  This article demonstrates the applicability of the parallel-in-time method
Parareal to the numerical solution of the Einstein gravity equations for the
spherical collapse of a massless scalar field. To account for the shrinking of
the spatial domain in time, a tailored load balancing scheme is proposed and
compared to load balancing based on number of time steps alone. The performance
of Parareal is studied for both the sub-critical and black hole case; our
experiments show that Parareal generates substantial speedup and, in the
super-critical regime, can reproduce Choptuik's black hole mass scaling law.
