Livelock

- if res is never smaller than TOL, the program spins endlessly in Livelock
- the race may be fixed with a barrier before the single, such that the match function will work better
- also, decide on the maximum number of iterations, rather than an infinite loop

C$omp parallel private(id)

id = omp_get_thread_num()

n = omp_get_num_threads()

10 continue

phases(id) = update(u,id)

c$omp single

res = match(phases,n)

c$omp end single

if(res.lt.TOL) goto 20

goto 10

20 continue

c$omp end parallel

C$omp barrier

c$omp single

res = match(phases,n)

icount = icount + 1

c$omp end single

if(res.lt.TOL.or

icount.gt.MAX)goto 20

goto 10

20 continue

c$omp end parallel

The following code shows a race condition and a livelock: