pthread 相同 ID 并输出 self_t

Question

我希望我能把我的问题说得很清楚，我正在编程 pthread，简单地说，我计算所需的线程数，并将创建的线程传递给函数并返回，函数确实在不同的块上转置；所以每个线程都有自己的块。

为了检查我是否发送了不同的线程，我运行 pthread_t self_t，但面临两个问题： 这似乎只使用了一个相同的线程，并且我总是有关于 selt_t 类型输出的警告消息，下面的代码简化显示主要品脱。 有什么想法我哪里出错了吗？

这里首先是struct和main：

pthread_mutex_t mutexZ;       // Mutex initialize
int array[nn][nn];

struct v
{
  int i, j; // threaded Row,Col
  int n, y; // 
  int iMAX; // 
};

void *transposeM(void *arg);

int main(int argc, char *argv[])
{

  int Thread_Num = 10; 
  pthread_t t_ID[Thread_Num]; // the number of threads depending on # blocks

  printf("Thread_Num %d\n", Thread_Num);

  struct v *data = (struct v *) malloc(sizeof(struct v));

  int i, j; //loop varables

  //#############################################################
  printf("Matrix Initial before Transpose Done\n"); 
  // printing the Matrix Before any transpose if needed testing

 for (i = 0; i < nn; i++){
  for(j = 0; j< nn; j++){
    array[i][j] = i*nn + j;
    printf("%d ", array[i][j]); 
   }
   printf("\n");}


  //************************************************************/
  // Initialize the mutex 
  pthread_mutex_init(&mutexZ, NULL);
  pthread_attr_t attr; //Set of thread attributes
  pthread_attr_init(&attr);

  int n, y; // Loop Variables for tiling 

  //************************************************************/ 
  //Start of loop transpose:

  int start = 0;

  for (n = 0; n < nn; n += TILE) 
  {
    data->n = n; // row

    for (y = 0; y <= n; y += TILE) {
      data->y = y; // column

      printf("y Tile:%d  \n", y);
      printf("Start before:%d  \n", start);

      //Transpose the other blocks, thread created for each Block transposed

      pthread_create(&(t_ID[start]), NULL, transposeM, (void*) data); // Send the thread to the function
      pthread_join(t_ID[start], NULL);

      if (start < Thread_Num)
      {
        start = start + 1;

      }
      printf("Start after:%d  \n", start);

    } // End the Y column TileJump loop
  } // End of n Row TileJump loop
} 

根据注释修改，

void *transposeM(void *arg)
{
  // Transposing the tiles
  struct v *data = arg;
  int i, j; //loop row and column
  int temp = 0;
  pthread_mutex_lock(&mutexZ); //lock the running thread here,so keeps block until thread that holds     mutex releases it

  pthread_t self_t; // To check the thread id - my check not Mandetory to use
  self_t = pthread_self();
  printf("Thread number Main = %u \n ", self_t); //here we used u% coz seems the pthread_t is unsigned long data type

  //*******************************************************
  //here some function to work
  //########################################################

  pthread_mutex_unlock(&mutexZ);
  pthread_exit(NULL);

  return (NULL);

} // End

Answer 1

您的代码存在两个概念性问题：

1. 您将相同的引用/地址传递给每个线程，使每个线程处理相同的数据。
2. 创建线程后立即加入线程。作为连接块，直到要连接的线程结束，这使所有线程的运行顺序化。

为了解决 1. 为每个线程创建 data 指向的唯一实例。

修复 2. 将对 pthread_join() 的调用移出创建线程的循环，并将其置于创建循环后的第二个循环中。

...

printf("Thread_Num %d\n", Thread_Num);

pthread_t t_ID[Thread_Num]; // the number of threads depending on # blocks
struct v data_ID[Thread_Num] = {0}; // define an instance of data for ech thread

...

for (n = 0; n < nn; n += TILE) //limit of row
{
  struct v * data = data_ID + start; // assign thread specific instance

  data->n = n; // row

  for (y = 0; y <= n; y += TILE) // limit of column -here removd the =n, then diagonal tile is not     transposed
  {
    ...
    pthread_create(&(t_ID[start]), NULL, transposeM, (void*) data); // Send the thread to the function
    ...
  }
} // End the Y column TileJump loop

for (;start >= 0; --start)
{
  pthread_join(t_ID[start], NULL);
}

...

对线程函数的修改：

void *transposeM(void *arg)
{
  struct v *data = arg;

  ...

  pthread_t self = pthread_self(); // better naming

  ...

  pthread_exit(NULL); // the thread functions exits here.

  return NULL; // this is never reached, but is necessary to calm down thr compiler.
} // End