edu.rit.pj.reduction

Class SharedLongArray

java.lang.Object

edu.rit.pj.reduction.SharedLongArray

public class SharedLongArray
extends java.lang.Object

Class SharedLongArray provides an array reduction variable with elements of type long.

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

Note: Class SharedLongArray is implemented using class java.util.concurrent.atomic.AtomicLongArray.

Constructor Summary

Constructors

Constructor and Description
SharedLongArray(int len) Construct a new long array reduction variable with the given length.
SharedLongArray(long[] array) Construct a new long array reduction variable whose elements are copied from the given array.

Method Summary

Modifier and Type	Method and Description
long	addAndGet(int i, long value) Add the given value to this array reduction variable at the given index and return the new value.
boolean	compareAndSet(int i, long expect, long update) Atomically set this array reduction variable at the given index to the given updated value if the current value equals the expected value.
long	decrementAndGet(int i) Subtract one from this array reduction variable at the given index and return the new value.
long	get(int i) Returns this array reduction variable's current value at the given index.
long	getAndAdd(int i, long value) Add the given value to this array reduction variable at the given index and return the previous value.
long	getAndDecrement(int i) Subtract one from this array reduction variable at the given index and return the previous value.
long	getAndIncrement(int i) Add one to this array reduction variable at the given index and return the previous value.
long	getAndSet(int i, long value) Set this array reduction variable at the given index to the given value and return the previous value.
long	incrementAndGet(int i) Add one to this array reduction variable at the given index and return the new value.
int	length() Returns this array reduction variable's length.
void	reduce(int dstoff, long[] src, int srcoff, int len, LongOp op) Combine a portion of this array reduction variable with a portion of the given array using the given operation.
long	reduce(int i, long value, LongOp op) Combine this array reduction variable at the given index with the given value using the given operation.
void	reduce(long[] src, LongOp op) Combine this array reduction variable with the given array using the given operation.
void	set(int i, long value) Set this array reduction variable at the given index to the given value.
java.lang.String	toString() Returns a string version of this array reduction variable.
boolean	weakCompareAndSet(int i, long expect, long update) Atomically set this array reduction variable at the given index 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

SharedLongArray

public SharedLongArray(int len)

Construct a new long array reduction variable with the given length. Each array element is initially 0.

Parameters:

len - Length.

Throws:

java.lang.NegativeArraySizeException - (unchecked exception) Thrown if len < 0.

SharedLongArray

public SharedLongArray(long[] array)

Construct a new long array reduction variable whose elements are copied from the given array.

Parameters:

array - Array to copy.

Throws:

java.lang.NullPointerException - (unchecked exception) Thrown if array is null.

Method Detail

length

public int length()

Returns this array reduction variable's length.

Returns:

Length.

get

public long get(int i)

Returns this array reduction variable's current value at the given index.

Parameters:

i - Index.

Returns:

Current value.

set

public void set(int i,
                long value)

Set this array reduction variable at the given index to the given value.

Parameters:

i - Index.

value - New value.

getAndSet

public long getAndSet(int i,
                      long value)

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

Parameters:

i - Index.

value - New value.

Returns:

Previous value.

compareAndSet

public boolean compareAndSet(int i,
                             long expect,
                             long update)

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

Parameters:

i - Index.

expect - Expected value.

update - Updated value.

Returns:

True if the update happened, false otherwise.

weakCompareAndSet

public boolean weakCompareAndSet(int i,
                                 long expect,
                                 long update)

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

Parameters:

i - Index.

expect - Expected value.

update - Updated value.

Returns:

True if the update happened, false otherwise.

getAndIncrement

public long getAndIncrement(int i)

Add one to this array reduction variable at the given index and return the previous value.

Parameters:

i - Index.

Returns:

Previous value.

getAndDecrement

public long getAndDecrement(int i)

Subtract one from this array reduction variable at the given index and return the previous value.

Parameters:

i - Index.

Returns:

Previous value.

getAndAdd

public long getAndAdd(int i,
                      long value)

Add the given value to this array reduction variable at the given index and return the previous value.

Parameters:

i - Index.

value - Value to add.

Returns:

Previous value.

incrementAndGet

public long incrementAndGet(int i)

Add one to this array reduction variable at the given index and return the new value.

Parameters:

i - Index.

Returns:

New value.

decrementAndGet

public long decrementAndGet(int i)

Subtract one from this array reduction variable at the given index and return the new value.

Parameters:

i - Index.

Returns:

New value.

addAndGet

public long addAndGet(int i,
                      long value)

Add the given value to this array reduction variable at the given index and return the new value.

Parameters:

i - Index.

value - Value to add.

Returns:

New value.

reduce

public long reduce(int i,
                   long value,
                   LongOp op)

Combine this array reduction variable at the given index with the given value using the given operation. (This array [i]) is set to (this array [i]) op (value), then (this array [i]) is returned.

Parameters:

i - Index.

value - Value.

op - Binary operation.

Returns:

(This array [i]) op (value).

reduce

public void reduce(long[] src,
                   LongOp op)

Combine this array reduction variable with the given array using the given operation. For each index i from 0 to this array's length-1, (this array [i]) is set to (this array [i]) op (src[i]).

The reduce() method is multiple thread safe on a per-element basis. Each individual array element is updated atomically, but the array as a whole is not updated atomically.

Parameters:

src - Source array.

op - Binary operation.

Throws:

java.lang.NullPointerException - (unchecked exception) Thrown if src is null. Thrown if op is null.

java.lang.IndexOutOfBoundsException - (unchecked exception) Thrown if any array index would be out of bounds.

reduce

public void reduce(int dstoff,
                   long[] src,
                   int srcoff,
                   int len,
                   LongOp op)

Combine a portion of this array reduction variable with a portion of the given array using the given operation. For each index i from 0 to len-1, (this array [dstoff+i]) is set to (this array [dstoff+i]) op (src[srcoff+i]).

The reduce() method is multiple thread safe on a per-element basis. Each individual array element is updated atomically, but the array as a whole is not updated atomically.

Parameters:

dstoff - Index of first element to update in this array.

src - Source array.

srcoff - Index of first element to update from in the source array.

len - Number of array elements to update.

op - Binary operation.

Throws:

java.lang.NullPointerException - (unchecked exception) Thrown if src is null. Thrown if op is null.

java.lang.IndexOutOfBoundsException - (unchecked exception) Thrown if len < 0. Thrown if any array index would be out of bounds.

toString

public java.lang.String toString()

Returns a string version of this array reduction variable.

Overrides:

toString in class java.lang.Object

Returns:

String version.