edu.rit.pj.reduction

Class SharedShortArray

java.lang.Object

edu.rit.pj.reduction.SharedShortArray

public class SharedShortArray
extends java.lang.Object

Class SharedShortArray provides an array reduction variable with elements of type short.

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

Note: Class SharedShortArray is implemented using class java.util.concurrent.atomic.AtomicIntegerArray. Each short array element is stored as an int whose values are restricted to the range of type short.

Constructor Summary

Constructors

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

Method Summary

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

SharedShortArray

public SharedShortArray(int len)

Construct a new short 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.

SharedShortArray

public SharedShortArray(short[] array)

Construct a new short 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 short 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,
                short value)

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

Parameters:

i - Index.

value - New value.

getAndSet

public short getAndSet(int i,
                       short 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,
                             short expect,
                             short 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,
                                 short expect,
                                 short 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 short 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 short 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 short getAndAdd(int i,
                       short 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 short 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 short 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 short addAndGet(int i,
                       short 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 short reduce(int i,
                    short value,
                    ShortOp 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(short[] src,
                   ShortOp 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,
                   short[] src,
                   int srcoff,
                   int len,
                   ShortOp 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.