java parallelisation problem - parallelisation is as slow as serialisation

I have been developing an individual base model. All you need to know is that individuals are born, reproduce and die. I have a GUI in which i can see these processes happening.

I have a mac pro, with 8 cores and 16GB ram.

Considering that the simulation will have to be repeated a few times to get error bars, etc, I thought i could run the main class and then have separate simulations (all run from the same program) ran on separate cores. Simple. Each parallel simulation would have no knowledge of the other simulations, hence no need for synchronization blocks.

When the main method is run, it invokes the constructor of the main class - which creates the other objects and the simulation begins. Hence - to parallelise - I created a fixed thread pool which would all separately invoke the main class constructor and multiple (well, 8, the number of cores) simulations.

BUT - it is running as slow as if I was running the simulations in serial. The animation in the GUIs for each simulation are updated in order, not simultaneously.

In fact, if I run the program 8 times simultaneously from the command line (and place in the background with '&') it is much faster and behaves much more like I would have hoped. Which is irritating!

At the start of the simulation some IO operations are performed to read in data about the individuals, but only at the start.

Interestingly, the first objects to be created by the `parallel' processes were made at the same memory addresses - but I don't think that is a problem.

If anybody has any insight into this lack of performance from the java concurrency tools, why the program appears to be running in serial and why simply running the main method from the command line 8 times is better than attempting to parallelise that would be most helpful.

Because to be frank I am losing faith in java's parallelisation capabilities.

Cheers

James

        noOfProcessor开发者_如何学Cs = (byte)Runtime.getRuntime().availableProcessors();
        ExecutorService eservice = Executors.newFixedThreadPool( noOfProcessors );

        List<Future> futuresList = new ArrayList<Future>();

        for( int i = 0; i < noOfProcessors; i++ ){
            futuresList.add( eservice.submit( new simulation() ) );

        }//end for

        for( Future future : futuresList ){

            try{

                future.get();

            }catch( InterruptedException ex ){
                Logger.getLogger( simPanel.class.getName() ).log( Level.SEVERE, null, ex );
                System.exit( 1 );
            }catch( ExecutionException ex ){
                Logger.getLogger( simPanel.class.getName() ).log( Level.SEVERE, null, ex );
                System.exit( 1 );
            }//end try-catch

        }//end for loop

While not too familiar with Java's Executors class, the serial behaviour seems to indicate that your thread pool is running all threads on the same processor. Perhaps it has something to do with how the JVM handles threads? Anyway, see if you can create separate processes in Java and see if that makes a difference.