join() - have this thread wait until one or more threads have finished.
joining are already terminated,
they are trivially and immediately joined.
t1 = thread(Quote(fit1 = method1(x,y)))
t2 = thread(Quote(fit2 = method2(x,y)))
t3 = thread(Quote(fit3 = method3(x,y)))
values = join(t1,t2,t3)
ans = min(values) # now compute the minimum of the answers