edu.rit.pj.reduction

Class SharedObject<T>

java.lang.Object

edu.rit.pj.reduction.SharedObject<T>

Type Parameters:

T - Object data type.

public class SharedObject<T>
extends java.lang.Object

Class SharedObject provides a reduction variable for a value of an object type.

Class SharedObject is multiple thread safe. The methods use lock-free atomic compare-and-set.

Note: Class SharedObject is implemented using class java.util.concurrent.atomic.AtomicReference.

Constructor Summary

Constructors

Constructor and Description
SharedObject() Construct a new object reduction variable with the initial value null.
SharedObject(T initialValue) Construct a new object reduction variable with the given initial value.

Method Summary

Modifier and Type	Method and Description
boolean	compareAndSet(T expect, T update) Atomically set this reduction variable to the given updated value if the current value equals the expected value.
T	get() Returns this reduction variable's current value.
T	getAndSet(T value) Set this reduction variable to the given value and return the previous value.
T	reduce(T value, ObjectOp<T> op) Combine this reduction variable with the given value using the given operation.
void	set(T value) Set this reduction variable to the given value.
java.lang.String	toString() Returns a string version of this reduction variable.
boolean	weakCompareAndSet(T expect, T update) Atomically set this reduction variable to the given updated value if the current value equals the expected value.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SharedObject

public SharedObject()

Construct a new object reduction variable with the initial value null.

SharedObject

public SharedObject(T initialValue)

Construct a new object reduction variable with the given initial value.

Parameters:

initialValue - Initial value.

Method Detail

get

public T get()

Returns this reduction variable's current value.

Returns:

Current value.

set

public void set(T value)

Set this reduction variable to the given value.

Parameters:

value - New value.

getAndSet

public T getAndSet(T value)

Set this reduction variable to the given value and return the previous value.

Parameters:

value - New value.

Returns:

Previous value.

compareAndSet

public boolean compareAndSet(T expect,
                             T update)

Atomically set this reduction variable to the given updated value if the current value equals the expected value.

Parameters:

expect - Expected value.

update - Updated value.

Returns:

True if the update happened, false otherwise.

weakCompareAndSet

public boolean weakCompareAndSet(T expect,
                                 T update)

Atomically set this reduction variable to the given updated value if the current value equals the expected value. May fail spuriously.

Parameters:

expect - Expected value.

update - Updated value.

Returns:

True if the update happened, false otherwise.

reduce

public T reduce(T value,
                ObjectOp<T> op)

Combine this reduction variable with the given value using the given operation. The result is stored back into this reduction variable and is returned.

Parameters:

value - Value.

op - Binary operation.

Returns:

(This variable) op (value).

toString

public java.lang.String toString()

Returns a string version of this reduction variable.

Overrides:

toString in class java.lang.Object

Returns:

String version.