[lokar]

You want every distinct item to have the same chance at the end. So when items repeat you need to reduce (not increase) the odds of keeping any given occurrence.

[throwaway14356]

does that mean you could also split the set in half multiple times then run it on each half of a half (etc) and combine it with its other half?

that would seem simpler to me.

edit: oh but then you would need to keep the results which defeats the purpose

[lokar]

You would need to assume a uniform distribution of items, which I don’t think this does