  We consider the determination of the finite temperature phase transition in
the Yang--Mills SU(3) gauge theory. We compute the difference of the spatial
and temporal energy density at a physical Wilson flow time. This difference is
zero in the confined phase and becomes non zero in the deconfined phase. We
locate the phase transition by using a new technique based on an exponential
smoothing spline. This method is an alternative to the determination of the
phase transition based on the Polyakov loop susceptibility and can also be used
with dynamical fermions.
