From: Dave Korn <dave.korn.cygwin@googlemail.com>
To: Robert Dewar <dewar@adacore.com>
Cc: Jae Hyuk Kwak <wrice127@gmail.com>, gcc@gnu.org
Subject: Re: Hash Function for "switch statement"
Date: Fri, 19 Mar 2010 22:43:00 -0000 [thread overview]
Message-ID: <4BA3FF48.5070703@gmail.com> (raw)
In-Reply-To: <4BA3F5AD.8070600@adacore.com>
On 19/03/2010 22:07, Robert Dewar wrote:
> You miss my point, doing a mod with 256 is an AWFUL hash algorithm
> since it only uses the low order 8 bits!
This statement is only true contingent on a number of significant
assumptions you haven't stated - assumptions which can easily be violated.
> I think you will find that people on this mailing list know all about
> hash tables
I think you should get down from that high horse before you come down with
an embarrassing bump.
> So this does not get around the possibility of a bad luck worst case.
Perfect hashing does exactly that. That's why it's "popular for hashing
keywords for compilers", and indeed why it "ought to be popular for optimizing
switch statements":
http://burtleburtle.net/bob/hash/perfect.html
cheers,
DaveK
next prev parent reply other threads:[~2010-03-19 22:30 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-14 20:48 Jae Hyuk Kwak
2010-03-15 3:12 ` Basile Starynkevitch
2010-03-15 8:00 ` Jae Hyuk Kwak
2010-03-16 1:41 ` Jae Hyuk Kwak
2010-03-16 7:12 ` Basile Starynkevitch
2010-03-16 6:00 ` Dave Korn
[not found] ` <20100317200410.GA13807@hungry-tiger.westford.ibm.com>
2010-03-18 6:39 ` Jae Hyuk Kwak
2010-03-18 11:20 ` Andrew Haley
[not found] ` <20100318151753.GA4065@hungry-tiger.westford.ibm.com>
2010-03-19 5:26 ` Jae Hyuk Kwak
2010-03-19 12:26 ` Frank Ch. Eigler
2010-03-19 18:11 ` Jae Hyuk Kwak
[not found] ` <20100319165443.GA9993@hungry-tiger.westford.ibm.com>
2010-03-19 21:26 ` Jae Hyuk Kwak
2010-03-19 21:30 ` Robert Dewar
2010-03-19 21:53 ` Jae Hyuk Kwak
2010-03-19 22:18 ` Robert Dewar
2010-03-19 22:43 ` Dave Korn [this message]
2010-03-19 23:28 ` Robert Dewar
2010-03-19 22:57 ` Jae Hyuk Kwak
2010-03-19 23:33 ` Robert Dewar
2010-03-19 23:33 ` Robert Dewar
2010-03-19 22:24 ` Dave Korn
2010-03-19 23:09 ` Robert Dewar
2010-03-19 23:17 ` Robert Dewar
2010-03-19 19:14 ` Andrew Haley
2010-03-22 12:44 Unruh, Erwin
2010-03-22 13:22 ` Robert Dewar
2010-03-22 16:29 ` Andrew Haley
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