Pivoting

[Hal Murray]

Stromeko at Nexgo.DE said:
> Even if you only consider physical hardware, based on the  projected
> lifetime of automotive qualified systems (15 years or longer)  you have to
> expect a much longer actual lifetime in the field. 

ianbruene at gmail.com said:
> 19:14 <ianbruene> One should always put a multiplier on one's
> estimate of how long their code will be in use: code expected to
> last for 5 years lasting 20 got us Y2K. ...

Right.  I think there are two issues tangled up here.

One is that there is a tradeoff between building in a long lifetime and 
catching problems during a normal lifetime.  I'm not sure which is more 
likely.  Consider what happens if a server gets fired up with a broken clock 
and starts answering all requests with 1970.  Do you want to reject that, or 
pivot it to 2036?

The other is that there really is a 20 year rollover with old GPS units.  
(Newer units have 13 bits.)  I think that turns into 3 choices:
  Don't support really old GPS units.
  Advertise the default lifetime.
  Allow the user to specify the pivot time and/or life time, either at build 
time or at run time or both.

---------

How long have computers been used in cars?  When did they start using 
software complicated enough to support a system time-of-day clock?  What's 
their track record for long lifetime bugs?


-- 
These are my opinions.  I hate spam.