Re: pointer questions

["Jeffrey R. Carter" <spam@spam.com>]

Dr. Adrian Wrigley wrote:

> This is exactly the situation.  The "Things" were about 36 bytes each
> and I changed to having around 20 million pointers to things.
> Single bit errors in pointers had a much more significant effect
> than single bit errors in "Things" (which tended to be ignored
> for various reasons).

Right. I don't think I'd ever want to consider a continually running program 
with 20 million pointers. What did that buy you over the single-pointer version?

> well speculated! (was it so unclear?)

Thanks. I wasn't clear what was causing the crashes at 1st. With a little more 
thought, it seemed likely it was dereferencing a pointer with a flipped bit.

> Another "feature" I observed was that files could stay cached by the OS
> for months, and accumulate the occasional single-bit error.  But when you
> evict the cached pages and read the data again, the errors disappear.
> Plenty of scope for very rare Heisenbugs.

Interesting. It's not something you normally have to think about; most programs 
don't run for that long. I remember a noticeable # of bit errors during a solar 
maximum about 1980, but don't recall it repeating in 1991 or 2002.

-- 
Jeff Carter
"In the frozen land of Nador they were forced to
eat Robin's minstrels, and there was much rejoicing."
Monty Python & the Holy Grail
70