Sat Solver

OK, in case you haven't heard about what's coming up in the package management stack in openSUSE 11.0, feature is Sat Solver. Here is the link on it http://en.opensuse.org/Libzypp/Sat_Solver


Let me say this, jbj from rpm-5 likes it some much, he wants to incorporate this into rpm-5.

Sat Solver is written in C. I strongly suggest you get to know libzypp and sat solver, so you can better handle your system.

I already posted a similar topic - http://forums.suselinuxsupport.de/in...howtopic=64995

Great! And I did see it. This is different. I'm not talking speed, but dependency resolution. So, since I did not want to steal your thread, and the topic is different, I started a new thread.

For those of you interested in the code of sat solver, here ya go; http://svn.opensuse.org/svn/zypp/trunk/sat-solver/

Sat solver is written in C.

I like looking at the code, as the code tells me how it works. It's a great way to better understand the howto, or gain tips and tricks.

If you wish to contribute, and know C, then look at this http://svn.opensuse.org/svn/zypp/trunk/sat...er/doc/PLANNING

Open issues

1. Architecture handling
Ensure 'best' architecture is choosen on fresh install [DONE]
Ensure update keeps architecture [DONE]
Ensure dist-upgrade chooses 'best' architecture

2. Logging
Improve logging so solver decisions are comprehensible

3. weak dependencies [DONE]
to support 'recommends'
mark rules as 'weak' so trackback on assignment conflict can
disable such rules and continue

4. reverse dependencies [DONE]
essentialfor, supplements
will be almost for free when weak rules are implemented
still rules have to be marked 'reverse' for logging and proposal
correctness

5. Syntax
Define syntax for 'boolean expression' capability
How to express and, or, not within a .spec file ?
See 'extended reldeps' below

6. Locale supplements [DONE]
support local(de), locale(de,at,ch) and locale(<package>:de)
eventually extend 'package' to reldep, e.g. locale(package > 5.3-2:de)

7. Modalias supplements [DONE]
support modalias(<modalias-regexp>) and modalias(<package>:<modalias-regexp>)
eventually extend 'package' to reldep, e.g. modalias(package >5.3-2:<modalias-regexp>)

8. Architecture rules
architecture-specific dependencies

9. Locks [NOT A SOLVER ISSUE]
ability to keep packages at a specific version
ability to prevent installation of specific packages / reldep

10. Extended reldeps [DONE IN PART]
Boolean AND, OR
Compare architecture
Compare namespace

11. Syntax of dependencies [DONE]
Two types of conjunctions:

1. "a>5 AND b>5" => a and b can be provided by different solvables
2. "a>5 WITH b>5" => 'and' operation but a and b are provided by same
solvable. (the 'with' operator is a naming
proposal)

12. Boolean expressions
Full range of boolean operators (AND, OR, NOT) and
conditionals (IF/THEN/ELSE) for dependencies.

13. Source priorities [DONE IN PART]
Prefer solvables from specific sources

14. split-provides
Support for package splits, renames

15. better solution proposals
if transactions are unsolvable, offer understandable proposals what
to change to make the transaction solvable.

16. multiple solutions
compute all possible solutions and rank them

17. solution ranking
configurable solution ranking
best sources, newest packages, smallest download size,
smallest install size, lowest number of installs, lowest number of
updates, lowest number of removals, prefer most popular packages,
prefer vendor,
[/b]

sat solver introduces a new format for metadata called helix. I can't tell you much about it yet, but here's the code. http://svn.opensuse.org/viewcvs/zypp/trunk...amp;view=markup