From: Roland Orre <orre@nada.kth.se>
Cc: Greg Troxel <gdt@ir.bbn.com>
Subject: Re: Efficiency and flexibility of hash-tables
Date: 10 Feb 2003 18:09:30 +0100 [thread overview]
Message-ID: <1044896969.1032.317.camel@localhost> (raw)
In-Reply-To: <xy77kc8krhr.fsf@nada.kth.se>
On Mon, 2003-02-10 at 17:52, Mikael Djurfeldt wrote:
> The idea of having an upper threshold comes from the idea of
> maintaining the load factor of the hash table in a reasonable
> interval. But the purpose of the load factor is to prevent to large
> clusters forming in the same hash bucket. What about simply counting
> the pairs in a bucket during insertion and rehashing when we reach a
> threshold? Then no extra data needs to be stored in the table. (We
> would need to globally serialize rehashing with an external mutex,
> though.)
The risk with this is that if the hash function in a specific situation
is bad, not spreading enough, we may form clusters anyway. With a
risk that we will reallocate hash tables much too often.
> Another disadvantage is that the tables wouldn't shrink. Is this an
> issue?
For most of our applications it isn't because we will reallocate all
hash tables after each run.
In all my code over the years hash-remove! is very very rare.
Best regards
Rolan
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next prev parent reply other threads:[~2003-02-10 17:09 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-02-08 11:00 Efficiency and flexibility of hash-tables Joris van der Hoeven
2003-02-08 13:57 ` Roland Orre
2003-02-08 14:14 ` Joris van der Hoeven
2003-02-08 14:55 ` Roland Orre
2003-02-08 15:14 ` Joris van der Hoeven
2003-02-08 15:31 ` Mikael Djurfeldt
2003-02-11 11:14 ` Joris van der Hoeven
2003-02-11 11:28 ` Joris van der Hoeven
2003-02-11 12:50 ` Mikael Djurfeldt
2003-02-08 15:44 ` Roland Orre
2003-02-10 9:55 ` Andreas Rottmann
2003-02-10 14:24 ` Greg Troxel
2003-02-10 15:00 ` Roland Orre
2003-02-10 16:52 ` Mikael Djurfeldt
2003-02-10 17:09 ` Roland Orre [this message]
2003-02-10 17:11 ` Mikael Djurfeldt
2003-02-11 13:59 ` Resizing hash tables in Guile Mikael Djurfeldt
2003-02-11 17:34 ` Roland Orre
2003-02-12 11:41 ` Marius Vollmer
2003-02-12 16:10 ` Marius Vollmer
2003-02-12 17:53 ` Mikael Djurfeldt
2003-02-12 20:17 ` Roland Orre
2003-02-13 9:35 ` Mikael Djurfeldt
2003-02-13 13:55 ` Harvey J. Stein
2003-02-13 14:24 ` Joris van der Hoeven
2003-02-13 18:30 ` Harvey J. Stein
2003-02-13 20:02 ` Paul Jarc
2003-02-13 9:52 ` Joris van der Hoeven
2003-02-12 20:55 ` Rob Browning
2003-02-13 10:43 ` Mikael Djurfeldt
2003-02-12 20:47 ` Efficiency and flexibility of hash-tables Paul Jarc
2003-02-12 21:58 ` Roland Orre
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