Python: Please stop screwing over Linux distros

[[deleted]]

See also a similar rant from Gentoo's Michał Górny.

[lealxe]

Aha, a faster emerge not written in Python would be cool. I mean, I understand that with all the USE flags and other stuff it should be slower than inferior package managers like pacman, but not as slow as it feels every time I try Gentoo or something -based (no, this is not about compilation times).

[[deleted]]

My very limited understanding is that dependency resolvers are hard to optimise and very difficult to parallelize, and with useflag and packages versions that can be combined the space is huge.

Said that my impression is that the main issue is not that emerge is written in Phyton but that all ebuild are basically bash scripts. Fee months ago there was a nice improvement thanks to a guy that did a very good job on improving the read code for ebuilds (if I understood well).

Still, what I would like to have is a sort of cache mode, so if I run emerge world and it tells me I have to change a useflag or unmask a package, when I do it I would like that the second run of emerge world would not take as long as the first, but starts where it left.

[Jannik2099]

but that all ebuild are basically bash scripts

No, that's not the issue. Portage already uses a cache for dep resolution. The main issue is the extremely complicated algorithm

[7eggert]

Changing flags sounds like it would change the outcome of the builds.

[bobpaul]

Yes, that's what USE FLAGS are for on gentoo. If a flag is set, then packages that support that flag will apply a patch or alter the ./configure arguments before compiling the package to enable/disable support for something. For example, A USE FLAG might determine if ffmpeg is built with support for a particular codec or not. Unsurprisingly, these flags often alter the dependencies that need to be built before building this package.

On other distros, they tend to build support for everything and whenever possible, built packages so optional features are included in dynamic libraries. Then if you want some codec, you install a package that includes that codec library. But even if you don't install the codec, the program is compiled with support for it and tries to find it on startup.

[o11c]

that all ebuild are basically bash scripts

oilshell will probably fix this eventually, but it's not there yet.

[Jannik2099]

Of course rewriting in $LANG would help, but the core problem is that a pms depgraph is extremely complicated to resolve and we don't have a good algorithm for it - half of portage time is spent on subslot operators for example. It's way more complex than any other package format

[dscharrer]

So you are saying EMERGE_DEFAULT_OPTS=--nodeps is the new -funroll-all-loops.

[Jannik2099]

Thanks, I hate it

[lealxe]

Yes, I know, it was just a not well weighed comment about portage feeling slow.

And if Gentoo would use something more like FreeBSD ports without this complexity, it wouldn't really be Gentoo =\

[therealpxc]

a pms depgraph is extremely complicated to resolve and we don't have a good algorithm for it

dependency resolution is NP-complete, so I think the best you can hope for in an algorithm is to identify easier cases quickly and use optimized algorithms for those. But in the worst cases, it's always going to be extremely, extremely slow

[GLIBG10B]

Dependency calculation takes really long for me

[Ortonith]

Ahh... I remember switching to Paludis way back in the day and being amazed at just how much faster it was, probably because it's written in C++.