XXX-GENP:  Generate random momentum variables.

There is a version of this program for each 'mc' application (eg,
net-genp).  It is not usually necessary to run this program, since
xxx-mc generates momentum variables automatically if they don't
already exist but are needed for the current Markov chain operations.
However, xxx-genp is needed to implement xxx-circ, since the automatic
generation disturbs random number synchronization.

Usage:

    xxx-genp log-file 

Here, 'xxx' is a prefix identifying the particular incarnaton of this
program (eg, 'dist' or 'net').

If the last mc-spec command (see mc-spec.doc) uses operations that
require momentum variables, this program generates random values for
the momenta, and appends these values to the log file, with index the
same as the index of the last record currently in the log file.

If no mc-spec command has been done, or the last such command involved
only operations that don't require momentum, the xxx-genp command
silently does nothing.  This is the behaviour needed to implement
xxx-circ (see xxx-circ.doc).

            Copyright (c) 2000 by Radford M. Neal