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runoff: reuse IRV Numba tally helpers for head-to-head round #46

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runoff: reuse IRV Numba tally helpers for head-to-head round #46

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30 changes: 18 additions & 12 deletions elsim/methods/runoff.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,14 @@
import numpy as np

from elsim.methods._common import (_all_indices, _get_tiebreak, _no_tiebreak,
_order_tiebreak_keep, _random_tiebreak)
from elsim.methods._common import (
_all_indices,
_get_tiebreak,
_inc_rank_idx,
_no_tiebreak,
_order_tiebreak_keep,
_random_tiebreak,
_tally_at_rank_idx,
)

_tiebreak_map = {'order': _order_tiebreak_keep,
'random': _random_tiebreak,
Expand Down Expand Up @@ -93,19 +100,18 @@ def runoff(election, tiebreaker=None):
if None in finalists:
return None

# TODO: Can this be vectorized or numbafied?
finalist_0 = finalists[0]
finalist_1 = finalists[1]

finalist_0_tally = 0
finalist_1_tally = 0

for ballot in election:
ballot_list = ballot.tolist()
if ballot_list.index(finalist_0) < ballot_list.index(finalist_1):
finalist_0_tally += 1
else:
finalist_1_tally += 1
n_cands = election.shape[1]
cand_tallies = np.empty(n_cands, dtype=np.uint)
voter_top_rank_idx = np.zeros(n_voters, dtype=np.uint8)
eliminated_cands = set(range(n_cands)) - {finalist_0, finalist_1}
if eliminated_cands:
_inc_rank_idx(election, voter_top_rank_idx, eliminated_cands)
_tally_at_rank_idx(cand_tallies, election, voter_top_rank_idx)
finalist_0_tally = cand_tallies[finalist_0]
finalist_1_tally = cand_tallies[finalist_1]

assert finalist_0_tally + finalist_1_tally == n_voters

Expand Down
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