線程對象不同步

Question

所以我寫了這個程序來運行這個機器人類的多個線程使用cyclicbarrier來同步線程。由於我對循環屏障的理解很少，我認爲它會自動同步我的線程，但似乎沒有。基於我的進度整數值，我的機器人線程需要做什麼才能同步？

public class Robot implements Runnable{ 
public static final int on = 0x0001; 
public static final int clockwise = 0x0002; 
public static final int counter = 0x0004; 
int opcode; 
int moveCount = 0; 
int rotation, increment, progress = 0; 
boolean CW; 

ProgressBar prgBar; 
CyclicBarrier cyclicBarrier; 
Controller c; 
Motor m; 

public Robot(CyclicBarrier cyclicBarrier, Motor m) 
{ 
    opcode = 0; 
    this.cyclicBarrier = cyclicBarrier; 
    this.m = m; 
} 




public void run(){ 
    System.out.println("Running: "); 

    try { 
     while(progress <= 24){ 
      i = m.Engage(this, i, increment/4); 
      prgBar.setProgress(this, progress); 
     } 
     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 1"); 
     cyclicBarrier.await(); 

     while(progress <= 49){ 
      i = m.Engage(this, i, increment/2); 
      prgBar.setProgress(this, progress); 
     } 
     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 2"); 
     cyclicBarrier.await(); 

     while(progress <= 74){ 
      i = m.Engage(this, i, ((increment/4)*3)); 
      prgBar.setProgress(this, progress); 
     } 
     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 3"); 
     cyclicBarrier.await(); 

     while(progress <= 99){ 
      i = m.Engage(this, i, increment); 
      prgBar.setProgress(this, progress); 
     } 
     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 4"); 
     cyclicBarrier.await(); 

    } catch (Exception e){ 
     e.printStackTrace(); 
    } 
    prgBar.setProgress(this, progress); 
    System.out.println("Engaging: "); 
} 

公共類控制器{

public static void main(String[] args){ 
    CyclicBarrier cyclicBarrier = new CyclicBarrier(4); 
    Motor m = new Motor(); 


    Robot xRob = new Robot(cyclicBarrier, m); 
    Robot yRob = new Robot(cyclicBarrier, m); 
    Robot zRob = new Robot(cyclicBarrier, m); 

    Thread xRobThread = new Thread(xRob); 
    Thread yRobThread = new Thread(yRob); 
    Thread zRobThread = new Thread(zRob); 

    boolean clockwise = true, counterClockwise = false; 




    m.setMotor(clockwise, 14400, xRob); 
    m.setMotor(clockwise, 7200, yRob); 
    m.setMotor(counterClockwise, 28800, zRob); 

    xRobThread.start(); 
    yRobThread.start(); 
    zRobThread.start(); 

    try { 
     xRobThread.join(); 
     yRobThread.join(); 
     zRobThread.join(); 
    } catch (InterruptedException e) { 
     e.printStackTrace(); 
    } 


    System.out.printf("x = %d y = %d z = %d\n\n", xRob.moveCount, yRob.moveCount, zRob.moveCount); 

} 
} 

Answer 1

是什麼，當你運行它的程序呢？你在想什麼它要做什麼？ （即，你認爲「同步我的線程」是什麼意思？）

至少，您的更新現在包含足夠的信息讓我猜測，並且我猜測程序掛起。您的main（）例程爲四方創建一個新的CyclicBarrier，然後創建三個線程。每個線程調用cyclicBarrier.await（），但我沒有看到任何第四方。在四個線程調用await（）之前，屏障不會打開。

---

附加信息：

OK，讓我們假設你有一個循環，使某種形式的「進步」。你可以到達的進展等待一定的閾值的第一個線程爲他人做這樣的事情趕上：

double progress = 0.0; 
static final double CHECKPOINT = 0.5; 
static final double FINISHED = 1.0; 
boolean reachedCheckpoint = false; 

while (progress < FINISHED) { 
    progress = makeSomeProgress(); 
    if (! reachedCheckpoint && progress >= CHECKPOINT) { 
     cyclicBarrier.await(); 
     reachedCheckpoint = true; 
    } 
} 

很顯然，如果你想有一個以上的程序會較爲複雜檢查站，但這是基本的想法。請記住，構建CyclicBarrier的「參與方」數量必須與實際使用它的線程數完全相等。

Answer 2

我將barrier1設置爲〜25％，barrier2設置爲〜50％等等，我想在循環中走多遠，並且我通過在lop結束時輸出當前位置來更新i每個線程。我一遍又一遍地做同樣的事情，直到它達到進度的結束。

public void run(){ 
    System.out.println("Running: "); 
    barrier1 = increment/4; 
    barrier2 = increment/2; 
    barrier3 = ((increment/4)*3); 
    barrier4 = increment; 
    try { 
     i = m.Engage(this, i, barrier1); 
     prgBar.setProgress(this, progress); 

     System.out.println("Sleeping: "); 
     Thread.sleep(1000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 1"); 
     cyclicBarrier.await(); 


     i = m.Engage(this, i, barrier2); 
     prgBar.setProgress(this, progress); 

     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 2"); 
     cyclicBarrier.await(); 


     i = m.Engage(this, i, barrier3); 
     prgBar.setProgress(this, progress); 

     System.out.println("Sleeping: "); 
     Thread.sleep(3000); 
     System.out.println(Thread.currentThread().getName()+ " waiting at barrier 3"); 
     cyclicBarrier.await(); 


     m.Engage(this, i, barrier4); 
     prgBar.setProgress(this, progress); 

    } catch (Exception e){ 
     e.printStackTrace(); 
    } 
    prgBar.setProgress(this, progress); 
    System.out.println(Thread.currentThread().getName()+ " closing."); 
    Thread.currentThread().interrupt(); 
    System.out.println("Engaging: "); 
}