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Speed up resolution by approximating unsatisfied names #148

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Speed up resolution by approximating unsatisfied names #148

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48 changes: 20 additions & 28 deletions src/resolvelib/resolvers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -212,18 +212,6 @@ def _get_preference(self, name: KT) -> Preference:
backtrack_causes=self.state.backtrack_causes,
)

def _is_current_pin_satisfying(
self, name: KT, criterion: Criterion[RT, CT]
) -> bool:
try:
current_pin = self.state.mapping[name]
except KeyError:
return False
return all(
self._p.is_satisfied_by(requirement=r, candidate=current_pin)
for r in criterion.iter_requirement()
)

def _get_updated_criteria(
self, candidate: CT
) -> dict[KT, Criterion[RT, CT]]:
Expand Down Expand Up @@ -419,24 +407,31 @@ def resolve(
for round_index in range(max_rounds):
self._r.starting_round(index=round_index)

unsatisfied_names = [
key
for key, criterion in self.state.criteria.items()
if not self._is_current_pin_satisfying(key, criterion)
]
# In most cases approximate_unsatisfied_names is equal to a fully
# calculated unsatisfied names, but in some cases it is a subset.
# To fully calculate unsatified names you also need to check each
# criteria not satified by this for all requirements, i.e.
# self._p.is_satisfied_by(requirement, candidate=criteria_name)
#
# However as this is only used to pick a backtrack preference and
# because when all requirements are satisfied
# self.state.criteria.keys() == self.state.mapping.keys()
# then it is enough to take this approximate form and skip
# expensively looping through each requirement
approximate_unsatisfied_names = (
self.state.criteria.keys() - self.state.mapping.keys()
)

# All criteria are accounted for. Nothing more to pin, we are done!
if not unsatisfied_names:
if not approximate_unsatisfied_names:
self._r.ending(state=self.state)
return self.state

# keep track of satisfied names to calculate diff after pinning
satisfied_names = set(self.state.criteria.keys()) - set(
unsatisfied_names
)
approximate_satisfied_names = self.state.mapping.keys()

# Choose the most preferred unpinned criterion to try.
name = min(unsatisfied_names, key=self._get_preference)
name = min(approximate_unsatisfied_names, key=self._get_preference)
failure_criterion = self._attempt_to_pin_criterion(name)

if failure_criterion:
Expand All @@ -453,12 +448,9 @@ def resolve(
else:
# discard as information sources any invalidated names
# (unsatisfied names that were previously satisfied)
newly_unsatisfied_names = {
key
for key, criterion in self.state.criteria.items()
if key in satisfied_names
and not self._is_current_pin_satisfying(key, criterion)
}
newly_unsatisfied_names = approximate_satisfied_names - (
self.state.criteria.keys() - self.state.mapping.keys()
)
self._remove_information_from_criteria(
self.state.criteria, newly_unsatisfied_names
)
Expand Down
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