abstract = "The distribution of reversible programs tends to a
limit as their size increases. For problems with a
Hamming distance fitness function the limiting
distribution is binomial with an exponentially small
chance (but non~zero) chance of perfect solution.
Sufficiently good reversible circuits are more common.
Expected RMS error is also calculated. Random unitary
matrices may suggest possible extension to quantum
computing. Using the genetic programming (GP)
benchmark, the six multiplexor, circuits of Toffoli
gates are shown to give a fitness landscape amenable to
evolutionary search. Minimal CCNOT solutions to the six
multiplexer are found but larger circuits are more