//
// parallel 
//
#include <omp.h>
#include <stdio.h> 

int main()
{
    int nthreads=0, tid=0, tidd=0;  
    
    omp_set_nested(1); // 打开并行域嵌套功能 
    
    #pragma omp parallel private(tid) num_threads(2) 
    {
        tid=omp_get_thread_num(); // Obtain thread id
        printf("Hello world from OpenMP thread %d\n", tid);
        
        #pragma omp parallel private(tidd) num_threads(3)
		{
            tidd=omp_get_thread_num(); // Obtain thread id
            printf("sub-thread %d of thread %d\n", tidd, tid);
		} 
    }
    
    return 0;
}