Re: Bug#385670: apt is calculation wrong dependencies
On Thu, Sep 21, 2006 at 01:58:44AM +0200, Daniel Leidert <daniel.leidert.spam@gmx.net> was heard to say:
> But if xserver-xorg-video-all is not going to be installed, all the
> xserver-xorg-video-* packages should not be newly installed. A second
> thought: The installed xserver-xorg-video-* provide
> xserver-xorg-video-all and when they are upgraded they provide
> xserver-xorg-video-1.0, so the dependecies of xserver-xorg should be
> fulfilled. The second issue seems to prove, what Goswin said. But the
> other issue is probably based on another bug.
The problem here is that the apt dependency resolver is not very good;
it will happily install A, install a B that's required by A, then remove
A in favor of an alternative C -- without removing B as well. As I
never really understood how the apt resolver works, I don't know if it
can be fixed without a major overhaul. I do know that aptitude's
resolver never encounters the problem described above. [0]
Daniel
[0] I think it's possible in principle to have non-minimal solutions
from aptitude, but even the theoretical examples I came up with
require convoluted dependency chains, and I've never seen it in
practice.
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