def get_init_assignments_for_lloyd(data, the_binwidths):
# Lloyd can run into trouble if the most extreme assignment points are
# larger in magnitude than the most extreme datapoints, which can happen
# with the uniform quantization, so we just get rid of those initial points.
assgnmnts, _, _, _ = uni(data, the_binwidths, placement_scheme='on_mean')
min_data = np.min(data, axis=0)
max_data = np.max(data, axis=0)
if data.ndim == 1:
min_coeff = np.where(min_data < 0, 0.9, 1.1)
max_coeff = np.where(max_data < 0, 1.1, 0.9)
min_mask = (assgnmnts <= min_coeff * min_data)
max_mask = (assgnmnts >= max_coeff * max_data)
zero_mask = min_mask + max_mask
else:
min_coeff = np.where(min_data < 0, 0.9, 1.1)
max_coeff = np.where(max_data < 0, 1.1, 0.9)
min_mask = np.any(assgnmnts[:, :] <= (min_coeff * min_data)[None, :],
axis=1)
max_mask = np.any(assgnmnts[:, :] >= (max_coeff * max_data)[None, :],
axis=1)
zero_mask = min_mask + max_mask
num_apts_orig = assgnmnts.shape[0]
num_apts_new = assgnmnts.shape[0] - len(zero_mask.nonzero()[0])
assgnmnts = np.delete(assgnmnts, np.where(zero_mask), axis=0)
print("Trimmed extreme assignment points: {} -> {}".format(
num_apts_orig, num_apts_new))
return assgnmnts
def get_init_assignments_for_lloyd(data, the_binwidths):
# Lloyd can run into trouble if the most extreme assignment points are
# larger in magnitude than the most extreme datapoints, which can happen
# with the uniform quantization, so we just get rid of those initial points.
assgnmnts, _, _, _ = uni(data,
the_binwidths,
placement_scheme='on_mode')
min_data = np.min(data, axis=0)
max_data = np.max(data, axis=0)
if data.ndim == 1:
assgnmnts = np.delete(assgnmnts,
np.where(assgnmnts < 0.9 * min_data))
assgnmnts = np.delete(assgnmnts,
np.where(assgnmnts > 0.9 * max_data))
return assgnmnts
else:
assgnmnts = np.delete(
assgnmnts,
np.where(assgnmnts[:, 0] < 0.9 * min_data[0]),
axis=0)
assgnmnts = np.delete(
assgnmnts,
np.where(assgnmnts[:, 0] > 0.9 * max_data[0]),
axis=0)
assgnmnts = np.delete(
assgnmnts,
np.where(assgnmnts[:, 1] < 0.9 * min_data[1]),
axis=0)
assgnmnts = np.delete(
assgnmnts,
np.where(assgnmnts[:, 1] > 0.9 * max_data[1]),
axis=0)
return assgnmnts
random_laplacian_samps[:, i])
pickle.dump(dummy_data, open(samples_fname, 'wb'))
# # next uniform vector (Nd)
uni_2d_rates = []
uni_2d_MSEs = []
uni_binwidth = list(np.linspace(8, 32, 50))
for binwidth in uni_binwidth:
print('RD curve, vector uniform, binwidth=', binwidth)
uni_2d_MSE = []
uni_2d_rate = []
for cluster in range(int(DATA_DIM / QUANT_DIM)):
cluster_data = dummy_data[:, cluster * QUANT_DIM:(cluster + 1) *
QUANT_DIM]
_, _, uni_2d_MSEc, uni_2d_ratec = uni(cluster_data,
np.array([binwidth] *
QUANT_DIM),
placement_scheme='on_mean')
uni_2d_MSE.append(uni_2d_MSEc)
uni_2d_rate.append(uni_2d_ratec)
uni_2d_MSE = np.sum(np.array(uni_2d_MSE))
uni_2d_rate = np.sum(np.array(uni_2d_rate))
uni_2d_MSEs.append(uni_2d_MSE / DATA_DIM)
uni_2d_rates.append(uni_2d_rate / DATA_DIM)
# # next suboptimal generalized Lloyd (2d)
# # Inefficient
# gl_2d_rates = []
# gl_2d_MSEs = []
# for binwidth in np.linspace(8, 60, 50):
# print('RD curve, suboptimal vector Lloyd, binwidth=', binwidth)
# init_assignments, _, _, _ = uni(dummy_data, np.array([binwidth]*DATA_DIM),
def compute_quantization_wrapper(data,
quant_method='uni',
clusters=None,
binwidth=1,
placement_scheme='on_mean',
lagrange_mult=1.,
nn_method='brute_break',
device='cpu'):
"""
Parameters
data: ndarray (d,n)
quant_method: str {'uni', 'lloyd', 'opt_lloyd'}
clusters: [cluster1, cluster2, ...] where cluster1 = [idx_1, idx_2, ...]
binwidth: float or ndarray(n)
placement_scheme: str {'on_mode', 'on_median', 'on_mean', 'on_zero'}
lagrange_mult: float
nn_method: str {'brute_np', 'brute_scipy', 'brute_break', 'kdtree'}
device: str {'numpy', 'cpu', 'cuda', ...}
Returns
a_pts, c_ass, MSE, rate
"""
data_dim = data.shape[1]
if clusters is None:
clusters = [list(range(data_dim))]
if isinstance(binwidth, np.ndarray):
assert (binwidth.shape == (data_dim, ))
else:
binwidth = np.array([float(binwidth)] * data_dim)
a_pts_all = []
c_ass_all = []
MSE_total = 0
rate_total = 0
for cluster in clusters:
cluster_dim = len(cluster)
Xc = data[:, cluster]
binwidth_c = binwidth[cluster]
print('cluster of size {}:'.format(cluster_dim), cluster)
if quant_method == 'uni':
a_pts, c_ass, MSE, rate = uni(Xc,
binwidth_c,
placement_scheme=placement_scheme)
elif quant_method == 'lloyd':
init_apts, _, _, _ = uni(Xc,
binwidth_c,
placement_scheme=placement_scheme)
a_pts, c_ass, MSE, rate = gl(Xc,
init_apts,
force_const_num_assignment_pts=False)
elif quant_method == 'opt_lloyd':
init_apts, _, _, _ = uni(Xc,
binwidth_c,
placement_scheme=placement_scheme)
init_cword_len = (-1. * np.log2(1. / len(init_apts)) * np.ones(
(len(init_apts), )))
if device == 'numpy':
a_pts, c_ass, MSE, rate = opt_gl_numpy(
Xc,
init_apts,
init_cword_len,
lagrange_mult=lagrange_mult,
nn_method=nn_method)
else:
try:
a_pts, c_ass, MSE, rate = opt_gl_torch(
Xc,
init_apts,
init_cword_len,
lagrange_mult=lagrange_mult,
nn_method=nn_method,
device=device)
except RuntimeError as e:
# Cuda mem error; Use numpy
print("Runtime error: {}".format(e))
print("Switching to numpy")
a_pts, c_ass, MSE, rate = opt_gl_numpy(
Xc,
init_apts,
init_cword_len,
lagrange_mult=lagrange_mult,
nn_method=nn_method)
else:
raise ValueError("Invalid quant_method {}".format(quant_method))
print('MSE', MSE, 'rate', rate)
a_pts_all.append(a_pts)
c_ass_all.append(c_ass)
MSE_total += MSE
rate_total += rate
return a_pts_all, c_ass_all, MSE_total, rate_total
def main():
#############################################################################
# first we'll visualize different solutions found uniform scalar quantization
# as well as by the 4 variants of Lloyd that all have similar rates
#############################################################################
random_laplacian_samps = np.random.laplace(scale=10, size=(50000, 2))
dummy_data = np.copy(random_laplacian_samps)
dummy_data[:, 1] = (np.abs(random_laplacian_samps[:, 0]) +
random_laplacian_samps[:, 1])
############################################################
# Uniform scalar quantization of each coefficient separately
BINWIDTH_COMPONENT_0 = 11.
BINWIDTH_COMPONENT_1 = 11.
starttime = time.time()
uni_apts_s0, uni_assignments_s0, uni_MSE_s0, uni_rate_s0 = uni(
dummy_data[:, 0], BINWIDTH_COMPONENT_0, placement_scheme='on_mode')
uni_apts_s1, uni_assignments_s1, uni_MSE_s1, uni_rate_s1 = uni(
dummy_data[:, 1], BINWIDTH_COMPONENT_1, placement_scheme='on_mode')
print("Time to compute uniform scalar quantizations:",
time.time() - starttime)
uni_fig_s0 = plot_1d_and_2d_assignments(
uni_apts_s0,
dummy_data[:, 0],
uni_assignments_s0,
'uniform_scalar',
100,
title='Uniform scalar quantization, component 0')
uni_fig_s1 = plot_1d_and_2d_assignments(
uni_apts_s1,
dummy_data[:, 1],
uni_assignments_s1,
'uniform_scalar',
100,
title='Uniform scalar quantization, component 1')
print('The rate for the uniform scalar quantizer is',
(uni_rate_s0 + uni_rate_s1) / 2, 'bits per component')
print('The MSE for the uniform scalar quantizer is',
(uni_MSE_s0 + uni_MSE_s1) / 2, 'luminace units per component')
print('===========================')
def get_init_assignments_for_lloyd(data, the_binwidths):
# Lloyd can run into trouble if the most extreme assignment points are
# larger in magnitude than the most extreme datapoints, which can happen
# with the uniform quantization, so we just get rid of those initial points.
assgnmnts, _, _, _ = uni(data,
the_binwidths,
placement_scheme='on_mode')
min_data = np.min(data, axis=0)
max_data = np.max(data, axis=0)
if data.ndim == 1:
assgnmnts = np.delete(assgnmnts,
np.where(assgnmnts < 0.9 * min_data))
assgnmnts = np.delete(assgnmnts,
np.where(assgnmnts > 0.9 * max_data))
return assgnmnts
else:
mask_min = np.any(assgnmnts[:, :] < 0.9 * min_data[None, :],
axis=1)
mask_max = np.any(assgnmnts[:, :] > 0.9 * max_data[None, :],
axis=1)
assgnmnts = np.delete(assgnmnts,
np.where(mask_min + mask_max),
axis=0)
return assgnmnts
##########################################################
# Lloyd scalar quantization of each coefficient separately
INIT_BW_C0 = 27 # we need way fewer in this case, bigger starting bins
INIT_BW_C1 = 27
starttime = time.time()
init_assignments = get_init_assignments_for_lloyd(dummy_data[:, 0],
INIT_BW_C0)
gl_apts_s0, gl_assignments_s0, gl_MSE_s0, gl_rate_s0 = gl(
dummy_data[:, 0], init_assignments)
init_assignments = get_init_assignments_for_lloyd(dummy_data[:, 1],
INIT_BW_C1)
gl_apts_s1, gl_assignments_s1, gl_MSE_s1, gl_rate_s1 = gl(
dummy_data[:, 1], init_assignments)
print("Time to compute separate (suboptimal) scalar quantizations:",
time.time() - starttime)
gl_fig_s0 = plot_1d_and_2d_assignments(
gl_apts_s0,
dummy_data[:, 0],
gl_assignments_s0,
'lloyd_scalar',
100,
title='Suboptimal Lloyd scalar quantization, component 0')
gl_fig_s1 = plot_1d_and_2d_assignments(
gl_apts_s1,
dummy_data[:, 1],
gl_assignments_s1,
'lloyd_scalar',
100,
title='Suboptimal Lloyd scalar quantization, component 1')
print('The rate for the suboptimal scalar Lloyd quantizer is',
(gl_rate_s0 + gl_rate_s1) / 2, 'bits per component')
print('The MSE for the suboptial scalar Lloyd quantizer is',
(gl_MSE_s0 + gl_MSE_s1) / 2, 'luminace units per component')
print('===========================')
#############################################################################
# we'll try Lloyd scalar quantization again but this time the optimal version
INIT_BW_C0 = 20
INIT_BW_C1 = 20
#^ We'll give ourselves more clusters, but turn up the lambda and these will
# be pruned down. After some trial and error these settings give us something
# close to the rate of the non-optimal version
starttime = time.time()
init_assignments = get_init_assignments_for_lloyd(dummy_data[:, 0],
INIT_BW_C0)
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
opt_gl_apts_s0, opt_gl_assignments_s0, opt_gl_MSE_s0, opt_gl_rate_s0 = \
opt_gl(dummy_data[:, 0], init_assignments,
init_cword_len, lagrange_mult=0.6)
init_assignments = get_init_assignments_for_lloyd(dummy_data[:, 1],
INIT_BW_C1)
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
opt_gl_apts_s1, opt_gl_assignments_s1, opt_gl_MSE_s1, opt_gl_rate_s1 = \
opt_gl(dummy_data[:, 1], init_assignments,
init_cword_len, lagrange_mult=0.6)
print("Time to compute separate (optimal) scalar quantizations:",
time.time() - starttime)
opt_gl_fig_s0 = plot_1d_and_2d_assignments(
opt_gl_apts_s0,
dummy_data[:, 0],
opt_gl_assignments_s0,
'optimal_lloyd_scalar',
100,
title='Optimal Lloyd scalar quantization, component 0')
opt_gl_fig_s1 = plot_1d_and_2d_assignments(
opt_gl_apts_s1,
dummy_data[:, 1],
opt_gl_assignments_s1,
'optimal_lloyd_scalar',
100,
title='Optimal Lloyd scalar quantization, component 1')
print('The rate for the optimal scalar Lloyd quantizer is',
(opt_gl_rate_s0 + opt_gl_rate_s1) / 2, 'bits per component')
print('The MSE for the optimal scalar Lloyd quantizer is',
(opt_gl_MSE_s0 + opt_gl_MSE_s1) / 2, 'luminace units per component')
print('===========================')
# ##########################################
# Now we can try Uniform VECTOR quantization
BINWIDTHS = np.array([10., 10.])
starttime = time.time()
uni_2d_apts, uni_2d_assignments, uni_2d_MSE, uni_2d_rate = uni(
dummy_data, BINWIDTHS, placement_scheme='on_mode')
print("Time to compute uniform vector quantizations:",
time.time() - starttime)
uni_2d_fig_s0 = plot_1d_and_2d_assignments(
uni_2d_apts,
dummy_data,
uni_2d_assignments,
'uniform_vector',
100,
title='Uniform vector quantization')
print('The rate for the uniform vector quantizer is', uni_2d_rate / 2,
'bits per component')
print('The MSE for the uniform vector quantizer is', uni_2d_MSE / 2,
'luminace units per component')
print('===========================')
##########################################################################
# Now we use the generalized Lloyd to do joint encoding of both components
BINWIDTHS = np.array([29., 30.])
starttime = time.time()
init_assignments = get_init_assignments_for_lloyd(dummy_data, BINWIDTHS)
gl_2d_apts, gl_2d_assignments, gl_2d_MSE, gl_2d_rate = gl(
dummy_data, init_assignments)
print("Time to compute 2d (suboptimal) vector quantization:",
time.time() - starttime)
gl_2d_fig = plot_1d_and_2d_assignments(
gl_2d_apts,
dummy_data,
gl_2d_assignments,
'lloyd_vector',
100,
title='Generalized (vector) Lloyd quantization')
print('The rate for the suboptimal 2d Lloyd quantizer is', gl_2d_rate / 2,
'bits per component')
print('The MSE for the suboptimal 2d Lloyd quantizer is', gl_2d_MSE / 2,
'luminace units per component')
print('===========================')
#######################################################
# We can compare this to the optimal generalized Lloyd
BINWIDTHS = np.array([23., 24.])
starttime = time.time()
init_assignments = get_init_assignments_for_lloyd(dummy_data, BINWIDTHS)
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
opt_gl_2d_apts, opt_gl_2d_assignments, opt_gl_2d_MSE, opt_gl_2d_rate = \
opt_gl(dummy_data, init_assignments, init_cword_len, lagrange_mult=0.1)
print("Time to compute 2d (optimal) vector quantization:",
time.time() - starttime)
opt_gl_2d_fig = plot_1d_and_2d_assignments(
opt_gl_2d_apts,
dummy_data,
opt_gl_2d_assignments,
'optimal_lloyd_vector',
100,
title='Optimal generalized (vector) Lloyd quantization')
print('The rate for the optimal 2d Lloyd quantizer is', opt_gl_2d_rate / 2,
'bits per component')
print('The MSE for the optimal 2d Lloyd quantizer is', opt_gl_2d_MSE / 2,
'luminace units per component')
plt.show()
##########################################################################
# Okay, now let's sweep out some rate-distortion curves using this dataset
##########################################################################
# uniform scalar first
uni_rates = []
uni_MSEs = []
for binwidth in np.linspace(4, 32, 50):
_, _, uni_MSE_s0, uni_rate_s0 = uni(dummy_data[:, 0],
binwidth,
placement_scheme='on_mode')
_, _, uni_MSE_s1, uni_rate_s1 = uni(dummy_data[:, 1],
binwidth,
placement_scheme='on_mode')
uni_rates.append((uni_rate_s0 + uni_rate_s1) / 2)
uni_MSEs.append((uni_MSE_s0 + uni_MSE_s1) / 2)
# for the Lloyd curves I'm going to start the initialization in exactly
# the same places as the uniform so we can see the improvement that Optimal
# Lloyd provides
# suboptimal scalar Lloyd
gl_rates = []
gl_MSEs = []
for binwidth in np.linspace(4, 32, 50):
print('RD curve, suboptimal scalar lloyd, binwidth=', binwidth)
init_assignments, _, _, _ = uni(dummy_data[:, 0],
binwidth,
placement_scheme='on_mode')
_, _, gl_MSE_s0, gl_rate_s0 = gl(dummy_data[:, 0],
init_assignments,
force_const_num_assignment_pts=False)
#^ make this correspond to optimal lloyd with lambda=0.0.
init_assignments, _, _, _ = uni(dummy_data[:, 1],
binwidth,
placement_scheme='on_mode')
_, _, gl_MSE_s1, gl_rate_s1 = gl(dummy_data[:, 1],
init_assignments,
force_const_num_assignment_pts=False)
#^ make this correspond to optimal lloyd with lambda=0.0.
gl_rates.append((gl_rate_s0 + gl_rate_s1) / 2)
gl_MSEs.append((gl_MSE_s0 + gl_MSE_s1) / 2)
# next optimal scalar Lloyd
opt_gl_rates = []
opt_gl_MSEs = []
binwidth = 4
for lagrange_w in np.linspace(0.0, 4.0, 50):
print('RD curve, optimal scalar lloyd, lagrange mult=', lagrange_w)
init_assignments, _, _, _ = uni(dummy_data[:, 0],
binwidth,
placement_scheme='on_mode')
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
_, _, opt_gl_MSE_s0, opt_gl_rate_s0 = opt_gl(dummy_data[:, 0],
init_assignments,
init_cword_len,
lagrange_mult=lagrange_w)
init_assignments, _, _, _ = uni(dummy_data[:, 1],
binwidth,
placement_scheme='on_mode')
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
_, _, opt_gl_MSE_s1, opt_gl_rate_s1 = opt_gl(dummy_data[:, 1],
init_assignments,
init_cword_len,
lagrange_mult=lagrange_w)
opt_gl_rates.append((opt_gl_rate_s0 + opt_gl_rate_s1) / 2)
opt_gl_MSEs.append((opt_gl_MSE_s0 + opt_gl_MSE_s1) / 2)
# plot the three scalar variants
plt.figure(figsize=(20, 20))
plt.plot(uni_MSEs, uni_rates, label='Uniform Scalar', linewidth=4)
plt.plot(gl_MSEs, gl_rates, label='Suboptimal Scalar Lloyd', linewidth=4)
plt.plot(opt_gl_MSEs,
opt_gl_rates,
label='Optimal Scalar Lloyd',
linewidth=4)
plt.legend(fontsize=15)
plt.title('Rate-distortion performance of different scalar quantization ' +
'schemes',
fontsize=20)
plt.xlabel('Distortion (Mean squared error)', fontsize=15)
plt.ylabel('Rate (bits per component)', fontsize=15)
# next uniform vector (2d)
uni_2d_rates = []
uni_2d_MSEs = []
for binwidth in np.linspace(8, 32, 50):
_, _, uni_2d_MSE, uni_2d_rate = uni(dummy_data,
np.array([binwidth, binwidth]),
placement_scheme='on_mode')
uni_2d_rates.append(uni_2d_rate / 2)
uni_2d_MSEs.append(uni_2d_MSE / 2)
# next suboptimal generalized Lloyd (2d)
gl_2d_rates = []
gl_2d_MSEs = []
for binwidth in np.linspace(8, 60, 50):
print('RD curve, suboptimal vector Lloyd, binwidth=', binwidth)
init_assignments, _, _, _ = uni(dummy_data,
np.array([binwidth, binwidth]),
placement_scheme='on_mode')
_, _, gl_2d_MSE, gl_2d_rate = gl(dummy_data,
init_assignments,
force_const_num_assignment_pts=False)
#^ make this correspond to optimal lloyd with lambda=0.0.
gl_2d_rates.append(gl_2d_rate / 2)
gl_2d_MSEs.append(gl_2d_MSE / 2)
# finally, the optimal generalized Lloyd
opt_gl_2d_rates = []
opt_gl_2d_MSEs = []
binwidth = 8
for lagrange_w in np.linspace(0.0, 4.0, 50):
print('RD curve, optimal vector Lloyd, lagrange mult=', lagrange_w)
init_assignments, _, _, _ = uni(dummy_data,
np.array([binwidth, binwidth]),
placement_scheme='on_mode')
init_cword_len = (-1. * np.log2(1. / len(init_assignments)) * np.ones(
(len(init_assignments), )))
_, _, opt_gl_2d_MSE, opt_gl_2d_rate = opt_gl(dummy_data,
init_assignments,
init_cword_len,
lagrange_mult=lagrange_w)
opt_gl_2d_rates.append(opt_gl_2d_rate / 2)
opt_gl_2d_MSEs.append(opt_gl_2d_MSE / 2)
# plot the three 2D variants
plt.figure(figsize=(20, 20))
plt.plot(uni_2d_MSEs, uni_2d_rates, label='Uniform 2D', linewidth=4)
plt.plot(gl_2d_MSEs, gl_2d_rates, label='Suboptimal 2D Lloyd', linewidth=4)
plt.plot(opt_gl_2d_MSEs,
opt_gl_2d_rates,
label='Optimal 2D Lloyd',
linewidth=4)
plt.legend(fontsize=15)
plt.title('Rate-distortion performance of different vector quantization ' +
'schemes',
fontsize=20)
plt.xlabel('Distortion (Mean squared error)', fontsize=15)
plt.ylabel('Rate (bits per component)', fontsize=15)
# plot all the variants together
plt.figure(figsize=(20, 20))
plt.plot(uni_MSEs, uni_rates, label='Uniform Scalar', linewidth=4)
plt.plot(gl_MSEs, gl_rates, label='Suboptimal Scalar Lloyd', linewidth=4)
plt.plot(opt_gl_MSEs,
opt_gl_rates,
label='Optimal Scalar Lloyd',
linewidth=4)
plt.plot(uni_2d_MSEs, uni_2d_rates, label='Uniform 2D', linewidth=4)
plt.plot(gl_2d_MSEs, gl_2d_rates, label='Suboptimal 2D Lloyd', linewidth=4)
plt.plot(opt_gl_2d_MSEs,
opt_gl_2d_rates,
label='Optimal 2D Lloyd',
linewidth=4)
plt.legend(fontsize=15)
plt.title('Rate-distortion performance of 4 variants ' +
'of Lloyd/LBG\nplus 2 variants of uniform quantization',
fontsize=20)
plt.xlabel('Distortion (Mean squared error)', fontsize=15)
plt.ylabel('Rate (bits per component)', fontsize=15)
plt.show()
