edu.rit.pj.reduction
Class SharedLongArray

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

public class SharedLongArray
extends Object

Class SharedLongArray provides an array reduction variable with elements of type long.

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

Note: Class SharedLongArray is implemented using class java.util.concurrent.atomic.AtomicLongArray.


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

SharedLongArray

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

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

SharedLongArray

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

Parameters:
i - Index.
value - New value.

getAndSet

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