An implementation of the heuristic GCD algorithm, first introduced by B.W.
Char, K.O. Geddes and G.H. Gonnet, as described in J.H. Davenport and
J. Padget, ``HEUGCD: How Elementary Upperbounds Generate Cheaper Data'',
Proc. of EUROCAL '85, Vol 2, 18-28, published as Lecture Notes on Comp.
Science, No. 204, Springer-Verlag, Berlin, 1985, is also available on an
experimental basis. To use this algorithm, the switch {\tt
HEUGCD}\ttindex{HEUGCD} should be on in addition to {\tt GCD}. Note that
if both {\tt EZGCD} and {\tt HEUGCD} are on, the former takes precedence.