edu.rit.pj.reduction

Class SharedByteArray

java.lang.Object

edu.rit.pj.reduction.SharedByteArray

public class SharedByteArray
extends java.lang.Object

Class SharedByteArray provides an array reduction variable with elements of type byte.

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

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

Constructor Summary

Constructors

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

Method Summary

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

SharedByteArray

public SharedByteArray(int len)

Construct a new byte 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.

SharedByteArray

public SharedByteArray(byte[] array)

Construct a new byte 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 byte 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,
                byte value)

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

Parameters:

i - Index.

value - New value.

getAndSet

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