def local_search():
# This function carries out a local search to improve
# the current guess. You can only examine *ONE* possible
# update to the current solution per call. That is, at
# most one of the current medians should change from
# call to call. Note that this procedure is greedy
# and will only update the current solution if its
# new guess yields a better cost
####################################################
##
## TO DO: Complete this function to perform simple
## local search for better solutions to the
## K-medians problem.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
point = random.randint(0, Kmedians_global_data.N - 1)
median = random.randint(0, Kmedians_global_data.K - 1)
temp_medians = list(Kmedians_global_data.current_medians)
temp_medians.pop(median)
temp_medians.append(Kmedians_global_data.all_points[point])
if Kmedians_global_data.current_cost(
temp_medians) < Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians):
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
return
def local_search():
# This function carries out a local search to improve
# the current guess. You can only examine *ONE* possible
# update to the current solution per call. That is, at
# most one of the current medians should change from
# call to call. Note that this procedure is greedy
# and will only update the current solution if its
# new guess yields a better cost
####################################################
##
## TO DO: Complete this function to perform simple
## local search for better solutions to the
## K-medians problem.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
point =random.randint(0, Kmedians_global_data.N-1)
median = random.randint(0, Kmedians_global_data.K-1)
temp_medians = list(Kmedians_global_data.current_medians)
temp_medians.pop(median)
temp_medians.append(Kmedians_global_data.all_points[point])
if Kmedians_global_data.current_cost(temp_medians) < Kmedians_global_data.current_cost(Kmedians_global_data.current_medians):
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
return
def deterministic_annealing():
# This function carries out a local search using the
# deterministic annealing method as discussed in lecture.
# The 'temperature' is set by the initKmedians function.
# Each call to this function will try a new solution
# and accept it under the conditions specified by the
# deterministic annealing method.
# temperature as T=T*D, where D<1.0 is a decay factor that
# controls how quickly the temperature decreases.
# Both the temperature and decay factor are global
# variables.
# Each call to this function can examine only *ONE*
# guess at the solution.
####################################################
# THE SAME NEIGHBOURHOOD DEFINITION APPLIES AS FOR
# LOCAL SEARCH ABOVE
####################################################
####################################################
##
## TO DO: Complete this function to perform
## local search with deterministic annealing.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
T = Kmedians_global_data.Temperature = Kmedians_global_data.Temperature * Kmedians_global_data.Decay
medians = try_new_medians()
if not medians:
return
med_cost = Kmedians_global_data.current_cost(medians)
cur_cost = Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians)
delta_t = abs(med_cost - cur_cost)
probability = math.exp(-delta_t / T)
r = random.random()
if med_cost > cur_cost:
if r < probability:
Kmedians_global_data.current_medians = medians
else:
Kmedians_global_data.current_medians = medians
print med_cost
return
def MainLoop():
global iters
global screen_shot_on_done
global screeny_filename
temp = list(Kmedians_global_data.current_medians)
if iters < 150:
if Kmedians_global_data.Temperature <= 0:
local_search()
if temp == Kmedians_global_data.current_medians:
iters = iters + 1
else:
iters = 0
else:
deterministic_annealing()
if temp == Kmedians_global_data.current_medians:
iters = iters + 1
else:
iters = 0
renderFrame()
UpdateFrame()
else:
print 'No improvement for past 150 iterations. Search stop.\n'
print "Press 'q' to quit\n"
print "final cost:", Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians)
if not screen_shot_on_done:
exit(0)
def local_search():
# This function carries out a local search to improve
# the current guess. You can only examine *ONE* possible
# update to the current solution per call. That is, at
# most one of the current medians should change from
# call to call. Note that this procedure is greedy
# and will only update the current solution if its
# new guess yields a better cost
#####################################################
# NEIGHBOURHOOD DEFINITION:
# At each step, one of the current guesses for your
# median locations can be swaped for another
# point as long as the distance between the current
# guess and the point is less than 250 units
# (this is Euclidean distance of course)
# This means that you CAN NOT SWAP with just any
# point! Make sure your updates consider this
# simple neighbourhood structure.
#
# If the proposed swap is more than 250 units away,
# do not perform the sawp! just return from this
# function with the same guess you started with.
######################################################
####################################################
##
## TO DO: Complete this function to perform simple
## local search for better solutions to the
## K-medians problem.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
medians = try_new_medians()
if not medians:
return
med_cost = Kmedians_global_data.current_cost(medians)
cur_cost = Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians)
if med_cost < cur_cost:
Kmedians_global_data.current_medians = medians
print med_cost
return
def deterministic_annealing():
# This function carries out a local search using the
# deterministic annealing method as discussed in lecture.
# The 'temperature' is set by the initKmedians function.
# Each call to this function will try a new solution
# and accept it under the conditions specified by the
# deterministic annealing method.
# Also, each call to this function will update the
# temperature as T=T*D, where D<1.0 is a decay factor that
# controls how quickly the temperature decreases.
# Both the temperature and decay factor are global
# variables.
# Each call to this function can examine only *ONE*
# guess at the solution.
####################################################
##
## TO DO: Complete this function to perform
## local search with deterministic annealing.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
point = random.randint(0, Kmedians_global_data.N - 1)
median = random.randint(0, Kmedians_global_data.K - 1)
temp_medians = list(Kmedians_global_data.current_medians)
temp_medians.pop(median)
temp_medians.append(Kmedians_global_data.all_points[point])
if Kmedians_global_data.current_cost(
temp_medians) < Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians):
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
else:
# get the probability
cost_diff = abs(
Kmedians_global_data.current_cost(temp_medians) -
Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians))
probability = math.exp(-cost_diff / Kmedians_global_data.Temperature)
# generate a random float between 0 and 1
rand_float = random.random()
if probability > rand_float:
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
Kmedians_global_data.Temperature = Kmedians_global_data.Temperature * Kmedians_global_data.Decay
return
def deterministic_annealing():
# This function carries out a local search using the
# deterministic annealing method as discussed in lecture.
# The 'temperature' is set by the initKmedians function.
# Each call to this function will try a new solution
# and accept it under the conditions specified by the
# deterministic annealing method.
# Also, each call to this function will update the
# temperature as T=T*D, where D<1.0 is a decay factor that
# controls how quickly the temperature decreases.
# Both the temperature and decay factor are global
# variables.
# Each call to this function can examine only *ONE*
# guess at the solution.
####################################################
##
## TO DO: Complete this function to perform
## local search with deterministic annealing.
##
## Make sure your code updates the global
## 'current_medians' list!
####################################################
point =random.randint(0, Kmedians_global_data.N-1)
median = random.randint(0, Kmedians_global_data.K-1)
temp_medians = list(Kmedians_global_data.current_medians)
temp_medians.pop(median)
temp_medians.append(Kmedians_global_data.all_points[point])
if Kmedians_global_data.current_cost(temp_medians) < Kmedians_global_data.current_cost(Kmedians_global_data.current_medians):
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
else:
# get the probability
cost_diff = abs(Kmedians_global_data.current_cost(temp_medians) - Kmedians_global_data.current_cost(Kmedians_global_data.current_medians))
probability = math.exp(-cost_diff/Kmedians_global_data.Temperature)
# generate a random float between 0 and 1
rand_float = random.random()
if probability > rand_float:
Kmedians_global_data.current_medians = temp_medians
print Kmedians_global_data.current_cost(temp_medians)
Kmedians_global_data.Temperature = Kmedians_global_data.Temperature*Kmedians_global_data.Decay
return
def deterministic_annealing():
# This function carries out a local search using the
# deterministic annealing method as discussed in lecture.
# The 'temperature' is set by the initKmedians function.
# Each call to this function will try a new solution
# and accept it under the conditions specified by the
# deterministic annealing method.
# Also, each call to this function will update the
# temperature as T=T*D, where D<1.0 is a decay factor that
# controls how quickly the temperature decreases.
# Both the temperature and decay factor are global
# variables.
# Each call to this function can examine only *ONE*
# guess at the solution.
####################################################
# THE SAME NEIGHBOURHOOD DEFINITION APPLIES AS FOR
# LOCAL SEARCH ABOVE
####################################################
# all_points - List of [x,y] point coordinates
# current_medians - List of [x,y] with current medians
# N - Number of points
# K - Number of medians
# Temperature - Temperature for deterministic annealing
# Decay - Decay factor for deterministic annealing
g.current_cost(g.current_medians)
old_median = random.choice(g.current_medians)
new_median = random.choice(g.all_points)
if distance(old_median, new_median) > 250:
return
new_medians = g.current_medians[:]
new_medians.remove(old_median)
new_medians.append(new_median)
dT = abs(g.current_cost(g.current_medians) - g.current_cost(new_medians))
P = exp(-dT/g.Temperature)
g.Temperature *= g.Decay
print("temp: %f" % g.Temperature)
print("cost: %f" % g.current_cost(g.current_medians))
if g.current_cost(g.current_medians) > g.current_cost(new_medians):
g.current_medians = new_medians
elif random.random() < P:
g.current_medians = new_medians
return
def local_search():
# This function carries out a local search to improve
# the current guess. You can only examine *ONE* possible
# update to the current solution per call. That is, at
# most one of the current medians should change from
# call to call. Note that this procedure is greedy
# and will only update the current solution if its
# new guess yields a better cost
#####################################################
# NEIGHBOURHOOD DEFINITION:
# At each step, one of the current guesses for your
# median locations can be swaped for another
# point as long as the distance between the current
# guess and the point is less than 250 units
# (this is Euclidean distance of course)
# This means that you CAN NOT SWAP with just any
# point! Make sure your updates consider this
# simple neighbourhood structure.
#
# If the proposed swap is more than 250 units away,
# do not perform the sawp! just return from this
# function with the same guess you started with.
#####################################################
g.current_cost(g.current_medians)
old_median = random.choice(g.current_medians)
new_median = random.choice(g.all_points)
if distance(old_median, new_median) > 250:
return
new_medians = g.current_medians[:]
new_medians.remove(old_median)
new_medians.append(new_median)
if g.current_cost(g.current_medians) > g.current_cost(new_medians):
g.current_medians = new_medians
print g.current_cost(g.current_medians)
def initKmedians(seedNo, N, K, screeny=False, filename=''):
global N_comps
global sigs
global pis
global mus
global blank
global screen_shot_on_done
global screeny_filename
screen_shot_on_done = screeny
if filename:
screeny_filename = filename
Kmedians_global_data.N = N
Kmedians_global_data.K = K
if N < 50 or N > 5000:
print 'Value of N should be between 50 and 5000. Using 100\n'
Kmedians_global_data.N = 100
if K < 1 or K > 15:
print 'Value of K should be between 1 and 15. Using 10\n'
Kmedians_global_data.K = 5
random.seed(31415)
if seedNo >= 0:
pisum = 0
for i in range(N_comps + 1):
pis.append(random.random())
mus.append([random.randint(1, 1022), randint(1, 1022)])
sigs.append([random.randint(50, 500)])
pisum = pisum + pis[i]
for i in range(N_comps + 1):
pis[i] = pis[i] / pisum
else:
blank = open('TO_dense.ppm')
pis.append(7)
mus.append([165, 697])
sigs.append(70)
pis.append(7)
mus.append([185, 530])
sigs.append(100)
pis.append(7)
mus.append([490, 590])
sigs.append(55)
pis.append(7)
mus.append([710, 475])
sigs.append(70)
pis.append(4)
mus.append([300, 250])
sigs.append(150)
pis.append(2.5)
mus.append([950, 340])
sigs.append(140)
pis.append(1.5)
mus.append([610, 230])
sigs.append(200)
pis.append(0.5)
mus.append([512, 512])
sigs.append(1)
pisum = 0
for i in range(N_comps + 1):
pisum = pisum + pis[i]
for i in range(N_comps + 1):
pis[i] = pis[i] / pisum
for i in range(Kmedians_global_data.N):
done = 0
while not done:
dice = random.random()
pisum = 0
idx = 0
while idx < N_comps:
pisum = pisum + pis[idx]
if pisum >= dice:
break
idx = idx + 1
if idx < N_comps:
mu = mus[idx]
sig = sigs[idx]
pt = list([
random.normal(mu[0], sig, 1),
random.normal(mu[1], sig, 1)
])
if pt[0] > 0 and pt[0] < 1023 and pt[1] > 0 and pt[1] < 1023:
done = 1
else:
pt = [random.randint(1, 1023), random.randint(1, 1023)]
done = 1
if seedNo < 0 and done:
pix = list(blank.getpixel(tuple([round(pt[0]), round(pt[1])])))
if pix[0] == 0 and pix[1] == 0 and pix[2] == 0:
done = 0
if done == 1:
Kmedians_global_data.all_points.append(pt)
random.seed(abs(seedNo))
for i in range(Kmedians_global_data.K):
Kmedians_global_data.current_medians.append(
Kmedians_global_data.all_points[random.randint(0, N - 1)])
print 'Initial K-medians guess:\n'
print Kmedians_global_data.current_medians
print 'Initial assignment cost (average distance from a point to the closest candidate median):\n'
print Kmedians_global_data.current_cost(
Kmedians_global_data.current_medians)
