Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.lang.java.programmer > #34497
| From | Eric Sosman <esosman@comcast-dot-net.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Floating-point hash keys (Was: Java Source of Meiyan Hash Scrambler?) |
| Date | 2016-06-06 12:02 -0400 |
| Organization | A noiseless patient Spider |
| Message-ID | <nj46ra$usq$1@dont-email.me> (permalink) |
| References | <8d97fe56-983e-412d-bf46-73f46c3e1bae@googlegroups.com> <nj3nuq$5i8$1@dont-email.me> <nj3pcj$5nj$1@news.albasani.net> |
On 6/6/2016 8:13 AM, Jan Burse wrote:
> [... poor scattering of Float.hashCode() and Double.hashCode() ...]
It's a bit tangential, but I've been wondering: Why do you want to
use floating-point numbers as hash keys?
There's nothing wrong with a Float or Double key once you have it
(aside from the weaknesses you've noticed for zero-rich mantissas),
but my question is: How do you calculate such a key accurately? We
all know that computations can be "identical" in a mathematical sense
but quite different computationally. If you store something with a
key X and later run a "similar" calculation to get X' (different by
a ULP or so), the hash table won't find the original entry.
So: Are these Floats and Doubles "really" floating-point numbers,
or are they "proxies" for something else? If so, it might be wiser
to use the "something else" as the key instead.
--
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM
Back to comp.lang.java.programmer | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Java Source of Meiyan Hash Scrambler? bursejan@gmail.com - 2016-06-05 17:22 -0700
Re: Java Source of Meiyan Hash Scrambler? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-06 07:48 -0400
Re: Java Source of Meiyan Hash Scrambler? Jan Burse <janburse@fastmail.fm> - 2016-06-06 14:13 +0200
TreeBins Problem and Float/Double (Was: Java Source of Meiyan Hash Scrambler?) Jan Burse <janburse@fastmail.fm> - 2016-06-06 14:45 +0200
Re: Java Source of Meiyan Hash Scrambler? Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-06 08:47 -0400
Floating-point hash keys (Was: Java Source of Meiyan Hash Scrambler?) Eric Sosman <esosman@comcast-dot-net.invalid> - 2016-06-06 12:02 -0400
Re: Floating-point hash keys (Was: Java Source of Meiyan Hash Scrambler?) Roedy Green <inquiry@mindprod.com> - 2016-06-09 05:33 -0700
Re: Floating-point hash keys (Was: Java Source of Meiyan Hash Scrambler?) Jan Burse <janburse@fastmail.fm> - 2016-06-09 16:27 +0200
Re: Java Source of Meiyan Hash Scrambler? Roedy Green <inquiry@mindprod.com> - 2016-06-07 03:24 -0700
Re: Java Source of Meiyan Hash Scrambler? Jan Burse <janburse@fastmail.fm> - 2016-06-07 15:38 +0200
Re: Java Source of Meiyan Hash Scrambler? Jan Burse <janburse@fastmail.fm> - 2016-06-07 15:39 +0200
Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Jan Burse <janburse@fastmail.fm> - 2016-06-07 15:42 +0200
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Roedy Green <inquiry@mindprod.com> - 2016-06-09 05:29 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Mike Amling <mamling@chaff.us> - 2016-06-09 08:00 -0500
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Eric Douglas <e.d.programmer@gmail.com> - 2016-06-09 06:07 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Jerry Stuckle <jstucklex@attglobal.net> - 2016-06-09 11:41 -0400
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Roedy Green <inquiry@mindprod.com> - 2016-06-11 01:17 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Daniel Pitts <usenet@coloraura.com> - 2016-06-11 12:31 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Mike Amling <mamling@chaff.us> - 2016-06-12 15:42 -0500
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Daniel Pitts <usenet@coloraura.com> - 2016-06-12 21:03 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Roedy Green <inquiry@mindprod.com> - 2016-06-13 14:13 -0700
Re: Sideremark II ( Re: Java Source of Meiyan Hash Scrambler?) Roedy Green <inquiry@mindprod.com> - 2016-06-10 14:11 -0700
Re: Java Source of Meiyan Hash Scrambler? Roedy Green <inquiry@mindprod.com> - 2016-06-07 20:38 -0700
Re: Java Source of Meiyan Hash Scrambler? Roedy Green <inquiry@mindprod.com> - 2016-06-09 05:15 -0700
Re: Java Source of Meiyan Hash Scrambler? Jan Burse <janburse@fastmail.fm> - 2016-06-09 16:26 +0200
Re: Java Source of Meiyan Hash Scrambler? Roedy Green <inquiry@mindprod.com> - 2016-06-12 02:28 -0700
Re: Java Source of Meiyan Hash Scrambler? j4n bur53 <janburse@fastmail.fm> - 2016-06-12 12:03 +0200
Re: Java Source of Meiyan Hash Scrambler? Andreas Leitgeb <avl@logic.at> - 2016-06-13 14:07 +0000
Re: Java Source of Meiyan Hash Scrambler? Andreas Leitgeb <avl@logic.at> - 2016-06-13 14:17 +0000
Re: Java Source of Meiyan Hash Scrambler? Andreas Leitgeb <avl@logic.at> - 2016-06-13 14:20 +0000
Re: Java Source of Meiyan Hash Scrambler? j4n bur53 <janburse@fastmail.fm> - 2016-06-13 16:23 +0200
csiph-web