Files
simulationexam/network/importance_sampling.py
T
2015-12-20 13:43:45 -05:00

93 lines
3.0 KiB
Python

from random import Random
from network.network import create_network, get_number_of_activated_antenna
class AntennaGenerator(object):
def __init__(self, box_size, random):
self.box_size = box_size
self._antennas = list(range(box_size * box_size))
self.random = random
def get_random_antenna(self):
idx, prob = self.get_random_index_and_its_probability()
if idx == -1:
self._antennas = []
return -1, prob
choosen_antenna = self._antennas[idx]
self._remove_antenna(idx)
return choosen_antenna, prob
class SuccesiveAntennaGenerator(AntennaGenerator):
def _remove_antenna(self, idx):
ant = self._antennas[idx]
if ant == -1:
self._antennas = []
return ant
if (ant + 1) % self.box_size:
self._antennas = self._antennas[idx + 2:]
else:
self._antennas = self._antennas[idx + 1:]
if ant + self.box_size < self.box_size * self.box_size:
self._antennas.remove(ant + self.box_size)
def get_random_index_and_its_probability(self):
idx = self.random.randint(-1, len(self._antennas)-1)
prob = (len(self._antennas) + 1) ** -1
return idx, prob
class BadAntennaGenerator(SuccesiveAntennaGenerator):
'''this antenna generator does not return 'real' probabilities
and thus cannot be used in importance_sampling'''
def _remove_antenna(self, idx):
ant = self._antennas[idx]
to_remove = {ant, ant + self.box_size, ant - self.box_size}
if (ant + 1) % self.box_size:
to_remove.add(ant + 1)
if ant % self.box_size:
to_remove.add(ant - 1)
self._antennas = [a for a in self._antennas if a not in to_remove]
class BetterSuccesiveAntennaGenerator(SuccesiveAntennaGenerator):
def _get_random_index(self, max_number_inclusive):
if max_number_inclusive < 1:
return self.random.randint(-1, max_number_inclusive)
mean_ = max_number_inclusive/2
x = int(self.random.expovariate(mean_**-1))
if x > max_number_inclusive:
return -1
return x
def get_random_index_and_its_probability(self):
idx = self._get_random_index(len(self._antennas)-1)
prob = (len(self._antennas) + 1) ** -1
return idx, prob
def get_random_network(box_size, random, Generator):
antenna_generator = Generator(box_size, random)
antennas = []
antenna, network_prob = antenna_generator.get_random_antenna()
while antenna != -1:
antennas.append(antenna)
antenna, p = antenna_generator.get_random_antenna()
network_prob *= p
return create_network(antennas), network_prob
def estimate_number_of_activated_antenna(n, box_size, random, Generator):
ret, sum_of_probs = 0, 0
for i in range(n):
network, p = get_random_network(box_size, random, Generator)
ret += get_number_of_activated_antenna(network) / p
sum_of_probs += p**-1
return ret / sum_of_probs