Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!wuarchive!rex!samsung!emory!stiatl!srchtec!johnb
From: johnb@srchtec.UUCP (John Baldwin)
Newsgroups: comp.lang.c
Subject: Re: Mircosoft C V5.1 floating point problem.
Message-ID: <172@srchtec.UUCP>
Date: 9 Aug 90 14:22:49 GMT
References: <5587@castle.ed.ac.uk>
Organization: search technology, inc.
Lines: 27

In article <5587@castle.ed.ac.uk> elee24@castle.ed.ac.uk (H Bruce) writes:
>I am working on a large program that has suddenly starting crashing with
>the following error:
>
>floating pointing exection 
>M6101 invalid
> [...deleted...]
>The manual says it is caused by operating on a NAN (not a number !) which is
>not much help.

Can you post some code fragments that show what you're doing in floating point
just prior to the error?  To oversimplify, NAN is a representation chosen to
provide more information than a simple underflow.  A recent article in
_IEEE_Computer_ suggested an enhanced FP representation including some extra
values such as +RAIL and -RAIL (like an op-amp)... you might want to read it.

In general, you've probably reached some kind of intermediate underflow or
overflow condition if you're getting a NAN.

QUESTION: are you using the fast-fp library, the 8087 emulator, or a real
          hardware 8087???  Maybe something isn't getting initialized right?

-- 
John T. Baldwin                      |  johnb@srchtec.uucp
Search Technology, Inc.              |  johnb%srchtec.uucp@mathcs.emory.edu
standard disclaimer:                 |  ...uunet!samsung!emory!stiatl!srchtec..
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