2 This file is a part of libcds - Concurrent Data Structures library
4 (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2016
6 Source code repo: http://github.com/khizmax/libcds/
7 Download: http://sourceforge.net/projects/libcds/files/
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31 #ifndef CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H
32 #define CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H
34 #include <cds/intrusive/details/base.h>
35 #include <cds/details/marked_ptr.h>
36 #include <cds/algo/bitop.h>
37 #include <cds/os/timer.h>
38 #include <cds/urcu/options.h>
40 namespace cds { namespace intrusive {
41 /// SkipListSet related definitions
42 /** @ingroup cds_intrusive_helper
45 /// The maximum possible height of any skip-list
46 static unsigned int const c_nHeightLimit = 32;
51 - \p GC - garbage collector
52 - \p Tag - a \ref cds_intrusive_hook_tag "tag"
54 template <class GC, typename Tag = opt::none>
58 typedef GC gc; ///< Garbage collector
59 typedef Tag tag; ///< tag
61 typedef cds::details::marked_ptr<node, 1> marked_ptr; ///< marked pointer
62 typedef typename gc::template atomic_marked_ptr< marked_ptr> atomic_marked_ptr; ///< atomic marked pointer specific for GC
64 typedef atomic_marked_ptr tower_item_type;
70 atomic_marked_ptr m_pNext; ///< Next item in bottom-list (list at level 0)
71 unsigned int m_nHeight; ///< Node height (size of \p m_arrNext array). For node at level 0 the height is 1.
72 atomic_marked_ptr * m_arrNext; ///< Array of next items for levels 1 .. m_nHeight - 1. For node at level 0 \p m_arrNext is \p nullptr
73 atomics::atomic<unsigned int> m_nUnlink; ///< How many levels has been unlinked
80 , m_arrNext( nullptr )
85 /// Constructs a node's tower of height \p nHeight
86 void make_tower( unsigned int nHeight, atomic_marked_ptr * nextTower )
88 assert( nHeight > 0 );
89 assert( (nHeight == 1 && nextTower == nullptr) // bottom-list node
90 || (nHeight > 1 && nextTower != nullptr) // node at level of more than 0
93 m_arrNext = nextTower;
95 atomics::atomic_thread_fence( atomics::memory_order_release );
99 atomic_marked_ptr * release_tower()
101 atomic_marked_ptr * pTower = m_arrNext;
107 atomic_marked_ptr * get_tower() const
112 bool has_tower() const
114 return m_nHeight > 1;
118 /// Access to element of next pointer array
119 atomic_marked_ptr& next( unsigned int nLevel )
121 assert( nLevel < height());
122 assert( nLevel == 0 || (nLevel > 0 && m_arrNext != nullptr));
124 return nLevel ? m_arrNext[ nLevel - 1] : m_pNext;
127 /// Access to element of next pointer array (const version)
128 atomic_marked_ptr const& next( unsigned int nLevel ) const
130 assert( nLevel < height());
131 assert( nLevel == 0 || nLevel > 0 && m_arrNext != nullptr );
133 return nLevel ? m_arrNext[ nLevel - 1] : m_pNext;
136 /// Access to element of next pointer array (synonym for \p next() function)
137 atomic_marked_ptr& operator[]( unsigned int nLevel )
139 return next( nLevel );
142 /// Access to element of next pointer array (synonym for \p next() function)
143 atomic_marked_ptr const& operator[]( unsigned int nLevel ) const
145 return next( nLevel );
148 /// Height of the node
149 unsigned int height() const
154 /// Clears internal links
157 assert( m_arrNext == nullptr );
158 m_pNext.store( marked_ptr(), atomics::memory_order_release );
162 bool is_cleared() const
164 return m_pNext == atomic_marked_ptr()
165 && m_arrNext == nullptr
169 bool level_unlinked( unsigned nCount = 1 )
171 return m_nUnlink.fetch_add( nCount, std::memory_order_relaxed ) + 1 == height();
178 struct default_hook {
179 typedef undefined_gc gc;
180 typedef opt::none tag;
185 template < typename HookType, typename... Options>
188 typedef typename opt::make_options< default_hook, Options...>::type options;
189 typedef typename options::gc gc;
190 typedef typename options::tag tag;
191 typedef node<gc, tag> node_type;
192 typedef HookType hook_type;
199 - \p opt::gc - garbage collector
200 - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
202 template < typename... Options >
203 struct base_hook: public hook< opt::base_hook_tag, Options... >
208 \p MemberOffset defines offset in bytes of \ref node member into your structure.
209 Use \p offsetof macro to define \p MemberOffset
212 - \p opt::gc - garbage collector
213 - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
215 template < size_t MemberOffset, typename... Options >
216 struct member_hook: public hook< opt::member_hook_tag, Options... >
219 static const size_t c_nMemberOffset = MemberOffset;
225 \p NodeTraits defines type traits for node.
226 See \ref node_traits for \p NodeTraits interface description
229 - \p opt::gc - garbage collector
230 - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
232 template <typename NodeTraits, typename... Options >
233 struct traits_hook: public hook< opt::traits_hook_tag, Options... >
236 typedef NodeTraits node_traits;
240 /// Option specifying random level generator
242 The random level generator is an important part of skip-list algorithm.
243 The node height in the skip-list have a probabilistic distribution
244 where half of the nodes that have level \p i pointers also have level <tt>i+1</tt> pointers
246 The random level generator should provide such distribution.
248 The \p Type functor interface is:
250 struct random_generator {
251 static unsigned int const c_nUpperBound = 32;
253 unsigned int operator()();
258 - \p c_nUpperBound - constant that specifies the upper bound of random number generated.
259 The generator produces a number from range <tt>[0 .. c_nUpperBound)</tt> (upper bound excluded).
260 \p c_nUpperBound must be no more than 32.
261 - <tt>random_generator()</tt> - the constructor of generator object initialises the generator instance (its internal state).
262 - <tt>unsigned int operator()()</tt> - the main generating function. Returns random level from range 0..31.
264 Stateful generators are supported.
266 Available \p Type implementations:
267 - \p skip_list::xorshift
268 - \p skip_list::turbo_pascal
270 template <typename Type>
271 struct random_level_generator {
273 template <typename Base>
274 struct pack: public Base
276 typedef Type random_level_generator;
281 /// Xor-shift random level generator
283 The simplest of the generators described in George
284 Marsaglia's "Xorshift RNGs" paper. This is not a high-quality
285 generator but is acceptable for skip-list.
287 The random generator should return numbers from range [0..31].
289 From Doug Lea's ConcurrentSkipListMap.java.
293 atomics::atomic<unsigned int> m_nSeed;
296 /// The upper bound of generator's return value. The generator produces random number in range <tt>[0..c_nUpperBound)</tt>
297 static unsigned int const c_nUpperBound = c_nHeightLimit;
299 /// Initializes the generator instance
302 m_nSeed.store( (unsigned int) cds::OS::Timer::random_seed(), atomics::memory_order_relaxed );
305 /// Main generator function
306 unsigned int operator()()
308 /* ConcurrentSkipListMap.java
309 private int randomLevel() {
313 randomSeed = x ^= x << 5;
314 if ((x & 0x80000001) != 0) // test highest and lowest bits
317 while (((x >>>= 1) & 1) != 0) ++level;
321 unsigned int x = m_nSeed.load( atomics::memory_order_relaxed );
325 m_nSeed.store( x, atomics::memory_order_relaxed );
326 unsigned int nLevel = ((x & 0x00000001) != 0) ? 0 : cds::bitop::LSB( (~(x >> 1)) & 0x7FFFFFFF );
327 assert( nLevel < c_nUpperBound );
332 /// Turbo-pascal random level generator
334 This uses a cheap pseudo-random function that was used in Turbo Pascal.
336 The random generator should return numbers from range [0..31].
338 From Doug Lea's ConcurrentSkipListMap.java.
343 atomics::atomic<unsigned int> m_nSeed;
346 /// The upper bound of generator's return value. The generator produces random number in range <tt>[0..c_nUpperBound)</tt>
347 static unsigned int const c_nUpperBound = c_nHeightLimit;
349 /// Initializes the generator instance
352 m_nSeed.store( (unsigned int) cds::OS::Timer::random_seed(), atomics::memory_order_relaxed );
355 /// Main generator function
356 unsigned int operator()()
359 private int randomLevel() {
362 randomSeed = r * 134775813 + 1;
364 while ((r <<= 1) > 0)
371 The low bits are apparently not very random (the original used only
372 upper 16 bits) so we traverse from highest bit down (i.e., test
373 sign), thus hardly ever use lower bits.
375 unsigned int x = m_nSeed.load( atomics::memory_order_relaxed ) * 134775813 + 1;
376 m_nSeed.store( x, atomics::memory_order_relaxed );
377 unsigned int nLevel = ( x & 0x80000000 ) ? (31 - cds::bitop::MSBnz( (x & 0x7FFFFFFF) | 1 )) : 0;
378 assert( nLevel < c_nUpperBound );
383 /// \p SkipListSet internal statistics
384 template <typename EventCounter = cds::atomicity::event_counter>
386 typedef EventCounter event_counter ; ///< Event counter type
388 event_counter m_nNodeHeightAdd[c_nHeightLimit] ; ///< Count of added node of each height
389 event_counter m_nNodeHeightDel[c_nHeightLimit] ; ///< Count of deleted node of each height
390 event_counter m_nInsertSuccess ; ///< Count of success insertion
391 event_counter m_nInsertFailed ; ///< Count of failed insertion
392 event_counter m_nInsertRetries ; ///< Count of unsuccessful retries of insertion
393 event_counter m_nUpdateExist ; ///< Count of \p update() call for existed node
394 event_counter m_nUpdateNew ; ///< Count of \p update() call for new node
395 event_counter m_nUnlinkSuccess ; ///< Count of successful call of \p unlink
396 event_counter m_nUnlinkFailed ; ///< Count of failed call of \p unlink
397 event_counter m_nEraseSuccess ; ///< Count of successful call of \p erase
398 event_counter m_nEraseFailed ; ///< Count of failed call of \p erase
399 event_counter m_nEraseRetry ; ///< Count of retries while erasing node
400 event_counter m_nFindFastSuccess ; ///< Count of successful call of \p find and all derivatives (via fast-path)
401 event_counter m_nFindFastFailed ; ///< Count of failed call of \p find and all derivatives (via fast-path)
402 event_counter m_nFindSlowSuccess ; ///< Count of successful call of \p find and all derivatives (via slow-path)
403 event_counter m_nFindSlowFailed ; ///< Count of failed call of \p find and all derivatives (via slow-path)
404 event_counter m_nRenewInsertPosition ; ///< Count of renewing position events while inserting
405 event_counter m_nLogicDeleteWhileInsert; ///< Count of events "The node has been logically deleted while inserting"
406 event_counter m_nEraseWhileInsert ; ///< Count of events "The node has been disposed while inserting"
407 event_counter m_nNotFoundWhileInsert ; ///< Count of events "Inserting node is not found"
408 event_counter m_nFastErase ; ///< Fast erase event counter
409 event_counter m_nFastEraseHelped ; ///< Fast erase with helping of other thread
410 event_counter m_nFastExtract ; ///< Fast extract event counter
411 event_counter m_nFastExtractHelped ; ///< Fast extract with helping of other thread
412 event_counter m_nSlowErase ; ///< Slow erase event counter
413 event_counter m_nSlowExtract ; ///< Slow extract event counter
414 event_counter m_nExtractSuccess ; ///< Count of successful call of \p extract
415 event_counter m_nExtractFailed ; ///< Count of failed call of \p extract
416 event_counter m_nExtractRetries ; ///< Count of retries of \p extract call
417 event_counter m_nExtractMinSuccess ; ///< Count of successful call of \p extract_min
418 event_counter m_nExtractMinFailed ; ///< Count of failed call of \p extract_min
419 event_counter m_nExtractMinRetries ; ///< Count of retries of \p extract_min call
420 event_counter m_nExtractMaxSuccess ; ///< Count of successful call of \p extract_max
421 event_counter m_nExtractMaxFailed ; ///< Count of failed call of \p extract_max
422 event_counter m_nExtractMaxRetries ; ///< Count of retries of \p extract_max call
423 event_counter m_nEraseWhileFind ; ///< Count of erased item while searching
424 event_counter m_nExtractWhileFind ; ///< Count of extracted item while searching (RCU only)
425 event_counter m_nMarkFailed ; ///< Count of failed node marking (logical deletion mark)
428 void onAddNode( unsigned int nHeight )
430 assert( nHeight > 0 && nHeight <= sizeof(m_nNodeHeightAdd) / sizeof(m_nNodeHeightAdd[0]));
431 ++m_nNodeHeightAdd[nHeight - 1];
433 void onRemoveNode( unsigned int nHeight )
435 assert( nHeight > 0 && nHeight <= sizeof(m_nNodeHeightDel) / sizeof(m_nNodeHeightDel[0]));
436 ++m_nNodeHeightDel[nHeight - 1];
439 void onInsertSuccess() { ++m_nInsertSuccess ; }
440 void onInsertFailed() { ++m_nInsertFailed ; }
441 void onInsertRetry() { ++m_nInsertRetries ; }
442 void onUpdateExist() { ++m_nUpdateExist ; }
443 void onUpdateNew() { ++m_nUpdateNew ; }
444 void onUnlinkSuccess() { ++m_nUnlinkSuccess ; }
445 void onUnlinkFailed() { ++m_nUnlinkFailed ; }
446 void onEraseSuccess() { ++m_nEraseSuccess ; }
447 void onEraseFailed() { ++m_nEraseFailed ; }
448 void onEraseRetry() { ++m_nEraseRetry; }
449 void onFindFastSuccess() { ++m_nFindFastSuccess ; }
450 void onFindFastFailed() { ++m_nFindFastFailed ; }
451 void onFindSlowSuccess() { ++m_nFindSlowSuccess ; }
452 void onFindSlowFailed() { ++m_nFindSlowFailed ; }
453 void onEraseWhileFind() { ++m_nEraseWhileFind ; }
454 void onExtractWhileFind() { ++m_nExtractWhileFind ; }
455 void onRenewInsertPosition() { ++m_nRenewInsertPosition; }
456 void onLogicDeleteWhileInsert() { ++m_nLogicDeleteWhileInsert; }
457 void onEraseWhileInsert() { ++m_nEraseWhileInsert; }
458 void onNotFoundWhileInsert() { ++m_nNotFoundWhileInsert; }
459 void onFastErase() { ++m_nFastErase; }
460 void onFastEraseHelped() { ++m_nFastEraseHelped; }
461 void onFastExtract() { ++m_nFastExtract; }
462 void onFastExtractHelped() { ++m_nFastExtractHelped; }
463 void onSlowErase() { ++m_nSlowErase; }
464 void onSlowExtract() { ++m_nSlowExtract; }
465 void onExtractSuccess() { ++m_nExtractSuccess; }
466 void onExtractFailed() { ++m_nExtractFailed; }
467 void onExtractRetry() { ++m_nExtractRetries; }
468 void onExtractMinSuccess() { ++m_nExtractMinSuccess; }
469 void onExtractMinFailed() { ++m_nExtractMinFailed; }
470 void onExtractMinRetry() { ++m_nExtractMinRetries; }
471 void onExtractMaxSuccess() { ++m_nExtractMaxSuccess; }
472 void onExtractMaxFailed() { ++m_nExtractMaxFailed; }
473 void onExtractMaxRetry() { ++m_nExtractMaxRetries; }
474 void onMarkFailed() { ++m_nMarkFailed; }
478 /// \p SkipListSet empty internal statistics
481 void onAddNode( unsigned int /*nHeight*/ ) const {}
482 void onRemoveNode( unsigned int /*nHeight*/ ) const {}
483 void onInsertSuccess() const {}
484 void onInsertFailed() const {}
485 void onInsertRetry() const {}
486 void onUpdateExist() const {}
487 void onUpdateNew() const {}
488 void onUnlinkSuccess() const {}
489 void onUnlinkFailed() const {}
490 void onEraseSuccess() const {}
491 void onEraseFailed() const {}
492 void onEraseRetry() const {}
493 void onFindFastSuccess() const {}
494 void onFindFastFailed() const {}
495 void onFindSlowSuccess() const {}
496 void onFindSlowFailed() const {}
497 void onEraseWhileFind() const {}
498 void onExtractWhileFind() const {}
499 void onRenewInsertPosition() const {}
500 void onLogicDeleteWhileInsert() const {}
501 void onEraseWhileInsert() const {}
502 void onNotFoundWhileInsert() const {}
503 void onFastErase() const {}
504 void onFastEraseHelped() const {}
505 void onFastExtract() const {}
506 void onFastExtractHelped() const {}
507 void onSlowErase() const {}
508 void onSlowExtract() const {}
509 void onExtractSuccess() const {}
510 void onExtractFailed() const {}
511 void onExtractRetry() const {}
512 void onExtractMinSuccess() const {}
513 void onExtractMinFailed() const {}
514 void onExtractMinRetry() const {}
515 void onExtractMaxSuccess() const {}
516 void onExtractMaxFailed() const {}
517 void onExtractMaxRetry() const {}
518 void onMarkFailed() const {}
523 // For internal use only!!!
524 template <typename Type>
525 struct internal_node_builder {
526 template <typename Base>
527 struct pack: public Base
529 typedef Type internal_node_builder;
534 /// \p SkipListSet traits
539 Possible values are: \p skip_list::base_hook, \p skip_list::member_hook, \p skip_list::traits_hook.
541 typedef base_hook<> hook;
543 /// Key comparison functor
545 No default functor is provided. If the option is not specified, the \p less is used.
547 typedef opt::none compare;
549 /// specifies binary predicate used for key compare.
551 Default is \p std::less<T>.
553 typedef opt::none less;
557 The functor used for dispose removed items. Default is \p opt::v::empty_disposer.
559 typedef opt::v::empty_disposer disposer;
563 The type for item counting feature.
564 By default, item counting is disabled (\p atomicity::empty_item_counter),
565 \p atomicity::item_counter enables it.
567 typedef atomicity::empty_item_counter item_counter;
569 /// C++ memory ordering model
571 List of available memory ordering see \p opt::memory_model
573 typedef opt::v::relaxed_ordering memory_model;
575 /// Random level generator
577 The random level generator is an important part of skip-list algorithm.
578 The node height in the skip-list have a probabilistic distribution
579 where half of the nodes that have level \p i pointers also have level <tt>i+1</tt> pointers
580 (i = 0..30). So, the height of a node is in range [0..31].
582 See \p skip_list::random_level_generator option setter.
584 typedef turbo_pascal random_level_generator;
588 Although the skip-list is an intrusive container,
589 an allocator should be provided to maintain variable randomly-calculated height of the node
590 since the node can contain up to 32 next pointers.
591 The allocator specified is used to allocate an array of next pointers
592 for nodes which height is more than 1.
594 typedef CDS_DEFAULT_ALLOCATOR allocator;
596 /// back-off strategy
598 If the option is not specified, the \p cds::backoff::Default is used.
600 typedef cds::backoff::Default back_off;
602 /// Internal statistics
604 By default, internal statistics is disabled (\p skip_list::empty_stat).
605 Use \p skip_list::stat to enable it.
607 typedef empty_stat stat;
609 /// RCU deadlock checking policy (only for \ref cds_intrusive_SkipListSet_rcu "RCU-based SkipListSet")
611 List of available options see \p opt::rcu_check_deadlock
613 typedef opt::v::rcu_throw_deadlock rcu_check_deadlock;
616 // For internal use only!!!
617 typedef opt::none internal_node_builder;
621 /// Metafunction converting option list to \p SkipListSet traits
624 - \p opt::hook - hook used. Possible values are: \p skip_list::base_hook, \p skip_list::member_hook, \p skip_list::traits_hook.
625 If the option is not specified, <tt>skip_list::base_hook<></tt> and \p gc::HP is used.
626 - \p opt::compare - key comparison functor. No default functor is provided.
627 If the option is not specified, the \p opt::less is used.
628 - \p opt::less - specifies binary predicate used for key comparison. Default is \p std::less<T>.
629 - \p opt::disposer - the functor used for dispose removed items. Default is \p opt::v::empty_disposer. Due the nature
630 of GC schema the disposer may be called asynchronously.
631 - \p opt::item_counter - the type of item counting feature. Default is disabled, i.e. \p atomicity::empty_item_counter.
632 To enable it use \p atomicity::item_counter
633 - \p opt::memory_model - C++ memory ordering model. Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
634 or \p opt::v::sequential_consistent (sequentially consisnent memory model).
635 - \p skip_list::random_level_generator - random level generator. Can be \p skip_list::xorshift,
636 \p skip_list::turbo_pascal (the default) or
637 user-provided one. See \p skip_list::random_level_generator option description for explanation.
638 - \p opt::allocator - although the skip-list is an intrusive container,
639 an allocator should be provided to maintain variable randomly-calculated height of the node
640 since the node can contain up to 32 next pointers. The allocator option is used to allocate an array of next pointers
641 for nodes which height is more than 1. Default is \ref CDS_DEFAULT_ALLOCATOR.
642 - \p opt::back_off - back-off strategy, default is \p cds::backoff::Default.
643 - \p opt::stat - internal statistics. By default, it is disabled (\p skip_list::empty_stat).
644 To enable it use \p skip_list::stat
646 template <typename... Options>
648 # ifdef CDS_DOXYGEN_INVOKED
649 typedef implementation_defined type ; ///< Metafunction result
651 typedef typename cds::opt::make_options<
652 typename cds::opt::find_type_traits< traits, Options... >::type
660 template <typename Node>
661 class head_node: public Node
663 typedef Node node_type;
664 typename node_type::atomic_marked_ptr m_Tower[skip_list::c_nHeightLimit];
667 head_node( unsigned int nHeight )
669 for ( size_t i = 0; i < sizeof(m_Tower) / sizeof(m_Tower[0]); ++i )
670 m_Tower[i].store( typename node_type::marked_ptr(), atomics::memory_order_relaxed );
672 node_type::make_tower( nHeight, m_Tower );
675 node_type * head() const
677 return const_cast<node_type *>( static_cast<node_type const *>(this));
681 template <typename NodeType, typename AtomicNodePtr, typename Alloc>
682 struct intrusive_node_builder
684 typedef NodeType node_type;
685 typedef AtomicNodePtr atomic_node_ptr;
686 typedef Alloc allocator_type;
688 typedef cds::details::Allocator< atomic_node_ptr, allocator_type > tower_allocator;
690 template <typename RandomGen>
691 static node_type * make_tower( node_type * pNode, RandomGen& gen )
693 return make_tower( pNode, gen() + 1 );
696 static node_type * make_tower( node_type * pNode, unsigned int nHeight )
699 pNode->make_tower( nHeight, tower_allocator().NewArray( nHeight - 1, nullptr ));
703 static void dispose_tower( node_type * pNode )
705 unsigned int nHeight = pNode->height();
707 tower_allocator().Delete( pNode->release_tower(), nHeight );
710 struct node_disposer {
711 void operator()( node_type * pNode )
713 dispose_tower( pNode );
718 // Forward declaration
719 template <class GC, typename NodeTraits, typename BackOff, bool IsConst>
722 } // namespace details
725 } // namespace skip_list
727 // Forward declaration
728 template <class GC, typename T, typename Traits = skip_list::traits >
731 }} // namespace cds::intrusive
733 #endif // #ifndef CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H