| Re: [chrony-dev] [GIT] chrony/chrony.git branch, master, updated. 1.25-pre1-18-g20a4340 |
[ Thread Index |
Date Index
| More chrony.tuxfamily.org/chrony-dev Archives
]
On Tue, Apr 12, 2011 at 09:32:31PM +0100, Ed W wrote:
> On 12/04/2011 15:05, Miroslav Lichvar wrote:
> > Hm, I just had a crash while I was messing with the tick value outside
> > chronyd. The sourcestats stddev ended up as -nan which caused assert
> > failure in find_best_sample_index. It seems to be caused by commit
> > c88801. The sample weight calculation is not stable when there is a
> > large jump in distance, the stddev from the regress function is used
> > in the next weight calculation, which are getting bigger and the
> > stddev smaller until it reaches the limit of double and fails.
> >
> > I'm not sure how to fix it yet.
> >
>
> We live in a finite world? Bound the result?
That would fix the crash, but not the underlying cause which I think
beside bogus values reported in the sourcestats report might have a bad
effect on frequency stability.
It seems the problem is that in the weights calculation is used
weighted variance, which can create the positive feedback. Using
unweighted variance instead should fix it nicely.
--
Miroslav Lichvar
---
To unsubscribe email chrony-dev-request@xxxxxxxxxxxxxxxxxxxx with "unsubscribe" in the subject.
For help email chrony-dev-request@xxxxxxxxxxxxxxxxxxxx with "help" in the subject.
Trouble? Email listmaster@xxxxxxxxxxxxxxxxxxxx.