Source code for PoliciesMultiPlayers.CentralizedCycling

# -*- coding: utf-8 -*-
""" CentralizedCycling: a multi-player policy which uses a centralized intelligence to affect users an offset, each one take an orthogonal arm based on (offset + t) % nbArms.

- It allows to have absolutely *no* collision, if there is more channels than users (always assumed).
- And it is perfectly fair on every run: each chosen arm is played successively by each player.
- Note that it is NOT affecting players on the best arms: it has no knowledge of the means of the arms, only of the number of arms nbArms.
from __future__ import division, print_function  # Python 2 compatibility

__author__ = "Lilian Besson"
__version__ = "0.1"

import numpy as np

    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 Cycling(BaseCentralizedPolicy): """ Cycling: select an arm as (offset + t) % nbArms, with offset being decided by the CentralizedCycling multi-player policy. """
[docs] def __init__(self, nbArms, offset): """Cycling with an offset.""" self.nbArms = nbArms #: Number of arms self.offset = offset #: Offset self.t = -1 #: Internal time
[docs] def __str__(self): return "Cycling({})".format(self.offset)
[docs] def startGame(self): """Nothing to do.""" pass
[docs] def getReward(self, arm, reward): """Nothing to do.""" pass
[docs] def choice(self): """Chose cycling arm.""" self.t += 1 return (self.offset + self.t) % self.nbArms
[docs]class CentralizedCycling(BaseMPPolicy): """ CentralizedCycling: a multi-player policy which uses a centralize intelligence to affect users an offset, each one take an orthogonal arm based on (offset + t) % nbArms. """
[docs] def __init__(self, nbPlayers, nbArms, lower=0., amplitude=1.): """ - nbPlayers: number of players to create (in self._players). - nbArms: number of arms. Examples: >>> import random; random.seed(0); import numpy as np; np.random.seed(0) >>> s = CentralizedCycling(2, 3) >>> [ child.choice() for child in s.children ] [2, 1] >>> [ child.choice() for child in s.children ] [0, 2] >>> [ child.choice() for child in s.children ] [1, 0] >>> [ 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 CentralizedCycling class has to be > 0." 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 if nbPlayers <= nbArms: self._offsets = np.random.choice(nbArms, size=nbPlayers, replace=False) # Random offsets else: self._offsets = np.zeros(nbPlayers, dtype=int) self._offsets[:nbArms] = np.random.permutation(nbArms) # Try to minimize the number of doubled offsets, so all the other players are affected to the *same* arm # 1. first option : chose a random offset, everyone else uses it. Plus: minimize collisions trashArm = np.random.choice(nbArms) self._offsets[nbArms:] = trashArm # XXX this "trash" arm with max number of collision will cycle: that's the best we can do! # Shuffle it once, just to be even more fair in average (by repetitions) np.random.shuffle(self._offsets) # print("CentralizedCycling: 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 use an offset of {} ...".format(playerId + 1, self._offsets[playerId])) # DEBUG self._players[playerId] = Cycling(nbArms, self._offsets[playerId]) self.children[playerId] = ChildPointer(self, playerId) self._printNbCollisions() # DEBUG
[docs] def __str__(self): return "CentralizedCycling({} x {})".format(self.nbPlayers, str(self._players[0]))
[docs] def _printNbCollisions(self): """ Print number of collisions. """ nbPlayersAlone = len(set(self._offsets)) 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._offsets == armId) if nbAffected > 1: print(" - For arm number {}, there is {} different child player affected on this arm ...".format(armId + 1, nbAffected))