def test_requires_no_duplicates():
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, {1}]])
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[{1}, 1]])
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, 2, {3, 1}]])
def test_borda_count_ranked_choice_with_ties():
ballots = RankedChoiceBallotBox([[1, 2, 3], [{1, 2, 3}], [1, {2, 3}]])
election = Election(ballots)
# assert election.ranking_by_borda_count() == [1, 2, 3]
assert election.ranking_by_borda_count(include_score=True) == [(1, 4),
(2, 1),
(3, 0)]
def evaluate_vote_induction_method(dataset, intransitivity_resolver,
incompleteness_resolver):
"""Computes the Kendall tau distance between original pairwise votes from a dataset and the collapsed rankings.
Uses the Kendall tau on the output of the specified social choice method.
:param dataset: a list of 4-tuples, each representing a pairwise vote followed by a voter uuid
:param intransitivity_resolver: a function that takes a win-graph and returns an acyclic win-graph
:param incompleteness_resolver: a function that takes a win-graph and a set of candidates
and produces a fully-connected win-graph with each candidate
:return: a float in [-1, 1]
"""
voter_to_vote_set = {vote[3]: [] for vote in dataset}
candidates = {v[0] for v in dataset} | {v[1] for v in dataset}
num_pairs = len(candidates) * (len(candidates) - 1) // 2
# vote_sets should be a mapping from each voter to the contents of each of their votes.
for vote in dataset:
voter_to_vote_set[vote[3]].append(vote[0:3])
# This is the pairwise election that serves as a baseline "ground truth" for the
# vote induction method.
pairwise_election = Election(
PairwiseBallotBox([vote[0:3] for vote in dataset]))
ranked_choice_ballots = []
for vote_set in voter_to_vote_set.values():
transitive_votes = intransitivity_resolver(vote_set)
complete_votes = incompleteness_resolver(transitive_votes)
ordering = list(nx.topological_sort(complete_votes))
ranked_choice_ballots.append(ordering)
ranking_election = Election(RankedChoiceBallotBox(ranked_choice_ballots))
pairwise_ranking = pairwise_election.ranking_by_ranked_pairs()
ranked_choice_ranking = ranking_election.ranking_by_ranked_pairs()
tau = ranking_similarity.kendalls_tau(pairwise_ranking,
ranked_choice_ranking)
print(
f"tau={tau},{intransitivity_resolver.func.__name__},{incompleteness_resolver.func.__name__}"
)
def election():
example_votes = RankedChoiceBallotBox([[1, 2, 3, 4], [1, 3, 2, 4],
[1, 2, 3, 4], [1, 2, 4, 3]])
return Election(example_votes)
def test_no_candidate_repeats():
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, 1]])
def test_rankings_can_include_ties():
RankedChoiceBallotBox([[{1, 2}]])
RankedChoiceBallotBox([[1, {2, 4}, {3, 5}]])
def test_candidates_no_duplicates():
with pytest.raises(InvalidElectionDataException):
RankedChoiceBallotBox([[1, 2, 3]], candidates=[1, 1, 2, 3])
def test_requires_full_ballots():
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, 2]], candidates=[1, 2, 3])
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, 2, 3, 4]], candidates=[1, 2, 3])
def test_require_full_ballots_with_candidate_inference():
with pytest.raises(InvalidBallotDataException):
RankedChoiceBallotBox([[1, 2, 3, 4], [4, 3, 2, 1], [3, 2, 1]])