X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=cds%2Fintrusive%2Fimpl%2Fskip_list.h;h=ccab53ce810eda4230f45c665940874d805868c7;hb=40e34e6d0b104b6f5aff506ad67d43fd410e52bc;hp=3574937aec07991f6478fba18792e6ee5915a35b;hpb=9f4651a5d26ac3b768c57e54c643988fb4eab9ef;p=libcds.git diff --git a/cds/intrusive/impl/skip_list.h b/cds/intrusive/impl/skip_list.h index 3574937a..ccab53ce 100644 --- a/cds/intrusive/impl/skip_list.h +++ b/cds/intrusive/impl/skip_list.h @@ -1,4 +1,32 @@ -//$$CDS-header$$ +/* + This file is a part of libcds - Concurrent Data Structures library + + (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 @@ -37,7 +65,7 @@ namespace cds { namespace intrusive { 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() @@ -47,7 +75,7 @@ namespace cds { namespace intrusive { 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(); @@ -56,12 +84,12 @@ namespace cds { namespace intrusive { 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; @@ -80,7 +108,7 @@ namespace cds { namespace intrusive { for (;;) { marked_ptr p = m_guard.protect( refHead[0], gc_protect ); - if ( !p.ptr() ) { + if ( !p.ptr()) { // empty skip-list m_guard.clear(); break; @@ -88,7 +116,7 @@ namespace cds { namespace intrusive { 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; } @@ -105,7 +133,7 @@ namespace cds { namespace intrusive { 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 @@ -345,9 +373,6 @@ namespace cds { namespace intrusive { typedef typename traits::back_off back_off; ///< Back-off strategy typedef typename traits::stat stat; ///< internal statistics type - //@cond - typedef cds::intrusive::skip_list::implementation_tag implementation_tag; - //@endcond public: typedef typename gc::template guarded_ptr< value_type > guarded_ptr; ///< Guarded pointer @@ -366,6 +391,12 @@ namespace cds { namespace intrusive { 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 @@ -382,844 +413,625 @@ namespace cds { namespace intrusive { 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 \p update() + 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 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 - 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 - 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( 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_acquire ); + // Assignment operator + iterator& operator = (iterator const& src); - if ( pPred->next( nLevel ).load( memory_model::memory_order_acquire ).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_acquire, 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( 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 + 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_acquire ); + 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_acquire ).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_acquire, atomics::memory_order_relaxed )) - { - if ( nLevel == 0 ) { - gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node ); - m_Stat.onEraseWhileFind(); - } - } - 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; + } - return (pos.pCur = pCur.ptr()) != nullptr; - } + if ( !insert_at_position( val, pNode, pos, f )) { + m_Stat.onInsertRetry(); + continue; + } - bool find_max_position( position& pos ) - { - node_type * pPred; - marked_node_ptr pSucc; - marked_node_ptr pCur; + increase_height( nHeight ); + ++m_ItemCounter; + m_Stat.onAddNode( nHeight ); + m_Stat.onInsertSuccess(); + scp.release(); + return true; + } + } - // Hazard pointer array: - // pPred: [nLevel * 2] - // pSucc: [nLevel * 2 + 1] + /// Updates the node + /** + The operation performs inserting or changing data with lock-free manner. - retry: - pPred = m_Head.head(); + 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. - for ( int nLevel = static_cast( 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 ( 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. - marked_node_ptr p( pCur.ptr() ); - if ( pPred->next( nLevel ).compare_exchange_strong( p, marked_node_ptr( pSucc.ptr() ), - memory_model::memory_order_acquire, atomics::memory_order_relaxed )) - { - if ( nLevel == 0 ) { - gc::retire( node_traits::to_value_ptr( pCur.ptr() ), dispose_node ); - m_Stat.onEraseWhileFind(); - } - } - 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; - } + Returns std::pair 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. + @warning See \ref cds_intrusive_item_creating "insert item troubleshooting" + */ template - bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f ) + std::pair update( value_type& val, Func func, bool bInsert = true ) { - unsigned int nHeight = pNode->height(); + typename gc::Guard gNew; + gNew.assign( &val ); - 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; - // Insert at level 0 + 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 ); - } - - // Insert at level 1..max - 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 - bool try_remove_at( node_type * pDel, position& pos, Func f ) - { - assert( pDel != nullptr ); - - marked_node_ptr pSucc; - - // logical deletion (marking) - for ( unsigned int nLevel = pDel->height() - 1; nLevel > 0; --nLevel ) { - while ( true ) { - pSucc = pDel->next(nLevel); - if ( pSucc.bits() || pDel->next(nLevel).compare_exchange_weak( pSucc, pSucc | 1, - memory_model::memory_order_release, atomics::memory_order_relaxed )) - { - break; - } + if ( !bInsert ) { + scp.release(); + return std::make_pair( false, false ); } - } - - while ( true ) { - marked_node_ptr p( pDel->next(0).load(memory_model::memory_order_relaxed).ptr() ); - if ( pDel->next(0).compare_exchange_strong( p, p | 1, memory_model::memory_order_release, atomics::memory_order_relaxed )) - { - f( *node_traits::to_value_ptr( pDel )); - - // Physical deletion - // try fast erase - p = pDel; - for ( int nLevel = static_cast( pDel->height() - 1 ); nLevel >= 0; --nLevel ) { - 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) ) - { - // 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() ) { - // Another thread is deleting pDel right now - return false; - } + if ( !bTowerOk ) { + build_node( pNode ); + nHeight = pNode->height(); + bTowerMade = pNode->has_tower(); + bTowerOk = true; } - m_Stat.onEraseRetry(); - } - } - - enum finsd_fastpath_result { - find_fastpath_found, - find_fastpath_not_found, - find_fastpath_abort - }; - template - 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( 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 - 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 - bool find_with_( Q& val, Compare cmp, Func f ) + //@cond + template + CDS_DEPRECATED("ensure() is deprecated, use update()") + std::pair 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 a key + 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 &val . - template - bool get_with_( typename guarded_ptr::native_guard& guard, Q const& val, Compare cmp ) - { - return find_with_( val, cmp, [&guard](value_type& found, Q const& ) { guard.set(&found); } ); - } + The \p disposer specified in \p Traits class template parameter is called + by garbage collector \p GC asynchronously. - template - 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 - bool extract_( typename guarded_ptr::native_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(); - guard.clear(); - 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.set( 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 + guarded_ptr extract( Q const& key ) + { + return extract_( key, key_comparator()); } - bool extract_min_( typename guarded_ptr::native_guard& gDel ) + /// 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. + + \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 + guarded_ptr extract_with( Q const& key, Less pred ) { - position pos; + CDS_UNUSED( pred ); + return extract_( key, cds::opt::details::make_comparator_from_less()); + } - for (;;) { - if ( !find_min_position( pos ) ) { - // The list is empty - m_Stat.onExtractMinFailed(); - gDel.clear(); - return false; - } + /// 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. - node_type * pDel = pos.pCur; + @note Due the concurrent nature of the list, the function extracts nearly 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. - unsigned int nHeight = pDel->height(); - gDel.set( node_traits::to_value_ptr(pDel) ); + 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. - if ( try_remove_at( pDel, pos, [](value_type const&) {} )) { - --m_ItemCounter; - m_Stat.onRemoveNode( nHeight ); - m_Stat.onExtractMinSuccess(); - 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_min()); + if ( gp ) { + // Deal with gp + //... } - - m_Stat.onExtractMinRetry(); + // Destructor of gp releases internal HP guard } - } - - bool extract_max_( typename guarded_ptr::native_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(); - gDel.clear(); - 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 nearly 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.set( 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 + 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 + 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" ); - - gc::check_available_guards( c_nHazardPtrCount ); - - // Barrier for head node - atomics::atomic_thread_fence( memory_model::memory_order_release ); + CDS_UNUSED( pred ); + return erase_( key, cds::opt::details::make_comparator_from_less(), [](value_type const&) {} ); } - /// Clears and destructs the skip-list - ~SkipListSet() - { - clear(); - } + /// 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. - public: - /// Iterator type - typedef skip_list::details::iterator< gc, node_traits, back_off, false > iterator; + The \p Func interface is + \code + struct functor { + void operator()( value_type const& item ); + }; + \endcode - /// Const iterator type - typedef skip_list::details::iterator< gc, node_traits, back_off, true > const_iterator; + If the item with key equal to \p key is not found the function return \p false. - /// Returns a forward iterator addressing the first element in a set - iterator begin() + Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type. + */ + template + bool erase( Q const& key, Func f ) { - return iterator( *m_Head.head() ); + return erase_( key, key_comparator(), f ); } - /// 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() ); - } + /// 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 that addresses the location succeeding the last element in a set. - iterator end() + \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 + bool erase_with( Q const& key, Less pred, Func f ) { - return iterator(); + CDS_UNUSED( pred ); + return erase_( key, cds::opt::details::make_comparator_from_less(), f ); } - /// Returns a forward const iterator that addresses the location succeeding the last element in a set. - const_iterator end() 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 find 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 + bool find( Q& key, Func f ) { - return const_iterator(); + return find_with_( key, key_comparator(), f ); } - /// Returns a forward const iterator that addresses the location succeeding the last element in a set. - const_iterator cend() const + //@cond + template + bool find( Q const& key, Func f ) { - return const_iterator(); + return find_with_( key, key_comparator(), f ); } + //@endcond - public: - /// Inserts new node + /// Finds the key \p key with \p pred predicate for comparing /** - The function inserts \p val in the set if it does not contain - an item with key equal to \p val. + The function is an analog of \ref cds_intrusive_SkipListSet_hp_find_func "find(Q&, Func)" + but \p pred is used for key compare. - Returns \p true if \p val is placed into the set, \p false otherwise. + \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. */ - bool insert( value_type& val ) + template + bool find_with( Q& key, Less pred, Func f ) { - return insert( val, []( value_type& ) {} ); + CDS_UNUSED( pred ); + return find_with_( key, cds::opt::details::make_comparator_from_less(), f ); } - - /// Inserts new node - /** - This function is intended for derived non-intrusive containers. - - The function allows to split creating of new item into two part: - - create item with key only - - insert new item into the set - - if inserting is success, calls \p f functor to initialize value-field of \p val. - - 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 - bool insert( value_type& val, Func f ) + //@cond + template + bool find_with( Q const& key, Less pred, Func f ) { - 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; - - 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(); - - m_Stat.onInsertFailed(); - return false; - } - - if ( !bTowerOk ) { - build_node( pNode ); - nHeight = pNode->height(); - bTowerMade = - bTowerOk = true; - } - - if ( !insert_at_position( val, pNode, pos, f )) { - m_Stat.onInsertRetry(); - continue; - } - - increase_height( nHeight ); - ++m_ItemCounter; - m_Stat.onAddNode( nHeight ); - m_Stat.onInsertSuccess(); - scp.release(); - return true; - } + CDS_UNUSED( pred ); + return find_with_( key, cds::opt::details::make_comparator_from_less(), f ); } + //@endcond - /// Updates the node + /// Checks whether the set contains \p key /** - 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 - 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. - - Returns std::pair where \p first is \p true if operation is successfull, - 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. - - @warning See \ref cds_intrusive_item_creating "insert item troubleshooting" + The function searches the item with key equal to \p key + and returns \p true if it is found, and \p false otherwise. */ - template - std::pair update( value_type& val, Func func, bool bInsert = true ) + template + bool contains( 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; - - 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(); - - func( false, *node_traits::to_value_ptr(pos.pCur), val ); - m_Stat.onUpdateExist(); - return std::make_pair( true, false ); - } - - if ( !bInsert ) { - scp.release(); - return std::make_pair( false, false ); - } - - if ( !bTowerOk ) { - build_node( pNode ); - nHeight = pNode->height(); - bTowerMade = - bTowerOk = true; - } - - if ( !insert_at_position( val, pNode, pos, [&func]( value_type& item ) { func( true, item, item ); })) { - m_Stat.onInsertRetry(); - continue; - } - - increase_height( nHeight ); - ++m_ItemCounter; - scp.release(); - m_Stat.onAddNode( nHeight ); - m_Stat.onUpdateNew(); - return std::make_pair( true, true ); - } + return find_with_( key, key_comparator(), [](value_type& , Q const& ) {} ); } - //@cond - // Deprecated, use update() instead - template - std::pair ensure( value_type& val, Func func ) + template + CDS_DEPRECATED("deprecated, use contains()") + bool find( Q const& key ) { - return update( val, func, true ); + return contains( key ); } //@endcond - /// Unlinks the item \p val from the set + /// Checks whether the set contains \p key using \p pred predicate for searching /** - 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. - - Difference between \p erase() and \p %unlink() functions: \p %erase() finds a key - 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 &val . - - The \p disposer specified in \p Traits class template parameter is called - by garbage collector \p GC asynchronously. - - The function returns \p true if success and \p false otherwise. + The function is similar to contains( key ) 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 unlink( value_type& val ) + template + bool contains( Q const& key, Less pred ) { - position pos; - - if ( !find_position( val, pos, key_comparator(), false ) ) { - m_Stat.onUnlinkFailed(); - return false; - } - - node_type * pDel = pos.pCur; - assert( key_comparator()( *node_traits::to_value_ptr( pDel ), val ) == 0 ); - - unsigned int nHeight = pDel->height(); - 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.onUnlinkSuccess(); - return true; - } - - m_Stat.onUnlinkFailed(); - return false; + CDS_UNUSED( pred ); + return find_with_( key, cds::opt::details::make_comparator_from_less(), [](value_type& , Q const& ) {} ); } + //@cond + template + CDS_DEPRECATED("deprecated, use contains()") + bool find_with( Q const& key, Less pred ) + { + return contains( key, pred ); + } + //@endcond - /// 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. - - Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type. + /// 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 \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 + 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. + @note Each \p guarded_ptr object uses one GC's guard which can be limited resource. Usage: \code @@ -1227,376 +1039,666 @@ namespace cds { namespace intrusive { skip_list theList; // ... { - skip_list::guarded_ptr gp(theList.extract( 5 )); + skip_list::guarded_ptr gp(theList.get( 5 )); if ( gp ) { // Deal with gp - // ... + //... } - // Destructor of gp releases internal HP guard + // Destructor of guarded_ptr releases internal HP guard } \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 - guarded_ptr extract( Q const& key ) + guarded_ptr get( Q const& key ) { - guarded_ptr gp; - extract_( gp.guard(), key, key_comparator() ); - return gp; + return get_with_( key, key_comparator()); } - /// Extracts the item from the set with comparing functor \p pred + /// Finds \p key and return the item found /** - The function is an analog of \ref cds_intrusive_SkipListSet_hp_extract "extract(Q const&)" - but \p pred predicate is used for key comparing. + The function is an analog of \ref cds_intrusive_SkipListSet_hp_get "get( 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 - guarded_ptr extract_with( Q const& key, Less pred ) + guarded_ptr get_with( Q const& key, Less pred ) { CDS_UNUSED( pred ); - guarded_ptr gp; - extract_( gp.guard(), key, cds::opt::details::make_comparator_from_less() ); - return gp; + return get_with_( key, cds::opt::details::make_comparator_from_less()); } - /// Extracts an item with minimal key from the list + /// Returns item count in the set /** - 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. + 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; + } - @note Due the concurrent nature of the list, the function extracts nearly 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. - - 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. + /// Checks if the set is empty + bool empty() const + { + return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr; + } - Usage: + /// Clears the set (not 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 - 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 - } + set.clear(); + assert( set.empty()); \endcode + the assertion could be raised. + + For each item the \ref disposer will be called after unlinking. */ - guarded_ptr extract_min() + void clear() { - guarded_ptr gp; - extract_min_( gp.guard() ); - return gp; + while ( extract_min_()); } - /// 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. + /// 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; + } - @note Due the concurrent nature of the list, the function extracts nearly 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. + /// Returns const reference to internal statistics + stat const& statistics() const + { + return m_Stat; + } - 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. + 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; + } - 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 - //... - } - // Destructor of gp releases internal HP guard - } - \endcode - */ - guarded_ptr extract_max() + template + node_type * build_node( Q v ) { - guarded_ptr gp; - extract_max_( gp.guard() ); - return gp; + return node_builder::make_tower( v, m_RandomLevelGen ); } - /// 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. + static value_type * gc_protect( marked_node_ptr p ) + { + return node_traits::to_value_ptr( p.ptr() ); + } - Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type. - */ - template - bool erase( Q const& key ) + static void dispose_node( value_type * pVal ) { - return erase_( key, key_comparator(), [](value_type const&) {} ); + assert( pVal != nullptr ); + typename node_builder::node_disposer()( node_traits::to_node_ptr( pVal ) ); + disposer()( pVal ); } - /// 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. + void help_remove( int nLevel, node_type* pPred, marked_node_ptr pCur, marked_node_ptr pSucc ) + { + marked_node_ptr p( pCur.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 - bool erase_with( Q const& key, Less pred ) + 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(); + } + } + } + } + + template + bool find_position( Q const& val, position& pos, Compare cmp, bool bStopIfFound ) { - CDS_UNUSED( pred ); - return erase_( key, cds::opt::details::make_comparator_from_less(), [](value_type const&) {} ); + node_type * pPred; + marked_node_ptr pSucc; + marked_node_ptr pCur; + + // Hazard pointer array: + // pPred: [nLevel * 2] + // pSucc: [nLevel * 2 + 1] + + retry: + pPred = m_Head.head(); + int nCmp = 1; + + for ( int nLevel = static_cast( 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 ( pCur.ptr() == nullptr ) { + // end of 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 { + 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(); + } + + if ( nCmp != 0 ) + return false; + + found: + pos.pCur = pCur.ptr(); + return pCur.ptr() && nCmp == 0; } - /// 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. + bool find_min_position( position& pos ) + { + node_type * pPred; + marked_node_ptr pSucc; + marked_node_ptr pCur; - The \p Func interface is - \code - struct functor { - void operator()( value_type const& item ); - }; - \endcode + // Hazard pointer array: + // pPred: [nLevel * 2] + // pSucc: [nLevel * 2 + 1] - If the item with key equal to \p key is not found the function return \p false. + retry: + pPred = m_Head.head(); - Note the compare functor should accept a parameter of type \p Q that can be not the same as \p value_type. - */ - template - bool erase( Q const& key, Func f ) + for ( int nLevel = static_cast( 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 ); + + // 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(); + } + + return ( pos.pCur = pCur.ptr() ) != nullptr; + } + + bool find_max_position( position& pos ) { - return erase_( key, key_comparator(), f ); + node_type * pPred; + marked_node_ptr pSucc; + marked_node_ptr pCur; + + // Hazard pointer array: + // pPred: [nLevel * 2] + // pSucc: [nLevel * 2 + 1] + + retry: + pPred = m_Head.head(); + + for ( int nLevel = static_cast( 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 ( 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 ); + } + } + + // Next level + pos.pPrev[nLevel] = pPred; + pos.pSucc[nLevel] = pCur.ptr(); + } + + return ( pos.pCur = pCur.ptr() ) != nullptr; } - /// 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. + template + bool insert_at_position( value_type& val, node_type * pNode, position& pos, Func f ) + { + unsigned int const nHeight = pNode->height(); - \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 - bool erase_with( Q const& key, Less pred, Func f ) + for ( unsigned int nLevel = 1; nLevel < nHeight; ++nLevel ) + pNode->next( nLevel ).store( marked_node_ptr(), memory_model::memory_order_relaxed ); + + // Insert at level 0 + { + 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; + } + } + } + return true; + } + + template + bool try_remove_at( node_type * pDel, position& pos, Func f ) + { + assert( pDel != nullptr ); + + marked_node_ptr pSucc; + back_off bkoff; + + // 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(); + } + } + } + + 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 ) ); + + // Physical deletion + // try fast erase + p = pDel; + + for ( int nLevel = static_cast( pDel->height() - 1 ); nLevel >= 0; --nLevel ) { + + 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; + } + } + + // 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(); + } + } + + enum finsd_fastpath_result { + find_fastpath_found, + find_fastpath_not_found, + find_fastpath_abort + }; + template + finsd_fastpath_result find_fastpath( Q& val, Compare cmp, Func f ) + { + node_type * pPred; + marked_node_ptr pCur; + marked_node_ptr pNull; + + // guard array: + // 0 - pPred on level N + // 1 - pCur on level N + typename gc::template GuardArray<2> guards; + back_off bkoff; + unsigned attempt = 0; + + try_again: + pPred = m_Head.head(); + for ( int nLevel = static_cast( m_nHeight.load( memory_model::memory_order_relaxed ) - 1 ); nLevel >= 0; --nLevel ) { + pCur = guards.protect( 1, pPred->next( nLevel ), gc_protect ); + + while ( pCur != pNull ) { + if ( pCur.bits() ) { + // pPred is being removed + if ( ++attempt < 4 ) { + bkoff(); + goto try_again; + } + + 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 + bool find_slowpath( Q& val, Compare cmp, Func f ) { - CDS_UNUSED( pred ); - return erase_( key, cds::opt::details::make_comparator_from_less(), 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; + } + else + return false; } - /// 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 find function argument. + template + 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 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 key is found, \p false otherwise. - */ - template - bool find( Q& key, Func f ) + template + guarded_ptr get_with_( Q const& val, Compare cmp ) { - return find_with_( key, 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(); } - //@cond - template - bool find( Q const& key, Func f ) + + template + bool erase_( Q const& val, Compare cmp, Func f ) { - return find_with_( key, key_comparator(), f ); - } - //@endcond + position pos; - /// 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. + if ( !find_position( val, pos, cmp, false ) ) { + m_Stat.onEraseFailed(); + 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 - bool find_with( Q& key, Less pred, Func f ) - { - CDS_UNUSED( pred ); - return find_with_( key, cds::opt::details::make_comparator_from_less(), f ); - } - //@cond - template - bool find_with( Q const& key, Less pred, Func f ) - { - CDS_UNUSED( pred ); - return find_with_( key, cds::opt::details::make_comparator_from_less(), f ); - } - //@endcond + 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 ); - /// Finds \p key - /** \anchor cds_intrusive_SkipListSet_hp_find_val - The function searches the item with key equal to \p key - and returns \p true if it is found, and \p false otherwise. + unsigned int nHeight = pDel->height(); + if ( try_remove_at( pDel, pos, f ) ) { + --m_ItemCounter; + m_Stat.onRemoveNode( nHeight ); + m_Stat.onEraseSuccess(); + 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. - */ - template - bool find( Q const& key ) - { - return find_with_( key, key_comparator(), [](value_type& , Q const& ) {} ); + m_Stat.onEraseFailed(); + return false; } - /// Finds \p key 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 - bool find_with( Q const& key, Less pred ) + template + guarded_ptr extract_( Q const& val, Compare cmp ) { - CDS_UNUSED( pred ); - return find_with_( key, cds::opt::details::make_comparator_from_less(), [](value_type& , Q const& ) {} ); - } + position pos; - /// 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. + guarded_ptr gp; + for (;;) { + if ( !find_position( val, pos, cmp, false ) ) { + m_Stat.onExtractFailed(); + return guarded_ptr(); + } - 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. + 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(theList.get( 5 )); - if ( gp ) { - // 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 - guarded_ptr get( Q const& key ) + guarded_ptr extract_min_() { + position pos; + guarded_ptr gp; - get_with_( gp.guard(), key, key_comparator() ); - return gp; - } + for ( ;;) { + if ( !find_min_position( pos ) ) { + // The list is empty + m_Stat.onExtractMinFailed(); + return guarded_ptr(); + } - /// 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. + node_type * pDel = pos.pCur; - \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 - guarded_ptr get_with( Q const& key, Less pred ) - { - CDS_UNUSED( pred ); - guarded_ptr gp; - get_with_( gp.guard(), key, cds::opt::details::make_comparator_from_less() ); - return gp; - } + unsigned int nHeight = pDel->height(); + gp.reset( node_traits::to_value_ptr( pDel ) ); - /// 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; - } + if ( try_remove_at( pDel, pos, []( value_type const& ) {} ) ) { + --m_ItemCounter; + m_Stat.onRemoveNode( nHeight ); + m_Stat.onExtractMinSuccess(); + return gp; + } - /// Checks if the set is empty - bool empty() const - { - return m_Head.head()->next( 0 ).load( memory_model::memory_order_relaxed ) == nullptr; + m_Stat.onExtractMinRetry(); + } } - /// Clears the set (not 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. - - 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.guard() )); + 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 m_nHeight; ///< estimated high level + mutable stat m_Stat; ///< internal statistics + //@endcond }; }} // namespace cds::intrusive