RE : crazy run-time fluctuations (mostly super-slow) -- a bit more data

Oiliver --

Maxima currently runs on top of Common Lisp as its implementation
language (despite Maxima's insistance on calling it "Lisp" nearly
everywhere, dishonoring McCarthy's request that "Lisp" be used to denote
this large family of languages, not any specific dialect such as "Common
Lisp").  That's what Maxima's lisp operator invokes.  You need to learn
about the behavior of random on Common Lisp to understand what you are
seeing.  It would be silly to waste the time of members of the maxima
list to compose explanations of what is well described in the ANS for
Common Lisp.

The most accessible (free) version of the ANS is available at
http://www.lispworks.com/documentation/HyperSpec/Front/index.htm Please
see the entires for random, random-state, *random-state*, and
copy-random-state.  That should explain everything.