Debians commandline package manager https://git.kalnischkies.de/apt/atom?h=main 2026-01-31T16:30:20Z 2026-01-31T16:30:20Z Julian Andres Klode jak@debian.org 2025-12-29T17:47:15Z urn:sha1:1fbb857b6b2cbddcea9e8b03aa0c766c72e91f34 Instead of tracking dependencies and reverse dependencies, install classical watchers. This vastly streamlines the propagation code and allows us to easily switch to literals in the next step. This implementation watches _all_ solutions rather than using the modern 2-watched literals scheme or the intermediate head/tail watchers. Ultimately a more effective watcher scheme would be interesting but not a significant priority seeing as most of the solver runtime is spent not in propagation but in problem translation. decision trees -------------- The new watchers produce slightly different decision trees, sometimes subtly changing solutions. Notably in various observed examples in Ubuntu 25.04, courier was installed as an MTA instead of postfix: The old decision tree was: apcupsd:amd64 -> mailutils:amd64=1:3.18-1 -> mailutils:amd64 -> postfix:amd64=3.9.1-10ubuntu1 The new decision tree is: lsb:amd64 -> lsb-core:amd64 -> courier-mta:amd64=1.3.13-1 The difference here being that lsb-core declares a mail-transport-agent dependency whereas mailutils depends on `default-mta | mail-transport-agency`; but both are effectively subject to selection at similar time. Further work is needed to optimize selection. A notable choice may also be to deal with broken packages like lsb-core that declare dependencies solely on a virtual package by reconstructing the default provider for that package utilizing default-* dependencies or similar notions. Likewise in the test suite, explanations are different in some uninstallable cases. backtracking ~~~~~~~~~~~~ The following major changes were observed in the 25.04 test suite: -tmp/regression-remove/07f0a068-36c2-11f0-b7c1-fa163e171f02:18 +tmp/regression-remove/07f0a068-36c2-11f0-b7c1-fa163e171f02:3 -tmp/regression-remove/32078f70-3734-11f0-a75a-fa163ec8ca8c:64 +tmp/regression-remove/32078f70-3734-11f0-a75a-fa163ec8ca8c:19 Other test cases showed little deviation, +/- 1, generally the same amount of backtracking. performance ~~~~~~~~~~~ Running Ubuntu's regression test suite resulted in no significant performance difference being observable. Before: 290s user time; 16.66% solver After: 299s user time; 17.36% solver Tests where run with make -j 8 and solver performance extracted perf report --symbol-filter=ResolveExternal --stdio 2026-01-05T21:20:24Z Julian Andres Klode jak@debian.org 2025-12-28T15:56:28Z urn:sha1:21d099878ed8c34f3b13747bcec380e0402e57a3 The previous use of decision here conflicted with the use of decision level and the general notion of having made a decision, because the assignment might have been propagated as a matter of fact. 2025-03-08T22:18:05Z Julian Andres Klode julian.klode@canonical.com 2025-03-06T19:07:30Z urn:sha1:3967b75ae4a10d0d79560dfecb8eb210aad4f4f2 Introduce a new function, LongWhyStr() that returns a longer reason for why something is being installed (or not). This does the same path walk as the other function does, but it renders the clauses at each level, and one per line, so the whole output is a lot more informative. It is a separate function to keep the existing debug messages use the simple single line implication graph We remove the other special case in AddWork() for empty solutions to mke use of the general case in Solve() instead, and then adapt the case in Solve() to the same case as in Enqueue(). This also happens to fix the bug that when we encountered an empty clause we just printed the clause had no solution, but not how we got to install the package with the clause. Adapt the test suite for the changes which is an annoying amount of paperwork. 2025-02-14T18:04:56Z Julian Andres Klode julian.klode@canonical.com 2025-02-05T19:11:35Z urn:sha1:f870bd44522d195199987b0e073d495eed060495 If a dependency can be satisfied by all versions of a package, add the package to the clause instead of the version object. This works only if there are no providers for the package: Providers are quite hard to enumerate over and make sure that all versions of a package satisfy the provider dependency. Implement arbitrary selection between packages and versions for the CompareProviders class: We pick the best version for each package and then pit them against each other. 2025-01-30T13:50:15Z Julian Andres Klode julian.klode@canonical.com 2024-11-02T12:55:39Z urn:sha1:3523efb15d48ce3c6f9212f50dfc892497ba9dcb Instead of directly propagating in a recursive fashion, queue propagations in a queue and work on them in a loop per the miniSAT paper. We call Propagate() only at the end of the FromDepCache() function and then in the Solve loop. Delaying the initial propagation means that we get a stronger reasoning: Assume you have x->a->b->c, y->c and you install x,y: - Previously we traversed: x, y, x->a, a->b, b->c, (y->c) - but now we traverse: x, y, x->a, y->c, a->b, (b->c) Notably c now has the implication y->c instead of x->a->b->c. Inside the solver we need to call Propagate in a loop: Propagating facts can fail and we then backtrack. If backtracking is succesful, we have gained a new fact to propagate. 2024-05-24T15:01:35Z Julian Andres Klode julian.klode@canonical.com 2024-05-19T18:04:47Z urn:sha1:b5997949909ee9d5e9981c8311aea97c7b2620fd Highlights: - test-bug-618848-always-respect-user-requests: (Do not) Support 3.0 solver A manually installed package is never removed just because we request the removal of its dependency in solver3. - test-bug-657695-resolver-breaks-on-virtuals: Support 3.0 solver For manually installed packages, solver 3.0 would require some new xserver-xorg-video-driver to Conflict+Replace+Provides the old one (once the logic is implemented), but that does seem reasonable. - test-bug-720597-build-dep-purge: Support 3.0 solver This needs a simple aptmark auto because pkga is removed by the build-dep. But further adjustments are necessary because it weirdly tested for no autoremovable packages before installing pkgc. - test-bug-960705-*: Support 3.0 solver Bit awkward to deal with; notably the protect to conflict doesn't actually work anymore and that is a feature these days. 2021-11-17T16:32:18Z Julian Andres Klode julian.klode@canonical.com 2021-11-17T15:29:09Z urn:sha1:891efe3b201a104445ea723a3a5b9b434a78c364 Suggesting the removal of Essential and Protected packages as a solution leads to situations where YouTubers end up removing their desktop. Let's not remove such packages ourselves. 2015-12-19T22:04:34Z David Kalnischkies david@kalnischkies.de 2015-12-15T16:20:26Z urn:sha1:3abb6a6a1e485b3bc899b64b0a1b7dc2db25a9c2 This doesn't allow all tests to run cleanly, but it at least allows to write tests which could run successfully in such environments. Git-Dch: Ignore 2015-03-16T17:01:54Z David Kalnischkies david@kalnischkies.de 2015-03-09T23:59:44Z urn:sha1:25b86db159fbc3c043628e285c0c1ef24dec2c6e We use test{success,failure} now all over the place in the framework, so its only consequencial to do this in the situations in which we test for a specific output as well. Git-Dch: Ignore 2011-02-15T15:04:46Z Michael Vogt mvo@debian.org 2011-02-15T15:04:46Z urn:sha1:adee3bae782f5b7d83819bf92ab419663ef4ee64