Class NetBarrier

java.lang.Object
org.jcsp.lang.Barrier
org.jcsp.net2.NetBarrier
All Implemented Interfaces:
Serializable, Networked
public final class NetBarrier extends Barrier implements Networked
This class is a networked implementation of the standard JCSP Barrier.

The NetBarrier is a networked version of the JCSP Barrier, a synchronization primitive similar to the standard event in CSP. The networked implementation follows the standard interface for a local Barrier, with the addition of the interface defining a networked construct. Internally, the two constructs behave differently due to the distributed nature of the NetBarrier.

Client and Server Ends

Unlike a normal Barrier, a NetBarrier has two types, based on whether the Barrier is the hosting end or an attached, synchronizing end. These are differentiated between as server and client ends. The server end, like the input end of a networked channel, will be declared first. The location of this server end can then be used to connect a number of client ends to. The server end can declare an initial number of expected client ends, which it waits for enrolls from before beginning any sync operations. This value can be set to 0 if need be. Each end of a barrier must also declare the number of local syncing processes, creating a two tier construct:

Process ---> NetBarrier (client) ---> NetBarrier (server)

Creating NetBarriers

To create a NetBarrier, a similar method is used as a networked channel. A Barrier Name Server is provided for declaring named barriers, or the NetBarrierEnd factory can be used. First, creation of a sever end:

int locallyEnrolled = 5;
int remoteEnrolled = 1;
NetBarrier bar = NetBarrierEnd.netBarrier(locallyEnrolled, remoteEnrolled);

A client end requires the location of this barrier to allow creation:

NetBarrierLocation loc;
int locallyEnrolled = 5;
NetBarrier bar = NetBarrierEnd.netBarrier(loc, locallyEnrolled);

These barriers can then be used as normal.

IMPLMENTATION NOTE

To save on resources, a NetBarrier does not have an internal process controlling it (although other implementations may decide to do this). Because of this, the declaring (server) end of the barrier must always have at least one process enrolled with it to ensure that the SYNC operation occurs. If there is a danger that the enrolled processes on the server node will become 0, it is safer to define a process that is only responsible for SYNCing with the barrier. This minor overhead in certain circumstances is seen as a better approach than all NetBarriers being a process within JCSP, where processes are expensive in resources.

public void run() {
while (true) {
bar.sync(); }}

Author:
Kevin Chalmers (networked part), P.H. Welch (Barrier)
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    destroy()
    Destroys the Barrier
    void
    enroll()
    Enrolls locally with the Barrier
    NetLocation
    getLocation()
    Returns the location of this barrier
    void
    reset(int numToEnroll)
    Resets the number of locally enrolled processes.
    void
    resign()
    Resigns an local process from the barrier
    void
    sync()
    Performs a SYNC operation with the Barrier throws JCSPNetworkException Thrown if something goes wrong in the underlying architecture

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • reset

      public void reset(int numToEnroll)
      Resets the number of locally enrolled processes. A dangerous operation.
      Overrides:
      reset in class Barrier
      Parameters:
      numToEnroll - The number of processes to reset the enrolled to.

    • sync

      public void sync() throws JCSPNetworkException
      Performs a SYNC operation with the Barrier throws JCSPNetworkException Thrown if something goes wrong in the underlying architecture
      Overrides:
      sync in class Barrier
      Throws:
      JCSPNetworkException - Thrown if something goes wrong in the underlying architecture

    • enroll

      public void enroll() throws JCSPNetworkException
      Enrolls locally with the Barrier
      Overrides:
      enroll in class Barrier
      Throws:
      JCSPNetworkException - Thrown if the barrier is not a state where it can be enrolled with

    • resign

      public void resign() throws JCSPNetworkException
      Resigns an local process from the barrier
      Overrides:
      resign in class Barrier
      Throws:
      JCSPNetworkException - Thrown if something bad happens within the underlying architecture

    • destroy

      public void destroy() throws JCSPNetworkException
      Destroys the Barrier
      Specified by:
      destroy in interface Networked
      Throws:
      JCSPNetworkException - Thrown if something goes wrong in the underlying architecture

    • getLocation

      public NetLocation getLocation()
      Returns the location of this barrier
      Specified by:
      getLocation in interface Networked
      Returns:
      The location of this channel