# -*- coding: utf-8 -*-
""" OracleNotFair: a multi-player policy with full knowledge and centralized intelligence to affect users to a FIXED arm, among the best arms.
- It allows to have absolutely *no* collision, if there is more channels than users (always assumed).
- But it is NOT fair on ONE run: the best arm is played only by one player.
- Note that in average, it is fair (who plays the best arm is randomly decided).
- Note that it IS affecting players on the best arms: it requires full knowledge of the means of the arms, not simply the number of arms.
- Note that they need a perfect knowledge on the arms, even this is not physically plausible.
"""
from __future__ import division, print_function # Python 2 compatibility
__author__ = "Lilian Besson"
__version__ = "0.1"
import numpy as np
try:
from .BaseMPPolicy import BaseMPPolicy
from .BaseCentralizedPolicy import BaseCentralizedPolicy
from .ChildPointer import ChildPointer
except ImportError:
from BaseMPPolicy import BaseMPPolicy
from BaseCentralizedPolicy import BaseCentralizedPolicy
from ChildPointer import ChildPointer
[docs]class Fixed(BaseCentralizedPolicy):
""" Fixed: always select a fixed arm, as decided by the OracleNotFair multi-player policy.
"""
[docs] def __init__(self, nbArms, armIndex):
"""Fixed on this arm."""
self.nbArms = nbArms #: Number of arms
self.armIndex = armIndex #: Index of fixed arm
[docs] def __str__(self):
return "Fixed({})".format(self.armIndex)
[docs] def startGame(self):
"""Nothing to do."""
pass
[docs] def getReward(self, arm, reward):
"""Nothing to do."""
pass
[docs] def choice(self):
"""Chose fixed arm."""
return self.armIndex
[docs]class OracleNotFair(BaseMPPolicy):
""" OracleNotFair: a multi-player policy which uses a centralized intelligence to affect users to affect users to a FIXED arm, among the best arms.
"""
[docs] def __init__(self, nbPlayers, armsMAB, lower=0., amplitude=1.):
"""
- nbPlayers: number of players to create (in self._players).
- armsMAB: MAB object that represents the arms.
Examples:
>>> import sys; sys.path.insert(0, '..'); from Environment import MAB; from Arms import Bernoulli
>>> import random; random.seed(0); import numpy as np; np.random.seed(0)
>>> problem = MAB({'arm_type': Bernoulli, 'params': [0.1, 0.5, 0.9]}) # doctest: +ELLIPSIS,+NORMALIZE_WHITESPACE
...
>>> s = OracleNotFair(2, problem)
>>> [ child.choice() for child in s.children ]
[2, 1]
>>> [ child.choice() for child in s.children ]
[2, 1]
- To get a list of usable players, use ``s.children``.
- Warning: ``s._players`` is for internal use
"""
assert nbPlayers > 0, "Error, the parameter 'nbPlayers' for OracleNotFair class has to be > 0."
nbArms = armsMAB.nbArms
if nbPlayers > nbArms:
print("Warning, there is more users than arms ... (nbPlayers > nbArms)") # XXX
# Attributes
self.nbPlayers = nbPlayers #: Number of players
self.nbArms = nbArms #: Number of arms
# Internal vectorial memory
means = np.array([arm.mean for arm in armsMAB.arms])
if nbPlayers <= nbArms:
self._affectations = np.argsort(means)[-nbPlayers:] # Decide the affectations of the centralized players
else:
self._affectations = np.zeros(nbPlayers, dtype=int)
self._affectations[:nbArms] = np.random.permutation(nbArms)
# Try to minimize the number of doubled affectations, so all the other players are affected to the *same* arm
worseArm = np.argmin(means)
self._affectations[nbArms:] = worseArm
# XXX this "trash" arm with max number of collision will not change, but it's the worse arm, so we are optimal!
# Shuffle it once, just to be fair in average
np.random.shuffle(self._affectations)
# print("OracleNotFair: initialized with {} arms and {} players ...".format(nbArms, nbPlayers)) # DEBUG
# print("It decided to use this affectation of arms :") # DEBUG
# Internal object memory
self._players = [None] * nbPlayers
self.children = [None] * nbPlayers #: List of children, fake algorithms
for playerId in range(nbPlayers):
# print(" - Player number {} will always choose the arm number {} ...".format(playerId + 1, self._affectations[playerId])) # DEBUG
self._players[playerId] = Fixed(nbArms, self._affectations[playerId])
self.children[playerId] = ChildPointer(self, playerId)
self._printNbCollisions() # DEBUG
[docs] def __str__(self):
return "OracleNotFair({} x {})".format(self.nbPlayers, str(self._players[0]))
[docs] def _printNbCollisions(self):
""" Print number of collisions. """
nbPlayersAlone = len(set(self._affectations))
if nbPlayersAlone != self.nbPlayers:
print("\n==> This affectation will bring collisions! Exactly {} at each step...".format(self.nbPlayers - nbPlayersAlone))
for armId in range(self.nbArms):
nbAffected = np.count_nonzero(self._affectations == armId)
if nbAffected > 1:
print(" - For arm number {}, there is {} different child player affected on this arm ...".format(armId + 1, nbAffected))