edu.rit.pj.reduction
Class SharedFloatArray

java.lang.Object
  extended by edu.rit.pj.reduction.SharedFloatArray

public class SharedFloatArray
extends Object

Class SharedFloatArray provides an array reduction variable with elements of type float.

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

Note: Class SharedFloatArray is implemented using class java.util.concurrent.atomic.AtomicIntegerArray. Each float array element is stored as an int whose bit pattern is the same as the float value.


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

SharedFloatArray

public SharedFloatArray(int len)
Construct a new float array reduction variable with the given length. Each array element is initially 0.

Parameters:
len - Length.
Throws:
NegativeArraySizeException - (unchecked exception) Thrown if len < 0.

SharedFloatArray

public SharedFloatArray(float[] array)
Construct a new float 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 float 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,
                float value)
Set this array reduction variable at the given index to the given value.

Parameters:
i - Index.
value - New value.

getAndSet

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


Copyright © 2005-2012 by Alan Kaminsky. All rights reserved. Send comments to ark­@­cs.rit.edu.