Better implementation of random_permutation

Robert Dodier <robert.dodier at gmail.com> writes:
> Hmm, this is the same Knuth shuffle expressed in a different way,
> right?

It's the slightly more efficient "inside-out" variant of the Knuth
shuffle, a.k.a. Fisher-Yates shuffle.

> If so the only problem I see is that the random numbers should
> come from Maxima's $RANDOM and not CL RANDOM

Oops, good catch!  Unfortunately, $RANDOM is much slower than CL RANDOM.
On my machine, it's about 37 times slower.

When using $RANDOM, my new $RANDOM_PERMUTATION is only faster on my
machine for lists with hundreds of elements:

  For size 10000, it's faster: ratio=5.15
  For size 1000,  it's faster: ratio=1.23
  For size 100,   it's slower: ratio=0.95
  For size 10,    it's slower: ratio=0.93

     Mark