| From: | Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> |
|---|---|
| To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
| Cc: | omid omoomi <oomoomi(at)hotmail(dot)com>, BKermani(at)illumina(dot)com, pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: Median |
| Date: | 2000-07-19 02:12:35 |
| Message-ID: | 39750E93.D7D9517E@alumni.caltech.edu |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | 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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