Every processor (master and slave) allocate memory
for arrays such as <tt>SR</tt>, <tt>F</tt>, &hellip; according to the number
of atoms <tt>NP</tt>.

<p>
Needed before calling <tt>eval_parallel</tt>.

<p>
Effective only when MD++ is compiled for parallel runs,
e.g. with <tt>SYS = mpicc</tt> or <tt>SYS = mpigpp</tt>.
