The initialization includes starting the slave processes, calculating
the partition factor, $D$, and providing the slave processes with
unique identifying information. This information is stored in the
.bigGP object on each slave process. Note that in general, the number of processes (number of slave
processes, P, plus one for the master) should not exceed the number of
physical cores on the machine(s) available.
bigGP.init also sets up random number generation on the slaves,
using parallelRNGpkg when specified, and setting appropriate
seeds on each slave process.