openmp中的数据共享

Question

在编写多线程程序时，默认的做法是在所有线程之间共享内存，并且需要指定什么是私有的。是否可以将所有数据声明为私有数据？

致敬，-Mohd

Answer 1

你可能想看看thread local storage。

Answer 2

你可以的，for example

#include <omp.h>
#include <stdio.h>
#include <stdlib.h>

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

/* Fork a team of threads giving them their own copies of variables */
#pragma omp parallel private(nthreads, tid)
  {

  /* Obtain thread number */
  tid = omp_get_thread_num();
  printf("Hello World from thread = %d\n", tid);

  /* Only master thread does this */
  if (tid == 0) 
    {
    nthreads = omp_get_num_threads();
    printf("Number of threads = %d\n", nthreads);
    }

  }  /* All threads join master thread and disband */

}

但是，不能将共享数据替换为异步消息，因为不能保证openmp任务异步运行：

Use Threads Correctly = Isolation + Asynchronous Messages