how to parallelize a java program? [closed]

开发者_如何学Python It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 11 years ago.

am developing a program in java to solve linear equations using parallel programming. I've written the code for solving it. How to modify it to work on multicore processor? give me few examples. i heard of mpi (message passing interface). how to use it in my code?

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The simplest way is to use ThreadPoolExecutors, you can see the Tutorial here.

An example could be:

import java.util.concurrent.*;
import java.util.*;

class MyThreadPoolExecutor
{
    int poolSize = 2;

    int maxPoolSize = 2;

    long keepAliveTime = 10;

    ThreadPoolExecutor threadPool = null;

    final ArrayBlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(
            5);

    public MyThreadPoolExecutor()
    {
        threadPool = new ThreadPoolExecutor(poolSize, maxPoolSize,
                keepAliveTime, TimeUnit.SECONDS, queue);

    }

    public void runTask(Runnable task)
    {
        // System.out.println("Task count.."+threadPool.getTaskCount() );
        // System.out.println("Queue Size before assigning the
        // task.."+queue.size() );
        threadPool.execute(task);
        // System.out.println("Queue Size after assigning the
        // task.."+queue.size() );
        // System.out.println("Pool Size after assigning the
        // task.."+threadPool.getActiveCount() );
        // System.out.println("Task count.."+threadPool.getTaskCount() );
        System.out.println("Task count.." + queue.size());

    }

    public void shutDown()
    {
        threadPool.shutdown();
    }

    public static void main(String args[])
    {
        MyThreadPoolExecutor mtpe = new MyThreadPoolExecutor();
        // start first one
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("First Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
        // start second one
        /*
         * try{ Thread.sleep(500); }catch(InterruptedException
         * ie){}
         */
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("Second Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
        // start third one
        /*
         * try{ Thread.sleep(500); }catch(InterruptedException
         * ie){}
         */
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("Third Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
        // start fourth one
        /*
         * try{ Thread.sleep(500); }catch(InterruptedException
         * ie){}
         */
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("Fourth Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
        // start fifth one
        /*
         * try{ Thread.sleep(500); }catch(InterruptedException
         * ie){}
         */
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("Fifth Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
        // start Sixth one
        /*
         * try{ Thread.sleep(500); }catch(InterruptedException
         * ie){}
         */
        mtpe.runTask(new Runnable()
        {
            public void run()
            {
                for (int i = 0; i < 10; i++)
                {
                    try
                    {
                        System.out.println("Sixth Task");
                        Thread.sleep(1000);
                    } catch (InterruptedException ie)
                    {
                    }
                }
            }
        });
            mtpe.shutDown();
    }

}

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you can't the only thing you can do is multi threading and hope that the OS Supervisor will share your processes over multiple cores.

See http://download.oracle.com/javase/1.5.0/docs/api/java/lang/Thread.html