-//$$CDS-header$$
+/*
+ This file is a part of libcds - Concurrent Data Structures library
-#ifndef __CDS_INTRUSIVE_IMPL_SKIP_LIST_H
-#define __CDS_INTRUSIVE_IMPL_SKIP_LIST_H
+ (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
+
+ Source code repo: http://github.com/khizmax/libcds/
+ Download: http://sourceforge.net/projects/libcds/files/
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+ list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#ifndef CDSLIB_INTRUSIVE_IMPL_SKIP_LIST_H
+#define CDSLIB_INTRUSIVE_IMPL_SKIP_LIST_H
#include <type_traits>
#include <memory>
#include <cds/intrusive/details/skip_list_base.h>
#include <cds/opt/compare.h>
#include <cds/details/binary_functor_wrapper.h>
-#include <cds/gc/guarded_ptr.h>
namespace cds { namespace intrusive {
typedef BackOff back_off;
typedef typename node_traits::node_type node_type;
typedef typename node_traits::value_type value_type;
- static bool const c_isConst = IsConst;
+ static CDS_CONSTEXPR bool const c_isConst = IsConst;
- typedef typename std::conditional< c_isConst, value_type const &, value_type &>::type value_ref;
+ typedef typename std::conditional< c_isConst, value_type const&, value_type&>::type value_ref;
protected:
typedef typename node_type::marked_ptr marked_ptr;
protected:
static value_type * gc_protect( marked_ptr p )
{
- return node_traits::to_value_ptr( p.ptr() );
+ return node_traits::to_value_ptr( p.ptr());
}
void next()
back_off bkoff;
for (;;) {
- if ( m_pNode->next( m_pNode->height() - 1 ).load( atomics::memory_order_acquire ).bits() ) {
+ if ( m_pNode->next( m_pNode->height() - 1 ).load( atomics::memory_order_acquire ).bits()) {
// Current node is marked as deleted. So, its next pointer can point to anything
// In this case we interrupt our iteration and returns end() iterator.
*this = iterator();
marked_ptr p = m_guard.protect( (*m_pNode)[0], gc_protect );
node_type * pp = p.ptr();
- if ( p.bits() ) {
+ if ( p.bits()) {
// p is marked as deleted. Spin waiting for physical removal
bkoff();
continue;
}
- else if ( pp && pp->next( pp->height() - 1 ).load( atomics::memory_order_relaxed ).bits() ) {
+ else if ( pp && pp->next( pp->height() - 1 ).load( atomics::memory_order_relaxed ).bits()) {
// p is marked as deleted. Spin waiting for physical removal
bkoff();
continue;
for (;;) {
marked_ptr p = m_guard.protect( refHead[0], gc_protect );
- if ( !p.ptr() ) {
+ if ( !p.ptr()) {
// empty skip-list
m_guard.clear();
break;
node_type * pp = p.ptr();
// Logically deleted node is marked from highest level
- if ( !pp->next( pp->height() - 1 ).load( atomics::memory_order_acquire ).bits() ) {
+ if ( !pp->next( pp->height() - 1 ).load( atomics::memory_order_acquire ).bits()) {
m_pNode = pp;
break;
}
iterator( iterator const& s)
: m_pNode( s.m_pNode )
{
- m_guard.assign( node_traits::to_value_ptr(m_pNode) );
+ m_guard.assign( node_traits::to_value_ptr(m_pNode));
}
value_type * operator ->() const
return *this;
}
- iterator& operator = (const iterator& src)
+ iterator& operator =(const iterator& src)
{
m_pNode = src.m_pNode;
m_guard.copy( src.m_guard );
The lock-free variant of skip-list is implemented according to book
- [2008] M.Herlihy, N.Shavit "The Art of Multiprocessor Programming",
chapter 14.4 "A Lock-Free Concurrent Skiplist".
- \note The algorithm described in this book cannot be directly adapted for C++ (roughly speaking,
- the algo contains a lot of bugs). The \b libcds implementation applies the approach discovered
- by M.Michael in his \ref cds_intrusive_MichaelList_hp "lock-free linked list".
<b>Template arguments</b>:
- - \p GC - Garbage collector used. Note the \p GC must be the same as the GC used for item type \p T (see skip_list::node).
- - \p T - type to be stored in the list. The type must be based on skip_list::node (for skip_list::base_hook)
- or it must have a member of type skip_list::node (for skip_list::member_hook).
- - \p Traits - type traits. See skip_list::type_traits for explanation.
-
- It is possible to declare option-based list with cds::intrusive::skip_list::make_traits metafunction istead of \p Traits template
- argument.
- Template argument list \p Options of cds::intrusive::skip_list::make_traits metafunction are:
- - opt::hook - hook used. Possible values are: skip_list::base_hook, skip_list::member_hook, skip_list::traits_hook.
- If the option is not specified, <tt>skip_list::base_hook<></tt> and gc::HP is used.
- - 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 comparison. Default is \p std::less<T>.
- - opt::disposer - the functor used for dispose removed items. Default is opt::v::empty_disposer. Due the nature
- of GC schema the disposer may be called asynchronously.
- - opt::item_counter - the type of item counting feature. Default is \ref atomicity::empty_item_counter that is no item counting.
- - 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).
- - skip_list::random_level_generator - random level generator. Can be skip_list::xorshift, skip_list::turbo_pascal or
- user-provided one. See skip_list::random_level_generator option description for explanation.
- Default is \p %skip_list::turbo_pascal.
- - opt::allocator - although the skip-list is an intrusive container,
- an allocator should be provided to maintain variable randomly-calculated height of the node
- since the node can contain up to 32 next pointers. The allocator option is used to allocate an array of next pointers
- for nodes which height is more than 1. Default is \ref CDS_DEFAULT_ALLOCATOR.
- - opt::back_off - back-off strategy used. If the option is not specified, the cds::backoff::Default is used.
- - opt::stat - internal statistics. Available types: skip_list::stat, skip_list::empty_stat (the default)
-
- \warning The skip-list requires up to 67 hazard pointers that may be critical for some GCs for which
+ - \p GC - Garbage collector used. Note the \p GC must be the same as the GC used for item type \p T, see \p skip_list::node.
+ - \p T - type to be stored in the list. The type must be based on \p skip_list::node (for \p skip_list::base_hook)
+ or it must have a member of type \p skip_list::node (for \p skip_list::member_hook).
+ - \p Traits - skip-list traits, default is \p skip_list::traits.
+ It is possible to declare option-based list with \p cds::intrusive::skip_list::make_traits metafunction istead of \p Traits
+ template argument.
+
+ @warning The skip-list requires up to 67 hazard pointers that may be critical for some GCs for which
the guard count is limited (like as \p gc::HP). Those GCs should be explicitly initialized with
hazard pointer enough: \code cds::gc::HP myhp( 67 ) \endcode. Otherwise an run-time exception may be raised
when you try to create skip-list object.
- \note There are several specializations of \p %SkipListSet for each \p GC. You should include:
- - <tt><cds/intrusive/skip_list_hp.h></tt> for gc::HP garbage collector
- - <tt><cds/intrusive/skip_list_ptb.h></tt> for gc::PTB garbage collector
- - <tt><cds/intrusive/skip_list_nogc.h></tt> for \ref cds_intrusive_SkipListSet_nogc for persistent set
+ There are several specializations of \p %SkipListSet for each \p GC. You should include:
+ - <tt><cds/intrusive/skip_list_hp.h></tt> for \p gc::HP garbage collector
+ - <tt><cds/intrusive/skip_list_dhp.h></tt> for \p gc::DHP garbage collector
+ - <tt><cds/intrusive/skip_list_nogc.h></tt> for \ref cds_intrusive_SkipListSet_nogc for append-only set
- <tt><cds/intrusive/skip_list_rcu.h></tt> for \ref cds_intrusive_SkipListSet_rcu "RCU type"
<b>Iterators</b>
so, the element cannot be reclaimed while the iterator object is alive.
However, passing an iterator object between threads is dangerous.
- \warning Due to concurrent nature of skip-list set it is not guarantee that you can iterate
+ @warning Due to concurrent nature of skip-list set it is not guarantee that you can iterate
all elements in the set: any concurrent deletion can exclude the element
pointed by the iterator from the set, and your iteration can be terminated
before end of the set. Therefore, such iteration is more suitable for debugging purpose only
Remember, each iterator object requires 2 additional hazard pointers, that may be
- a limited resource for \p GC like as \p gc::HP (for \p gc::PTB the count of
+ a limited resource for \p GC like as \p gc::HP (for \p gc::DHP the count of
guards is unlimited).
The iterator class supports the following minimalistic interface:
bool operator !=(iterator const& i ) const;
};
\endcode
- Note, the iterator object returned by \ref end, \p cend member functions points to \p nullptr and should not be dereferenced.
+ Note, the iterator object returned by \p end(), \p cend() member functions points to \p nullptr and should not be dereferenced.
<b>How to use</b>
- You should incorporate skip_list::node into your struct \p T and provide
- appropriate skip_list::type_traits::hook in your \p Traits template parameters. Usually, for \p Traits you
- define a struct based on skip_list::type_traits.
+ You should incorporate \p skip_list::node into your struct \p T and provide
+ appropriate \p skip_list::traits::hook in your \p Traits template parameters. Usually, for \p Traits you
+ define a struct based on \p skip_list::traits.
- Example for gc::HP and base hook:
+ Example for \p gc::HP and base hook:
\code
// Include GC-related skip-list specialization
#include <cds/intrusive/skip_list_hp.h>
};
- // Declare type_traits
- struct my_traits: public cds::intrusive::skip_list::type_traits
+ // Declare your traits
+ struct my_traits: public cds::intrusive::skip_list::traits
{
typedef cds::intrusive::skip_list::base_hook< cds::opt::gc< cds::gc::HP > > hook;
typedef my_data_cmp compare;
class GC
,typename T
#ifdef CDS_DOXYGEN_INVOKED
- ,typename Traits = skip_list::type_traits
+ ,typename Traits = skip_list::traits
#else
,typename Traits
#endif
class SkipListSet
{
public:
- typedef T value_type ; ///< type of value stored in the skip-list
- typedef Traits options ; ///< Traits template parameter
+ typedef GC gc; ///< Garbage collector
+ typedef T value_type; ///< type of value stored in the skip-list
+ typedef Traits traits; ///< Traits template parameter
- typedef typename options::hook hook ; ///< hook type
- typedef typename hook::node_type node_type ; ///< node type
+ typedef typename traits::hook hook; ///< hook type
+ typedef typename hook::node_type node_type; ///< node type
# ifdef CDS_DOXYGEN_INVOKED
typedef implementation_defined key_comparator ; ///< key comparison functor based on opt::compare and opt::less option setter.
# else
- typedef typename opt::details::make_comparator< value_type, options >::type key_comparator;
+ typedef typename opt::details::make_comparator< value_type, traits >::type key_comparator;
# endif
- typedef typename options::disposer disposer ; ///< disposer used
- typedef typename get_node_traits< value_type, node_type, hook>::type node_traits ; ///< node traits
+ typedef typename traits::disposer disposer; ///< item disposer
+ typedef typename get_node_traits< value_type, node_type, hook>::type node_traits; ///< node traits
- typedef GC gc ; ///< Garbage collector
- typedef typename options::item_counter item_counter ; ///< Item counting policy used
- typedef typename options::memory_model memory_model ; ///< Memory ordering. See cds::opt::memory_model option
- typedef typename options::random_level_generator random_level_generator ; ///< random level generator
- typedef typename options::allocator allocator_type ; ///< allocator for maintaining array of next pointers of the node
- typedef typename options::back_off back_off ; ///< Back-off strategy
- typedef typename options::stat stat ; ///< internal statistics type
+ typedef typename traits::item_counter item_counter; ///< Item counting policy
+ typedef typename traits::memory_model memory_model; ///< Memory ordering, see \p cds::opt::memory_model option
+ typedef typename traits::random_level_generator random_level_generator; ///< random level generator
+ typedef typename traits::allocator allocator_type; ///< allocator for maintaining array of next pointers of the node
+ typedef typename traits::back_off back_off; ///< Back-off strategy
+ typedef typename traits::stat stat; ///< internal statistics type
public:
- typedef cds::gc::guarded_ptr< gc, value_type > guarded_ptr; ///< Guarded pointer
+ typedef typename gc::template guarded_ptr< value_type > guarded_ptr; ///< Guarded pointer
/// Max node height. The actual node height should be in range <tt>[0 .. c_nMaxHeight)</tt>
/**
The max height is specified by \ref skip_list::random_level_generator "random level generator" constant \p m_nUpperBound
- but it should be no more than 32 (\ref skip_list::c_nHeightLimit).
+ but it should be no more than 32 (\p skip_list::c_nHeightLimit).
*/
static unsigned int const c_nMaxHeight = std::conditional<
(random_level_generator::c_nUpperBound <= skip_list::c_nHeightLimit),
static unsigned int const c_nMinHeight = 5;
//@endcond
+ // c_nMaxHeight * 2 - pPred/pSucc guards
+ // + 1 - for erase, unlink
+ // + 1 - for clear
+ // + 1 - for help_remove()
+ static size_t const c_nHazardPtrCount = c_nMaxHeight * 2 + 3; ///< Count of hazard pointer required for the skip-list
+
protected:
- typedef typename node_type::atomic_marked_ptr atomic_node_ptr ; ///< Atomic marked node pointer
- typedef typename node_type::marked_ptr marked_node_ptr ; ///< Node marked pointer
+ typedef typename node_type::atomic_marked_ptr atomic_node_ptr; ///< Atomic marked node pointer
+ typedef typename node_type::marked_ptr marked_node_ptr; ///< Node marked pointer
protected:
//@cond
typedef skip_list::details::intrusive_node_builder< node_type, atomic_node_ptr, allocator_type > intrusive_node_builder;
typedef typename std::conditional<
- std::is_same< typename options::internal_node_builder, cds::opt::none >::value
+ std::is_same< typename traits::internal_node_builder, cds::opt::none >::value
,intrusive_node_builder
- ,typename options::internal_node_builder
+ ,typename traits::internal_node_builder
>::type node_builder;
- typedef std::unique_ptr< node_type, typename node_builder::node_disposer > scoped_node_ptr;
+ typedef std::unique_ptr< node_type, typename node_builder::node_disposer > scoped_node_ptr;
- // c_nMaxHeight * 2 - pPred/pSucc guards
- // + 1 - for erase, unlink
- // + 1 - for clear
- static size_t const c_nHazardPtrCount = c_nMaxHeight * 2 + 2;
struct position {
node_type * pPrev[ c_nMaxHeight ];
node_type * pSucc[ c_nMaxHeight ];
- typename gc::template GuardArray< c_nMaxHeight * 2 > guards ; ///< Guards array for pPrev/pSucc
-
- node_type * pCur ; // guarded by guards; needed only for *ensure* function
+ typename gc::template GuardArray< c_nMaxHeight * 2 > guards; ///< Guards array for pPrev/pSucc
+ node_type * pCur; // guarded by one of guards
};
//@endcond
- protected:
- skip_list::details::head_node< node_type > m_Head ; ///< head tower (max height)
-
- item_counter m_ItemCounter ; ///< item counter
- random_level_generator m_RandomLevelGen ; ///< random level generator instance
- atomics::atomic<unsigned int> m_nHeight ; ///< estimated high level
- mutable stat m_Stat ; ///< internal statistics
-
- protected:
- //@cond
- unsigned int random_level()
+ public:
+ /// Default constructor
+ /**
+ The constructor checks whether the count of guards is enough
+ for skip-list and may raise an exception if not.
+ */
+ SkipListSet()
+ : m_Head( c_nMaxHeight )
+ , m_nHeight( c_nMinHeight )
{
- // Random generator produces a number from range [0..31]
- // We need a number from range [1..32]
- return m_RandomLevelGen() + 1;
- }
+ static_assert( (std::is_same< gc, typename node_type::gc >::value), "GC and node_type::gc must be the same type" );
- template <typename Q>
- node_type * build_node( Q v )
- {
- return node_builder::make_tower( v, m_RandomLevelGen );
- }
+ gc::check_available_guards( c_nHazardPtrCount );
- static value_type * gc_protect( marked_node_ptr p )
- {
- return node_traits::to_value_ptr( p.ptr() );
+ // Barrier for head node
+ atomics::atomic_thread_fence( memory_model::memory_order_release );
}
- static void dispose_node( value_type * pVal )
+ /// Clears and destructs the skip-list
+ ~SkipListSet()
{
- assert( pVal != nullptr );
- typename node_builder::node_disposer()( node_traits::to_node_ptr(pVal) );
- disposer()( pVal );
+ destroy();
}
- template <typename Q, typename Compare >
- bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound )
- {
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
+ public:
+ ///@name Forward iterators (only for debugging purpose)
+ //@{
+ /// Iterator type
+ /**
+ The forward iterator 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 (like as \p gc::HP), a guard is a limited resource per thread, so an exception (or assertion) "no free guard"
+ may be thrown if the limit of guard count per thread is exceeded.
+ - The iterator cannot be moved across thread boundary because it contains thread-private GC's guard.
+ - Iterator ensures thread-safety even if you delete the item the iterator points to. However, in case of concurrent
+ deleting operations there is no guarantee that you iterate all item in the list.
+ Moreover, a crash is possible when you try to iterate the next element that has been deleted by concurrent thread.
+
+ @warning Use this iterator on the concurrent container for debugging purpose only.
+
+ The iterator interface:
+ \code
+ class iterator {
+ public:
+ // Default constructor
+ iterator();
- // Hazard pointer array:
- // pPred: [nLevel * 2]
- // pSucc: [nLevel * 2 + 1]
+ // Copy construtor
+ iterator( iterator const& src );
- retry:
- pPred = m_Head.head();
- int nCmp = 1;
+ // Dereference operator
+ value_type * operator ->() const;
- for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
- pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ));
- while ( true ) {
- pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
- if ( pCur.bits() ) {
- // pCur.bits() means that pPred is logically deleted
- goto retry;
- }
+ // Dereference operator
+ value_type& operator *() const;
- if ( pCur.ptr() == nullptr ) {
- // end of the list at level nLevel - goto next level
- break;
- }
+ // Preincrement operator
+ iterator& operator ++();
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_relaxed );
+ // Assignment operator
+ iterator& operator = (iterator const& src);
- if ( pPred->next( nLevel ).load( memory_model::memory_order_relaxed ).all() != pCur.ptr() )
- goto retry;
+ // Equality operators
+ bool operator ==(iterator const& i ) const;
+ bool operator !=(iterator const& i ) const;
+ };
+ \endcode
+ */
+ typedef skip_list::details::iterator< gc, node_traits, back_off, false > iterator;
- if ( pSucc.bits() ) {
- // pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 ) {
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- m_Stat.onEraseWhileFind();
- }
- }
- goto retry;
- }
- else {
- nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr()), val );
- if ( nCmp < 0 ) {
- pPred = pCur.ptr();
- pos.guards.copy( nLevel * 2, nLevel * 2 + 1 ) ; // pPrev guard := cur guard
- }
- else if ( nCmp == 0 && bStopIfFound )
- goto found;
- else
- break;
- }
- }
+ /// Const iterator type
+ typedef skip_list::details::iterator< gc, node_traits, back_off, true > const_iterator;
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
- }
+ /// Returns a forward iterator addressing the first element in a set
+ iterator begin()
+ {
+ return iterator( *m_Head.head());
+ }
- if ( nCmp != 0 )
- return false;
+ /// Returns a forward const iterator addressing the first element in a set
+ const_iterator begin() const
+ {
+ return const_iterator( *m_Head.head());
+ }
+ /// Returns a forward const iterator addressing the first element in a set
+ const_iterator cbegin() const
+ {
+ return const_iterator( *m_Head.head());
+ }
- found:
- pos.pCur = pCur.ptr();
- return pCur.ptr() && nCmp == 0;
+ /// Returns a forward iterator that addresses the location succeeding the last element in a set.
+ iterator end()
+ {
+ return iterator();
}
- bool find_min_position( position& pos )
+ /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
+ const_iterator end() const
{
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
+ return const_iterator();
+ }
+ /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
+ const_iterator cend() const
+ {
+ return const_iterator();
+ }
+ //@}
- // Hazard pointer array:
- // pPred: [nLevel * 2]
- // pSucc: [nLevel * 2 + 1]
+ public:
+ /// Inserts new node
+ /**
+ The function inserts \p val in the set if it does not contain
+ an item with key equal to \p val.
- retry:
- pPred = m_Head.head();
+ Returns \p true if \p val is placed into the set, \p false otherwise.
+ */
+ bool insert( value_type& val )
+ {
+ return insert( val, []( value_type& ) {} );
+ }
- for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
- pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ));
- pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
+ /// Inserts new node
+ /**
+ This function is intended for derived non-intrusive containers.
- // pCur.bits() means that pPred is logically deleted
- // head cannot be deleted
- assert( pCur.bits() == 0 );
+ 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 \p f functor to initialize value-field of \p val.
- if ( pCur.ptr() ) {
+ The functor signature is:
+ \code
+ void func( value_type& val );
+ \endcode
+ where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
+ \p val no any other changes could be made on this set's item by concurrent threads.
+ The user-defined functor is called only if the inserting is success.
+ */
+ template <typename Func>
+ bool insert( value_type& val, Func f )
+ {
+ typename gc::Guard gNew;
+ gNew.assign( &val );
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_relaxed );
+ node_type * pNode = node_traits::to_node_ptr( val );
+ scoped_node_ptr scp( pNode );
+ unsigned int nHeight = pNode->height();
+ bool bTowerOk = pNode->has_tower(); // nHeight > 1 && pNode->get_tower() != nullptr;
+ bool bTowerMade = false;
- if ( pPred->next( nLevel ).load( memory_model::memory_order_relaxed ).all() != pCur.ptr() )
- goto retry;
+ position pos;
+ while ( true )
+ {
+ if ( find_position( val, pos, key_comparator(), true )) {
+ // scoped_node_ptr deletes the node tower if we create it
+ if ( !bTowerMade )
+ scp.release();
- if ( pSucc.bits() ) {
- // pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 )
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- }
- goto retry;
- }
+ m_Stat.onInsertFailed();
+ return false;
}
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
- }
+ if ( !bTowerOk ) {
+ build_node( pNode );
+ nHeight = pNode->height();
+ bTowerMade = pNode->has_tower();
+ bTowerOk = true;
+ }
+
+ if ( !insert_at_position( val, pNode, pos, f )) {
+ m_Stat.onInsertRetry();
+ continue;
+ }
- return (pos.pCur = pCur.ptr()) != nullptr;
+ increase_height( nHeight );
+ ++m_ItemCounter;
+ m_Stat.onAddNode( nHeight );
+ m_Stat.onInsertSuccess();
+ scp.release();
+ return true;
+ }
}
- bool find_max_position( position& pos )
- {
- node_type * pPred;
- marked_node_ptr pSucc;
- marked_node_ptr pCur;
+ /// Updates the node
+ /**
+ The operation performs inserting or changing data with lock-free manner.
- // Hazard pointer array:
- // pPred: [nLevel * 2]
- // pSucc: [nLevel * 2 + 1]
+ If the item \p val is not found in the set, then \p val is inserted into the set
+ iff \p bInsert is \p true.
+ Otherwise, the functor \p func is called with item found.
+ The functor \p func signature is:
+ \code
+ void func( bool bNew, value_type& item, value_type& val );
+ \endcode
+ with arguments:
+ - \p bNew - \p true if the item has been inserted, \p false otherwise
+ - \p item - item of the set
+ - \p val - argument \p val passed into the \p %update() function
+ If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
+ refer to the same thing.
- retry:
- pPred = m_Head.head();
+ Returns std::pair<bool, bool> where \p first is \p true if operation is successful,
+ i.e. the node has been inserted or updated,
+ \p second is \p true if new item has been added or \p false if the item with \p key
+ already exists.
- for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
- pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ));
- while ( true ) {
- pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
- if ( pCur.bits() ) {
- // pCur.bits() means that pPred is logically deleted
- goto retry;
- }
+ @warning See \ref cds_intrusive_item_creating "insert item troubleshooting"
+ */
+ template <typename Func>
+ std::pair<bool, bool> update( value_type& val, Func func, bool bInsert = true )
+ {
+ typename gc::Guard gNew;
+ gNew.assign( &val );
- if ( pCur.ptr() == nullptr ) {
- // end of the list at level nLevel - goto next level
- break;
- }
-
- // pSucc contains deletion mark for pCur
- pSucc = pCur->next( nLevel ).load( memory_model::memory_order_relaxed );
-
- if ( pPred->next( nLevel ).load( memory_model::memory_order_relaxed ).all() != pCur.ptr() )
- goto retry;
-
- if ( pSucc.bits() ) {
- // pCur is marked, i.e. logically deleted.
- marked_node_ptr p( pCur.ptr() );
- if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
- memory_model::memory_order_release, atomics::memory_order_relaxed ))
- {
- if ( nLevel == 0 )
- gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
- }
- goto retry;
- }
- else {
- if ( !pSucc.ptr() )
- break;
-
- pPred = pCur.ptr();
- pos.guards.copy( nLevel * 2, nLevel * 2 + 1 ); // pPrev guard := cur guard
- //pos.guards.copy( nLevel * 2, gCur ) ; // pPrev guard := gCur
- }
- }
-
- // Next level
- pos.pPrev[ nLevel ] = pPred;
- pos.pSucc[ nLevel ] = pCur.ptr();
- }
-
- return (pos.pCur = pCur.ptr()) != nullptr;
- }
-
- template <typename Func>
- bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f )
- {
- unsigned int nHeight = pNode->height();
-
- for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel )
- pNode->next(nLevel).store( marked_node_ptr(), memory_model::memory_order_relaxed );
+ node_type * pNode = node_traits::to_node_ptr( val );
+ scoped_node_ptr scp( pNode );
+ unsigned int nHeight = pNode->height();
+ bool bTowerOk = pNode->has_tower();
+ bool bTowerMade = false;
+ position pos;
+ while ( true )
{
- marked_node_ptr p( pos.pSucc[0] );
- pNode->next( 0 ).store( p, memory_model::memory_order_release );
- if ( !pos.pPrev[0]->next(0).compare_exchange_strong( p, marked_node_ptr(pNode), memory_model::memory_order_release, atomics::memory_order_relaxed ) ) {
- return false;
- }
- f( val );
- }
-
- for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel ) {
- marked_node_ptr p;
- while ( true ) {
- marked_node_ptr q( pos.pSucc[ nLevel ]);
- if ( !pNode->next( nLevel ).compare_exchange_strong( p, q, memory_model::memory_order_release, atomics::memory_order_relaxed )) {
- // pNode has been marked as removed while we are inserting it
- // Stop inserting
- assert( p.bits() );
- m_Stat.onLogicDeleteWhileInsert();
- return true;
- }
- p = q;
- if ( pos.pPrev[nLevel]->next(nLevel).compare_exchange_strong( q, marked_node_ptr( pNode ), memory_model::memory_order_release, atomics::memory_order_relaxed ) )
- break;
+ bool bFound = find_position( val, pos, key_comparator(), true );
+ if ( bFound ) {
+ // scoped_node_ptr deletes the node tower if we create it before
+ if ( !bTowerMade )
+ scp.release();
- // Renew insert position
- m_Stat.onRenewInsertPosition();
- if ( !find_position( val, pos, key_comparator(), false )) {
- // The node has been deleted while we are inserting it
- m_Stat.onNotFoundWhileInsert();
- return true;
- }
+ func( false, *node_traits::to_value_ptr(pos.pCur), val );
+ m_Stat.onUpdateExist();
+ return std::make_pair( true, false );
}
- }
- return true;
- }
- template <typename Func>
- bool try_remove_at( node_type * pDel, position& pos, Func f )
- {
- assert( pDel != nullptr );
-
- marked_node_ptr pSucc;
- typename gc::Guard gSucc;
-
- // logical deletion (marking)
- for ( unsigned int nLevel = pDel->height() - 1; nLevel > 0; --nLevel ) {
- while ( true ) {
- pSucc = gSucc.protect( pDel->next(nLevel), gc_protect );
- if ( pSucc.bits() || pDel->next(nLevel).compare_exchange_weak( pSucc, pSucc | 1,
- memory_model::memory_order_acquire, atomics::memory_order_relaxed ))
- {
- break;
- }
+ if ( !bInsert ) {
+ scp.release();
+ return std::make_pair( false, false );
}
- }
-
- while ( true ) {
- pSucc = gSucc.protect( pDel->next(0), gc_protect );
- marked_node_ptr p( pSucc.ptr() );
- if ( pDel->next(0).compare_exchange_strong( p, marked_node_ptr(p.ptr(), 1),
- memory_model::memory_order_acquire, atomics::memory_order_relaxed ))
- {
- f( *node_traits::to_value_ptr( pDel ));
-
- // Physical deletion
- // try fast erase
- p = pDel;
- for ( int nLevel = static_cast<int>( pDel->height() - 1 ); nLevel >= 0; --nLevel ) {
- pSucc = gSucc.protect( pDel->next(nLevel), gc_protect );
- if ( !pos.pPrev[nLevel]->next(nLevel).compare_exchange_strong( p, marked_node_ptr(pSucc.ptr()),
- memory_model::memory_order_release, atomics::memory_order_relaxed) )
- {
- // Make slow erase
- find_position( *node_traits::to_value_ptr( pDel ), pos, key_comparator(), false );
- m_Stat.onSlowErase();
- return true;
- }
- }
- // Fast erasing success
- gc::retire( node_traits::to_value_ptr( pDel ), dispose_node );
- m_Stat.onFastErase();
- return true;
- }
- else {
- if ( p.bits() ) {
- return false;
- }
+ if ( !bTowerOk ) {
+ build_node( pNode );
+ nHeight = pNode->height();
+ bTowerMade = pNode->has_tower();
+ bTowerOk = true;
}
- }
- }
-
- enum finsd_fastpath_result {
- find_fastpath_found,
- find_fastpath_not_found,
- find_fastpath_abort
- };
- template <typename Q, typename Compare, typename Func>
- finsd_fastpath_result find_fastpath( Q& val, Compare cmp, Func f )
- {
- node_type * pPred;
- typename gc::template GuardArray<2> guards;
- marked_node_ptr pCur;
- marked_node_ptr pNull;
- back_off bkoff;
-
- pPred = m_Head.head();
- for ( int nLevel = static_cast<int>( m_nHeight.load(memory_model::memory_order_relaxed) - 1 ); nLevel >= 0; --nLevel ) {
- pCur = guards.protect( 1, pPred->next(nLevel), gc_protect );
- if ( pCur == pNull )
+ if ( !insert_at_position( val, pNode, pos, [&func]( value_type& item ) { func( true, item, item ); })) {
+ m_Stat.onInsertRetry();
continue;
-
- while ( pCur != pNull ) {
- if ( pCur.bits() ) {
- unsigned int nAttempt = 0;
- while ( pCur.bits() && nAttempt++ < 16 ) {
- bkoff();
- pCur = guards.protect( 1, pPred->next(nLevel), gc_protect );
- }
- bkoff.reset();
-
- if ( pCur.bits() ) {
- // Maybe, we are on deleted node sequence
- // Abort searching, try slow-path
- return find_fastpath_abort;
- }
- }
-
- if ( pCur.ptr() ) {
- int nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr() ), val );
- if ( nCmp < 0 ) {
- guards.copy( 0, 1 );
- pPred = pCur.ptr();
- pCur = guards.protect( 1, pCur->next(nLevel), gc_protect );
- }
- else if ( nCmp == 0 ) {
- // found
- f( *node_traits::to_value_ptr( pCur.ptr() ), val );
- return find_fastpath_found;
- }
- else // pCur > val - go down
- break;
- }
}
- }
-
- return find_fastpath_not_found;
- }
-
- template <typename Q, typename Compare, typename Func>
- bool find_slowpath( Q& val, Compare cmp, Func f )
- {
- position pos;
- if ( find_position( val, pos, cmp, true )) {
- assert( cmp( *node_traits::to_value_ptr( pos.pCur ), val ) == 0 );
- f( *node_traits::to_value_ptr( pos.pCur ), val );
- return true;
+ increase_height( nHeight );
+ ++m_ItemCounter;
+ scp.release();
+ m_Stat.onAddNode( nHeight );
+ m_Stat.onUpdateNew();
+ return std::make_pair( true, true );
}
- else
- return false;
}
-
- template <typename Q, typename Compare, typename Func>
- bool find_with_( Q& val, Compare cmp, Func f )
+ //@cond
+ template <typename Func>
+ CDS_DEPRECATED("ensure() is deprecated, use update()")
+ std::pair<bool, bool> ensure( value_type& val, Func func )
{
- switch ( find_fastpath( val, cmp, f )) {
- case find_fastpath_found:
- m_Stat.onFindFastSuccess();
- return true;
- case find_fastpath_not_found:
- m_Stat.onFindFastFailed();
- return false;
- default:
- break;
- }
+ return update( val, func, true );
+ }
+ //@endcond
- if ( find_slowpath( val, cmp, f )) {
- m_Stat.onFindSlowSuccess();
- return true;
- }
+ /// Unlinks the item \p val from the set
+ /**
+ The function searches the item \p val in the set and unlink it from the set
+ if it is found and is equal to \p val.
- m_Stat.onFindSlowFailed();
- return false;
- }
+ Difference between \p erase() and \p %unlink() functions: \p %erase() finds <i>a key</i>
+ and deletes the item found. \p %unlink() finds an item by key and deletes it
+ only if \p val is an item of that set, i.e. the pointer to item found
+ is equal to <tt> &val </tt>.
- template <typename Q, typename Compare>
- bool get_with_( typename gc::Guard& guard, Q const& val, Compare cmp )
- {
- return find_with_( val, cmp, [&guard](value_type& found, Q const& ) { guard.assign(&found); } );
- }
+ The \p disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously.
- template <typename Q, typename Compare, typename Func>
- bool erase_( Q const& val, Compare cmp, Func f )
+ The function returns \p true if success and \p false otherwise.
+ */
+ bool unlink( value_type& val )
{
position pos;
- if ( !find_position( val, pos, cmp, false ) ) {
- m_Stat.onEraseFailed();
+ if ( !find_position( val, pos, key_comparator(), false )) {
+ m_Stat.onUnlinkFailed();
return false;
}
node_type * pDel = pos.pCur;
- typename gc::Guard gDel;
- gDel.assign( node_traits::to_value_ptr(pDel) );
- assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+ assert( key_comparator()( *node_traits::to_value_ptr( pDel ), val ) == 0 );
unsigned int nHeight = pDel->height();
- if ( try_remove_at( pDel, pos, f )) {
+ typename gc::Guard gDel;
+ gDel.assign( node_traits::to_value_ptr(pDel));
+
+ if ( node_traits::to_value_ptr( pDel ) == &val && try_remove_at( pDel, pos, [](value_type const&) {} )) {
--m_ItemCounter;
m_Stat.onRemoveNode( nHeight );
- m_Stat.onEraseSuccess();
+ m_Stat.onUnlinkSuccess();
return true;
}
- m_Stat.onEraseFailed();
+ m_Stat.onUnlinkFailed();
return false;
}
- template <typename Q, typename Compare>
- bool extract_( typename gc::Guard& guard, Q const& val, Compare cmp )
- {
- position pos;
+ /// Extracts the item from the set with specified \p key
+ /** \anchor cds_intrusive_SkipListSet_hp_extract
+ The function searches an item with key equal to \p key in the set,
+ unlinks it from the set, and returns it as \p guarded_ptr object.
+ If \p key is not found the function returns an empty guarded pointer.
- for (;;) {
- if ( !find_position( val, pos, cmp, false ) ) {
- m_Stat.onExtractFailed();
- return false;
- }
+ Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- node_type * pDel = pos.pCur;
- guard.assign( node_traits::to_value_ptr(pDel));
- assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+ The \p disposer specified in \p Traits class template parameter is called automatically
+ by garbage collector \p GC specified in class' template parameters when returned \p guarded_ptr object
+ will be destroyed or released.
+ @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
- unsigned int nHeight = pDel->height();
- if ( try_remove_at( pDel, pos, [](value_type const&) {} )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractSuccess();
- return true;
+ Usage:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
+ {
+ skip_list::guarded_ptr gp(theList.extract( 5 ));
+ if ( gp ) {
+ // Deal with gp
+ // ...
}
-
- m_Stat.onExtractRetry();
+ // Destructor of gp releases internal HP guard
}
+ \endcode
+ */
+ template <typename Q>
+ guarded_ptr extract( Q const& key )
+ {
+ return extract_( key, key_comparator());
}
- bool extract_min_( typename gc::Guard& gDel )
- {
- position pos;
+ /// Extracts the item from the set with comparing functor \p pred
+ /**
+ The function is an analog of \ref cds_intrusive_SkipListSet_hp_extract "extract(Q const&)"
+ but \p pred predicate is used for key comparing.
- for (;;) {
- if ( !find_min_position( pos ) ) {
- // The list is empty
- m_Stat.onExtractMinFailed();
- return false;
- }
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less>
+ guarded_ptr extract_with( Q const& key, Less pred )
+ {
+ CDS_UNUSED( pred );
+ return extract_( key, cds::opt::details::make_comparator_from_less<Less>());
+ }
- node_type * pDel = pos.pCur;
+ /// Extracts an item with minimal key from the list
+ /**
+ The function searches an item with minimal key, unlinks it, and returns it as \p guarded_ptr object.
+ If the skip-list is empty the function returns an empty guarded pointer.
- unsigned int nHeight = pDel->height();
- gDel.assign( node_traits::to_value_ptr(pDel) );
+ @note Due the concurrent nature of the list, the function extracts <i>nearly</i> minimum key.
+ It means that the function gets leftmost item 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 list traversing.
- if ( try_remove_at( pDel, pos, [](value_type const&) {} )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractMinSuccess();
- return true;
- }
+ The \p disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC automatically when returned \p guarded_ptr object
+ will be destroyed or released.
+ @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
- m_Stat.onExtractMinRetry();
+ Usage:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
+ {
+ skip_list::guarded_ptr gp(theList.extract_min());
+ if ( gp ) {
+ // Deal with gp
+ //...
+ }
+ // Destructor of gp releases internal HP guard
}
- }
-
- bool extract_max_( typename gc::Guard& gDel )
+ \endcode
+ */
+ guarded_ptr extract_min()
{
- position pos;
+ return extract_min_();
+ }
- for (;;) {
- if ( !find_max_position( pos ) ) {
- // The list is empty
- m_Stat.onExtractMaxFailed();
- return false;
- }
+ /// Extracts an item with maximal key from the list
+ /**
+ The function searches an item with maximal key, unlinks it, and returns the pointer to item
+ as \p guarded_ptr object.
+ If the skip-list is empty the function returns an empty \p guarded_ptr.
- node_type * pDel = pos.pCur;
+ @note Due the concurrent nature of the list, the function extracts <i>nearly</i> maximal key.
+ It means that the function gets rightmost item and tries to unlink it.
+ During unlinking, a concurrent thread may insert an item with key greater than rightmost item's key.
+ So, the function returns the item with maximum key at the moment of list traversing.
- unsigned int nHeight = pDel->height();
- gDel.assign( node_traits::to_value_ptr(pDel) );
+ The \p disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously when returned \ref guarded_ptr object
+ will be destroyed or released.
+ @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
- if ( try_remove_at( pDel, pos, [](value_type const&) {} )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onExtractMaxSuccess();
- return true;
+ Usage:
+ \code
+ typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
+ {
+ skip_list::guarded_ptr gp( theList.extract_max( gp ));
+ if ( gp ) {
+ // Deal with gp
+ //...
}
-
- m_Stat.onExtractMaxRetry();
+ // Destructor of gp releases internal HP guard
}
+ \endcode
+ */
+ guarded_ptr extract_max()
+ {
+ return extract_max_();
}
- void increase_height( unsigned int nHeight )
+ /// Deletes the item from the set
+ /** \anchor cds_intrusive_SkipListSet_hp_erase
+ The function searches an item with key equal to \p key in the set,
+ unlinks it from the set, and returns \p true.
+ If the item with key equal to \p key is not found the function return \p false.
+
+ Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ */
+ template <typename Q>
+ bool erase( Q const& key )
{
- unsigned int nCur = m_nHeight.load( memory_model::memory_order_relaxed );
- if ( nCur < nHeight )
- m_nHeight.compare_exchange_strong( nCur, nHeight, memory_model::memory_order_release, atomics::memory_order_relaxed );
+ return erase_( key, key_comparator(), [](value_type const&) {} );
}
- //@endcond
- public:
- /// Default constructor
+ /// Deletes the item from the set with comparing functor \p pred
/**
- The constructor checks whether the count of guards is enough
- for skip-list and may raise an exception if not.
+ The function is an analog of \ref cds_intrusive_SkipListSet_hp_erase "erase(Q const&)"
+ but \p pred predicate is used for key comparing.
+
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
*/
- SkipListSet()
- : m_Head( c_nMaxHeight )
- , m_nHeight( c_nMinHeight )
+ template <typename Q, typename Less>
+ bool erase_with( Q const& key, Less pred )
{
- static_assert( (std::is_same< gc, typename node_type::gc >::value), "GC and node_type::gc must be the same type" );
+ CDS_UNUSED( pred );
+ return erase_( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type const&) {} );
+ }
- gc::check_available_guards( c_nHazardPtrCount );
+ /// Deletes the item from the set
+ /** \anchor cds_intrusive_SkipListSet_hp_erase_func
+ The function searches an item with key equal to \p key in the set,
+ call \p f functor with item found, unlinks it from the set, and returns \p true.
+ The \ref disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously.
- // Barrier for head node
- atomics::atomic_thread_fence( memory_model::memory_order_release );
- }
+ The \p Func interface is
+ \code
+ struct functor {
+ void operator()( value_type const& item );
+ };
+ \endcode
- /// Clears and destructs the skip-list
- ~SkipListSet()
+ If the item with key equal to \p key is not found the function return \p false.
+
+ Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ */
+ template <typename Q, typename Func>
+ bool erase( Q const& key, Func f )
{
- clear();
+ return erase_( key, key_comparator(), f );
}
- public:
- /// Iterator type
- typedef skip_list::details::iterator< gc, node_traits, back_off, false > iterator;
-
- /// Const iterator type
- typedef skip_list::details::iterator< gc, node_traits, back_off, true > const_iterator;
+ /// Deletes the item from the set with comparing functor \p pred
+ /**
+ The function is an analog of \ref cds_intrusive_SkipListSet_hp_erase_func "erase(Q const&, Func)"
+ but \p pred predicate is used for key comparing.
- /// Returns a forward iterator addressing the first element in a set
- iterator begin()
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less, typename Func>
+ bool erase_with( Q const& key, Less pred, Func f )
{
- return iterator( *m_Head.head() );
+ CDS_UNUSED( pred );
+ return erase_( key, cds::opt::details::make_comparator_from_less<Less>(), f );
}
- /// Returns a forward const iterator addressing the first element in a set
- //@{
- const_iterator begin() const
+ /// Finds \p key
+ /** \anchor cds_intrusive_SkipListSet_hp_find_func
+ The function searches the item with key equal to \p key and calls the functor \p f for item found.
+ The interface of \p Func functor is:
+ \code
+ struct functor {
+ void operator()( value_type& item, Q& key );
+ };
+ \endcode
+ where \p item is the item found, \p key is the <tt>find</tt> function argument.
+
+ The functor can change non-key fields of \p item. Note that the functor is only guarantee
+ that \p item cannot be disposed during functor is executing.
+ The functor does not serialize simultaneous access to the set \p item. If such access is
+ possible you must provide your own synchronization on item level to exclude unsafe item modifications.
+
+ Note the compare functor specified for class \p Traits template parameter
+ should accept a parameter of type \p Q that can be not the same as \p value_type.
+
+ The function returns \p true if \p key is found, \p false otherwise.
+ */
+ template <typename Q, typename Func>
+ bool find( Q& key, Func f )
{
- return const_iterator( *m_Head.head() );
+ return find_with_( key, key_comparator(), f );
}
- const_iterator cbegin()
+ //@cond
+ template <typename Q, typename Func>
+ bool find( Q const& key, Func f )
{
- return const_iterator( *m_Head.head() );
+ return find_with_( key, key_comparator(), f );
}
- //@}
+ //@endcond
- /// Returns a forward iterator that addresses the location succeeding the last element in a set.
- iterator end()
+ /// Finds the key \p key with \p pred predicate for comparing
+ /**
+ The function is an analog of \ref cds_intrusive_SkipListSet_hp_find_func "find(Q&, Func)"
+ but \p pred is used for key compare.
+
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less, typename Func>
+ bool find_with( Q& key, Less pred, Func f )
{
- return iterator();
+ CDS_UNUSED( pred );
+ return find_with_( key, cds::opt::details::make_comparator_from_less<Less>(), f );
+ }
+ //@cond
+ template <typename Q, typename Less, typename Func>
+ bool find_with( Q const& key, Less pred, Func f )
+ {
+ CDS_UNUSED( pred );
+ return find_with_( key, cds::opt::details::make_comparator_from_less<Less>(), f );
}
+ //@endcond
- /// Returns a forward const iterator that addresses the location succeeding the last element in a set.
- //@{
- const_iterator end() const
+ /// Checks whether the set contains \p key
+ /**
+ The function searches the item with key equal to \p key
+ and returns \p true if it is found, and \p false otherwise.
+ */
+ template <typename Q>
+ bool contains( Q const& key )
{
- return const_iterator();
+ return find_with_( key, key_comparator(), [](value_type& , Q const& ) {} );
}
- const_iterator cend()
+ //@cond
+ template <typename Q>
+ CDS_DEPRECATED("deprecated, use contains()")
+ bool find( Q const& key )
{
- return const_iterator();
+ return contains( key );
}
- //@}
+ //@endcond
- public:
- /// Inserts new node
+ /// Checks whether the set contains \p key using \p pred predicate for searching
/**
- The function inserts \p val in the set if it does not contain
- an item with key equal to \p val.
-
- Returns \p true if \p val is placed into the set, \p false otherwise.
+ The function is similar to <tt>contains( key )</tt> but \p pred is used for key comparing.
+ \p Less functor has the interface like \p std::less.
+ \p Less must imply the same element order as the comparator used for building the set.
*/
- bool insert( value_type& val )
+ template <typename Q, typename Less>
+ bool contains( Q const& key, Less pred )
{
- return insert( val, []( value_type& ) {} );
+ CDS_UNUSED( pred );
+ return find_with_( key, cds::opt::details::make_comparator_from_less<Less>(), [](value_type& , Q const& ) {} );
+ }
+ //@cond
+ template <typename Q, typename Less>
+ CDS_DEPRECATED("deprecated, use contains()")
+ bool find_with( Q const& key, Less pred )
+ {
+ return contains( key, pred );
}
+ //@endcond
- /// Inserts new node
- /**
- This function is intended for derived non-intrusive containers.
+ /// Finds \p key and return the item found
+ /** \anchor cds_intrusive_SkipListSet_hp_get
+ The function searches the item with key equal to \p key
+ and returns the pointer to the item found as \p guarded_ptr.
+ If \p key is not found the function returns an empt guarded pointer.
- 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 \p f functor to initialize value-field of \p val.
+ The \p disposer specified in \p Traits class template parameter is called
+ by garbage collector \p GC asynchronously when returned \ref guarded_ptr object
+ will be destroyed or released.
+ @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
- The functor signature is:
+ Usage:
\code
- void func( value_type& val );
+ typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
+ skip_list theList;
+ // ...
+ {
+ skip_list::guarded_ptr gp(theList.get( 5 ));
+ if ( gp ) {
+ // Deal with gp
+ //...
+ }
+ // Destructor of guarded_ptr releases internal HP guard
+ }
\endcode
- where \p val is the item inserted. User-defined functor \p f should guarantee that during changing
- \p val no any other changes could be made on this set's item by concurrent threads.
- The user-defined functor is called only if the inserting is success and may be passed by reference
- using \p std::ref
+
+ Note the compare functor specified for class \p Traits template parameter
+ should accept a parameter of type \p Q that can be not the same as \p value_type.
*/
- template <typename Func>
- bool insert( value_type& val, Func f )
+ template <typename Q>
+ guarded_ptr get( Q const& key )
{
- typename gc::Guard gNew;
- gNew.assign( &val );
-
- node_type * pNode = node_traits::to_node_ptr( val );
- scoped_node_ptr scp( pNode );
- unsigned int nHeight = pNode->height();
- bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
- bool bTowerMade = false;
+ return get_with_( key, key_comparator());
+ }
- position pos;
- while ( true )
- {
- bool bFound = find_position( val, pos, key_comparator(), true );
- if ( bFound ) {
- // scoped_node_ptr deletes the node tower if we create it
- if ( !bTowerMade )
- scp.release();
+ /// Finds \p key and return the item found
+ /**
+ The function is an analog of \ref cds_intrusive_SkipListSet_hp_get "get( Q const&)"
+ but \p pred is used for comparing the keys.
- m_Stat.onInsertFailed();
- return false;
- }
-
- if ( !bTowerOk ) {
- build_node( pNode );
- nHeight = pNode->height();
- bTowerMade =
- bTowerOk = true;
- }
+ \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
+ in any order.
+ \p pred must imply the same element order as the comparator used for building the set.
+ */
+ template <typename Q, typename Less>
+ guarded_ptr get_with( Q const& key, Less pred )
+ {
+ CDS_UNUSED( pred );
+ return get_with_( key, cds::opt::details::make_comparator_from_less<Less>());
+ }
- if ( !insert_at_position( val, pNode, pos, f )) {
- m_Stat.onInsertRetry();
- continue;
- }
+ /// Returns item count in the set
+ /**
+ The value returned depends on item counter type provided by \p Traits template parameter.
+ If it is \p atomicity::empty_item_counter this function always returns 0.
+ Therefore, the function is not suitable for checking the set emptiness, use \p empty()
+ for this purpose.
+ */
+ size_t size() const
+ {
+ return m_ItemCounter;
+ }
- increase_height( nHeight );
- ++m_ItemCounter;
- m_Stat.onAddNode( nHeight );
- m_Stat.onInsertSuccess();
- scp.release();
- return true;
- }
+ /// Checks if the set is empty
+ bool empty() const
+ {
+ return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr;
}
- /// Ensures that the \p val exists in the set
+ /// Clears the set (not atomic)
/**
- The operation performs inserting or changing data with lock-free manner.
-
- If the item \p val is not found in the set, then \p val is inserted into the set.
- Otherwise, the functor \p func is called with item found.
- The functor signature is:
+ The function unlink all items from the set.
+ The function is not atomic, i.e., in multi-threaded environment with parallel insertions
+ this sequence
\code
- void func( bool bNew, value_type& item, value_type& val );
+ set.clear();
+ assert( set.empty());
\endcode
- with arguments:
- - \p bNew - \p true if the item has been inserted, \p false otherwise
- - \p item - item of the set
- - \p val - argument \p val passed into the \p ensure function
- If new item has been inserted (i.e. \p bNew is \p true) then \p item and \p val arguments
- refer to the same thing.
+ the assertion could be raised.
- The functor can 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.
+ For each item the \ref disposer will be called after unlinking.
+ */
+ void clear()
+ {
+ while ( extract_min_());
+ }
- You can pass \p func argument by value or by reference using \p std::ref.
+ /// Returns maximum height of skip-list. The max height is a constant for each object and does not exceed 32.
+ static CDS_CONSTEXPR unsigned int max_height() CDS_NOEXCEPT
+ {
+ return c_nMaxHeight;
+ }
- Returns std::pair<bool, bool> where \p first is \p true if operation is successfull,
- \p second is \p true if new item has been added or \p false if the item with \p key
- already is in the set.
- */
- template <typename Func>
- std::pair<bool, bool> ensure( value_type& val, Func func )
+ /// Returns const reference to internal statistics
+ stat const& statistics() const
{
- typename gc::Guard gNew;
- gNew.assign( &val );
+ return m_Stat;
+ }
- node_type * pNode = node_traits::to_node_ptr( val );
- scoped_node_ptr scp( pNode );
- unsigned int nHeight = pNode->height();
- bool bTowerOk = nHeight > 1 && pNode->get_tower() != nullptr;
- bool bTowerMade = false;
+ protected:
+ //@cond
+ unsigned int random_level()
+ {
+ // Random generator produces a number from range [0..31]
+ // We need a number from range [1..32]
+ return m_RandomLevelGen() + 1;
+ }
- position pos;
- while ( true )
- {
- bool bFound = find_position( val, pos, key_comparator(), true );
- if ( bFound ) {
- // scoped_node_ptr deletes the node tower if we create it before
- if ( !bTowerMade )
- scp.release();
+ template <typename Q>
+ node_type * build_node( Q v )
+ {
+ return node_builder::make_tower( v, m_RandomLevelGen );
+ }
- func( false, *node_traits::to_value_ptr(pos.pCur), val );
- m_Stat.onEnsureExist();
- return std::make_pair( true, false );
- }
+ static value_type * gc_protect( marked_node_ptr p )
+ {
+ return node_traits::to_value_ptr( p.ptr() );
+ }
- if ( !bTowerOk ) {
- build_node( pNode );
- nHeight = pNode->height();
- bTowerMade =
- bTowerOk = true;
- }
+ static void dispose_node( value_type * pVal )
+ {
+ assert( pVal != nullptr );
+ typename node_builder::node_disposer()( node_traits::to_node_ptr( pVal ) );
+ disposer()( pVal );
+ }
- if ( !insert_at_position( val, pNode, pos, [&func]( value_type& item ) { func( true, item, item ); })) {
- m_Stat.onInsertRetry();
- continue;
- }
+ void help_remove( int nLevel, node_type* pPred, marked_node_ptr pCur, marked_node_ptr pSucc )
+ {
+ marked_node_ptr p( pCur.ptr() );
- increase_height( nHeight );
- ++m_ItemCounter;
- scp.release();
- m_Stat.onAddNode( nHeight );
- m_Stat.onEnsureNew();
- return std::make_pair( true, true );
+ if ( pCur->is_upper_level( nLevel )) {
+ typename gc::Guard hp;
+ if ( hp.protect( pCur->next( nLevel ), gc_protect ) == pSucc &&
+ pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
+ memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
+ {
+ if ( pCur->level_unlinked() ) {
+ gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node );
+ m_Stat.onEraseWhileFind();
+ }
+ }
}
}
- /// Unlinks the item \p val from the set
- /**
- The function searches the item \p val in the set and unlink it from the set
- if it is found and is equal to \p val.
+ template <typename Q, typename Compare >
+ bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound )
+ {
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
- Difference between \ref erase and \p unlink functions: \p erase finds <i>a key</i>
- and deletes the item found. \p unlink finds an item by key and deletes it
- only if \p val is an item of that set, i.e. the pointer to item found
- is equal to <tt> &val </tt>.
+ // Hazard pointer array:
+ // pPred: [nLevel * 2]
+ // pSucc: [nLevel * 2 + 1]
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously.
+ retry:
+ pPred = m_Head.head();
+ int nCmp = 1;
- The function returns \p true if success and \p false otherwise.
- */
- bool unlink( value_type& val )
- {
- position pos;
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
+ pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ) );
+ while ( true ) {
+ pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
+ if ( pCur.bits() ) {
+ // pCur.bits() means that pPred is logically deleted
+ goto retry;
+ }
- if ( !find_position( val, pos, key_comparator(), false ) ) {
- m_Stat.onUnlinkFailed();
- return false;
- }
+ if ( pCur.ptr() == nullptr ) {
+ // end of list at level nLevel - goto next level
+ break;
+ }
- node_type * pDel = pos.pCur;
- assert( key_comparator()( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
- unsigned int nHeight = pDel->height();
- typename gc::Guard gDel;
- gDel.assign( node_traits::to_value_ptr(pDel) );
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
- if ( node_traits::to_value_ptr( pDel ) == &val && try_remove_at( pDel, pos, [](value_type const&) {} )) {
- --m_ItemCounter;
- m_Stat.onRemoveNode( nHeight );
- m_Stat.onUnlinkSuccess();
- return true;
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted
+ // try to help deleting pCur
+ help_remove( nLevel, pPred, pCur, pSucc );
+ goto retry;
+ }
+ else {
+ nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr() ), val );
+ if ( nCmp < 0 ) {
+ pPred = pCur.ptr();
+ pos.guards.copy( nLevel * 2, nLevel * 2 + 1 ); // pPrev guard := cur guard
+ }
+ else if ( nCmp == 0 && bStopIfFound )
+ goto found;
+ else
+ break;
+ }
+ }
+
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- m_Stat.onUnlinkFailed();
- return false;
+ if ( nCmp != 0 )
+ return false;
+
+ found:
+ pos.pCur = pCur.ptr();
+ return pCur.ptr() && nCmp == 0;
}
- /// Extracts the item from the set with specified \p key
- /** \anchor cds_intrusive_SkipListSet_hp_extract
- The function searches an item with key equal to \p key in the set,
- unlinks it from the set, and returns it in \p dest parameter.
- If the item with key equal to \p key is not found the function returns \p false.
+ bool find_min_position( position& pos )
+ {
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
- Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
+ // Hazard pointer array:
+ // pPred: [nLevel * 2]
+ // pSucc: [nLevel * 2 + 1]
- The \ref disposer specified in \p Traits class template parameter is called automatically
- by garbage collector \p GC specified in class' template parameters when returned \ref guarded_ptr object
- will be destroyed or released.
- @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
+ retry:
+ pPred = m_Head.head();
- Usage:
- \code
- typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
- skip_list theList;
- // ...
- {
- skip_list::guarded_ptr gp;
- theList.extract( gp, 5 );
- // Deal with gp
- // ...
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
+ pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ) );
+ pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
- // Destructor of gp releases internal HP guard
+ // pCur.bits() means that pPred is logically deleted
+ // head cannot be deleted
+ assert( pCur.bits() == 0 );
+
+ if ( pCur.ptr() ) {
+
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
+
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted.
+ // try to help deleting pCur
+ help_remove( nLevel, pPred, pCur, pSucc );
+ goto retry;
+ }
+ }
+
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- \endcode
- */
- template <typename Q>
- bool extract( guarded_ptr& dest, Q const& key )
- {
- return extract_( dest.guard(), key, key_comparator() );
- }
- /// Extracts the item from the set with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_extract "extract(Q const&)"
- but \p pred predicate is used for key comparing.
+ return ( pos.pCur = pCur.ptr() ) != nullptr;
+ }
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool extract_with( guarded_ptr& dest, Q const& key, Less pred )
+ bool find_max_position( position& pos )
{
- return extract_( dest.guard(), key, cds::opt::details::make_comparator_from_less<Less>() );
- }
+ node_type * pPred;
+ marked_node_ptr pSucc;
+ marked_node_ptr pCur;
- /// Extracts an item with minimal key from the list
- /**
- The function searches an item with minimal key, unlinks it, and returns the item found in \p dest parameter.
- If the skip-list is empty the function returns \p false.
+ // Hazard pointer array:
+ // pPred: [nLevel * 2]
+ // pSucc: [nLevel * 2 + 1]
- @note Due the concurrent nature of the list, the function extracts <i>nearly</i> minimum key.
- It means that the function gets leftmost item 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 list traversing.
+ retry:
+ pPred = m_Head.head();
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC automatically when returned \ref guarded_ptr object
- will be destroyed or released.
- @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
+ for ( int nLevel = static_cast<int>( c_nMaxHeight - 1 ); nLevel >= 0; --nLevel ) {
+ pos.guards.assign( nLevel * 2, node_traits::to_value_ptr( pPred ) );
+ while ( true ) {
+ pCur = pos.guards.protect( nLevel * 2 + 1, pPred->next( nLevel ), gc_protect );
+ if ( pCur.bits() ) {
+ // pCur.bits() means that pPred is logically deleted
+ goto retry;
+ }
- Usage:
- \code
- typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
- skip_list theList;
- // ...
- {
- skip_list::guarded_ptr gp;
- if ( theList.extract_min( gp )) {
- // Deal with gp
- //...
+ if ( pCur.ptr() == nullptr ) {
+ // end of the list at level nLevel - goto next level
+ break;
+ }
+
+ // pSucc contains deletion mark for pCur
+ pSucc = pCur->next( nLevel ).load( memory_model::memory_order_acquire );
+
+ if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).all() != pCur.ptr() )
+ goto retry;
+
+ if ( pSucc.bits() ) {
+ // pCur is marked, i.e. logically deleted.
+ // try to help deleting pCur
+ help_remove( nLevel, pPred, pCur, pSucc );
+ goto retry;
+ }
+ else {
+ if ( !pSucc.ptr() )
+ break;
+
+ pPred = pCur.ptr();
+ pos.guards.copy( nLevel * 2, nLevel * 2 + 1 );
+ }
}
- // Destructor of gp releases internal HP guard
+
+ // Next level
+ pos.pPrev[nLevel] = pPred;
+ pos.pSucc[nLevel] = pCur.ptr();
}
- \endcode
- */
- bool extract_min( guarded_ptr& dest)
- {
- return extract_min_( dest.guard() );
- }
- /// Extracts an item with maximal key from the list
- /**
- The function searches an item with maximal key, unlinks it, and returns the pointer to item found in \p dest parameter.
- If the skip-list is empty the function returns empty \p guarded_ptr.
+ return ( pos.pCur = pCur.ptr() ) != nullptr;
+ }
- @note Due the concurrent nature of the list, the function extracts <i>nearly</i> maximal key.
- It means that the function gets rightmost item and tries to unlink it.
- During unlinking, a concurrent thread may insert an item with key greater than rightmost item's key.
- So, the function returns the item with maximum key at the moment of list traversing.
+ template <typename Func>
+ bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f )
+ {
+ unsigned int const nHeight = pNode->height();
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously when returned \ref guarded_ptr object
- will be destroyed or released.
- @note Each \p guarded_ptr object uses the GC's guard that can be limited resource.
+ for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel )
+ pNode->next( nLevel ).store( marked_node_ptr(), memory_model::memory_order_relaxed );
- Usage:
- \code
- typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
- skip_list theList;
- // ...
+ // Insert at level 0
{
- skip_list::guarded_ptr gp;
- if ( theList.extract_max( gp )) {
- // Deal with gp
- //...
+ marked_node_ptr p( pos.pSucc[0] );
+ pNode->next( 0 ).store( p, memory_model::memory_order_relaxed );
+ if ( !pos.pPrev[0]->next( 0 ).compare_exchange_strong( p, marked_node_ptr( pNode ), memory_model::memory_order_release, atomics::memory_order_relaxed ))
+ return false;
+
+ f( val );
+ }
+
+ // Insert at level 1..max
+ for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel ) {
+ marked_node_ptr p;
+ while ( true ) {
+ marked_node_ptr pSucc( pos.pSucc[nLevel] );
+
+ // Set pNode->next
+ // pNode->next can have a "logical deleted" flag if another thread is removing pNode right now
+ if ( !pNode->next( nLevel ).compare_exchange_strong( p, pSucc,
+ memory_model::memory_order_acq_rel, atomics::memory_order_acquire ) )
+ {
+ // pNode has been marked as removed while we are inserting it
+ // Stop inserting
+ assert( p.bits() != 0 );
+ if ( pNode->level_unlinked( nHeight - nLevel ))
+ gc::retire( &val, dispose_node );
+ m_Stat.onLogicDeleteWhileInsert();
+ return true;
+ }
+ p = pSucc;
+
+ // Link pNode into the list at nLevel
+ if ( pos.pPrev[nLevel]->next( nLevel ).compare_exchange_strong( pSucc, marked_node_ptr( pNode ),
+ memory_model::memory_order_release, atomics::memory_order_relaxed ))
+ {
+ // go to next level
+ break;
+ }
+
+ // Renew insert position
+ m_Stat.onRenewInsertPosition();
+ if ( !find_position( val, pos, key_comparator(), false )) {
+ // The node has been deleted while we are inserting it
+ m_Stat.onNotFoundWhileInsert();
+ return true;
+ }
}
- // Destructor of gp releases internal HP guard
}
- \endcode
- */
- bool extract_max( guarded_ptr& dest )
- {
- return extract_max_( dest.guard() );
+ return true;
}
- /// Deletes the item from the set
- /** \anchor cds_intrusive_SkipListSet_hp_erase
- The function searches an item with key equal to \p val in the set,
- unlinks it from the set, and returns \p true.
- If the item with key equal to \p val is not found the function return \p false.
-
- Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- */
- template <typename Q>
- bool erase( Q const& val )
+ template <typename Func>
+ bool try_remove_at( node_type * pDel, position& pos, Func f )
{
- return erase_( val, key_comparator(), [](value_type const&) {} );
- }
+ assert( pDel != nullptr );
- /// Deletes the item from the set with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_erase "erase(Q const&)"
- but \p pred predicate is used for key comparing.
+ marked_node_ptr pSucc;
+ back_off bkoff;
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool erase_with( Q const& val, Less pred )
- {
- return erase_( val, cds::opt::details::make_comparator_from_less<Less>(), [](value_type const&) {} );
- }
+ // logical deletion (marking)
+ for ( unsigned int nLevel = pDel->height() - 1; nLevel > 0; --nLevel ) {
+ pSucc = pDel->next( nLevel ).load( memory_model::memory_order_relaxed );
+ if ( pSucc.bits() == 0 ) {
+ bkoff.reset();
+ while ( !( pDel->next( nLevel ).compare_exchange_weak( pSucc, pSucc | 1,
+ memory_model::memory_order_release, atomics::memory_order_acquire )
+ || pSucc.bits() != 0 ))
+ {
+ bkoff();
+ m_Stat.onMarkFailed();
+ }
+ }
+ }
- /// Deletes the item from the set
- /** \anchor cds_intrusive_SkipListSet_hp_erase_func
- The function searches an item with key equal to \p val in the set,
- call \p f functor with item found, unlinks it from the set, and returns \p true.
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously.
+ marked_node_ptr p( pDel->next( 0 ).load( memory_model::memory_order_relaxed ).ptr());
+ while ( true ) {
+ if ( pDel->next( 0 ).compare_exchange_strong( p, p | 1, memory_model::memory_order_release, atomics::memory_order_acquire ))
+ {
+ f( *node_traits::to_value_ptr( pDel ) );
- The \p Func interface is
- \code
- struct functor {
- void operator()( value_type const& item );
- };
- \endcode
- The functor can be passed by reference with <tt>boost:ref</tt>
+ // Physical deletion
+ // try fast erase
+ p = pDel;
- If the item with key equal to \p val is not found the function return \p false.
+ for ( int nLevel = static_cast<int>( pDel->height() - 1 ); nLevel >= 0; --nLevel ) {
- Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type.
- */
- template <typename Q, typename Func>
- bool erase( Q const& val, Func f )
- {
- return erase_( val, key_comparator(), f );
- }
+ pSucc = pDel->next( nLevel ).load( memory_model::memory_order_relaxed );
+ if ( pos.pPrev[nLevel]->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ),
+ memory_model::memory_order_acquire, atomics::memory_order_relaxed ) )
+ {
+ pDel->level_unlinked();
+ }
+ else {
+ // Make slow erase
+ find_position( *node_traits::to_value_ptr( pDel ), pos, key_comparator(), false );
+ m_Stat.onSlowErase();
+ return true;
+ }
+ }
- /// Deletes the item from the set with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_erase_func "erase(Q const&, Func)"
- but \p pred predicate is used for key comparing.
+ // Fast erasing success
+ gc::retire( node_traits::to_value_ptr( pDel ), dispose_node );
+ m_Stat.onFastErase();
+ return true;
+ }
+ else if ( p.bits()) {
+ // Another thread is deleting pDel right now
+ m_Stat.onEraseContention();
+ return false;
+ }
+ m_Stat.onEraseRetry();
+ bkoff();
+ }
+ }
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less, typename Func>
- bool erase_with( Q const& val, Less pred, Func f )
+ enum finsd_fastpath_result {
+ find_fastpath_found,
+ find_fastpath_not_found,
+ find_fastpath_abort
+ };
+ template <typename Q, typename Compare, typename Func>
+ finsd_fastpath_result find_fastpath( Q& val, Compare cmp, Func f )
{
- return erase_( val, cds::opt::details::make_comparator_from_less<Less>(), f );
- }
+ node_type * pPred;
+ marked_node_ptr pCur;
+ marked_node_ptr pNull;
- /// Finds the key \p val
- /** \anchor cds_intrusive_SkipListSet_hp_find_func
- The function searches the item with key equal to \p val and calls the functor \p f for item found.
- The interface of \p Func functor is:
- \code
- struct functor {
- void operator()( value_type& item, Q& val );
- };
- \endcode
- where \p item is the item found, \p val is the <tt>find</tt> function argument.
+ // guard array:
+ // 0 - pPred on level N
+ // 1 - pCur on level N
+ typename gc::template GuardArray<2> guards;
+ back_off bkoff;
+ unsigned attempt = 0;
- You can pass \p f argument by value or by reference using \p std::ref.
+ try_again:
+ pPred = m_Head.head();
+ for ( int nLevel = static_cast<int>( m_nHeight.load( memory_model::memory_order_relaxed ) - 1 ); nLevel >= 0; --nLevel ) {
+ pCur = guards.protect( 1, pPred->next( nLevel ), gc_protect );
- The functor can change non-key fields of \p item. Note that the functor is only guarantee
- that \p item cannot be disposed during functor is executing.
- The functor does not serialize simultaneous access to the set \p item. If such access is
- possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
+ while ( pCur != pNull ) {
+ if ( pCur.bits() ) {
+ // pPred is being removed
+ if ( ++attempt < 4 ) {
+ bkoff();
+ goto try_again;
+ }
- The \p val argument is non-const since it can be used as \p f functor destination i.e., the functor
- can modify both arguments.
+ return find_fastpath_abort;
+ }
- Note the compare functor specified for class \p Traits template parameter
- should accept a parameter of type \p Q that can be not the same as \p value_type.
+ if ( pCur.ptr() ) {
+ int nCmp = cmp( *node_traits::to_value_ptr( pCur.ptr()), val );
+ if ( nCmp < 0 ) {
+ guards.copy( 0, 1 );
+ pPred = pCur.ptr();
+ pCur = guards.protect( 1, pCur->next( nLevel ), gc_protect );
+ }
+ else if ( nCmp == 0 ) {
+ // found
+ f( *node_traits::to_value_ptr( pCur.ptr() ), val );
+ return find_fastpath_found;
+ }
+ else {
+ // pCur > val - go down
+ break;
+ }
+ }
+ }
+ }
- The function returns \p true if \p val is found, \p false otherwise.
- */
- template <typename Q, typename Func>
- bool find( Q& val, Func f )
- {
- return find_with_( val, key_comparator(), f );
+ return find_fastpath_not_found;
}
- /// Finds the key \p val with \p pred predicate for comparing
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_find_func "find(Q&, Func)"
- but \p pred is used for key compare.
-
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less, typename Func>
- bool find_with( Q& val, Less pred, Func f )
+ template <typename Q, typename Compare, typename Func>
+ bool find_slowpath( Q& val, Compare cmp, Func f )
{
- return find_with_( val, cds::opt::details::make_comparator_from_less<Less>(), f );
- }
+ position pos;
+ if ( find_position( val, pos, cmp, true ) ) {
+ assert( cmp( *node_traits::to_value_ptr( pos.pCur ), val ) == 0 );
- /// Finds the key \p val
- /** \anchor cds_intrusive_SkipListSet_hp_find_cfunc
- The function searches the item with key equal to \p val and calls the functor \p f for 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.
+ f( *node_traits::to_value_ptr( pos.pCur ), val );
+ return true;
+ }
+ else
+ return false;
+ }
- You can pass \p f argument by value or by reference using \p std::ref.
+ template <typename Q, typename Compare, typename Func>
+ bool find_with_( Q& val, Compare cmp, Func f )
+ {
+ switch ( find_fastpath( val, cmp, f ) ) {
+ case find_fastpath_found:
+ m_Stat.onFindFastSuccess();
+ return true;
+ case find_fastpath_not_found:
+ m_Stat.onFindFastFailed();
+ return false;
+ default:
+ break;
+ }
- The functor can change non-key fields of \p item. Note that the functor is only guarantee
- that \p item cannot be disposed during functor is executing.
- The functor does not serialize simultaneous access to the set \p item. If such access is
- possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
+ if ( find_slowpath( val, cmp, f ) ) {
+ m_Stat.onFindSlowSuccess();
+ return true;
+ }
- Note the compare functor specified for class \p Traits template parameter
- should accept a parameter of type \p Q that can be not the same as \p value_type.
+ m_Stat.onFindSlowFailed();
+ return false;
+ }
- 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 )
+ template <typename Q, typename Compare>
+ guarded_ptr get_with_( Q const& val, Compare cmp )
{
- return find_with_( val, key_comparator(), f );
+ guarded_ptr gp;
+ if ( find_with_( val, cmp, [&gp]( value_type& found, Q const& ) { gp.reset( &found ); } ) )
+ return gp;
+ return guarded_ptr();
}
- /// Finds the key \p val with \p pred predicate for comparing
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_find_cfunc "find(Q const&, Func)"
- but \p pred is used for key compare.
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less, typename Func>
- bool find_with( Q const& val, Less pred, Func f )
+ template <typename Q, typename Compare, typename Func>
+ bool erase_( Q const& val, Compare cmp, Func f )
{
- return find_with_( val, cds::opt::details::make_comparator_from_less<Less>(), f );
- }
+ position pos;
- /// Finds the key \p val
- /** \anchor cds_intrusive_SkipListSet_hp_find_val
- The function searches the item with key equal to \p val
- and returns \p true if it is found, and \p false otherwise.
+ if ( !find_position( val, pos, cmp, false ) ) {
+ m_Stat.onEraseFailed();
+ return false;
+ }
- Note the compare functor specified for class \p Traits template parameter
- should accept a parameter of type \p Q that can be not the same as \p value_type.
- */
- template <typename Q>
- bool find( Q const & val )
- {
- return find_with_( val, key_comparator(), [](value_type& , Q const& ) {} );
+ node_type * pDel = pos.pCur;
+ typename gc::Guard gDel;
+ gDel.assign( node_traits::to_value_ptr( pDel ) );
+ assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
+
+ unsigned int nHeight = pDel->height();
+ if ( try_remove_at( pDel, pos, f ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onEraseSuccess();
+ return true;
+ }
+
+ m_Stat.onEraseFailed();
+ return false;
}
- /// Finds the key \p val with comparing functor \p pred
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_find_val "find(Q const&)"
- but \p pred is used for comparing the keys.
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool find_with( Q const& val, Less pred )
+ template <typename Q, typename Compare>
+ guarded_ptr extract_( Q const& val, Compare cmp )
{
- return find_with_( val, cds::opt::details::make_comparator_from_less<Less>(), [](value_type& , Q const& ) {} );
- }
+ position pos;
- /// Finds the key \p val and return the item found
- /** \anchor cds_intrusive_SkipListSet_hp_get
- The function searches the item with key equal to \p val
- 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.
+ guarded_ptr gp;
+ for (;;) {
+ if ( !find_position( val, pos, cmp, false ) ) {
+ m_Stat.onExtractFailed();
+ return guarded_ptr();
+ }
- The \ref disposer specified in \p Traits class template parameter is called
- by garbage collector \p GC asynchronously when returned \ref guarded_ptr object
- will be destroyed or released.
- @note Each \p guarded_ptr object uses one GC's guard which can be limited resource.
+ node_type * pDel = pos.pCur;
+ gp.reset( node_traits::to_value_ptr( pDel ) );
+ assert( cmp( *node_traits::to_value_ptr( pDel ), val ) == 0 );
- Usage:
- \code
- typedef cds::intrusive::SkipListSet< cds::gc::HP, foo, my_traits > skip_list;
- skip_list theList;
- // ...
- {
- skip_list::guarded_ptr gp;
- if ( theList.get( gp, 5 )) {
- // Deal with gp
- //...
+ unsigned int nHeight = pDel->height();
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {} ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractSuccess();
+ return gp;
}
- // Destructor of guarded_ptr releases internal HP guard
+ m_Stat.onExtractRetry();
}
- \endcode
+ }
- Note the compare functor specified for class \p Traits template parameter
- 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 )
+ guarded_ptr extract_min_()
{
- return get_with_( ptr.guard(), val, key_comparator() );
- }
+ position pos;
- /// Finds the key \p val and return the item found
- /**
- The function is an analog of \ref cds_intrusive_SkipListSet_hp_get "get( guarded_ptr& ptr, Q const&)"
- but \p pred is used for comparing the keys.
+ guarded_ptr gp;
+ for ( ;;) {
+ if ( !find_min_position( pos ) ) {
+ // The list is empty
+ m_Stat.onExtractMinFailed();
+ return guarded_ptr();
+ }
- \p Less functor has the semantics like \p std::less but should take arguments of type \ref value_type and \p Q
- in any order.
- \p pred must imply the same element order as the comparator used for building the set.
- */
- template <typename Q, typename Less>
- bool get_with( guarded_ptr& ptr, Q const& val, Less pred )
- {
- return get_with_( ptr.guard(), val, cds::opt::details::make_comparator_from_less<Less>() );
- }
+ node_type * pDel = pos.pCur;
- /// Returns item count in the set
- /**
- The value returned depends on item counter type provided by \p Traits template parameter.
- If it is atomicity::empty_item_counter this function always returns 0.
- Therefore, the function is not suitable for checking the set emptiness, use \ref empty
- member function for this purpose.
- */
- size_t size() const
- {
- return m_ItemCounter;
- }
+ unsigned int nHeight = pDel->height();
+ gp.reset( node_traits::to_value_ptr( pDel ) );
- /// Checks if the set is empty
- bool empty() const
- {
- return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr;
- }
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {} ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractMinSuccess();
+ return gp;
+ }
- /// Clears the set (non-atomic)
- /**
- The function unlink all items from the set.
- The function is not atomic, i.e., in multi-threaded environment with parallel insertions
- this sequence
- \code
- set.clear();
- assert( set.empty() );
- \endcode
- the assertion could be raised.
+ m_Stat.onExtractMinRetry();
+ }
+ }
- For each item the \ref disposer will be called after unlinking.
- */
- void clear()
+ guarded_ptr extract_max_()
{
+ position pos;
+
guarded_ptr gp;
- while ( extract_min( gp ));
+ for ( ;;) {
+ if ( !find_max_position( pos ) ) {
+ // The list is empty
+ m_Stat.onExtractMaxFailed();
+ return guarded_ptr();
+ }
+
+ node_type * pDel = pos.pCur;
+
+ unsigned int nHeight = pDel->height();
+ gp.reset( node_traits::to_value_ptr( pDel ) );
+
+ if ( try_remove_at( pDel, pos, []( value_type const& ) {} ) ) {
+ --m_ItemCounter;
+ m_Stat.onRemoveNode( nHeight );
+ m_Stat.onExtractMaxSuccess();
+ return gp;
+ }
+
+ m_Stat.onExtractMaxRetry();
+ }
}
- /// Returns maximum height of skip-list. The max height is a constant for each object and does not exceed 32.
- static CDS_CONSTEXPR unsigned int max_height() CDS_NOEXCEPT
+ void increase_height( unsigned int nHeight )
{
- return c_nMaxHeight;
+ unsigned int nCur = m_nHeight.load( memory_model::memory_order_relaxed );
+ if ( nCur < nHeight )
+ m_nHeight.compare_exchange_strong( nCur, nHeight, memory_model::memory_order_relaxed, atomics::memory_order_relaxed );
}
- /// Returns const reference to internal statistics
- stat const& statistics() const
+ void destroy()
{
- return m_Stat;
+ node_type* p = m_Head.head()->next( 0 ).load( atomics::memory_order_relaxed ).ptr();
+ while ( p ) {
+ node_type* pNext = p->next( 0 ).load( atomics::memory_order_relaxed ).ptr();
+ dispose_node( node_traits::to_value_ptr( p ));
+ p = pNext;
+ }
}
+ //@endcond
+
+ private:
+ //@cond
+ skip_list::details::head_node< node_type > m_Head; ///< head tower (max height)
+
+ item_counter m_ItemCounter; ///< item counter
+ random_level_generator m_RandomLevelGen; ///< random level generator instance
+ atomics::atomic<unsigned int> m_nHeight; ///< estimated high level
+ mutable stat m_Stat; ///< internal statistics
+ //@endcond
};
}} // namespace cds::intrusive
-#endif // #ifndef __CDS_INTRUSIVE_IMPL_SKIP_LIST_H
+#endif // #ifndef CDSLIB_INTRUSIVE_IMPL_SKIP_LIST_H
projects / libcds.git / blobdiff