edu.rit.pj.reduction

Class SharedIntegerArray

java.lang.Object

edu.rit.pj.reduction.SharedIntegerArray

public class SharedIntegerArray
extends java.lang.Object

Class SharedIntegerArray provides an array reduction variable with elements of type int.

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

Note: Class SharedIntegerArray is implemented using class java.util.concurrent.atomic.AtomicIntegerArray.

Constructor Summary

Constructors

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

Method Summary

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

SharedIntegerArray

public SharedIntegerArray(int len)

Construct a new integer 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.

SharedIntegerArray

public SharedIntegerArray(int[] array)

Construct a new integer 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 int 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,
                int value)

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

Parameters:

i - Index.

value - New value.

getAndSet

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