Package edu.rit.pj.reduction

Class SharedObjectArray<T>

java.lang.Object
edu.rit.pj.reduction.SharedObjectArray<T>
Type Parameters:
T - Object data type.
public class SharedObjectArray<T> extends Object
Class SharedObjectArray provides an array reduction variable with elements of an object type.

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

Note: Class SharedObjectArray is implemented using class java.util.concurrent.atomic.AtomicReferenceArray.

Version:
24-Aug-2007
Author:
Alan Kaminsky

  • Constructor Summary

    Constructors
    Constructor
    Description
    SharedObjectArray(int len)
    Construct a new object array reduction variable with the given length.
    SharedObjectArray(T[] array)
    Construct a new object array reduction variable whose elements are copied from the given array.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    compareAndSet(int i, T expect, T update)
    Atomically set this array reduction variable at the given index to the given updated value if the current value equals the expected value.
    T
    get(int i)
    Returns this array reduction variable's current value at the given index.
    T
    getAndSet(int i, T value)
    Set this array reduction variable at the given index to the given value and return the previous value.
    int
    length()
    Returns this array reduction variable's length.
    void
    reduce(int dstoff, T[] src, int srcoff, int len, ObjectOp<T> op)
    Combine a portion of this array reduction variable with a portion of the given array using the given operation.
    T
    reduce(int i, T value, ObjectOp<T> op)
    Combine this array reduction variable at the given index with the given value using the given operation.
    void
    reduce(T[] src, ObjectOp<T> op)
    Combine this array reduction variable with the given array using the given operation.
    void
    set(int i, T 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, T expect, T 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 Details

    • SharedObjectArray

      public SharedObjectArray(int len)
      Construct a new object array reduction variable with the given length. Each array element is initially null.
      Parameters:
      len - Length.
      Throws:
      NegativeArraySizeException - (unchecked exception) Thrown if len < 0.

    • SharedObjectArray

      public SharedObjectArray(T[] array)
      Construct a new object 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 Details

    • length

      public int length()
      Returns this array reduction variable's length.
      Returns:
      Length.

    • get

      public T 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, T value)
      Set this array reduction variable at the given index to the given value.
      Parameters:
      i - Index.
      value - New value.

    • getAndSet

      public T getAndSet(int i, T 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, T expect, T 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, T expect, T 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.

    • reduce

      public T reduce(int i, T value, ObjectOp<T> 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(T[] src, ObjectOp<T> 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, T[] src, int srcoff, int len, ObjectOp<T> 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.