def countBallots(self):
"Count the votes using Condorcet voting."
# self.pMat[i][j]: number of votes ranking candidate i over candidate j
self.computePMat()
# Even though the Smith Set isn't needed for all completion methods
# it provides interesting info, so compute it always.
self.computeSmithSet()
if len(self.smithSet) == 1:
c0 = self.smithSet[0]
else:
# Do the completion
if self.completion == "Schwartz Sequential Dropping":
c0 = self.SchwartzSequentialDropping()
elif self.completion in ["IRV on Smith Set", "Borda on Smith Set"]:
# Copy ballots and get rid of candidates not in Smith set
withdrawList = []
for c in range(self.b.numCandidates):
if (c not in self.smithSet):
withdrawList.append(c)
dirtyBallots = self.b.copy()
dirtyBallots.withdrawn = withdrawList
dirtyBallots.numSeats = 1
cleanBallots = dirtyBallots.getCleanBallots()
if self.completion == "IRV on Smith Set":
self.e = IRV(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
elif self.completion == "Borda on Smith Set":
self.e = Borda(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
assert(len(self.e.winners) == 1)
# The Smith set is sorted. The winner just determined is the index
# of the winner in the Smith set.
cIndex = list(self.e.winners)[0]
c0 = self.smithSet[cIndex]
else:
assert(0)
self.winners = set([c0])
def countBallots(self):
"Count the votes using Condorcet voting."
# self.pMat[i][j]: number of votes ranking candidate i over candidate j
self.computePMat()
# Even though the Smith Set isn't needed for all completion methods
# it provides interesting info, so compute it always.
self.computeSmithSet()
if len(self.smithSet) == 1:
c0 = self.smithSet[0]
else:
# Do the completion
if self.completion == "Schwartz Sequential Dropping":
c0 = self.SchwartzSequentialDropping()
elif self.completion in ["IRV on Smith Set", "Borda on Smith Set"]:
# Copy ballots and get rid of candidates not in Smith set
withdrawList = []
for c in range(self.b.numCandidates):
if (c not in self.smithSet):
withdrawList.append(c)
dirtyBallots = self.b.copy()
dirtyBallots.withdrawn = withdrawList
dirtyBallots.numSeats = 1
cleanBallots = dirtyBallots.getCleanBallots()
if self.completion == "IRV on Smith Set":
self.e = IRV(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
elif self.completion == "Borda on Smith Set":
self.e = Borda(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
assert (len(self.e.winners) == 1)
# The Smith set is sorted. The winner just determined is the index
# of the winner in the Smith set.
cIndex = list(self.e.winners)[0]
c0 = self.smithSet[cIndex]
else:
assert (0)
self.winners = set([c0])
class Condorcet(NonIterative, MethodPlugin):
"Implement Condorcet voting with several options for completion methods"
methodName = "Condorcet"
longMethodName = "Condorcet Voting"
onlySingleWinner = True
status = 1
htmlBody = """
<p>Condorcet voting elects the candidate who wins all pairwise
elections against the other candidates. In relatively rare
situations, a cycle will occur where no Condorcet winner exists (i.e.,
every candidte is beaten by at least one other candidate). The set
of candidates in the cycle is called the Smith set. In this instance,
a "completion method" is used to choose the winner from the Smith set.
There are three choices for the completion method:</p>
<ul>
<li> Schwartz sequential dropping
<li> Instant runoff voting on the Smith set
<li> Borda count on the Smith set
</ul>
"""
htmlHelp = (MethodPlugin.htmlBegin % (longMethodName, longMethodName)) +\
htmlBody + MethodPlugin.htmlEnd
def __init__(self, b):
NonIterative.__init__(self, b)
MethodPlugin.__init__(self)
self.completion = "Schwartz Sequential Dropping"
self.createGuiOptions(["completionMethod"])
self.e = None
self.smithSet = []
self.SSDinfo = ""
self.pMat = []
self.dMat = []
def preCount(self):
NonIterative.preCount(self)
assert(self.completion in ["Schwartz Sequential Dropping",
"IRV on Smith Set",
"Borda on Smith Set"])
self.optionsMsg = "Using %s for the completion method." % self.completion
def computePMat(self):
"Compute the pairwise comparison matrix."
# Intialize space
self.pMat = []
for c in range(self.b.numCandidates):
self.pMat.append([0] * self.b.numCandidates)
# Compute pMat
for i in xrange(self.b.numWeightedBallots):
weight, ballot = self.b.getWeightedBallot(i)
remainingC = range(self.b.numCandidates)
for c in ballot:
remainingC.remove(c)
for d in remainingC:
self.pMat[c][d] += weight
def computeSmithSet(self):
"Compute the Smith set."
dMat = []
for c in range(self.b.numCandidates):
dMat.append([0] * self.b.numCandidates)
# compute the Smith set
# Adapted from code posted by Markus Schulze at
# http://groups.yahoo.com/group/election-methods-list/message/6493
self.smithSet = range(self.b.numCandidates)
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
if self.pMat[c][d] >= self.pMat[d][c]:
dMat[c][d] = True
else:
dMat[c][d] = False
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
for k in range(self.b.numCandidates):
if c != k and d != k:
if dMat[d][c] and dMat[c][k]:
dMat[d][k] = True
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
if ( (not dMat[c][d]) and
dMat[d][c] and
(c in self.smithSet) ):
self.smithSet.remove(c)
self.smithSet.sort()
def SchwartzSequentialDropping(self):
"Complete with SSD."
# Initialize the defeats matrix: dMat[i][j] gives the magnitude of i's
# defeat of j. If i doesn't defeat j, then dMat[i][j] == 0.
self.dMat = []
for c in range(self.b.numCandidates):
self.dMat.append([0] * self.b.numCandidates)
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
self.dMat[c][d] = self.pMat[c][d]
for c in range(self.b.numCandidates):
for d in range(c):
if self.pMat[c][d] > self.pMat[d][c]:
self.dMat[d][c] = 0
if self.pMat[c][d] < self.pMat[d][c]:
self.dMat[c][d] = 0
if self.pMat[c][d] == self.pMat[d][c]:
self.dMat[c][d] = self.dMat[d][c] = 0
# Determine "beatpath" magnitudes array: dMat[i][j] will be the
# maximum beatpath magnitudes array. The i,j entry is the greatest
# magnitude of any beatpath from i to j. A beatpath's magnitude is
# the magnitude of its weakest defeat.
changing = 1
while changing:
changing = 0
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
for k in range(self.b.numCandidates):
dmin = min (self.dMat[c][d], self.dMat[d][k])
if self.dMat[c][k] < dmin:
self.dMat[c][k] = dmin
changing = 1
ctng = range(self.b.numCandidates)[:]
for c in ctng[:]:
for d in ctng[:]:
if self.dMat[d][c] > self.dMat[c][d] and c in ctng:
ctng.remove(c)
if len(ctng) > 1:
ctng.sort()
self.SSDinfo = """
Candidates remaining after SSD: %s
Tie broken randomly.""" % self.b.joinList(ctng)
(c0, desc) = self.breakStrongTie(ctng)
else:
self.SSDinfo = ""
c0 = ctng[0]
return c0
def countBallots(self):
"Count the votes using Condorcet voting."
# self.pMat[i][j]: number of votes ranking candidate i over candidate j
self.computePMat()
# Even though the Smith Set isn't needed for all completion methods
# it provides interesting info, so compute it always.
self.computeSmithSet()
if len(self.smithSet) == 1:
c0 = self.smithSet[0]
else:
# Do the completion
if self.completion == "Schwartz Sequential Dropping":
c0 = self.SchwartzSequentialDropping()
elif self.completion in ["IRV on Smith Set", "Borda on Smith Set"]:
# Copy ballots and get rid of candidates not in Smith set
withdrawList = []
for c in range(self.b.numCandidates):
if (c not in self.smithSet):
withdrawList.append(c)
dirtyBallots = self.b.copy()
dirtyBallots.withdrawn = withdrawList
dirtyBallots.numSeats = 1
cleanBallots = dirtyBallots.getCleanBallots()
if self.completion == "IRV on Smith Set":
self.e = IRV(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
elif self.completion == "Borda on Smith Set":
self.e = Borda(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
assert(len(self.e.winners) == 1)
# The Smith set is sorted. The winner just determined is the index
# of the winner in the Smith set.
cIndex = list(self.e.winners)[0]
c0 = self.smithSet[cIndex]
else:
assert(0)
self.winners = set([c0])
class Condorcet(NonIterative, MethodPlugin):
"Implement Condorcet voting with several options for completion methods"
methodName = "Condorcet"
longMethodName = "Condorcet Voting"
onlySingleWinner = True
status = 1
htmlBody = """
<p>Condorcet voting elects the candidate who wins all pairwise
elections against the other candidates. In relatively rare
situations, a cycle will occur where no Condorcet winner exists (i.e.,
every candidte is beaten by at least one other candidate). The set
of candidates in the cycle is called the Smith set. In this instance,
a "completion method" is used to choose the winner from the Smith set.
There are three choices for the completion method:</p>
<ul>
<li> Schwartz sequential dropping
<li> Instant runoff voting on the Smith set
<li> Borda count on the Smith set
</ul>
"""
htmlHelp = (MethodPlugin.htmlBegin % (longMethodName, longMethodName)) +\
htmlBody + MethodPlugin.htmlEnd
def __init__(self, b):
NonIterative.__init__(self, b)
MethodPlugin.__init__(self)
self.completion = "Schwartz Sequential Dropping"
self.createGuiOptions(["completionMethod"])
self.e = None
self.smithSet = []
self.SSDinfo = ""
self.pMat = []
self.dMat = []
def preCount(self):
NonIterative.preCount(self)
assert (self.completion in [
"Schwartz Sequential Dropping", "IRV on Smith Set",
"Borda on Smith Set"
])
self.optionsMsg = "Using %s for the completion method." % self.completion
def computePMat(self):
"Compute the pairwise comparison matrix."
# Intialize space
self.pMat = []
for c in range(self.b.numCandidates):
self.pMat.append([0] * self.b.numCandidates)
# Compute pMat
for i in range(self.b.numWeightedBallots):
weight, ballot = self.b.getWeightedBallot(i)
remainingC = range(self.b.numCandidates)
for c in ballot:
remainingC.remove(c)
for d in remainingC:
self.pMat[c][d] += weight
def computeSmithSet(self):
"Compute the Smith set."
dMat = []
for c in range(self.b.numCandidates):
dMat.append([0] * self.b.numCandidates)
# compute the Smith set
# Adapted from code posted by Markus Schulze at
# http://groups.yahoo.com/group/election-methods-list/message/6493
self.smithSet = range(self.b.numCandidates)
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
if self.pMat[c][d] >= self.pMat[d][c]:
dMat[c][d] = True
else:
dMat[c][d] = False
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
for k in range(self.b.numCandidates):
if c != k and d != k:
if dMat[d][c] and dMat[c][k]:
dMat[d][k] = True
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
if c != d:
if ((not dMat[c][d]) and dMat[d][c]
and (c in self.smithSet)):
self.smithSet.remove(c)
self.smithSet.sort()
def SchwartzSequentialDropping(self):
"Complete with SSD."
# Initialize the defeats matrix: dMat[i][j] gives the magnitude of i's
# defeat of j. If i doesn't defeat j, then dMat[i][j] == 0.
self.dMat = []
for c in range(self.b.numCandidates):
self.dMat.append([0] * self.b.numCandidates)
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
self.dMat[c][d] = self.pMat[c][d]
for c in range(self.b.numCandidates):
for d in range(c):
if self.pMat[c][d] > self.pMat[d][c]:
self.dMat[d][c] = 0
if self.pMat[c][d] < self.pMat[d][c]:
self.dMat[c][d] = 0
if self.pMat[c][d] == self.pMat[d][c]:
self.dMat[c][d] = self.dMat[d][c] = 0
# Determine "beatpath" magnitudes array: dMat[i][j] will be the
# maximum beatpath magnitudes array. The i,j entry is the greatest
# magnitude of any beatpath from i to j. A beatpath's magnitude is
# the magnitude of its weakest defeat.
changing = 1
while changing:
changing = 0
for c in range(self.b.numCandidates):
for d in range(self.b.numCandidates):
for k in range(self.b.numCandidates):
dmin = min(self.dMat[c][d], self.dMat[d][k])
if self.dMat[c][k] < dmin:
self.dMat[c][k] = dmin
changing = 1
ctng = range(self.b.numCandidates)[:]
for c in ctng[:]:
for d in ctng[:]:
if self.dMat[d][c] > self.dMat[c][d] and c in ctng:
ctng.remove(c)
if len(ctng) > 1:
ctng.sort()
self.SSDinfo = """
Candidates remaining after SSD: %s
Tie broken randomly.""" % self.b.joinList(ctng)
(c0, desc) = self.breakStrongTie(ctng)
else:
self.SSDinfo = ""
c0 = ctng[0]
return c0
def countBallots(self):
"Count the votes using Condorcet voting."
# self.pMat[i][j]: number of votes ranking candidate i over candidate j
self.computePMat()
# Even though the Smith Set isn't needed for all completion methods
# it provides interesting info, so compute it always.
self.computeSmithSet()
if len(self.smithSet) == 1:
c0 = self.smithSet[0]
else:
# Do the completion
if self.completion == "Schwartz Sequential Dropping":
c0 = self.SchwartzSequentialDropping()
elif self.completion in ["IRV on Smith Set", "Borda on Smith Set"]:
# Copy ballots and get rid of candidates not in Smith set
withdrawList = []
for c in range(self.b.numCandidates):
if (c not in self.smithSet):
withdrawList.append(c)
dirtyBallots = self.b.copy()
dirtyBallots.withdrawn = withdrawList
dirtyBallots.numSeats = 1
cleanBallots = dirtyBallots.getCleanBallots()
if self.completion == "IRV on Smith Set":
self.e = IRV(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
elif self.completion == "Borda on Smith Set":
self.e = Borda(cleanBallots)
self.e.strongTieBreakMethod = self.strongTieBreakMethod
self.e.runElection()
assert (len(self.e.winners) == 1)
# The Smith set is sorted. The winner just determined is the index
# of the winner in the Smith set.
cIndex = list(self.e.winners)[0]
c0 = self.smithSet[cIndex]
else:
assert (0)
self.winners = set([c0])
