Re: [gentoo-dev] example conversion of gentoo-x86 current deps to unified dependencies

[Ben de Groot]

On 16 September 2012 21:15, Brian Harring <ferringb@×××××.com> wrote:
> On Sun, Sep 16, 2012 at 03:39:22PM +0800, Ben de Groot wrote:
>> Thanks. I have given it a quick overview for the qt herd. I still
>> don't see what using DEPENDENCIES adds to what we do now with separate
>> *DEPEND variables. I see no convincing reason to change what we do.
>
> Ok, so here's some stats: in the tree, we have 31360 ebuilds, and 194
> eclasses; grand total of 31554 sources of metadata content (I say
> metadata since vapier has eblits in use which are just phase
> functions- I'm not scanning those intentionally).
>
> Doing some simple scans of the tree, here's some stats; note these
> stats are duplicated in the glep (they're nice selling points, thus
> might as well):
>
> 1) 746 hits in the tree for COMMON_DEPEND; that's 2%, and the usages
> I'm aware of have been for literally, what it sounds like- depends
> that are both DEPEND and RDEPEND.
>
> 2) scanning for assignments of RDEPEND=.*|$\{?DEPEND\}? gets a hit on
> 5343 unique sources.  Searching for the inverse gets a hit on 10008
> unique sources.  Meaning that right there, ~48.6% of the tree is
> duplicating deps between the two forms.  This puts us to 16083 unique
> sources in the tree that would benefit in some form (~51%).
>
> 3) What's interesting about that 51% is the eapi groupings; in EAPI4,
> the autosetting of RDEPEND="${RDEPEND:-${DEPEND}}" was discontinued.
> Roughly 50% of the initial 51% match is EAPI4; the rest are eapi0-3.
>
> 4) Again, keep in mind that the grep's in use above are single line
> matches- I'm definitely missing some ebuilds, and for complex
> dependencies that are appended/set by the eclass, likely missing a lot
> of that too.
>
> So... basically, people are already doing this manually with their own
> intermediate vars.

And this works fine, so it doesn't warrant a cosmetic change.

> Just a rough but mildly entertaining stat there's basically 8.38MB
> worth of normalized, literal fricking dependency; using a crappy algo
> (rather than a human doing the deps who can do it better), 37.4%
> (3.1MB) of that is removed via going to dependencies.  It goes
> without saying that this would be a helluva lot less torturous on a
> proper PM implementation that parses the tree once, and renders- let
> alone repoman being able to avoid repeat scans of things it already
> has examined.
>
> Mind you, portage doesn't do that, but this would be good incentive to
> do a proper tree. :)

PM internals are not really relevant to us developers. Just make it work... ;-)

The current *DEPEND system works. So again, I don't see a convincing
reason for change.

>> As I've said before on IRC, we need a good costs/benefits overview.
>> Right now I only see costs (migrating ebuilds and eclasses) and no
>> benefits.
>
> Offhand... I wouldn't be pushing for this if I didn't think this would
> be a boon over all- both for devs, and PMs.
>
> I think the actual 'cost' probably got lost in the noise of the
> various flames; what I'm proposing is basically zero cost for devs, it
> shoves the work to the PM, leaving the option for devs to do a more
> fine grained form if they can.

As soon as you expose this to devs (ebuild/eclass developers and
maintainers), you can no longer talk about zero cost.

We either have the enormous cost of migrating the whole tree to the
new system — which I understand you are not advocating because of the
cost; or we have the (lower, but not zero) cost of maintaining two
systems in the tree, which developers will have to know and understand
in order to be able to deal with them correctly. The latter will also
make eclasses needlessly more complex.

So in my opinion it is folly either way, because the costs are high,
and the benefits only cosmetic.

> I'm starting a seperate thread w/ a glep for this; I think you should
> take a look at the exact details of the specification including how
> DEPEND/RDEPEND/PDEPEND are handled in parallel to DEPENDENCIES (short
> version: if existent, they're automatically folded into DEPENDENCIES
> in my proposal); the end result is basically zero pain transition,
> while enabling us to start getting gains.

Which gains? The glep only talks about cosmetics...

-- 
Cheers,

Ben | yngwin
Gentoo developer
Gentoo Qt project lead, Gentoo Wiki admin