I said:

...

One could modify Greg's suggestion slightly by attaching an auxiliary array of 256 random numbers to each of the members of the original array and then using the most efficient handy sort algorithm to sort those random numbers, dragging along their associated original array elements. This way it doesn't have a chance to interfere with the operation of the sorting algorithm, at the cost of an extra array.

Jim Choate responded:

If I understand the process. Each array would cycle through in parallel sorting 2 elements of each array. Once that was finished we'd then sort the arrays themselves according to some process. From your description it seems to imply that you're going to sort the 1st element descending at that point. This in effect mis-orders each array after every sort.

This sort of system is an IFS and could lead to determinism (ie a cycle of sort patterns that repeat endlessly) or chaos (ie a pattern that doesn't repeat). It in and of itself doesn't guarantee any randomness merely a continously munged sort.

I expressed myself badly. Steve Gibbons posted a message to Coderpunks expressing more clearly what I had in mind: Fill up the high bits of your N words with random numbers and the low bits with an index from 0 to N-1. Sort the array, then mask off the high bits. If the random numbers were unique, you are left with a randomly shuffled array. -- Jim Gillogly Trewesday, 9 Blotmath S.R. 1998, 16:48 12.19.5.11.12, 10 Eb 5 Zac, Seventh Lord of Night