedef traits::item_counter item_counter
 Item counting policy.
 
typedef traits::memory_model memory_model
 Memory ordering, see cds::opt::memory_model.
 
typedef traits::stat stat
 internal statistics type
 
typedef traits::key_extractor key_extractor
 key extracting functor
 
typedef traits::node_allocator node_allocator
 Allocator for internal node.
 
typedef traits::update_desc_allocator update_desc_allocator
 Update descriptor allocator.
 

Public Member Functions

 EllenBinTree ()
 Default constructor.
 
 ~EllenBinTree ()
 Clears the tree.
 
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 node. More...
 
bool unlink (value_type &val)
 Unlinks the item val from the tree. More...
 
template<typename Q >
bool erase (const Q &key)
 Deletes the item from the tree. More...
 
template<typename Q , typename Less >
bool erase_with (const Q &key, Less pred)
 Delete the item from the tree with comparing functor pred. More...
 
template<typename Q , typename Func >
bool erase (Q const &key, Func f)
 Deletes the item from the tree. More...
 
template<typename Q , typename Less , typename Func >
bool erase_with (Q const &key, Less pred, Func f)
 Delete the item from the tree with comparing functor pred. More...
 
guarded_ptr extract_min ()
 Extracts an item with minimal key from the tree. More...
 
guarded_ptr extract_max ()
 Extracts an item with maximal key from the tree. More...
 
template<typename Q >
guarded_ptr extract (Q const &key)
 Extracts an item from the tree. More...
 
template<typename Q , typename Less >
guarded_ptr extract_with (Q const &key, Less pred)
 Extracts an item from the tree using pred for searching. More...
 
template<typename Q >
bool contains (Q const &key) const
 Checks whether the set contains key. More...
 
template<typename Q , typename Less >
bool contains (Q const &key, Less pred) const
 Checks whether the set contains key using pred predicate for searching. More...
 
template<typename Q , typename Func >
bool find (Q &key, Func f) const
 Finds the key key. More...
 
template<typename Q , typename Less , typename Func >
bool find_with (Q &key, Less pred, Func f) const
 Finds the key key with comparing functor pred. More...
 
template<typename Q >
guarded_ptr get (Q const &key) const
 Finds key and returns the item found. More...
 
template<typename Q , typename Less >
guarded_ptr get_with (Q const &key, Less pred) const
 Finds key with predicate pred and returns the item found. More...
 
bool empty () const
 Checks if the tree is empty.
 
void clear ()
 Clears the tree (thread safe, not atomic) More...
 
void unsafe_clear ()
 Clears the tree (not thread safe) More...
 
size_t size () const
 Returns item count in the tree. More...
 
stat const & statistics () const
 Returns const reference to internal statistics.
 
bool check_consistency () const
 Checks internal consistency (not atomic, not thread-safe) More...
 

Static Public Attributes

static constexpr const size_t c_nHazardPtrCount = 9
 Count of hazard pointer required for the algorithm.
 

Protected Attributes

item_counter m_ItemCounter
 item counter
 
stat m_Stat
 internal statistics
 

Detailed Description

template<class GC, typename Key, typename T, class Traits = ellen_bintree::traits>
class cds::intrusive::EllenBinTree< GC, Key, T, Traits >

Ellen's et al binary search tree.

Source:

  • [2010] F.Ellen, P.Fatourou, E.Ruppert, F.van Breugel "Non-blocking Binary Search Tree"

EllenBinTree is an unbalanced leaf-oriented binary search tree that implements the set abstract data type. Nodes maintains child pointers but not parent pointers. Every internal node has exactly two children, and all data of type T currently in the tree are stored in the leaves. Internal nodes of the tree are used to direct find() operation along the path to the correct leaf. The keys (of Key type) stored in internal nodes may or may not be in the set. Key type is a subset of T type. There should be exactly defined a key extracting functor for converting object of type T to object of type Key.

Due to extract_min() and extract_max() member functions the EllenBinTree can act as a priority queue. In this case you should provide unique compound key, for example, the priority value plus some uniformly distributed random value.

Note
In the current implementation we do not use helping technique described in the original paper. In Hazard Pointer schema the helping is too complicated and does not give any observable benefits. Instead of helping, when a thread encounters a concurrent operation it just spins waiting for the operation done. Such solution allows greatly simplify implementation of the tree.
Attention
Recall the tree is unbalanced. The complexity of operations is O(log N) for uniformly distributed random keys, but in the worst case the complexity is O(N).
Note
Do not include <cds/intrusive/impl/ellen_bintree.h> header file explicitly. There are header file for each GC type:
  • <cds/intrusive/ellen_bintree_hp.h> - for Hazard Pointer GC cds::gc::HP
  • <cds/intrusive/ellen_bintree_dhp.h> - for Dynamic Hazard Pointer GC cds::gc::DHP
  • <cds/intrusive/ellen_bintree_rcu.h> - for RCU (see RCU-based EllenBinTree)

Template arguments :

Predicate requirements

Traits::less, Traits::compare and other predicates using with member fuctions should accept at least parameters of type T and Key in any combination. For example, for Foo struct with std::string key field the appropiate less functor is:

struct Foo: public cds::intrusive::ellen_bintree::node< ... >
{
std::string m_strKey;
...
};
struct less {
bool operator()( Foo const& v1, Foo const& v2 ) const
{ return v1.m_strKey < v2.m_strKey ; }
bool operator()( Foo const& v, std::string const& s ) const
{ return v.m_strKey < s ; }
bool operator()( std::string const& s, Foo const& v ) const
{ return s < v.m_strKey ; }
// Support comparing std::string and char const *
bool operator()( std::string const& s, char const * p ) const
{ return s.compare(p) < 0 ; }
bool operator()( Foo const& v, char const * p ) const
{ return v.m_strKey.compare(p) < 0 ; }
bool operator()( char const * p, std::string const& s ) const
{ return s.compare(p) > 0; }
bool operator()( char const * p, Foo const& v ) const
{ return v.m_strKey.compare(p) > 0; }
};

Usage examples see here

Member Function Documentation

§ check_consistency()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::check_consistency ( ) const
inline

Checks internal consistency (not atomic, not thread-safe)

The debugging function to check internal consistency of the tree.

§ clear()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
void cds::intrusive::EllenBinTree< GC, Key, T, Traits >::clear ( )
inline

Clears the tree (thread safe, not atomic)

The function unlink all items from the tree. The function is thread safe but not atomic: in multi-threaded environment with parallel insertions this sequence

tree.clear();
assert( tree.empty());

the assertion could be raised.

For each leaf the disposer will be called after unlinking.

§ contains() [1/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::contains ( Q const &  key) const
inline

Checks whether the set contains key.

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

§ contains() [2/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::contains ( Q const &  key,
Less  pred 
) const
inline

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

The function is similar to 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.

§ erase() [1/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::erase ( const Q &  key)
inline

Deletes the item from the tree.

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

Note the Traits::less and/or Traits::compare predicate should accept a parameter of type Q that can be not the same as value_type.

§ erase() [2/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Func >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::erase ( Q const &  key,
Func  f 
)
inline

Deletes the item from the tree.

The function searches an item with key equal to key in the tree, call f functor with item found, unlinks it from the tree, and returns true. The disposer specified in Traits 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 Traits::less and/or Traits::compare predicate should accept a parameter of type Q that can be not the same as value_type.

§ erase_with() [1/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::erase_with ( const Q &  key,
Less  pred 
)
inline

Delete the item from the tree with comparing functor pred.

The function is an analog of erase(Q const&) but pred predicate is used for key comparing. Less has the interface like std::less and should meet Predicate requirements. pred must imply the same element order as the comparator used for building the tree.

§ erase_with() [2/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less , typename Func >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::erase_with ( Q const &  key,
Less  pred,
Func  f 
)
inline

Delete the item from the tree with comparing functor pred.

The function is an analog of erase(Q const&, Func) but pred predicate is used for key comparing. Less has the interface like std::less and should meet Predicate requirements. pred must imply the same element order as the comparator used for building the tree.

§ extract()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q >
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::extract ( Q const &  key)
inline

Extracts an item from the tree.

The function searches an item with key equal to key in the tree, unlinks it, and returns a guarded pointer to an item found. If the item is not found the function returns an empty guarded_ptr.

guarded_ptr prevents disposer invocation for returned item, see cds::gc::guarded_ptr for explanation.

Note
Each guarded_ptr object uses the GC's guard that can be limited resource.

§ extract_max()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::extract_max ( )
inline

Extracts an item with maximal key from the tree.

The function searches an item with maximal key, unlinks it, and returns a guarded pointer to an item found. If the tree is empty the function returns an empty guarded_ptr.

Note
Due the concurrent nature of the tree, the function extracts nearly maximal key. It means that the function gets rightmost leaf of the tree and tries to unlink it. During unlinking, a concurrent thread may insert an item with key great than rightmost item's key. So, the function returns the item with maximal key at the moment of tree traversing.

The returned guarded_ptr prevents disposer invocation for returned item, see cds::gc::guarded_ptr for explanation.

Note
Each guarded_ptr object uses the GC's guard that can be limited resource.

§ extract_min()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::extract_min ( )
inline

Extracts an item with minimal key from the tree.

The function searches an item with minimal key, unlinks it, and returns a guarded pointer to an item found. If the tree is empty the function returns an empty guarded pointer.

Note
Due the concurrent nature of the tree, the function extracts nearly minimum key. It means that the function gets leftmost leaf of the tree and tries to unlink it. During unlinking, a concurrent thread may insert an item with key less than leftmost item's key. So, the function returns the item with minimum key at the moment of tree traversing.

The returned guarded_ptr prevents disposer invocation for returned item, see cds::gc::guarded_ptr for explanation.

Note
Each guarded_ptr object uses the GC's guard that can be limited resource.

§ extract_with()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less >
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::extract_with ( Q const &  key,
Less  pred 
)
inline

Extracts an item from the tree using pred for searching.

The function is an analog of extract(Q const&) but pred is used for key compare. Less has the interface like std::less and should meet Predicate requirements. pred must imply the same element order as the comparator used for building the tree.

§ find()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Func >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::find ( Q &  key,
Func  f 
) const
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. Note that the functor is only guarantee that item cannot be disposed during functor is executing. The functor does not serialize simultaneous access to the tree item. If such access is possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.

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

§ find_with()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less , typename Func >
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::find_with ( Q &  key,
Less  pred,
Func  f 
) const
inline

Finds the key key with comparing functor pred.

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

§ get()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q >
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::get ( Q const &  key) const
inline

Finds key and returns the item found.

The function searches the item with key equal to key and returns the item found as guarded_ptr object. The function returns an empty guarded pointer is key is not found.

guarded_ptr prevents disposer invocation for returned item, see cds::gc::guarded_ptr for explanation.

Note
Each guarded_ptr object uses the GC's guard that can be limited resource.

§ get_with()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Q , typename Less >
guarded_ptr cds::intrusive::EllenBinTree< GC, Key, T, Traits >::get_with ( Q const &  key,
Less  pred 
) const
inline

Finds key with predicate pred and returns the item found.

The function is an analog of get(Q const&) but pred is used for key comparing. Less functor has the interface like std::less and should meet Predicate requirements. pred must imply the same element order as the comparator used for building the tree.

§ insert() [1/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::insert ( value_type val)
inline

Inserts new node.

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

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

§ insert() [2/2]

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Func >
bool cds::intrusive::EllenBinTree< GC, Key, T, 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 tree
  • 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. User-defined functor f should guarantee that during changing val no any other changes could be made on this tree's item by concurrent threads. The user-defined functor is called only if the inserting is success.

§ size()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
size_t cds::intrusive::EllenBinTree< GC, Key, T, Traits >::size ( ) const
inline

Returns item count in the tree.

Only leaf nodes containing user data are counted.

The value returned depends on item counter type provided by Traits template parameter. If it is atomicity::empty_item_counter this function always returns 0. The function is not suitable for checking the tree emptiness, use empty() member function for this purpose.

§ unlink()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
bool cds::intrusive::EllenBinTree< GC, Key, T, Traits >::unlink ( value_type val)
inline

Unlinks the item val from the tree.

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

Difference between erase and unlink functions: erase finds a key and deletes the item found. unlink finds an item by key and deletes it only if val is a node, i.e. the pointer to item found is equal to &val .

The disposer specified in Traits class template parameter is called by garbage collector GC asynchronously.

The function returns true if success and false otherwise.

§ unsafe_clear()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
void cds::intrusive::EllenBinTree< GC, Key, T, Traits >::unsafe_clear ( )
inline

Clears the tree (not thread safe)

This function is not thread safe and may be called only when no other thread deals with the tree. The function is used in the tree destructor.

§ update()

template<class GC , typename Key , typename T , class Traits = ellen_bintree::traits>
template<typename Func >
std::pair<bool, bool> cds::intrusive::EllenBinTree< GC, Key, T, Traits >::update ( value_type val,
Func  func,
bool  bAllowInsert = true 
)
inline

Updates the node.

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

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

void func( 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 refer to the same thing.

The functor can 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.

Returns std::pair<bool, bool> where first is true if operation is successful, i.e. the node has been inserted or updated, second is true if new item has been added or false if the item with key already exists.

Warning
See insert item troubleshooting

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

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