From: Kilgallen@SpamCop.net (Larry Kilgallen)
Subject: Re: Hashing on System.Address
Date: 14 Jun 2005 03:42:47 -0500
Date: 2005-06-14T03:42:47-05:00 [thread overview]
Message-ID: <Q32uBJZaej4r@eisner.encompasserve.org> (raw)
In-Reply-To: wcc3brlrfj5.fsf@shell01.TheWorld.com
In article <wcc3brlrfj5.fsf@shell01.TheWorld.com>, Robert A Duff <bobduff@shell01.TheWorld.com> writes:
> "Matthew Heaney" <mheaney@on2.com> writes:
>
>> Duncan Sands wrote:
>> > Does anyone have an efficient portable algorithm for hashing
>> > on a System.Address?
>> >
>> > The Ada 2005 package Ada.Containers defines Hash_Type as
>> >
>> > type Hash_Type is mod implementation-defined;
>> >
>> > This is the target type I would like for the hash.
>>
>> Use System.Storage_Elements.To_Integer to convert the address to an
>> Integer_Address, and then convert that to type Hash_Type.
>
> It might be a good idea to divide that by 8, since most addresses have
> zeros in the low three bits.
Or it might not be, since he said portable. Looking at addresses of
_instructions_ (which are the closest to that pattern) on the machine
architectures on which VMS runs:
VAX - No restriction, 1 bit (odd and even) just as likely to be
one as the other
Alpha - 4 byte boundary, 4 bit (100) just as likely to be one
as the other
Itanium - 8 byte boundary for VLIW instructions, but in software
the last octet of the address is 0, 1 or 2 depending on
which instruction in the bundle is addressed.
next prev parent reply other threads:[~2005-06-14 8:42 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-13 20:18 Hashing on System.Address Duncan Sands
2005-06-13 21:31 ` Mark Lorenzen
2005-06-14 7:23 ` Duncan Sands
2005-06-14 20:18 ` Randy Brukardt
2005-06-15 7:27 ` Duncan Sands
2005-06-13 21:57 ` Matthew Heaney
2005-06-13 23:41 ` Robert A Duff
2005-06-14 2:22 ` Matthew Heaney
2005-06-14 7:27 ` Duncan Sands
2005-06-14 8:52 ` Alex R. Mosteo
2005-06-14 9:06 ` Duncan Sands
2005-06-14 9:09 ` Duncan Sands
2005-06-14 17:00 ` Pascal Obry
2005-06-14 20:03 ` Randy Brukardt
2005-06-14 23:20 ` Robert A Duff
2005-06-15 7:13 ` Duncan Sands
2005-06-14 8:44 ` Larry Kilgallen
2005-06-14 10:03 ` Marius Amado Alves
[not found] ` <abb2a2c53e3708803aa68bb87834b7bc@netcabo.pt>
2005-06-14 10:14 ` Duncan Sands
[not found] ` <200506141214.14213.baldrick@free.fr>
2005-06-14 10:29 ` Marius Amado Alves
[not found] ` <64f19b6707e4d19f5362900bbfb80b76@netcabo.pt>
2005-06-14 10:49 ` Marius Amado Alves
2005-06-14 8:42 ` Larry Kilgallen [this message]
2005-06-14 11:18 ` Duncan Sands
2005-06-14 7:18 ` Duncan Sands
2005-06-14 15:18 ` Matthew Heaney
2005-06-14 16:22 ` Duncan Sands
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