3 Parallel regions

How do I ensure that 3 pieces of code execute concurrently with OpenMP? In the following toy problem, sections A & B generate some data and section C polls the data and acts on it.

int main(int argc, char* argv[])
{   
    int G = -1,S = -1;
    #pragm开发者_开发问答a omp parallel sections default(none) shared(G,S,cout)
    {
        // Section A
        #pragma omp section
        {
            for(;;)
            {
                G = G_Generator();
                if(G == 0) break;
            }
        }
        // Section B
        #pragma omp section
        {
            for(;;)
            {
                S = S_Generator();
                if(S == 0) break;
            }
        }
        // Section C
        #pragma omp section
        {
            for(;;)
            {
                if(G == 1 || S == 1) Do_1();
                if(G == 2 || S == 2) Do_2();
                if(G == 0 || S == 0) break;
            }
        }
    }
return 0;
}

This doesn't work and I can't debug it. Is it possible that the polling section C can "miss" a G or S value of 1 or 2? The code just doesn't seem to achieve the desired results --- is this the right way to code in OpenMP? I've only parallelized loops before.

---

What you want to do is pipeline parallelism, and it will be difficult to synchronize correctly. If you want any parallelism at all, you will need a queue (probably a circular buffer) to store the data coming out of sections A and B until section C is ready for it. Look at page 147 of http://www.openmp.org/mp-documents/omp-hands-on-SC08.pdf for one example, but that is one-producer, one-consumer.