single winner

This module contains single-winner voting rules.

approval_winner(instance)

Returns the approval winners, i.e., the alternatives with the highest approval score (number of appearance in the first position).

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

borda_winner(instance)

Returns all the alternatives with the highest total Borda score.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

bucklin_voting_winner(instance)

Returns the Bucklin winners.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

copeland_winner(instance)

Returns the Copeland winners, i.e., the alternatives that win the highest number of pairwise comparisons.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

fallback_voting_winner(instance)

Returns the fallback voting winners.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

k_approval_winner(instance, k)

Returns all the alternatives with the highest approval score, i.e., that appear the highest number of time in the first k positions. Only applies to strict rankings.

Parameters:
plurality_winner(instance)

Returns all the alternatives with the highest plurality score, i.e., that appear the highest number of times in first position.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

satisfaction_approval_winner(instance)

Returns the satisfaction approval winners, i.e., the alternatives with the highest satisfaction approval score (sum of 1 divided by length of the first position, for all approvers).

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.

veto_winner(instance)

Returns all the alternatives with the smallest veto score, i.e., that appear the smallest number of times in the last indifference class.

Parameters:

instance (preflibtools.instances.preflibinstance.OrdinalInstance) – The instance.