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https://git.launchpad.net/~ubuntu-release/britney/+git/britney2-ubuntu
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installability: Exploit equvialency to reduce choices
For some cases, like aspell-dictionary, a number of packages can satisfy the dependency (e.g. all aspell-*). In the particular example, most (all?) of the aspell-* look so similar to the extent that reverse dependencies cannot tell two aspell-* packages apart (IRT to installability and co-installability). This patch attempts to help the installability tester by detecting such cases and reducing the number of candidates for a given choice. Reported-In: <20140716134823.GA11795@x230-buxy.home.ouaza.com> Signed-off-by: Niels Thykier <niels@thykier.net>
This commit is contained in:
Niels Thykier
parent
33049b2b1c
commit
e2ac08c62e
@ -12,6 +12,7 @@
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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from collections import defaultdict
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from contextlib import contextmanager
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from britney_util import ifilter_except, iter_except
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@ -28,7 +29,7 @@ class _RelationBuilder(object):
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self._new_breaks = set(binary_data[1])
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def add_dependency_clause(self, or_clause):
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def add_dependency_clause(self, or_clause, frozenset=frozenset):
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"""Add a dependency clause
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The clause must be a sequence of (name, version, architecture)
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@ -48,12 +49,12 @@ class _RelationBuilder(object):
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binary = self._binary
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itbuilder = self._itbuilder
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package_table = itbuilder._package_table
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reverse_package_table = itbuilder._reverse_package_table
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okay = False
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for dep_tuple in clause:
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okay = True
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reverse_relations = itbuilder._reverse_relations(dep_tuple)
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reverse_relations[0].add(binary)
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rdeps, _, rdep_relations = itbuilder._reverse_relations(dep_tuple)
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rdeps.add(binary)
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rdep_relations.add(clause)
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self._new_deps.add(clause)
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if not okay:
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@ -193,7 +194,7 @@ class InstallabilityTesterBuilder(object):
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if binary in self._reverse_package_table:
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return self._reverse_package_table[binary]
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rel = [set(), set()]
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rel = [set(), set(), set()]
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self._reverse_package_table[binary] = rel
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return rel
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@ -227,18 +228,21 @@ class InstallabilityTesterBuilder(object):
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# operations in _check_loop since we only have to check one
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# set (instead of two) and we remove a few duplicates here
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# and there.
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#
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# At the same time, intern the rdep sets
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for pkg in reverse_package_table:
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if pkg not in package_table:
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raise RuntimeError("%s/%s/%s referenced but not added!" % pkg)
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if not reverse_package_table[pkg][1]:
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# no rconflicts - ignore
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continue
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deps, con = package_table[pkg]
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if not con:
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con = intern_set(reverse_package_table[pkg][1])
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else:
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con = intern_set(con | reverse_package_table[pkg][1])
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package_table[pkg] = (deps, con)
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rdeps, rcon, rdep_relations = reverse_package_table[pkg]
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if rcon:
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if not con:
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con = intern_set(rcon)
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else:
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con = intern_set(con | rcon)
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package_table[pkg] = (deps, con)
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reverse_package_table[pkg] = (intern_set(rdeps), con,
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intern_set(rdep_relations))
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# Check if we can expand broken.
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for t in not_broken(iter_except(check.pop, KeyError)):
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@ -308,8 +312,95 @@ class InstallabilityTesterBuilder(object):
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# add all rdeps (except those already in the safe_set)
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check.update(reverse_package_table[pkg][0] - safe_set)
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eqv_table = self._build_eqv_packages_table(package_table,
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reverse_package_table)
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return InstallabilitySolver(package_table,
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reverse_package_table,
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self._testing, self._broken,
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self._essentials, safe_set)
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self._essentials, safe_set,
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eqv_table)
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def _build_eqv_packages_table(self, package_table,
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reverse_package_table,
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frozenset=frozenset):
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"""Attempt to build a table of equivalent packages
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This method attempts to create a table of packages that are
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equivalent (in terms of installability). If two packages (A
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and B) are equivalent then testing the installability of A is
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the same as testing the installability of B. This equivalency
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also applies to co-installability.
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The example cases:
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* aspell-*
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* ispell-*
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Cases that do *not* apply:
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* MTA's
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The theory:
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The packages A and B are equivalent iff:
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reverse_depends(A) == reverse_depends(B) AND
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conflicts(A) == conflicts(B) AND
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depends(A) == depends(B)
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Where "reverse_depends(X)" is the set of reverse dependencies
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of X, "conflicts(X)" is the set of negative dependencies of X
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(Breaks and Conflicts plus the reverse ones of those combined)
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and "depends(X)" is the set of strong dependencies of X
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(Depends and Pre-Depends combined).
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To be honest, we are actually equally interested another
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property as well, namely substitutability. The package A can
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always used instead of B, iff:
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reverse_depends(A) >= reverse_depends(B) AND
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conflicts(A) <= conflicts(B) AND
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depends(A) == depends(B)
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(With the same definitions as above). Note that equivalency
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is just a special-case of substitutability, where A and B can
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substitute each other (i.e. a two-way substituation).
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Finally, note that the "depends(A) == depends(B)" for
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substitutability is actually not a strict requirement. There
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are cases where those sets are different without affecting the
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property.
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"""
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# Despite talking about substitutability, the method currently
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# only finds the equivalence cases. Lets leave
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# substitutability for a future version.
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find_eqv_table = defaultdict(list)
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eqv_table = {}
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for pkg in reverse_package_table:
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rdeps = reverse_package_table[pkg][2]
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if not rdeps:
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# we don't care for things without rdeps (because
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# it is not worth it)
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continue
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deps, con = package_table[pkg]
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ekey = (deps, con, rdeps)
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find_eqv_table[ekey].append(pkg)
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for pkg_list in find_eqv_table.itervalues():
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if len(pkg_list) < 2:
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continue
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if (len(pkg_list) == 2 and pkg_list[0][0] == pkg_list[1][0]
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and pkg_list[0][2] == pkg_list[1][2]):
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# This is a (most likely) common and boring case. It
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# is when pkgA depends on pkgB and is satisfied with
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# any version available. However, at most one version
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# of pkgB will be available in testing, so other
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# filters will make this case redundant.
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continue
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eqv_set = frozenset(pkg_list)
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for pkg in pkg_list:
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eqv_table[pkg] = eqv_set
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return eqv_table
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@ -24,7 +24,7 @@ from britney_util import (ifilter_only, iter_except)
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class InstallabilitySolver(InstallabilityTester):
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def __init__(self, universe, revuniverse, testing, broken, essentials,
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safe_set):
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safe_set, eqv_table):
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"""Create a new installability solver
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universe is a dict mapping package tuples to their
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@ -44,7 +44,7 @@ class InstallabilitySolver(InstallabilityTester):
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(simplifies caches and dependency checking)
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"""
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InstallabilityTester.__init__(self, universe, revuniverse, testing,
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broken, essentials, safe_set)
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broken, essentials, safe_set, eqv_table)
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def solve_groups(self, groups):
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@ -20,7 +20,7 @@ from britney_util import iter_except
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class InstallabilityTester(object):
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def __init__(self, universe, revuniverse, testing, broken, essentials,
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safe_set):
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safe_set, eqv_table):
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"""Create a new installability tester
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universe is a dict mapping package tuples to their
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@ -51,6 +51,7 @@ class InstallabilityTester(object):
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self._essentials = essentials
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self._revuniverse = revuniverse
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self._safe_set = safe_set
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self._eqv_table = eqv_table
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# Cache of packages known to be broken - we deliberately do not
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# include "broken" in it. See _optimize for more info.
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@ -235,8 +236,9 @@ class InstallabilityTester(object):
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never.update(ess_never)
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# curry check_loop
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check_loop = partial(self._check_loop, universe, testing, musts,
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never, choices, cbroken)
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check_loop = partial(self._check_loop, universe, testing,
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self._eqv_table, musts, never, choices,
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cbroken)
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# Useful things to remember:
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@ -359,8 +361,9 @@ class InstallabilityTester(object):
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return verdict
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def _check_loop(self, universe, testing, musts, never,
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choices, cbroken, check):
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def _check_loop(self, universe, testing, eqv_table, musts, never,
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choices, cbroken, check, len=len,
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frozenset=frozenset):
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"""Finds all guaranteed dependencies via "check".
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If it returns False, t is not installable. If it returns True
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@ -368,8 +371,6 @@ class InstallabilityTester(object):
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returns True, then t is installable.
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"""
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# Local variables for faster access...
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l = len
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fset = frozenset
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not_satisfied = partial(ifilter, musts.isdisjoint)
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# While we have guaranteed dependencies (in check), examine all
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@ -401,9 +402,9 @@ class InstallabilityTester(object):
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# - not in testing
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# - known to be broken (by cache)
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# - in never
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candidates = fset((depgroup & testing) - never)
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candidates = frozenset((depgroup & testing) - never)
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if l(candidates) == 0:
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if len(candidates) == 0:
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# We got no candidates to satisfy it - this
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# package cannot be installed with the current
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# testing
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@ -413,21 +414,43 @@ class InstallabilityTester(object):
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cbroken.add(cur)
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testing.remove(cur)
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return False
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if l(candidates) == 1:
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if len(candidates) == 1:
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# only one possible solution to this choice and we
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# haven't seen it before
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check.update(candidates)
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musts.update(candidates)
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else:
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possible_eqv = set(x for x in candidates if x in eqv_table)
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if len(possible_eqv) > 1:
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# Exploit equvialency to reduce the number of
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# candidates if possible. Basically, this
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# code maps "similar" candidates into a single
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# candidate that will give a identical result
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# to any other candidate it eliminates.
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#
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# See InstallabilityTesterBuilder's
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# _build_eqv_packages_table method for more
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# information on how this works.
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new_cand = set(x for x in candidates if x not in possible_eqv)
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for chosen in iter_except(possible_eqv.pop, KeyError):
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new_cand.add(chosen)
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possible_eqv -= eqv_table[chosen]
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if len(new_cand) == 1:
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check.update(new_cand)
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musts.update(new_cand)
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continue
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candidates = frozenset(new_cand)
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# defer this choice till later
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choices.add(candidates)
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return True
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def _get_min_pseudo_ess_set(self, arch):
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if arch not in self._cache_ess:
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# The minimal essential set cache is not present -
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# compute it now.
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testing = self._testing
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eqv_table = self._eqv_table
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cbroken = self._cache_broken
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universe = self._universe
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safe_set = self._safe_set
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@ -439,8 +462,9 @@ class InstallabilityTester(object):
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not_satisified = partial(ifilter, start.isdisjoint)
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while ess_base:
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self._check_loop(universe, testing, start, ess_never,\
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ess_choices, cbroken, ess_base)
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self._check_loop(universe, testing, eqv_table,
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start, ess_never, ess_choices,
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cbroken, ess_base)
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if ess_choices:
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# Try to break choices where possible
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nchoice = set()
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