Re: How would Ariane 5 have behaved if overflow checking were not turned off?

["robin" <robin51@dodo.com.au>]

KK6GM wrote in message ...
>On Mar 16, 11:29 am, Hyman Rosen <hyro...@mail.com> wrote:
>> How about this for the essential flaw: Does it really make
>> sense to create data types in your program that are so closely
>> tied to external factors like rocket speed limits and angles?
>> Why not use data types that could handle the full range of
>> values from the sensor? The approach used seems incredibly
>> brittle, and in fact turned out to be so.

>Here's the alternative, for the Ariane situation.  A float value gets
>converted to a 16-bit integer.  The float value is too big to fit
>(let's say it's 33000).  What 16-bit int will that get converted to?
>-31000?

Would you believe 32767 (with appropriate sign).
That keeps the processor running, and it's slightly less than the
actual value.

>  Some random value?  How does continuing along with bogus data
>make the situation better?

It keeps the processor running, and the mission going.

>  Will the control loops really work OK with
>bogus feedback data?

>If you have determined via thorough analysis that the variable in
>question can only _ever_ have a valid range of e.g. -20000 to 20000,
>and it goes to 33000, what _is_ the right action?

Set it to 32767 with sign.
Alterrnativelty, use floating-point.