multithreading - omp parallel vs. omp parallel for

Question

What is the difference between these two?

[A]

#pragma omp parallel
{ 
    #pragma omp for
    for(int i = 1; i < 100; ++i)
    {
        ...
    }
}

[B]

#pragma omp parallel for
for(int i = 1; i < 100; ++i)
{
   ...
}

Answer 1

These are equivalent.

#pragma omp parallel spawns a group of threads, while #pragma omp for divides loop iterations between the spawned threads. You can do both things at once with the fused #pragma omp parallel for directive.