Re: [gentoo-dev] [RFC] Forced/automatic USE flag constraints (codename: ENFORCED_USE)

[Ciaran McCreesh <ciaran.mccreesh@googlemail.com>]

On Tue, 30 May 2017 09:42:45 +0200
Alexis Ballier <aballier@gentoo.org> wrote:
> Oh crap, this requires to solve SAT.

The main problem would not be solving SAT, in this case. The problem is
providing the right answer when not enough information is given.
Spitting out a resolution which satisfies every dependency isn't
typically that difficult. Spitting out a resolution which doesn't
just turn off all your use flags and uninstall most of your programs is
the hard part.

> Not hard as in you need a Ph.D. in algorithms to solve it but the
> kind of hardness almost every cryptographic algorithm used today, and
> in the foreseeable future, relies on.

Hrm, you're a bit off, there. SAT solving in practice isn't usually
that bad unless either your inputs are huge or they're deliberately
crafted to be ultra-nasty. Being NP-complete just means that instances
that will hit exponential behaviour exist, not that those instances
will occur in the application area you care about.

-- 
Ciaran McCreesh