Package com.Ostermiller.util

Class Parallelizer

java.lang.Object
com.Ostermiller.util.Parallelizer
public class Parallelizer extends Object
Runs multiple jobs in parallel, n threads at a time, and waits until all threads are complete before continuing.

Typically, Parallelizer would be used to run each of the items- in a for loop at the same time. For example the following for loop: 

 for (int i=0; i<10; i++){
    System.out.println("Hello World " + i);
 }
 System.out.println("done");
To this: 
 Parallelizer parallelizer = new Parallelizer();
 for (int i=0; i<10; i++){
     final int j = i;
     parallelizer.run(
         new Runnable(){
             System.out.println("Hello World " + j);
         }
     );
 }
 parallelizer.join();
 System.out.println("done");
More information about this class is available from ostermiller.org.
Since:
ostermillerutils 1.05.00
Author:
Matt Conway, Stephen Ostermiller - https://ostermiller.org/contact.pl?regarding=Java+Utilities

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
    INFINITE_THREAD_LIMIT
    Constant that may be passed concurrentThreadLimit argument of the constructor indicating that no limit should be placed on the number of threads that are allowed to run concurrently.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Parallelizer()
    Create a new Parallelizer with no limit on the number of threads that will be allowed to be run concurrently.
    Parallelizer(int concurrentThreadLimit)
    Create a new Parallelizer with the specified limit on the number of threads that will be allowed to be run concurrently.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    done()
    Return true iff all jobs that have been requested to run in this Parallelizer have completed.
    void
    dumpStack()
    Dump the stack of each running thread.
    Thread[]
    getRunningThreads()
    Gets a list of all running threads.
    void
    interrupt()
    All currently running threads will be interrupted.
    void
    join()
    Block until all the jobs in this Parallelizer have run and then return.
    void
    run(Runnable job)
    Run the given job.
    void
    run(Runnable job, String threadName)
    Run the given job.
    void
    run(ThreadGroup threadGroup, Runnable job)
    Run the given job.
    void
    run(ThreadGroup threadGroup, Runnable job, String threadName)
    Run the given job.
    void
    run(ThreadGroup threadGroup, Runnable job, String threadName, long stackSize)
    Run the given job.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • INFINITE_THREAD_LIMIT

      public static final int INFINITE_THREAD_LIMIT
      Constant that may be passed concurrentThreadLimit argument of the constructor indicating that no limit should be placed on the number of threads that are allowed to run concurrently.
      Since:
      ostermillerutils 1.05.00
      See Also:

  • Constructor Details

    • Parallelizer

      public Parallelizer()
      Create a new Parallelizer with no limit on the number of threads that will be allowed to be run concurrently.
      Since:
      ostermillerutils 1.05.00

    • Parallelizer

      public Parallelizer(int concurrentThreadLimit)
      Create a new Parallelizer with the specified limit on the number of threads that will be allowed to be run concurrently.

      When the concurrent thread limit is reached and the parallelizer gets a new thread to run, the new thread will be queued until a thread finishes.

      Parameters:
      concurrentThreadLimit - number of threads that will be allowed to run simultaneously or INFINITE_THREAD_LIMIT for no limit.
      Throws:
      IllegalArgumentException - if concurrentThreadLimit not a whole number or INFINITE_THREAD_LIMIT
      Since:
      ostermillerutils 1.05.00

  • Method Details

    • run

      public void run(Runnable job)
      Run the given job. The given job is either run immediately or if the max number of concurrent jobs are already running, it is queued to be run when some job is finished.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Parameters:
      job - job which is to be run in parallel with other jobs.
      Throws:
      Error - if any thread that is already running has thrown an Error.
      NullPointerException - if job is null.
      Since:
      ostermillerutils 1.05.00

    • run

      public void run(Runnable job, String threadName)
      Run the given job. The given job is either run immediately or if the max number of concurrent jobs are already running, it is queued to be run when some job is finished.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Parameters:
      job - job which is to be run in parallel with other jobs.
      threadName - name for the thread that will be created to run the job (null for auto generated thread name)
      Throws:
      Error - if any thread that is already running has thrown an Error.
      NullPointerException - if job is null.
      Since:
      ostermillerutils 1.05.00

    • run

      public void run(ThreadGroup threadGroup, Runnable job)
      Run the given job. The given job is either run immediately or if the max number of concurrent jobs are already running, it is queued to be run when some job is finished.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Parameters:
      threadGroup - group in which this job should be run (null for default group).
      job - job which is to be run in parallel with other jobs.
      Throws:
      Error - if any thread that is already running has thrown an Error.
      NullPointerException - if job is null.
      Since:
      ostermillerutils 1.05.00

    • run

      public void run(ThreadGroup threadGroup, Runnable job, String threadName)
      Run the given job. The given job is either run immediately or if the max number of concurrent jobs are already running, it is queued to be run when some job is finished.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Parameters:
      threadGroup - group in which this job should be run (null for default group).
      job - job which is to be run in parallel with other jobs.
      threadName - name for the thread that will be created to run the job (null for auto generated thread name)
      Throws:
      Error - if any thread that is already running has thrown an Error.
      NullPointerException - if job is null.
      Since:
      ostermillerutils 1.05.00

    • run

      public void run(ThreadGroup threadGroup, Runnable job, String threadName, long stackSize)
      Run the given job. The given job is either run immediately or if the max number of concurrent jobs are already running, it is queued to be run when some job is finished.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Parameters:
      threadGroup - group in which this job should be run (null for default group).
      job - job which is to be run in parallel with other jobs.
      threadName - name for the thread that will be created to run the job (null for auto generated thread name)
      stackSize - system dependent stack size suggestion for thread creation (0 for default stack size).
      Throws:
      Error - if any thread that is already running has thrown an Error.
      NullPointerException - if job is null.
      Since:
      ostermillerutils 1.05.00

    • done

      public boolean done()
      Return true iff all jobs that have been requested to run in this Parallelizer have completed.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Returns:
      Whether all jobs are done or not.
      Throws:
      Error - if any of the running threads has thrown an Error.
      Since:
      ostermillerutils 1.05.00

    • interrupt

      public void interrupt()
      All currently running threads will be interrupted. The threads interrupted threads may die, causing jobs that were queued but not yet started, to start.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Throws:
      Error - if any of the running threads has thrown an Error.
      Since:
      ostermillerutils 1.05.00

    • dumpStack

      public void dumpStack()
      Dump the stack of each running thread.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Throws:
      Error - if any of the running threads has thrown an Error.
      Since:
      ostermillerutils 1.05.00

    • getRunningThreads

      public Thread[] getRunningThreads()
      Gets a list of all running threads. There may be jobs that are queued and do not yet have threads. These job are not returned.

      If this method throws an error, that error may be handled and this method may be called again as it will not re-throw the same instance of the error.

      Returns:
      an array of all currently running threads.
      Throws:
      Error - if any of the running threads has thrown an Error.
      Since:
      ostermillerutils 1.05.00

    • join

      public void join() throws InterruptedException
      Block until all the jobs in this Parallelizer have run and then return.

      If this method throws an exception or an error, that exception or error may be handled and this method may be called again as it will not re-throw the same instance of the exception or error.

      Throws:
      InterruptedException - if interrupted while waiting.
      RuntimeException - any running thread throws or has thrown a runtime exception.
      Error - if any of the running threads throws or has thrown an Error.
      Since:
      ostermillerutils 1.05.00