Class ConcurrentAutoTable

  • All Implemented Interfaces:
    Serializable

    public class ConcurrentAutoTable
    extends Object
    implements Serializable
    An auto-resizing table of longs, supporting low-contention CAS operations. Updates are done with CAS's to no particular table element. The intent is to support highly scalable counters, r/w locks, and other structures where the updates are associative, loss-free (no-brainer), and otherwise happen at such a high volume that the cache contention for CAS'ing a single word is unacceptable.
    Since:
    1.5
    Author:
    Cliff Click
    See Also:
    Serialized Form
    • Constructor Detail

      • ConcurrentAutoTable

        public ConcurrentAutoTable()
    • Method Detail

      • add

        public void add​(long x)
        Add the given value to current counter value. Concurrent updates will not be lost, but addAndGet or getAndAdd are not implemented because the total counter value (i.e., get()) is not atomically updated. Updates are striped across an array of counters to avoid cache contention and has been tested with performance scaling linearly up to 768 CPUs.
      • decrement

        public void decrement()
        add(long) with -1
      • increment

        public void increment()
        add(long) with +1
      • set

        public void set​(long x)
        Atomically set the sum of the striped counters to specified value. Rather more expensive than a simple store, in order to remain atomic.
      • get

        public long get()
        Current value of the counter. Since other threads are updating furiously the value is only approximate, but it includes all counts made by the current thread. Requires a pass over the internally striped counters.
      • intValue

        public int intValue()
        Same as get(), included for completeness.
      • longValue

        public long longValue()
        Same as get(), included for completeness.
      • estimate_get

        public long estimate_get()
        A cheaper get(). Updated only once/millisecond, but as fast as a simple load instruction when not updating.
      • toString

        public String toString()
        Return the counter's long value converted to a string.
        Overrides:
        toString in class Object
      • print

        public void print()
        A more verbose print than toString(), showing internal structure. Useful for debugging.
      • internal_size

        public int internal_size()
        Return the internal counter striping factor. Useful for diagnosing performance problems.