def _check_loop(self, universe, testing, eqv_table, musts, never, choices, cbroken, check, len=len, frozenset=frozenset): """Finds all guaranteed dependencies via "check". If it returns False, t is not installable. If it returns True then "check" is exhausted. If "choices" are empty and this returns True, then t is installable. """ # Local variables for faster access... not_satisfied = partial(ifilter, musts.isdisjoint) # While we have guaranteed dependencies (in check), examine all # of them. for cur in iter_except(check.pop, KeyError): (deps, cons) = universe[cur] if cons: # Conflicts? if cur in never: # cur adds a (reverse) conflict, so check if cur # is in never. # # - there is a window where two conflicting # packages can be in check. Example "A" depends # on "B" and "C". If "B" conflicts with "C", # then both "B" and "C" could end in "check". return False # We must install cur for the package to be installable, # so "obviously" we can never choose any of its conflicts never.update(cons & testing) # depgroup can be satisifed by picking something that is # already in musts - lets pick that (again). :) for depgroup in not_satisfied(deps): # Of all the packages listed in the relation remove those that # are either: # - not in testing # - known to be broken (by cache) # - in never candidates = frozenset((depgroup & testing) - never) if len(candidates) == 0: # We got no candidates to satisfy it - this # package cannot be installed with the current # testing if cur not in cbroken and depgroup.isdisjoint(never): # cur's dependency cannot be satisfied even if never was empty. # This means that cur itself is broken (as well). cbroken.add(cur) testing.remove(cur) return False if len(candidates) == 1: # only one possible solution to this choice and we # haven't seen it before check.update(candidates) musts.update(candidates) else: possible_eqv = set(x for x in candidates if x in eqv_table) if len(possible_eqv) > 1: # Exploit equivalency to reduce the number of # candidates if possible. Basically, this # code maps "similar" candidates into a single # candidate that will give a identical result # to any other candidate it eliminates. # # See InstallabilityTesterBuilder's # _build_eqv_packages_table method for more # information on how this works. new_cand = set(x for x in candidates if x not in possible_eqv) for chosen in iter_except(possible_eqv.pop, KeyError): new_cand.add(chosen) possible_eqv -= eqv_table[chosen] if len(new_cand) == 1: check.update(new_cand) musts.update(new_cand) continue candidates = frozenset(new_cand) # defer this choice till later choices.add(candidates) return True
def solve_groups(self, groups): sat_in_testing = self._testing.isdisjoint universe = self._universe revuniverse = self._revuniverse result = [] emitted = set() check = set() order = {} ptable = {} key2item = {} going_out = set() going_in = set() debug_solver = 0 try: debug_solver = int(os.environ.get('BRITNEY_DEBUG', '0')) except: pass # Build the tables for (item, adds, rms) in groups: key = str(item) key2item[key] = item order[key] = {'before': set(), 'after': set()} going_in.update(adds) going_out.update(rms) for a in adds: ptable[a] = key for r in rms: ptable[r] = key if debug_solver > 1: self._dump_groups(groups) # This large loop will add ordering constrains on each "item" # that migrates based on various rules. for (item, adds, rms) in groups: key = str(item) oldcons = set() newcons = set() for r in rms: oldcons.update(universe[r][1]) for a in adds: newcons.update(universe[a][1]) current = newcons & oldcons oldcons -= current newcons -= current if oldcons: # Some of the old binaries have "conflicts" that will # be removed. for o in ifilter_only(ptable, oldcons): # "key" removes a conflict with one of # "other"'s binaries, so it is probably a good # idea to migrate "key" before "other" other = ptable[o] if other == key: # "Self-conflicts" => ignore continue if debug_solver and other not in order[key]['before']: print("N: Conflict induced order: %s before %s" % (key, other)) order[key]['before'].add(other) order[other]['after'].add(key) for r in ifilter_only(revuniverse, rms): # The binaries have reverse dependencies in testing; # check if we can/should migrate them first. for rdep in revuniverse[r][0]: for depgroup in universe[rdep][0]: rigid = depgroup - going_out if not sat_in_testing(rigid): # (partly) satisfied by testing, assume it is okay continue if rdep in ptable: other = ptable[rdep] if other == key: # "Self-dependency" => ignore continue if debug_solver and other not in order[key]['after']: print("N: Removal induced order: %s before %s" % (key, other)) order[key]['after'].add(other) order[other]['before'].add(key) for a in adds: # Check if this item should migrate before others # (e.g. because they depend on a new [version of a] # binary provided by this item). for depgroup in universe[a][0]: rigid = depgroup - going_out if not sat_in_testing(rigid): # (partly) satisfied by testing, assume it is okay continue # okay - we got three cases now. # - "swap" (replace existing binary with a newer version) # - "addition" (add new binary without removing any) # - "removal" (remove binary without providing a new) # # The problem is that only the two latter requires # an ordering. A "swap" (in itself) should not # affect us. other_adds = set() other_rms = set() for d in ifilter_only(ptable, depgroup): if d in going_in: # "other" provides something "key" needs, # schedule accordingly. other = ptable[d] other_adds.add(other) else: # "other" removes something "key" needs, # schedule accordingly. other = ptable[d] other_rms.add(other) for other in (other_adds - other_rms): if debug_solver and other != key and other not in order[key]['after']: print("N: Dependency induced order (add): %s before %s" % (key, other)) order[key]['after'].add(other) order[other]['before'].add(key) for other in (other_rms - other_adds): if debug_solver and other != key and other not in order[key]['before']: print("N: Dependency induced order (remove): %s before %s" % (key, other)) order[key]['before'].add(other) order[other]['after'].add(key) ### MILESTONE: Partial-order constrains computed ### # At this point, we have computed all the partial-order # constrains needed. Some of these may have created strongly # connected components (SSC) [of size 2 or greater], which # represents a group of items that (we believe) must migrate # together. # # Each one of those components will become an "easy" hint. comps = self._compute_scc(order, ptable) merged = {} scc = {} # Now that we got the SSCs (in comps), we select on item from # each SSC to represent the group and become an ID for that # SSC. # * ssc[ssc_id] => All the items in that SSC # * merged[item] => The ID of the SSC to which the item belongs. # # We also "repair" the ordering, so we know in which order the # hints should be emitted. for com in comps: scc_id = com[0] scc[scc_id] = com merged[scc_id] = scc_id if len(com) > 1: so_before = order[scc_id]['before'] so_after = order[scc_id]['after'] for n in com: if n == scc_id: continue so_before.update(order[n]['before']) so_after.update(order[n]['after']) merged[n] = scc_id del order[n] if debug_solver: print("N: SCC: %s -- %s" % (scc_id, str(sorted(com)))) for com in comps: node = com[0] nbefore = set(merged[b] for b in order[node]['before']) nafter = set(merged[b] for b in order[node]['after']) # Drop self-relations (usually caused by the merging) nbefore.discard(node) nafter.discard(node) order[node]['before'] = nbefore order[node]['after'] = nafter if debug_solver: print("N: -- PARTIAL ORDER --") for com in sorted(order): if debug_solver and order[com]['before']: print("N: %s <= %s" % (com, str(sorted(order[com]['before'])))) if not order[com]['after']: # This component can be scheduled immediately, add it # to "check" check.add(com) elif debug_solver: print("N: %s >= %s" % (com, str(sorted(order[com]['after'])))) if debug_solver: print("N: -- END PARTIAL ORDER --") print("N: -- LINEARIZED ORDER --") for cur in iter_except(check.pop, KeyError): if order[cur]['after'] <= emitted: # This item is ready to be emitted right now if debug_solver: print("N: %s -- %s" % (cur, sorted(scc[cur]))) emitted.add(cur) result.append([key2item[x] for x in scc[cur]]) if order[cur]['before']: # There are components that come after this one. # Add it to "check": # - if it is ready, it will be emitted. # - else, it will be dropped and re-added later. check.update(order[cur]['before'] - emitted) if debug_solver: print("N: -- END LINEARIZED ORDER --") return result
def build(self): """Compile the installability tester This method will compile an installability tester from the information given and (where possible) try to optimise a few things. """ package_table = self._package_table reverse_package_table = self._reverse_package_table intern_set = self._intern_set safe_set = set() broken = self._broken not_broken = ifilter_except(broken) check = set(broken) def safe_set_satisfies(t): """Check if t's dependencies can be satisfied by the safe set""" if not package_table[t][0]: # If it has no dependencies at all, then it is safe. :) return True for depgroup in package_table[t][0]: if not any(dep for dep in depgroup if dep in safe_set): return False return True # Merge reverse conflicts with conflicts - this saves some # operations in _check_loop since we only have to check one # set (instead of two) and we remove a few duplicates here # and there. # # At the same time, intern the rdep sets for pkg in reverse_package_table: if pkg not in package_table: raise RuntimeError("%s/%s/%s referenced but not added!" % pkg) deps, con = package_table[pkg] rdeps, rcon, rdep_relations = reverse_package_table[pkg] if rcon: if not con: con = intern_set(rcon) else: con = intern_set(con | rcon) package_table[pkg] = (deps, con) reverse_package_table[pkg] = (intern_set(rdeps), con, intern_set(rdep_relations)) # Check if we can expand broken. for t in not_broken(iter_except(check.pop, KeyError)): # This package is not known to be broken... but it might be now isb = False for depgroup in package_table[t][0]: if not any(not_broken(depgroup)): # A single clause is unsatisfiable, the # package can never be installed - add it to # broken. isb = True break if not isb: continue broken.add(t) if t not in reverse_package_table: continue check.update(reverse_package_table[t][0] - broken) if broken: # Since a broken package will never be installable, nothing that depends on it # will ever be installable. Thus, there is no point in keeping relations on # the broken package. seen = set() empty_set = frozenset() null_data = (frozenset([empty_set]), empty_set) for b in (x for x in broken if x in reverse_package_table): for rdep in (r for r in not_broken(reverse_package_table[b][0]) if r not in seen): ndep = intern_set((x - broken) for x in package_table[rdep][0]) package_table[rdep] = (ndep, package_table[rdep][1] - broken) seen.add(rdep) # Since they won't affect the installability of any other package, we might as # as well null their data. This memory for these packages, but likely there # will only be a handful of these "at best" (fsvo of "best") for b in broken: package_table[b] = null_data if b in reverse_package_table: del reverse_package_table[b] # Now find an initial safe set (if any) check = set() for pkg in package_table: if package_table[pkg][1]: # has (reverse) conflicts - not safe continue if not safe_set_satisfies(pkg): continue safe_set.add(pkg) if pkg in reverse_package_table: # add all rdeps (except those already in the safe_set) check.update(reverse_package_table[pkg][0] - safe_set) # Check if we can expand the initial safe set for pkg in iter_except(check.pop, KeyError): if package_table[pkg][1]: # has (reverse) conflicts - not safe continue if safe_set_satisfies(pkg): safe_set.add(pkg) if pkg in reverse_package_table: # add all rdeps (except those already in the safe_set) check.update(reverse_package_table[pkg][0] - safe_set) eqv_table = self._build_eqv_packages_table(package_table, reverse_package_table) return InstallabilitySolver(package_table, reverse_package_table, self._testing, self._broken, self._essentials, safe_set, eqv_table)