[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: support for bitwise comparison of floats
From: |
Eric Blake |
Subject: |
Re: support for bitwise comparison of floats |
Date: |
Sun, 25 Mar 2007 08:00:47 -0600 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.10) Gecko/20070221 Thunderbird/1.5.0.10 Mnenhy/0.7.4.666 |
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
According to Bruno Haible on 3/25/2007 4:54 AM:
> Eric Blake wrote:
>> You can also assume IEEE rules, and compare against signed infinity:
>> 1 / +0. => +infinity
>> 1 / -0. => -infinity
>
> Nice trick :-)
Thanks for correcting my typo; which I realized after I sent my other
message. :)
>
> But here you depend on the IEEE rules for exceptions upon division by zero.
> - On Alpha processors, division by zero (and even overflow!) leads to a
> SIGFPE
> signal by default. And it requires the use of a system call to change
> the FP exceptions control mask (the <fenv.h> routines in glibc >= 2.1,
> the __setfpucw function in glibc 2.0). memcmp is certainly much cheaper.
Raw operations on bits is much faster than actual floating point in a
number of cases; as you have noted, the problem is the portability in
detecting where the raw bits are. Your method appears fine to me.
- --
Don't work too hard, make some time for fun as well!
Eric Blake address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
iD8DBQFGBoBe84KuGfSFAYARAqLNAJ4tA6sWiQhBHpuCW99z55TcvPEvDgCfXOKB
519nbAi5YgVMyMX8AuaRyvI=
=IMUI
-----END PGP SIGNATURE-----
- support for bitwise comparison of floats, Bruno Haible, 2007/03/24
- Re: support for bitwise comparison of floats, Eric Blake, 2007/03/24
- Re: support for bitwise comparison of floats, Bruno Haible, 2007/03/25
- Re: support for bitwise comparison of floats, Eric Blake, 2007/03/25
- Re: support for bitwise comparison of floats, Bruno Haible, 2007/03/25
- Re: support for bitwise comparison of floats, Eric Blake, 2007/03/25
- Re: support for bitwise comparison of floats, Ben Pfaff, 2007/03/25
Re: support for bitwise comparison of floats, Eric Blake, 2007/03/25
Re: support for bitwise comparison of floats, Paul Eggert, 2007/03/29