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Re: Floating point problems (accuracy).

From: Chris Lattner <sabre at nondot dot org>
To: Richard Henderson <rth at redhat dot com>
Cc: Phil Prentice <philp dot cheer at btinternet dot com>,James E Wilson <wilson at specifixinc dot com>, gcc at gcc dot gnu dot org,mike at stec dot clara dot co dot uk, gcc-help at gcc dot gnu dot org
Date: Tue, 18 Jan 2005 16:31:05 -0600 (CST)
Subject: Re: Floating point problems (accuracy).
References: <Pine.LNX.4.61.0501181533190.13706@nondot.org><20050118222752.GA5163@redhat.com>

On Tue, 18 Jan 2005, Richard Henderson wrote:

On Tue, Jan 18, 2005 at 03:38:33PM -0600, Chris Lattner wrote:
Note that this is severely slow down your code if it is FP intensive, but
it will produce correct results.
Modulo double rounding of course.

Care to elaborate?

  double X = ..
  float F1 = (float)(float)D;
  float F2 = (float)(double)(float)D;
  float F3 = (float)D;

Aren't F1, F2, and F3 identical?

-Chris

--
http://nondot.org/sabre/
http://llvm.cs.uiuc.edu/

Follow-Ups:
- Re: Floating point problems (accuracy).
  - From: James E Wilson
- Re: Floating point problems (accuracy).
  - From: Richard Henderson

References:
- Re: Floating point problems (accuracy).
  - From: Chris Lattner
- Re: Floating point problems (accuracy).
  - From: Richard Henderson

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