[Debian-astro-maintainers] Bug#788699: stellarium: Hangs after moving to the past/future by several days

[Tomasz Buchert]

On 15/06/15 01:42, Pawel T. Jochym wrote:
>
> W dniu 15.06.2015 o 01:28, Tomasz Buchert pisze:
> > On 15/06/15 00:46, Tomasz Buchert wrote:
> >> [...]
> >> Could it be a compiler bug that miscompiled the loop for
> >> 0.13.3-2?
> >
> > I take it back, now I think it is not compiler issue (see below).  I
> > extracted the parameters that make the loop infinite and made a
> > minimal program that shows the problem (attached).
> >
> > As you can see, it converges quite rapidly, but finally |E-Ep| stays
> > bigger than 1e-10 and E oscilates between 2 values. An engineer's way
> > to solve it would be to let the loop run for, say, 100 iterations,
> > and if it didn't converge, just show a warning.
> >
> > Cheers,
> > Tomasz
>
> Notice how close to parabolic this orbit is. Maybe we need a better
> algorithm for this range of params. Also numerical conditioning may
> be important in such a case.
>
> P.

Right, there are also divisions by (1 - e) which indeed make it
badly-defined for parabolic orbits. I agree that the algorithm should
be improved to handle this case better.

Oh, I've just found this: https://bugs.launchpad.net/stellarium/+bug/1030913
History repeats itself!

Tomasz
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