Re: Median
От | Thomas Lockhart |
---|---|
Тема | Re: Median |
Дата | |
Msg-id | 39750E93.D7D9517E@alumni.caltech.edu обсуждение исходный текст |
Ответ на | Re: Median (JanWieck@t-online.de (Jan Wieck)) |
Список | pgsql-sql |
> Maybe someone else has an idea. I implemented a different algorithm several years ago. It is an O(log(N)) process (unlike most other techniques), and was borrowed from the "Algorithms" book (it's at work; but it is the classic "yellow jacket" book with Fortran code and the other volume with *really bad* C code which looks like Fortran ;) Anyway, once the bugs were fixed (and there were several :( and a better endgame algorithm was coded, it was suitable for hypercube distributed processing, where you just exchange a small amount of info between iterations. And it involved simply *counting* how many values were above and below an initial or updated guess, then iterating on a new guess. afaik that wouldn't be suitable for the existing aggregate capabilities, but multi-pass algorithms would be nice to be able to do. - Thomas
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