  Nearly all the evolution equations of physics are time-reversible, in the
sense that a movie of the solution, played backwards, would obey exactly the
same differential equations as the original forward solution. By way of
contrast, stochastic approaches are typically not time-reversible, though they
could be made so by the simple expedient of storing their underlying
pseudorandom numbers in an array. Here we illustrate the notion of
time-reversible random number generators. In Version 1 we offered a suitable
reward for the first arXiv response furnishing a reversed version of an only
slightly-more-complicated pseudorandom number generator. Here we include
Professor Ricci-Tersenghi's prize-winning reversed version as described in his
arXiv:1305.1805 contribution: "The Solution to the Challenge in
`Time-Reversible Random Number Generators' by Wm. G. Hoover and Carol G.
Hoover".

Discrete Mathematics;Statistical Mechanics;Computational Physics