edu.rit.pj.reduction

Class SharedDoubleArray

java.lang.Object

edu.rit.pj.reduction.SharedDoubleArray

public class SharedDoubleArray
extends java.lang.Object

Class SharedDoubleArray provides an array reduction variable with elements of type double.

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

Note: Class SharedDoubleArray is implemented using class java.util.concurrent.atomic.AtomicLongArray. Each double array element is stored as a long whose bit pattern is the same as the double value.

Constructor Summary

Constructors

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

Method Summary

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

SharedDoubleArray

public SharedDoubleArray(int len)

Construct a new double 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.

SharedDoubleArray

public SharedDoubleArray(double[] array)

Construct a new double 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 double 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,
                double value)

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

Parameters:

i - Index.

value - New value.

getAndSet

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