Re: computationally intensive threading on multi-cpu works great in java1.6, poorly in 1.5

8 Dec 2006 01:36:27 -0800
Sure, here's the multi-threading utility code:

 * Created on 24-Jan-2006 Copyright (C) Eurobios, 2006.
package eurobios.threading;

import java.util.Iterator;
import java.util.List;

 * Utility class which handles all aspects of parallelising a set of
 * See {@link #run(int, Iterator, IRunItem)} for details of usage. An
 * calling pattern is:
 * <pre>
 * final Iterator dcIter = new SynchronizedIterator(locations,
 *, dcIter,
 * new ParalleliseOperations.IRunItem() {
 * public void run(Object object) {
 * ((DeliveryCollection) object).sequenceAndCalculate(tTypes,
 * pointTopology, params, optimizationParams, roadParams);
 * }
 * });
 * </pre>
 * Note that the reason you can't wrap up the actual processing inside
 * 'next()' call of the provided iterator is that that would lock up
 * synchronized next() method, causing other threads to wait.
 * <p>
 * Clients of this code include the PostDK-New project and
 * eurobios.routeoptimiser.
 * @author VinceD
public class ParalleliseOperations {

   * An implementation of this must be provided by our callers. It is
used to
   * trigger an operation on each object returned by the iterator.
   * @author VinceD
  public interface IRunItem {
    public void run(Object object) throws InterruptedException;

  public interface IRunnable {
    public void run() throws InterruptedException;

   * Class to manage all aspects of blocking the current thread until
   * calculations are done.
   * <p>
   * Basic usage:
   * <li>Create an instance, specifying the number of threads it will
   * <li>Create new threads and set them running, in such a fashion
   * {@link #threadFinished()} will be called when no more tasks
remain, or when
   * {@link #isAborted()} is true.
   * <li>Call {@link #waitUntilDone()} in the main thread. Your code
will now
   * block until all the managed threads are done.
   * @author VinceD
  private static class ThreadMonitor {
    public int runningThreads = 0;

    ThreadMonitor(int runningThreads) {
      this.runningThreads = runningThreads;

    RuntimeException abortReason = null;

    InterruptedException interruptedReason = null;

    synchronized void waitUntilDone() throws InterruptedException {
      if (runningThreads > 0) {
      if (interruptedReason != null) {
        throw interruptedReason;
      if (abortReason != null) {
        throw abortReason;

    synchronized boolean isAborted() {
      return abortReason != null;

    synchronized public void threadFinished() {
      if (runningThreads == 0) notify();

    synchronized public void threadFinished(RuntimeException interrupt)
      if (interrupt != null && abortReason == null) {
        abortReason = interrupt;

    synchronized public void threadFinished(InterruptedException
interrupt) {
      if (interrupt != null && interruptedReason == null) {
        interruptedReason = interrupt;


   * Run the given list of operations in parallel
   * @param parallelThreads
   * @param operations
   * @throws InterruptedException
  public static void run(int parallelThreads, final List<IRunnable>
      throws InterruptedException {
    run(parallelThreads, operations.iterator(), new IRunItem() {
      public void run(Object object) throws InterruptedException {
        ((IRunnable) object).run();

   * For all objects provided by operationIterator's 'next()' method,
   * ''. These operations will be farmed out to a
maximum of
   * 'parallelThreads' threads, and this method will only return once
all of the
   * operations are complete. The order with which the operations are
   * out is not defined, and therefore most code will want to ensure
   * results of interest are not dependent on that sequence.
   * <p>
   * It is assumed that 'operationIterator' is thread-safe, which means
that its
   * 'hasNext()' and 'next()' methods are synchronized.
   * <p>
   * If parallelThreads is less than 2, no new threads are created and
a basic
   * iteration in the main thread is used instead.
   * @param parallelThreads
   * @param operationIterator
   * @param runner
   * @throws InterruptedException
  public static void run(int parallelThreads, final Iterator
      final IRunItem runner) throws InterruptedException {
    if (parallelThreads <= 1) {
      while (operationIterator.hasNext()) {;
    } else {
      final ThreadMonitor groupOfThreads = new

      class LocalThread implements Runnable {
       int threadCounter;
     LocalThread(int threadCounter) {
     this.threadCounter = threadCounter;
        public void run() {
          try {
            // Each thread keeps asking for more operations until there
            // no more to provide.
            while (!groupOfThreads.isAborted() &&
operationIterator.hasNext()) {
              Object operation = null;
              // Lock the operationIterator while we query and remove
the next
              // operation.
              synchronized (operationIterator) {
                if (operationIterator.hasNext())
                  operation =;
              if (operation != null) {
// System.out.println("Thread " + threadCounter + "
            // and then notifies that it is done
          } catch (InterruptedException ie) {
            // or that an error was thrown
          } catch (RuntimeException ie) {
            // or that an error was thrown

      for (int thread = 0; thread < parallelThreads; thread++) {
        Thread thisThread = new Thread(new LocalThread(thread+1));
// thisThread.setPriority(java.lang.Thread.MAX_PRIORITY);




We use this for a variety of different operations, all fairly
computationally expensive, taking between 1/10sec and several seconds


On Dec 6, 11:16 pm, "hiwa" <> wrote: wrote:

Our application, at one stage of its processing, does some intensive
computation - in fact typically about 2000 such computations each of
which is entirely independent of the next. This seemed an ideal
candidate for multi-threading and running on a multi-cpu machine.

In fact with Java 1.6, we can happily get our 4-cpu server maxing out
on all cpus and performing the total computation very fast. But, with
java 1.5 (and no other differences), the same machine just uses about
25% of each cpu and takes a loooong time. These observations are both
on Windows XP and Windows 2003 server. We haven't used any special
command line flags except to allocate a decent amount of memory. We
normally run these threads without any special priority, but even
setting them to max priority makes no difference.

Interestingly on MacOS X, with Java 1.5, everything works well and a
dual-core Intel iMac runs the system with both cores at 100%.

Any ideas what is going on here? How can we get a java 1.5 jvm to
utilise all CPUs to the max?

thanks for any ideas or tips!

Vince.Could you show us the code, or, an SSCCE?

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