From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: Jan Hubicka <jh@suse.cz>
Cc: Richard Henderson <rth@redhat.com>, gcc-patches@gcc.gnu.org, aj@suse.de
Subject: Re: Converting floor to rint
Date: Thu, 07 Nov 2002 01:33:00 -0000 [thread overview]
Message-ID: <m3smydvi3z.fsf@soliton.integrable-solutions.net> (raw)
In-Reply-To: Jan Hubicka's message of "Thu, 7 Nov 2002 10:21:12 +0100"
Jan Hubicka <jh@suse.cz> writes:
| > Jan Hubicka <jh@suse.cz> writes:
| >
| > | On the related note. How bad would you consider converting
| > | floor(x) into rint(x-0.5) in the fast-math mode?
| >
| > If you think you do want to do that transformation, then I would
| > prefer this
| >
| > floor(x) -> nearbyint(x-0.5)
| >
| > | That transformation would do a miracles for i386, where rint is faster
| > | than floor by quite a lot and should suffice for 3D application in
| > | reliablility. I can imagine it to fail only for very large numbers...
| >
| > Not really. floor(1) == 1 and rint(1 - 0.5) maybe be 0 or 1 depending
| > on the current rounding mode.
| Hmm, is rint really expected to be dependent on the rouding mode?
| Man page claims:
| The nearbyint functions round their argument to an integer value
| in floating point format, using the current
| rounding direction and without raising the inexact
| exception.
|
| The rint functions do the same, but will raise the
| inexact exception when the result differs in value
| from the argument.
The C definition says:
7.12.9.3 The nearbyint functions
Synopsis
[#1]
#include <math.h>
double nearbyint(double x);
float nearbyintf(float x);
long double nearbyintl(long double x);
Description
[#2] The nearbyint functions round their argument to an
integer value in floating-point format, using the current
rounding direction and without raising the ``inexact''
floating-point exception.
Returns
[#3] The nearbyint functions return the rounded integer
value.
7.12.9.4 The rint functions
Synopsis
[#1]
#include <math.h>
double rint(double x);
float rintf(float x);
long double rintl(long double x);
Description
[#2] The rint functions differ from the nearbyint functions
(7.12.9.3) only in that the rint functions may raise the
``inexact'' floating-point exception if the result differs
in value from the argument.
Returns
[#3] The rint functions return the rounded integer value.
| I can builtinize nearbyint too if it makes sense.
Do we have framework to deal correctly with current rounding mode?
I not, I would say, leave it as is until we have the appropriate
machinery.
| I am bit confused by
| rint. Does it imply that rint will raise exception for any non-integral
| arugment?
And depending on the rounding mode.
-- Gaby
next prev parent reply other threads:[~2002-11-07 9:33 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-05 9:14 Simplify floating point conversions Jan Hubicka
2002-11-05 9:38 ` Richard Henderson
2002-11-05 9:42 ` Jan Hubicka
2002-11-06 1:23 ` Simplify floating point conversions II Jan Hubicka
2002-11-06 3:08 ` Michael Matz
2002-11-06 4:36 ` Jan Hubicka
2002-11-06 9:54 ` Jan Hubicka
2002-11-06 10:09 ` Richard Henderson
2002-11-06 13:11 ` Jan Hubicka
2002-11-06 13:19 ` Jan Hubicka
2002-11-06 13:35 ` Gabriel Dos Reis
2002-11-06 13:36 ` Jan Hubicka
2002-11-06 14:06 ` Gabriel Dos Reis
2002-11-06 14:29 ` Converting floor to rint Jan Hubicka
2002-11-06 14:47 ` Richard Henderson
2002-11-06 14:53 ` Jan Hubicka
2002-11-06 14:55 ` Gabriel Dos Reis
2002-11-07 1:21 ` Jan Hubicka
2002-11-07 1:32 ` Jakub Jelinek
2002-11-07 1:33 ` Gabriel Dos Reis [this message]
2002-11-07 1:44 ` Jan Hubicka
2002-11-07 1:52 ` Jakub Jelinek
2002-11-07 1:54 ` Jan Hubicka
2002-11-07 2:04 ` Jan Hubicka
2002-11-07 4:47 ` Gabriel Dos Reis
2002-11-07 4:56 ` Jan Hubicka
2002-11-07 5:14 ` Andreas Schwab
2002-11-07 5:27 ` Gabriel Dos Reis
2002-11-07 5:31 ` Jan Hubicka
2002-11-07 5:35 ` Andreas Schwab
2002-11-07 5:22 ` Gabriel Dos Reis
2002-11-07 5:43 ` Andreas Schwab
2002-11-07 6:23 ` Gabriel Dos Reis
2002-11-07 7:01 ` Jan Hubicka
2002-11-07 7:18 ` Gabriel Dos Reis
2002-11-06 13:48 ` Simplify floating point conversions III Jan Hubicka
2002-11-06 14:55 ` Richard Henderson
2002-11-07 2:54 ` Simplify floating point conversions IV Jan Hubicka
2002-11-18 15:01 ` Richard Henderson
2002-11-05 11:14 ` Simplify floating point conversions Geoff Keating
2002-11-06 1:09 ` Jan Hubicka
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=m3smydvi3z.fsf@soliton.integrable-solutions.net \
--to=gdr@integrable-solutions.net \
--cc=aj@suse.de \
--cc=gcc-patches@gcc.gnu.org \
--cc=jh@suse.cz \
--cc=rth@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).