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cds
1.4.0
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Split-ordered list. More...
#include <cds/intrusive/split_list.h>
Public Types | |
| typedef Traits | options |
| Traits template parameters. | |
| typedef GC | gc |
| Garbage collector. | |
| typedef OrderedList | ordered_list |
| type of ordered list used as base for split-list | |
| typedef ordered_list::value_type | value_type |
| type of value stored in the split-list | |
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typedef ordered_list::key_comparator | key_comparator |
| key comparision functor | |
| typedef ordered_list::disposer | disposer |
| Node disposer functor. | |
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typedef cds::opt::v::hash_selector < typename options::hash > ::type | hash |
Hash functor for value_type and all its derivatives that you use. | |
| typedef options::item_counter | item_counter |
| Item counter type. | |
| typedef options::back_off | back_off |
| back-off strategy for spinning | |
| typedef options::memory_model | memory_model |
| Memory ordering. See cds::opt::memory_model option. | |
| typedef iterator_type< false > | iterator |
| Forward iterator. More... | |
| typedef iterator_type< true > | const_iterator |
| Const forward iterator. More... | |
Public Member Functions | |
| SplitListSet () | |
| Initialize split-ordered list of default capacity. More... | |
| SplitListSet (size_t nItemCount, size_t nLoadFactor=1) | |
| Initialize split-ordered list. More... | |
| bool | insert (value_type &val) |
| Inserts new node. More... | |
| template<typename Func > | |
| bool | insert (value_type &val, Func f) |
| Inserts new node. More... | |
| template<typename Func > | |
| std::pair< bool, bool > | ensure (value_type &val, Func func) |
Ensures that the val exists in the set. More... | |
| bool | unlink (value_type &val) |
Unlinks the item val from the set. More... | |
| template<typename Q > | |
| bool | erase (Q const &val) |
| Deletes the item from the set. More... | |
| template<typename Q , typename Less > | |
| bool | erase_with (const Q &val, Less pred) |
Deletes the item from the set with comparing functor pred. More... | |
| template<typename Q , typename Func > | |
| bool | erase (Q const &val, Func f) |
| Deletes the item from the set. More... | |
| template<typename Q , typename Less , typename Func > | |
| bool | erase_with (Q const &val, Less pred, Func f) |
Deletes the item from the set with comparing functor pred. More... | |
| template<typename Q , typename Func > | |
| bool | find (Q &val, Func f) |
Finds the key val. More... | |
| template<typename Q , typename Less , typename Func > | |
| bool | find_with (Q &val, Less pred, Func f) |
Finds the key val with pred predicate for comparing. More... | |
| template<typename Q , typename Func > | |
| bool | find (Q const &val, Func f) |
Finds the key val. More... | |
| template<typename Q , typename Less , typename Func > | |
| bool | find_with (Q const &val, Less pred, Func f) |
Finds the key val with pred predicate for comparing. More... | |
| template<typename Q > | |
| bool | find (Q const &val) |
Finds the key val. More... | |
| template<typename Q , typename Less > | |
| bool | find_with (Q const &val, Less pred) |
Finds the key val with pred predicate for comparing. More... | |
| size_t | size () const |
| Returns item count in the set. | |
| bool | empty () const |
| Checks if the set is empty. More... | |
| void | clear () |
| Clears the set (non-atomic) More... | |
| iterator | begin () |
| Returns a forward iterator addressing the first element in a split-list. More... | |
| iterator | end () |
| Returns an iterator that addresses the location succeeding the last element in a split-list. More... | |
| const_iterator | begin () const |
| Returns a forward const iterator addressing the first element in a split-list. | |
| const_iterator | end () const |
| Returns an const iterator that addresses the location succeeding the last element in a split-list. | |
Protected Types | |
| typedef ordered_list::node_type | list_node_type |
| Node type as declared in ordered list. | |
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typedef split_list::node < list_node_type > | node_type |
| split-list node type | |
| typedef node_type | dummy_node_type |
| dummy node type | |
| typedef split_list::node_traits < typename ordered_list::node_traits > | node_traits |
| Split-list node traits. More... | |
Protected Attributes | |
| ordered_list_wrapper | m_List |
| Ordered list containing split-list items. | |
| bucket_table | m_Buckets |
| bucket table | |
| std::atomic< size_t > | m_nBucketCountLog2 |
| log2( current bucket count ) | |
| item_counter | m_ItemCounter |
| Item counter. | |
| hash | m_HashFunctor |
| Hash functor. | |
Split-ordered list.
Hash table implementation based on split-ordered list algorithm discovered by Ori Shalev and Nir Shavit, see
The split-ordered list is a lock-free implementation of an extensible unbounded hash table. It uses original recursive split-ordering algorithm discovered by Ori Shalev and Nir Shavit that allows to split buckets without moving an item on resizing.
Short description [from [2003] Ori Shalev, Nir Shavit "Split-Ordered Lists - Lock-free Resizable Hash Tables"]
The algorithm keeps all the items in one lock-free linked list, and gradually assigns the bucket pointers to the places in the list where a sublist of “correct” items can be found. A bucket is initialized upon first access by assigning it to a new “dummy” node (dashed contour) in the list, preceding all items that should be in that bucket. A newly created bucket splits an older bucket’s chain, reducing the access cost to its items. The table uses a modulo 2**i hash (there are known techniques for “pre-hashing” before a modulo 2**i hash to overcome possible binary correlations among values). The table starts at size 2 and repeatedly doubles in size.
Unlike moving an item, the operation of directing a bucket pointer can be done in a single CAS operation, and since items are not moved, they are never “lost”. However, to make this approach work, one must be able to keep the items in the list sorted in such a way that any bucket’s sublist can be “split” by directing a new bucket pointer within it. This operation must be recursively repeatable, as every split bucket may be split again and again as the hash table grows. To achieve this goal the authors introduced recursive split-ordering, a new ordering on keys that keeps items in a given bucket adjacent in the list throughout the repeated splitting process.
Magically, yet perhaps not surprisingly, recursive split-ordering is achieved by simple binary reversal: reversing the bits of the hash key so that the new key’s most significant bits (MSB) are those that were originally its least significant. The split-order keys of regular nodes are exactly the bit-reverse image of the original keys after turning on their MSB. For example, items 9 and 13 are in the 1 mod 4 bucket, which can be recursively split in two by inserting a new node between them.
To insert (respectively delete or search for) an item in the hash table, hash its key to the appropriate bucket using recursive split-ordering, follow the pointer to the appropriate location in the sorted items list, and traverse the list until the key’s proper location in the split-ordering (respectively until the key or a key indicating the item is not in the list is found). Because of the combinatorial structure induced by the split-ordering, this will require traversal of no more than an expected constant number of items.
The design is modular: to implement the ordered items list, you can use one of several non-blocking list-based set algorithms: MichaelList, LazyList.
Implementation
Template parameters are:
GC - Garbage collector used. Note the GC must be the same as the GC used for OrderedList OrderedList - ordered list implementation used as bucket for hash set, for example, MichaelList, LazyList. The intrusive ordered list implementation specifies the type T stored in the hash-set, the reclamation schema GC used by hash-set, the comparison functor for the type T and other features specific for the ordered list.Traits - type traits. See split_list::type_traits for explanation. Instead of defining Traits struct you may use option-based syntax with split_list::make_traits metafunction.There are several specialization of the split-list class for different GC:
<cds/intrusive/split_list_rcu.h> - see RCU-based split-list<cds/intrusive/split_list_nogc.h> - see persistent SplitListSet.Some member functions of split-ordered list accept the key parameter of type Q which differs from value_type. It is expected that type Q contains full key of value_type, and for equal keys of type Q and value_type the hash values of these keys must be equal too. The hash functor Traits::hash should accept parameters of both type:
How to use
First, you should choose ordered list type to use in your split-list set:
Second, you should declare split-list set container:
Now, you can use Foo_set in your application.
| typedef iterator_type<true> cds::intrusive::SplitListSet< GC, OrderedList, Traits >::const_iterator |
Const forward iterator.
For iterator's features and requirements see iterator
| typedef iterator_type<false> cds::intrusive::SplitListSet< GC, OrderedList, Traits >::iterator |
Forward iterator.
The forward iterator for a split-list has some features:
OrderedList Therefore, the use of iterators in concurrent environment is not good idea. Use the iterator on the concurrent container for debug purpose only.
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Split-list node traits.
This traits is intended for converting between underlying ordered list node type list_node_type and split-list node type node_type
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Initialize split-ordered list of default capacity.
The default capacity is defined in bucket table constructor. See split_list::expandable_bucket_table, split_list::static_ducket_table which selects by split_list::dynamic_bucket_table option.
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Initialize split-ordered list.
| nItemCount | estimate average of item count |
| nLoadFactor | load factor - average item count per bucket. Small integer up to 8, default is 1. |
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Clears the set (non-atomic)
The function unlink all items from the set. The function is not atomic. Therefore, clear may be used only for debugging purposes.
For each item the disposer is called after unlinking.
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Checks if the set is empty.
Emptiness is checked by item counting: if item count is zero then the set is empty. Thus, the correct item counting feature is an important part of split-list set implementation.
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Ensures that the val exists in the set.
The operation performs inserting or changing data with lock-free manner.
If the item val is not found in the set, then val is inserted into the set. Otherwise, the functor func is called with item found. The functor signature is:
with arguments:
bNew - true if the item has been inserted, false otherwiseitem - item of the setval - argument val passed into the ensure function If new item has been inserted (i.e. bNew is true) then item and val arguments refers to the same thing.The functor can change non-key fields of the item; however, func must guarantee that during changing no any other modifications could be made on this item by concurrent threads.
You can pass func argument by value or by reference using boost::ref or cds::ref.
Returns std::pair<bool, bool> where first is true if operation is successfull, second is true if new item has been added or false if the item with key already is in the set.
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Deletes the item from the set.
The function searches an item with key equal to val in the set, unlinks it from the set, and returns true. If the item with key equal to val is not found the function return false.
Difference between erase and unlink functions: erase finds a key and deletes the item found. unlink finds an item by key and deletes it only if val is an item of that set, i.e. the pointer to item found is equal to &val .
Note the hash functor should accept a parameter of type Q that can be not the same as value_type.
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Deletes the item from the set.
The function searches an item with key equal to val in the set, call f functor with item found, unlinks it from the set, and returns true. The disposer specified by OrderedList class template parameter is called by garbage collector GC asynchronously.
The Func interface is
The functor can be passed by reference with boost:ref
If the item with key equal to val is not found the function return false.
Note the hash functor should accept a parameter of type Q that can be not the same as value_type.
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Deletes the item from the set with comparing functor pred.
The function is an analog of erase(Q const&) but pred predicate is used for key comparing. Less has the interface like std::less. pred must imply the same element order as the comparator used for building the set.
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Deletes the item from the set with comparing functor pred.
The function is an analog of erase(Q const&, Func) but pred predicate is used for key comparing. Less has the interface like std::less. pred must imply the same element order as the comparator used for building the set.
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Finds the key val.
The function searches the item with key equal to val and calls the functor f for item found. The interface of Func functor is:
where item is the item found, val is the find function argument.
You can pass f argument by value or by reference using boost::ref or cds::ref.
The functor can change non-key fields of item. Note that the functor is only guarantee that item cannot be disposed during functor is executing. The functor does not serialize simultaneous access to the set item. If such access is possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
The val argument is non-const since it can be used as f functor destination i.e., the functor can modify both arguments.
Note the hash functor specified for class Traits template parameter should accept a parameter of type Q that can be not the same as value_type.
The function returns true if val is found, false otherwise.
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Finds the key val.
The function searches the item with key equal to val and calls the functor f for item found. The interface of Func functor is:
where item is the item found, val is the find function argument.
You can pass f argument by value or by reference using boost::ref or cds::ref.
The functor can change non-key fields of item. Note that the functor is only guarantee that item cannot be disposed during functor is executing. The functor does not serialize simultaneous access to the set item. If such access is possible you must provide your own synchronization schema on item level to exclude unsafe item modifications.
Note the hash functor specified for class Traits template parameter should accept a parameter of type Q that can be not the same as value_type.
The function returns true if val is found, false otherwise.
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Finds the key val.
The function searches the item with key equal to val and returns true if it is found, and false otherwise.
Note the hash functor specified for class Traits template parameter should accept a parameter of type Q that can be not the same as value_type. Otherwise, you may use find_with functions with explicit predicate for key comparing.
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Finds the key val with pred predicate for comparing.
The function is an analog of find(Q&, Func) but cmp is used for key compare. Less has the interface like std::less. cmp must imply the same element order as the comparator used for building the set.
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Finds the key val with pred predicate for comparing.
The function is an analog of find(Q const&, Func) but cmp is used for key compare. Less has the interface like std::less. cmp must imply the same element order as the comparator used for building the set.
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Finds the key val with pred predicate for comparing.
The function is an analog of find(Q const&) but cmp is used for key compare. Less has the interface like std::less. cmp must imply the same element order as the comparator used for building the set.
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Inserts new node.
The function inserts val in the set if it does not contain an item with key equal to val.
Returns true if val is placed into the set, false otherwise.
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Inserts new node.
This function is intended for derived non-intrusive containers.
The function allows to split creating of new item into two part:
f functor to initialize value-field of val.The functor signature is:
where val is the item inserted. User-defined functor f should guarantee that during changing val no any other changes could be made on this set's item by concurrent threads. The user-defined functor is called only if the inserting is success and may be passed by reference using boost::ref
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Unlinks the item val from the set.
The function searches the item val in the set and unlinks it from the set if it is found and is equal to val.
Difference between erase and unlink functions: erase finds a key and deletes the item found. unlink finds an item by key and deletes it only if val is an item of that set, i.e. the pointer to item found is equal to &val .
The function returns true if success and false otherwise.