Subject: Dan-0411 Bug & Computational Chemistry

From: "Gustavo A. Mercier Jr" <[email-masked]>
Date: Mon, 30 Jun 1997 09:21:31 -0400 (EDT)

HI!

As some of you may know, a bug has been uncovered in the PPro and PII
chips. See http://www.x86.org/secrets/Dan0411.html

For those following Usenet this is not news. Nevertheless,
I wonder what impact this will have in CCL applications
using PPro and PII chips. I have not seen our community
comment of this so I am putting on the "table" :-)

The bug is really a deviation from the IEEE Floating Point Standards.
The incorrect error flag is set when an float to integer conversion
results in an overflow.

Does anybody have any experience with or comments on the impact
of this bug in common applications like Amber, Gaussian, ADF, etc.?

Bye!

-- 
                                      ("`-/")_.-'"``-._
Gustavo A. Mercier,Jr.,MD,PhD         (. . `) -._    )-;-,_() 
Division of Nuclear Medicine          (v_,)'  _  )`-.\  ``-
Dept. of Radiology                    _;- _,-_/ / ((,'
University of Pennsylvania           ((,.-'  ((,/
3400 Spruce St.                  [email-masked]
Philadelphia, PA 19104         215-662-3069/3091 fax: 215-349-5843

---

From: Konrad Hinsen <[email-masked]>
Date: Mon, 30 Jun 1997 16:46:21 +0200

> of this bug in common applications like Amber, Gaussian, ADF, etc.?

For Fortran programs like the ones you mentioned, the treatment
of floating point errors is left to the Fortran library provided
by the compiler. As far as I know the Fortran standard does not
specify the response to such errors; I suppose most libraries would
terminate the program with an error message.

Anyway, a program that would ever let such a situation happen would
have a bug. It wouldn't work on other machines, for example. So I am
not really worried by this problem. It matters only to programs
that provide some form of exception handling, but Fortran programs
can't do that.
-- 
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