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Date: Thu, 21 Jul 2011 16:43:46 -0400
From: =?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>
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Subject: Re: Arithmetic overflow checking
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On 7/8/2011 1:23 PM, Gene Wirchenko wrote:
> On Thu, 07 Jul 2011 17:51:06 -0700, Peter Duniho
> <NpOeStPeAdM@NnOwSlPiAnMk.com>  wrote:
>> I would not worry about the "simple" or "efficient" criteria.  IMHO, if
>> one is deciding to apply overflow checking to every computation, one has
>> already abandoned the hope of efficiency.
>
>       Not necessarily.  If a rocket ends up being destroyed as a
> result, having the computing go a bit slower to save having to build
> another rocket would have been more efficient.

I am pretty sure that Peter was talking about the efficiency of
the computer program.

>                                                Unfortunately, this is
> not a made-up example.  See:
>            http://en.wikipedia.org/wiki/Ariane_5_Flight_501
> In the subsequent investigation, the cause of the problem was
> recreated.

It was an integer overflow. But the real problem was a bad software
process. If there had not been an integer overflow there could have
been many other types of problems.

>       Turn on those run-time checks unless speed *REALLY* is of
> paramount importance.  It usually is not.

I would agree with that.

Arne