Separation guarantee in Goemans Williamson algorithm In the original paper in Goemans-Williamson paper for max-cut, we need to sample a random vector r and 
we output 
$$
S = \{i : r^{T}x_{i} \geq 0\}
$$
where $x_{i}$ are column vector of a feasible solution of the SDP relaxation.

My question is are we guaranteed that there exists a certain $r$ such that the output is max-cut ?
Feige and Schechtman, On the optimality of the random hyperplane rounding technique for max cut, constructed a graph on which all $r$ only give an $\alpha$-approximation, where $\alpha$ is the worst-case approximation ratio of the Goemans–Williamson algorithm.