如何并行化一个java程序？

Question

我正在开发一个java程序来解决使用并行编程的线性方程。我已经编写了解决它的代码。如何修改它以在多核处理器上工作？给我几个例子。我听说过mpi（消息传递接口）。如何在我的代码中使用它？

Answer 1

你不可能做的唯一事情就是多线程，并希望OS Supervisor将在多个内核上共享你的进程。

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

Answer 2

最简单的方法是使用ThreadPoolExecutors，你可以看到教程here。

一个例子可以是：

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(); 
    } 

}