$.$ Some implementations of Pthreads define barriers. The function

int pthread barrier init$($

pthread barrier t$$ barrier p $/$ out $/,$

const pthread barrierattr t$$ attr p $/$ in $/,$

unsigned count $/$ in $/)$;

initializes a barrier object, barrier p$.$ As usual, we$$ll ignore the second argument and just pass in NULL. The last argument indicates the number of threads

that must reach the barrier before they can continue. The barrier itself is a call

to the function

int pthread barrier wait