Class NonBlockingHashMapLong<TypeV>
- java.lang.Object
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- java.util.AbstractMap<Long,TypeV>
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- org.jctools.maps.NonBlockingHashMapLong<TypeV>
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- Type Parameters:
TypeV
- the type of mapped values
- All Implemented Interfaces:
Serializable
,ConcurrentMap<Long,TypeV>
,Map<Long,TypeV>
public class NonBlockingHashMapLong<TypeV> extends AbstractMap<Long,TypeV> implements ConcurrentMap<Long,TypeV>, Serializable
A lock-free alternate implementation ofConcurrentHashMap
with primitive long keys, better scaling properties and generally lower costs. The use oflong
keys allows for faster compares and lower memory costs. The Map provides identical correctness properties as ConcurrentHashMap. All operations are non-blocking and multi-thread safe, including all update operations.NonBlockingHashMapLong
scales substatially better thanConcurrentHashMap
for high update rates, even with a large concurrency factor. Scaling is linear up to 768 CPUs on a 768-CPU Azul box, even with 100% updates or 100% reads or any fraction in-between. Linear scaling up to all cpus has been observed on a 32-way Sun US2 box, 32-way Sun Niagra box, 8-way Intel box and a 4-way Power box.The main benefit of this class over using plain
NonBlockingHashMap
withLong
keys is that it avoids the auto-boxing and unboxing costs. Since auto-boxing is automatic, it is easy to accidentally cause auto-boxing and negate the space and speed benefits.This class obeys the same functional specification as
Hashtable
, and includes versions of methods corresponding to each method of Hashtable. However, even though all operations are thread-safe, operations do not entail locking and there is not any support for locking the entire table in a way that prevents all access. This class is fully interoperable with Hashtable in programs that rely on its thread safety but not on its synchronization details.Operations (including put) generally do not block, so may overlap with other update operations (including other puts and removes). Retrievals reflect the results of the most recently completed update operations holding upon their onset. For aggregate operations such as putAll, concurrent retrievals may reflect insertion or removal of only some entries. Similarly, Iterators and Enumerations return elements reflecting the state of the hash table at some point at or since the creation of the iterator/enumeration. They do not throw
ConcurrentModificationException
. However, iterators are designed to be used by only one thread at a time.Very full tables, or tables with high re-probe rates may trigger an internal resize operation to move into a larger table. Resizing is not terribly expensive, but it is not free either; during resize operations table throughput may drop somewhat. All threads that visit the table during a resize will 'help' the resizing but will still be allowed to complete their operation before the resize is finished (i.e., a simple 'get' operation on a million-entry table undergoing resizing will not need to block until the entire million entries are copied).
This class and its views and iterators implement all of the optional methods of the
Map
andIterator
interfaces.Like
Hashtable
but unlikeHashMap
, this class does not allow null to be used as a value.- Since:
- 1.5
- Author:
- Cliff Click
- See Also:
- Serialized Form
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Nested Class Summary
Nested Classes Modifier and Type Class Description class
NonBlockingHashMapLong.IteratorLong
A class which implements theIterator
andEnumeration
interfaces, generified to theLong
class and supporting a non-auto-boxingNonBlockingHashMapLong.IteratorLong.nextLong()
function.-
Nested classes/interfaces inherited from class java.util.AbstractMap
AbstractMap.SimpleEntry<K extends Object,V extends Object>, AbstractMap.SimpleImmutableEntry<K extends Object,V extends Object>
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Constructor Summary
Constructors Constructor Description NonBlockingHashMapLong()
Create a new NonBlockingHashMapLong with default minimum size (currently set to 8 K/V pairs or roughly 84 bytes on a standard 32-bit JVM).NonBlockingHashMapLong(boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting the space-for-speed tradeoff.NonBlockingHashMapLong(int initial_sz)
Create a new NonBlockingHashMapLong with initial room for the given number of elements, thus avoiding internal resizing operations to reach an appropriate size.NonBlockingHashMapLong(int initial_sz, boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting both the initial size and the space-for-speed tradeoff.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
clear()
Removes all of the mappings from this map.boolean
contains(Object val)
Legacy method testing if some key maps into the specified value in this table.boolean
containsKey(long key)
Tests if the key in the table.boolean
containsKey(Object key)
Auto-boxing version ofcontainsKey(long)
.boolean
containsValue(Object val)
Returns true if this Map maps one or more keys to the specified value.Enumeration<TypeV>
elements()
Returns an enumeration of the values in this table.Set<Map.Entry<Long,TypeV>>
entrySet()
Returns aSet
view of the mappings contained in this map.TypeV
get(long key)
Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.TypeV
get(Object key)
Auto-boxing version ofget(long)
.Enumeration<Long>
keys()
Returns an enumeration of the auto-boxed keys in this table.Set<Long>
keySet()
Returns aSet
view of the keys contained in this map; with care the keys may be iterated over without auto-boxing.long[]
keySetLong()
Keys as a long array.void
print()
Verbose printout of table internals, useful for debugging.TypeV
put(long key, TypeV val)
Maps the specified key to the specified value in the table.TypeV
put(Long key, TypeV val)
Auto-boxing version ofput(long, TypeV)
.TypeV
putIfAbsent(long key, TypeV val)
Atomically, do aput(long, TypeV)
if-and-only-if the key is not mapped.TypeV
putIfAbsent(Long key, TypeV val)
Auto-boxing version ofputIfAbsent(long, TypeV)
.TypeV
remove(long key)
Removes the key (and its corresponding value) from this map.boolean
remove(long key, Object val)
Atomically do aremove(long)
if-and-only-if the key is mapped to a value which isequals
to the given value.TypeV
remove(Object key)
Auto-boxing version ofremove(long)
.boolean
remove(Object key, Object Val)
Auto-boxing version ofremove(long,Object)
.TypeV
replace(long key, TypeV val)
Atomically do aput(key,val)
if-and-only-if the key is mapped to some value already.boolean
replace(long key, TypeV oldValue, TypeV newValue)
Atomically do aput(key,newValue)
if-and-only-if the key is mapped a value which isequals
tooldValue
.TypeV
replace(Long key, TypeV Val)
Auto-boxing version ofreplace(long, TypeV)
.boolean
replace(Long key, TypeV oldValue, TypeV newValue)
Auto-boxing version ofreplace(long, TypeV)
.int
size()
Returns the number of key-value mappings in this map.Collection<TypeV>
values()
Returns aCollection
view of the values contained in this map.-
Methods inherited from class java.util.AbstractMap
clone, equals, hashCode, isEmpty, putAll, toString
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Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
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Methods inherited from interface java.util.concurrent.ConcurrentMap
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAll
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Constructor Detail
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NonBlockingHashMapLong
public NonBlockingHashMapLong()
Create a new NonBlockingHashMapLong with default minimum size (currently set to 8 K/V pairs or roughly 84 bytes on a standard 32-bit JVM).
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NonBlockingHashMapLong
public NonBlockingHashMapLong(int initial_sz)
Create a new NonBlockingHashMapLong with initial room for the given number of elements, thus avoiding internal resizing operations to reach an appropriate size. Large numbers here when used with a small count of elements will sacrifice space for a small amount of time gained. The initial size will be rounded up internally to the next larger power of 2.
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NonBlockingHashMapLong
public NonBlockingHashMapLong(boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting the space-for-speed tradeoff.true
optimizes for space and is the default.false
optimizes for speed and doubles space costs for roughly a 10% speed improvement.
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NonBlockingHashMapLong
public NonBlockingHashMapLong(int initial_sz, boolean opt_for_space)
Create a new NonBlockingHashMapLong, setting both the initial size and the space-for-speed tradeoff.true
optimizes for space and is the default.false
optimizes for speed and doubles space costs for roughly a 10% speed improvement.
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Method Detail
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print
public final void print()
Verbose printout of table internals, useful for debugging.
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size
public int size()
Returns the number of key-value mappings in this map.
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containsKey
public boolean containsKey(long key)
Tests if the key in the table.- Returns:
- true if the key is in the table
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contains
public boolean contains(Object val)
Legacy method testing if some key maps into the specified value in this table. This method is identical in functionality tocontainsValue(java.lang.Object)
, and exists solely to ensure full compatibility with classHashtable
, which supported this method prior to introduction of the Java Collections framework.- Parameters:
val
- a value to search for- Returns:
- true if this map maps one or more keys to the specified value
- Throws:
NullPointerException
- if the specified value is null
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put
public TypeV put(long key, TypeV val)
Maps the specified key to the specified value in the table. The value cannot be null.The value can be retrieved by calling
get(long)
with a key that is equal to the original key.- Parameters:
key
- key with which the specified value is to be associatedval
- value to be associated with the specified key- Returns:
- the previous value associated with key, or null if there was no mapping for key
- Throws:
NullPointerException
- if the specified value is null
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putIfAbsent
public TypeV putIfAbsent(long key, TypeV val)
Atomically, do aput(long, TypeV)
if-and-only-if the key is not mapped. Useful to ensure that only a single mapping for the key exists, even if many threads are trying to create the mapping in parallel.- Returns:
- the previous value associated with the specified key, or null if there was no mapping for the key
- Throws:
NullPointerException
- if the specified is value is null
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remove
public TypeV remove(long key)
Removes the key (and its corresponding value) from this map. This method does nothing if the key is not in the map.- Returns:
- the previous value associated with key, or null if there was no mapping for key
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remove
public boolean remove(long key, Object val)
Atomically do aremove(long)
if-and-only-if the key is mapped to a value which isequals
to the given value.- Throws:
NullPointerException
- if the specified value is null
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replace
public TypeV replace(long key, TypeV val)
Atomically do aput(key,val)
if-and-only-if the key is mapped to some value already.- Throws:
NullPointerException
- if the specified value is null
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replace
public boolean replace(long key, TypeV oldValue, TypeV newValue)
Atomically do aput(key,newValue)
if-and-only-if the key is mapped a value which isequals
tooldValue
.- Throws:
NullPointerException
- if the specified value is null
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clear
public void clear()
Removes all of the mappings from this map.
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containsValue
public boolean containsValue(Object val)
Returns true if this Map maps one or more keys to the specified value. Note: This method requires a full internal traversal of the hash table and is much slower thancontainsKey(long)
.- Specified by:
containsValue
in interfaceMap<Long,TypeV>
- Overrides:
containsValue
in classAbstractMap<Long,TypeV>
- Parameters:
val
- value whose presence in this map is to be tested- Returns:
- true if this Map maps one or more keys to the specified value
- Throws:
NullPointerException
- if the specified value is null
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get
public final TypeV get(long key)
Returns the value to which the specified key is mapped, ornull
if this map contains no mapping for the key.More formally, if this map contains a mapping from a key
k
to a valuev
such thatkey==k
, then this method returnsv
; otherwise it returnsnull
. (There can be at most one such mapping.)- Throws:
NullPointerException
- if the specified key is null
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remove
public TypeV remove(Object key)
Auto-boxing version ofremove(long)
.
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remove
public boolean remove(Object key, Object Val)
Auto-boxing version ofremove(long,Object)
.
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containsKey
public boolean containsKey(Object key)
Auto-boxing version ofcontainsKey(long)
.- Specified by:
containsKey
in interfaceMap<Long,TypeV>
- Overrides:
containsKey
in classAbstractMap<Long,TypeV>
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putIfAbsent
public TypeV putIfAbsent(Long key, TypeV val)
Auto-boxing version ofputIfAbsent(long, TypeV)
.- Specified by:
putIfAbsent
in interfaceConcurrentMap<Long,TypeV>
- Specified by:
putIfAbsent
in interfaceMap<Long,TypeV>
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replace
public TypeV replace(Long key, TypeV Val)
Auto-boxing version ofreplace(long, TypeV)
.
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put
public TypeV put(Long key, TypeV val)
Auto-boxing version ofput(long, TypeV)
.
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replace
public boolean replace(Long key, TypeV oldValue, TypeV newValue)
Auto-boxing version ofreplace(long, TypeV)
.
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elements
public Enumeration<TypeV> elements()
Returns an enumeration of the values in this table.- Returns:
- an enumeration of the values in this table
- See Also:
values()
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values
public Collection<TypeV> values()
Returns aCollection
view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. The collection supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Collection.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException
, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.
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keys
public Enumeration<Long> keys()
Returns an enumeration of the auto-boxed keys in this table. Warning: this version will auto-box all returned keys.- Returns:
- an enumeration of the auto-boxed keys in this table
- See Also:
keySet()
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keySet
public Set<Long> keySet()
Returns aSet
view of the keys contained in this map; with care the keys may be iterated over without auto-boxing. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from this map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException
, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.
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keySetLong
public long[] keySetLong()
Keys as a long array. Array may be zero-padded if keys are concurrently deleted.
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entrySet
public Set<Map.Entry<Long,TypeV>> entrySet()
Returns aSet
view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.The view's iterator is a "weakly consistent" iterator that will never throw
ConcurrentModificationException
, and guarantees to traverse elements as they existed upon construction of the iterator, and may (but is not guaranteed to) reflect any modifications subsequent to construction.Warning: the iterator associated with this Set requires the creation of
Map.Entry
objects with each iteration. TheNonBlockingHashMap
does not normally create or usingMap.Entry
objects so they will be created soley to support this iteration. Iterating usingMap.keySet()
orMap.values()
will be more efficient. In addition, this version requires auto-boxing the keys.
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