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Return-Path: <tege@matematik.su.se>
X-Address: Department of Mathematics, Stockholm University
S-106 91 Stockholm
SWEDEN
X-Phone: int+46 8 162000
X-Fax: int+46 8 6126717
X-Url: http://www.matematik.su.se
To: Paul.Zimmermann@loria.fr (Paul Zimmermann)
Subject: Re: Paul Zimmermann: changing rounding mode on Alpha with gcc
In-reply-to: Your message of "Wed, 17 Feb 1999 17:44:33 +0100."
<199902171644.RAA03746@leopold.loria.fr>
Date: Wed, 17 Feb 1999 19:21:05 +0100
From: Torbjorn Granlund <tege@matematik.su.se>
I once thought I had found a bug, but it was only the peculiar rounding
to nearest rule when we are just in the middle of two machine number,
where we round to the even lsb instead of rounding to infinity as we do
in math.
Been there... ;-) Note that it is simple to get this right with a single
logical expression. Perhaps this code,
roundup = (((m >> (EXP_BITS - 1)) & 1)
& (((m & STICKY_MASK) != 0) | ((m >> EXP_BITS) & 1)));
from my P754 library shows the idea.
Tobjörn
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