Use different stage games

As described in Play Contexts and Generic Prisoner’s Dilemma the default game used for the Prisoner’s Dilemma is given by:

>>> import axelrod as axl
>>> pd = axl.game.Game()
>>> pd
Axelrod game: (R,P,S,T) = (3, 1, 0, 5)
>>> pd.RPST()
(3, 1, 0, 5)

These Game objects are used to score matches, tournaments and Moran processes:

>>> pd.score((axl.Action.C, axl.Action.C))
(3, 3)
>>> pd.score((axl.Action.C, axl.Action.D))
(0, 5)
>>> pd.score((axl.Action.D, axl.Action.C))
(5, 0)
>>> pd.score((axl.Action.D, axl.Action.D))
(1, 1)

It is possible to run a matches, tournaments and Moran processes with a different game. For example here is the game of chicken:

>>> chicken = axl.game.Game(r=0, s=-1, t=1, p=-10)
>>> chicken
Axelrod game: (R,P,S,T) = (0, -10, -1, 1)
>>> chicken.RPST()
(0, -10, -1, 1)

Here is a simple tournament run with this game:

>>> players = [axl.Cooperator(), axl.Defector(), axl.TitForTat()]
>>> tournament = axl.Tournament(players, game=chicken)
>>> results = tournament.play()
>>> results.ranked_names
['Cooperator', 'Defector', 'Tit For Tat']

The default Prisoner’s dilemma has different results:

>>> tournament = axl.Tournament(players)
>>> results = tournament.play()
>>> results.ranked_names
['Defector', 'Tit For Tat', 'Cooperator']

Asymmetric games can also be implemented via the AsymmetricGame class with two Numpy arrays for payoff matrices:

>>> import numpy as np
>>> A = np.array([[3, 1], [1, 3]])
>>> B = np.array([[1, 3], [2, 1]])
>>> asymmetric_game = axl.AsymmetricGame(A, B)
>>> asymmetric_game  
Axelrod game with matrices: (array([[3, 1],
                                    [1, 3]]),
                             array([[1, 3],
                                    [2, 1]]))

Asymmetric games can also be different sizes (even if symmetric; regular games can currently only be 2x2), such as Rock Paper Scissors:

>>> A = np.array([[0, -1, 1], [1, 0, -1], [-1, 1, 0]])
>>> rock_paper_scissors = axl.AsymmetricGame(A, -A)
>>> rock_paper_scissors  
Axelrod game with matrices: (array([[ 0, -1,  1],
                                    [ 1,  0, -1],
                                    [-1,  1,  0]]),
                             array([[ 0,  1, -1],
                                    [-1,  0,  1],
                                    [ 1, -1,  0]]))

NB: Some features of Axelrod, such as strategy transformers, are specifically created for use with the iterated Prisoner’s Dilemma; they may break with games of other sizes. Note also that most strategies in Axelrod are Prisoners’ Dilemma strategies, so behave as though they are playing the Prisoners’ Dilemma; in the rock-paper-scissors example above, they will certainly never choose scissors (because their strategy action set is two actions!)

For a more detailed tutorial on how to implement another game into Axelrod, here is a tutorial using rock paper scissors as an example.