Package edu.rit.pj.reduction

Class SharedLongArray

java.lang.Object
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.

Version:
24-Aug-2007
Author:
Alan Kaminsky

  • Constructor Summary

    Constructors
    Constructor
    Description
    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

    Modifier and Type
    Method
    Description
    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 Details

    • 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 Details

    • 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.