def _overlap_dnf(dep_struct):
"""
Combine overlapping || groups using disjunctive normal form (DNF), in
order to minimize the number of packages chosen to satisfy cases like
"|| ( foo bar ) || ( bar baz )" as in bug #632026. Non-overlapping
groups are excluded from the conversion, since DNF leads to exponential
explosion of the formula.
When dep_struct does not contain any overlapping groups, no DNF
conversion will be performed, and dep_struct will be returned as-is.
Callers can detect this case by checking if the returned object has
the same identity as dep_struct. If the identity is different, then
DNF conversion was performed.
"""
if not _contains_disjunction(dep_struct):
return dep_struct
# map atom.cp to disjunctions
cp_map = collections.defaultdict(list)
# graph atom.cp, with edges connecting atoms in the same disjunction
overlap_graph = digraph()
# map id(disjunction) to index in dep_struct, for deterministic output
order_map = {}
order_key = lambda x: order_map[id(x)]
result = []
for i, x in enumerate(dep_struct):
if isinstance(x, list):
assert x and x[0] == '||', \
'Normalization error, nested conjunction found in %s' % (dep_struct,)
order_map[id(x)] = i
prev_cp = None
for atom in _iter_flatten(x):
if isinstance(atom, Atom) and not atom.blocker:
cp_map[atom.cp].append(x)
overlap_graph.add(atom.cp, parent=prev_cp)
prev_cp = atom.cp
if prev_cp is None: # only contains blockers
result.append(x)
else:
result.append(x)
# group together disjunctions having atom.cp overlap
traversed = set()
overlap = False
for cp in overlap_graph:
if cp in traversed:
continue
disjunctions = {}
stack = [cp]
while stack:
cp = stack.pop()
traversed.add(cp)
for x in cp_map[cp]:
disjunctions[id(x)] = x
for other_cp in itertools.chain(overlap_graph.child_nodes(cp),
overlap_graph.parent_nodes(cp)):
if other_cp not in traversed:
stack.append(other_cp)
if len(disjunctions) > 1:
overlap = True
# convert overlapping disjunctions to DNF
result.extend(
_dnf_convert(sorted(disjunctions.values(), key=order_key)))
else:
# pass through non-overlapping disjunctions
result.append(disjunctions.popitem()[1])
return result if overlap else dep_struct
def _overlap_dnf(dep_struct):
"""
Combine overlapping || groups using disjunctive normal form (DNF), in
order to minimize the number of packages chosen to satisfy cases like
"|| ( foo bar ) || ( bar baz )" as in bug #632026. Non-overlapping
groups are excluded from the conversion, since DNF leads to exponential
explosion of the formula.
When dep_struct does not contain any overlapping groups, no DNF
conversion will be performed, and dep_struct will be returned as-is.
Callers can detect this case by checking if the returned object has
the same identity as dep_struct. If the identity is different, then
DNF conversion was performed.
"""
if not _contains_disjunction(dep_struct):
return dep_struct
# map atom.cp to disjunctions
cp_map = collections.defaultdict(list)
# graph atom.cp, with edges connecting atoms in the same disjunction
overlap_graph = digraph()
# map id(disjunction) to index in dep_struct, for deterministic output
order_map = {}
order_key = lambda x: order_map[id(x)]
result = []
for i, x in enumerate(dep_struct):
if isinstance(x, list):
assert x and x[0] == '||', \
'Normalization error, nested conjunction found in %s' % (dep_struct,)
order_map[id(x)] = i
prev_cp = None
for atom in _iter_flatten(x):
if isinstance(atom, Atom) and not atom.blocker:
cp_map[atom.cp].append(x)
overlap_graph.add(atom.cp, parent=prev_cp)
prev_cp = atom.cp
if prev_cp is None: # only contains blockers
result.append(x)
else:
result.append(x)
# group together disjunctions having atom.cp overlap
traversed = set()
overlap = False
for cp in overlap_graph:
if cp in traversed:
continue
disjunctions = {}
stack = [cp]
while stack:
cp = stack.pop()
traversed.add(cp)
for x in cp_map[cp]:
disjunctions[id(x)] = x
for other_cp in itertools.chain(overlap_graph.child_nodes(cp),
overlap_graph.parent_nodes(cp)):
if other_cp not in traversed:
stack.append(other_cp)
if len(disjunctions) > 1:
overlap = True
# convert overlapping disjunctions to DNF
result.extend(_dnf_convert(
sorted(disjunctions.values(), key=order_key)))
else:
# pass through non-overlapping disjunctions
result.append(disjunctions.popitem()[1])
return result if overlap else dep_struct