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tech / alt.astronomy / Re: Win32: 0.0 / 0.0 = -NAN ? Win64: 0.0 / 0.0 = -1, #IND ?

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o Re: Win32: 0.0 / 0.0 = -NAN ? Win64: 0.0 / 0.0 = -1, #IND ?R Kym Horsell

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Subject: Re: Win32: 0.0 / 0.0 = -NAN ? Win64: 0.0 / 0.0 = -1, #IND ?
From: R Kym Horsell
Newsgroups: alt.astronomy
Organization: kymhorsell.com
Date: Sat, 30 Apr 2022 20:35 UTC
References: 1
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From: kym...@kymhorsell.com (R Kym Horsell)
Newsgroups: alt.astronomy
Subject: Re: Win32: 0.0 / 0.0 = -NAN ? Win64: 0.0 / 0.0 = -1, #IND ?
Date: Sat, 30 Apr 2022 20:35:04 -0000 (UTC)
Organization: kymhorsell.com
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Skybuck Flying <skybuckflying@gmail.com> wrote:
When exception masks are all enabled to stop the processor from throwing floating point exceptions the following calculation produces a somewhat strange result:

0.0 / 0.0 = -nan

The 754 standard says a floating divide by zero may see the hardware generate
a +ve or -ve infinity. Result is a special NaN.
If the exception is caught s/w may replace the result with something more
sensible like 0 but it might also terminate the process.

The old hack to handle things like this is add a MachEps (smallest number
that is not treated as 0 when added) i.e.  do x/(y+MachEps) .
In s/w you can sometimes do if(nan(result)) ... yourself.

...


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