pollPerturb.py

from methods import *
from voterModels import *

def pollPert(model, methodsAndStrats, nvot, ncand, niter, nwinners=1, perturbations=[-.2, -.02, .02, .2],
                pollingMethod=Approval, pollingStrat=Approval.zeroInfoBallot,
                pollingStratArgs={'pickiness':0.7}):
    ms = []
    for m in methodsAndStrats:
        if isinstance(m, type):
            ms.append((m, m.vaBallot, {}))
        elif len(m) == 2:
            ms.append((m[0], m[1], {}))
        else: ms.append(m)
    totalResults = {p:{m[0].__name__: [0,0,0] for m in ms} for p in perturbations}
    condResults = {p:{m[0].__name__: [0,0,0] for m in ms} for p in perturbations}
    nonCondResults = {p:{m[0].__name__: [0,0,0] for m in ms} for p in perturbations}
    for i in range(niter):
        electorate = model(nvot, ncand)
        basePolls = pollingMethod.results([pollingStrat(v) for v in electorate])
        if Condorcet.scenarioType(electorate) == 'cycle':
            condWinner = None
        else:
            condWinner = Condorcet.winnerSet([Condorcet.honBallot(v) for v in electorate])[0]
        for method, strat, stratArgs in ms:
            baseWinners = set(method.winnerSet([strat(v, polls=basePolls, electabilities=basePolls, **stratArgs)
                            for v in electorate], numWinners=nwinners))
            for pert in perturbations:
                for cand in range(ncand):
                    newPolls = basePolls.copy()
                    newPolls[cand] = min(1, max(0, newPolls[cand] + pert))
                    newWinners = set(method.winnerSet([strat(v, polls=newPolls, electabilities=newPolls, **stratArgs)
                                for v in electorate], numWinners=nwinners))
                    if newWinners != baseWinners:
                        if cand in newWinners and cand not in baseWinners:
                            changeType = 0
                        elif cand not in newWinners and cand in baseWinners:
                            changeType = 1
                        else: changeType = 2
                        totalResults[pert][method.__name__][changeType] += 1
                        if cand == condWinner:
                            condResults[pert][method.__name__][changeType] += 1
                        else:
                            nonCondResults[pert][method.__name__][changeType] += 1
    return totalResults, condResults, nonCondResults