edu.rit.pj.reduction
Class SharedCharacterArray

java.lang.Object
  edu.rit.pj.reduction.SharedCharacterArray

public class SharedCharacterArray
extends Object

Class SharedCharacterArray provides an array reduction variable with elements of type char.

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

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

Constructor Summary

SharedCharacterArray(char[] array)
Construct a new character array reduction variable whose elements are copied from the given array.

SharedCharacterArray(int len)
Construct a new character array reduction variable with the given length.

Method Summary

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

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SharedCharacterArray

public SharedCharacterArray(int len)

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

Parameters:

len - Length.

Throws:

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

SharedCharacterArray

public SharedCharacterArray(char[] array)

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

Parameters:

array - Array to copy.

Throws:

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 char 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,
                char value)

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

Parameters:

i - Index.

value - New value.

getAndSet

public char getAndSet(int i,
                      char 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,
                             char expect,
                             char 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,
                                 char expect,
                                 char 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 char 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 char 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 char getAndAdd(int i,
                      char 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 char 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 char 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 char addAndGet(int i,
                      char 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 char reduce(int i,
                   char value,
                   CharacterOp 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(char[] src,
                   CharacterOp 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:

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

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

reduce

public void reduce(int dstoff,
                   char[] src,
                   int srcoff,
                   int len,
                   CharacterOp 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:

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

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

toString

public String toString()

Returns a string version of this array reduction variable.

Overrides:

toString in class Object

Returns:

String version.