def test_clip():
# Test that clip can work with single arguments
X = T.tensor([0.0, -1.0, 1.0])
X_low = T.tensor([0.0, 0.0, 1.0])
X_high = T.tensor([0.0, -1.0, 0.0])
assert_array_equal(tl.clip(X, a_min=0.0), X_low)
assert_array_equal(tl.clip(X, a_max=0.0), X_high)
# More extensive test with a larger random tensor
rng = tl.check_random_state(0)
tensor = tl.tensor(rng.random_sample((10, 10, 10)).astype('float32'))
val1 = np.float32(rng.random_sample())
val2 = np.float32(rng.random_sample())
limits = [(min(val1, val2), max(val1, val2)), (-1, 2),
(tl.max(tensor) + 1, None), (None, tl.min(tensor) - 1),
(tl.max(tensor), None), (tl.min(tensor), None),
(None, tl.max(tensor)), (None, tl.min(tensor))]
for min_val, max_val in limits:
message = f"Tensor clipped incorrectly with min_val={min_val} and max_val={max_val}. Tensor bounds are ({tl.to_numpy(tl.min(tensor))}, {tl.to_numpy(tl.max(tensor))}"
if min_val is not None:
assert tl.all(tl.clip(tensor, min_val, None) >= min_val), message
assert tl.all(
tl.clip(tensor, min_val, max_val) >= min_val), message
if max_val is not None:
assert tl.all(tl.clip(tensor, None, max_val) <= max_val), message
assert tl.all(
tl.clip(tensor, min_val, max_val) <= max_val), message
def test_parafac2_normalize_factors():
rng = check_random_state(1234)
rank = 2 # Rank 2 so we only need to test rank of minimum and maximum
random_parafac2_tensor = random_parafac2(
shapes=[(15 + rng.randint(5), 30) for _ in range(25)],
rank=rank,
random_state=rng,
)
random_parafac2_tensor.factors[0] = random_parafac2_tensor.factors[0] + 0.1
norms = tl.ones(rank)
for factor in random_parafac2_tensor.factors:
norms = norms * tl.norm(factor, axis=0)
slices = parafac2_to_tensor(random_parafac2_tensor)
unnormalized_rec = parafac2(slices,
rank,
random_state=rng,
normalize_factors=False)
assert unnormalized_rec.weights[0] == 1
normalized_rec = parafac2(slices,
rank,
random_state=rng,
normalize_factors=True,
n_iter_max=1000)
assert tl.max(tl.abs(T.norm(normalized_rec.factors[0], axis=0) - 1)) < 1e-5
assert abs(tl.max(norms) -
tl.max(normalized_rec.weights)) / tl.max(norms) < 1e-2
assert abs(tl.min(norms) -
tl.min(normalized_rec.weights)) / tl.min(norms) < 1e-2
def test_tucker():
"""Test for the Tucker decomposition"""
rng = check_random_state(1234)
tol_norm_2 = 10e-3
tol_max_abs = 10e-1
tensor = tl.tensor(rng.random_sample((3, 4, 3)))
core, factors = tucker(tensor, rank=None, n_iter_max=200, verbose=True)
reconstructed_tensor = tucker_to_tensor((core, factors))
norm_rec = tl.norm(reconstructed_tensor, 2)
norm_tensor = tl.norm(tensor, 2)
assert ((norm_rec - norm_tensor) / norm_rec < tol_norm_2)
# Test the max abs difference between the reconstruction and the tensor
assert (tl.max(tl.abs(reconstructed_tensor - tensor)) < tol_max_abs)
# Test the shape of the core and factors
ranks = [2, 3, 1]
core, factors = tucker(tensor, rank=ranks, n_iter_max=100, verbose=1)
for i, rank in enumerate(ranks):
assert_equal(factors[i].shape, (tensor.shape[i], ranks[i]),
err_msg="factors[{}].shape={}, expected {}".format(
i, factors[i].shape, (tensor.shape[i], ranks[i])))
assert_equal(tl.shape(core)[i],
rank,
err_msg="Core.shape[{}]={}, "
"expected {}".format(i, core.shape[i], rank))
# Random and SVD init should converge to a similar solution
tol_norm_2 = 10e-1
tol_max_abs = 10e-1
core_svd, factors_svd = tucker(tensor,
rank=[3, 4, 3],
n_iter_max=200,
init='svd',
verbose=1)
core_random, factors_random = tucker(tensor,
rank=[3, 4, 3],
n_iter_max=200,
init='random',
random_state=1234)
rec_svd = tucker_to_tensor((core_svd, factors_svd))
rec_random = tucker_to_tensor((core_random, factors_random))
error = tl.norm(rec_svd - rec_random, 2)
error /= tl.norm(rec_svd, 2)
assert_(error < tol_norm_2,
'norm 2 of difference between svd and random init too high')
assert_(
tl.max(tl.abs(rec_svd - rec_random)) < tol_max_abs,
'abs norm of difference between svd and random init too high')
def test_parafac_power_iteration():
"""Test for symmetric Parafac optimized with robust tensor power iterations"""
rng = check_random_state(1234)
tol_norm_2 = 10e-1
tol_max_abs = 10e-1
shape = (5, 3, 4)
rank = 4
tensor = random_cp(shape, rank=rank, full=True, random_state=rng)
ktensor = parafac_power_iteration(tensor,
rank=10,
n_repeat=10,
n_iteration=10)
rec = tl.cp_to_tensor(ktensor)
error = tl.norm(rec - tensor, 2) / tl.norm(tensor, 2)
assert_(
error < tol_norm_2,
f'Norm 2 of reconstruction error={error} higher than tol={tol_norm_2}.'
)
error = tl.max(tl.abs(rec - tensor))
assert_(
error < tol_max_abs,
f'Absolute norm of reconstruction error={error} higher than tol={tol_max_abs}.'
)
def simplex_prox(tensor, parameter):
"""
Projects the input tensor on the simplex of radius parameter.
Parameters
----------
tensor : ndarray
parameter : float
Returns
-------
ndarray
References
----------
.. [1]: Held, Michael, Philip Wolfe, and Harlan P. Crowder.
"Validation of subgradient optimization."
Mathematical programming 6.1 (1974): 62-88.
"""
_, col = tl.shape(tensor)
tensor = tl.clip(tensor, 0, tl.max(tensor))
tensor_sort = tl.sort(tensor, axis=0, descending=True)
to_change = tl.sum(tl.where(
tensor_sort > (tl.cumsum(tensor_sort, axis=0) - parameter), 1.0, 0.0),
axis=0)
difference = tl.zeros(col)
for i in range(col):
if to_change[i] > 0:
difference = tl.index_update(
difference, tl.index[i],
tl.cumsum(tensor_sort, axis=0)[int(to_change[i] - 1), i])
difference = (difference - parameter) / to_change
return tl.clip(tensor - difference, a_min=0)
def test_symmetric_parafac_power_iteration(monkeypatch):
"""Test for symmetric Parafac optimized with robust tensor power iterations"""
rng = tl.check_random_state(1234)
tol_norm_2 = 10e-1
tol_max_abs = 10e-1
size = 5
rank = 4
true_factor = tl.tensor(rng.random_sample((size, rank)))
true_weights = tl.ones(rank)
tensor = tl.cp_to_tensor((true_weights, [true_factor] * 3))
weights, factor = symmetric_parafac_power_iteration(tensor,
rank=10,
n_repeat=10,
n_iteration=10)
rec = tl.cp_to_tensor((weights, [factor] * 3))
error = tl.norm(rec - tensor, 2)
error /= tl.norm(tensor, 2)
assert_(error < tol_norm_2, 'norm 2 of reconstruction higher than tol')
# Test the max abs difference between the reconstruction and the tensor
assert_(
tl.max(tl.abs(rec - tensor)) < tol_max_abs,
'abs norm of reconstruction error higher than tol')
assert_class_wrapper_correctly_passes_arguments(
monkeypatch,
symmetric_parafac_power_iteration,
SymmetricCP,
ignore_args={},
rank=3)
def test_parafac2_slice_and_tensor_input():
rank = 3
random_parafac2_tensor = random_parafac2(shapes=[(15, 30)
for _ in range(25)],
rank=rank,
random_state=1234)
tensor = parafac2_to_tensor(random_parafac2_tensor)
slices = parafac2_to_slices(random_parafac2_tensor)
slice_rec = parafac2(slices,
rank,
random_state=1234,
normalize_factors=False,
n_iter_max=100)
slice_rec_tensor = parafac2_to_tensor(slice_rec)
tensor_rec = parafac2(tensor,
rank,
random_state=1234,
normalize_factors=False,
n_iter_max=100)
tensor_rec_tensor = parafac2_to_tensor(tensor_rec)
assert tl.max(tl.abs(slice_rec_tensor - tensor_rec_tensor)) < 1e-8
def test_partial_tucker():
"""Test for the Partial Tucker decomposition"""
rng = tl.check_random_state(1234)
tol_norm_2 = 10e-3
tol_max_abs = 10e-1
tensor = tl.tensor(rng.random_sample((3, 4, 3)))
modes = [1, 2]
core, factors = partial_tucker(tensor, modes, rank=None, n_iter_max=200, verbose=True)
reconstructed_tensor = multi_mode_dot(core, factors, modes=modes)
norm_rec = tl.norm(reconstructed_tensor, 2)
norm_tensor = tl.norm(tensor, 2)
assert_((norm_rec - norm_tensor)/norm_rec < tol_norm_2)
# Test the max abs difference between the reconstruction and the tensor
assert_(tl.max(tl.abs(norm_rec - norm_tensor)) < tol_max_abs)
# Test the shape of the core and factors
ranks = [3, 1]
core, factors = partial_tucker(tensor, modes=modes, rank=ranks, n_iter_max=100, verbose=1)
for i, rank in enumerate(ranks):
assert_equal(factors[i].shape, (tensor.shape[i+1], ranks[i]),
err_msg="factors[{}].shape={}, expected {}".format(
i, factors[i].shape, (tensor.shape[i+1], ranks[i])))
assert_equal(core.shape, [tensor.shape[0]]+ranks, err_msg="Core.shape={}, "
"expected {}".format(core.shape, [tensor.shape[0]]+ranks))
# Test random_state fixes the core and the factor matrices
core1, factors1 = partial_tucker(tensor, modes=modes, rank=ranks, random_state=0)
core2, factors2 = partial_tucker(tensor, modes=modes, rank=ranks, random_state=0)
assert_array_equal(core1, core2)
for factor1, factor2 in zip(factors1, factors2):
assert_array_equal(factor1, factor2)
def test_parafac2_to_tensor():
rng = check_random_state(1234)
rank = 3
I = 25
J = 15
K = 30
weights, factors, projections = random_parafac2(shapes=[(J, K)] * I,
rank=rank,
random_state=rng)
constructed_tensor = parafac2_to_tensor((weights, factors, projections))
tensor_manual = T.zeros((I, J, K), **T.context(weights))
for i in range(I):
Bi = T.dot(projections[i], factors[1])
for j in range(J):
for k in range(K):
for r in range(rank):
tensor_manual = tl.index_update(
tensor_manual, tl.index[i, j,
k], tensor_manual[i, j, k] +
factors[0][i][r] * Bi[j][r] * factors[2][k][r])
assert_(tl.max(tl.abs(constructed_tensor - tensor_manual)) < 1e-6)
def monotonicity_prox(tensor, decreasing=False):
"""
This function projects each column of the input array on the set of arrays so that
x[1] <= x[2] <= ... <= x[n] (decreasing=False)
or
x[1] >= x[2] >= ... >= x[n] (decreasing=True)
is satisfied columnwise.
Parameters
----------
tensor : ndarray
decreasing : If it is True, function returns columnwise
monotone decreasing tensor. Otherwise, returned array
will be monotone increasing.
Default: True
Returns
-------
ndarray
A tensor of which columns' are monotonic.
References
----------
.. [1]: G. Chierchia, E. Chouzenoux, P. L. Combettes, and J.-C. Pesquet
"The Proximity Operator Repository. User's guide"
"""
if tl.ndim(tensor) == 1:
tensor = tl.reshape(tensor, [tl.shape(tensor)[0], 1])
elif tl.ndim(tensor) > 2:
raise ValueError(
"Monotonicity prox doesn't support an input which has more than 2 dimensions."
)
tensor_mon = tl.copy(tensor)
if decreasing:
tensor_mon = tl.flip(tensor_mon, axis=0)
row, column = tl.shape(tensor_mon)
cum_sum = tl.cumsum(tensor_mon, axis=0)
for j in range(column):
assisted_tensor = tl.zeros([row, row])
for i in range(row):
if i == 0:
assisted_tensor = tl.index_update(
assisted_tensor, tl.index[i, i:], cum_sum[i:, j] /
tl.tensor(tl.arange(row - i) + 1, **tl.context(tensor)))
else:
assisted_tensor = tl.index_update(
assisted_tensor, tl.index[i, i:],
(cum_sum[i:, j] - cum_sum[i - 1, j]) /
tl.tensor(tl.arange(row - i) + 1, **tl.context(tensor)))
tensor_mon = tl.index_update(tensor_mon, tl.index[:, j],
tl.max(assisted_tensor, axis=0))
for i in reversed(range(row - 1)):
if tensor_mon[i, j] > tensor_mon[i + 1, j]:
tensor_mon = tl.index_update(tensor_mon, tl.index[i, j],
tensor_mon[i + 1, j])
if decreasing:
tensor_mon = tl.flip(tensor_mon, axis=0)
return tensor_mon
def print_weight(model_path):
model = load_model(model_path)
conv_norm = list()
conv_max = list()
conv_min = list()
depconv_norm = list()
depconv_max = list()
depconv_min = list()
for layer in model.layers:
print(layer.name)
if layer.get_weights() and type(layer).__name__ != 'DepthwiseConv2D':
conv, _ = layer.get_weights()
conv_norm.append(tt.norm(conv))
conv_max.append(tt.max(conv))
conv_min.append(tt.min(conv))
# plt.figure(figsize=(10,10))
# plt.imshow(my_unfold(conv, -1))
# plt.colorbar()
# plt.show()
# plt.clf()
elif layer.get_weights() and type(layer).__name__ == 'DepthwiseConv2D':
w = layer.get_weights()
depconv_norm.append(tt.norm(w[0]))
depconv_max.append(tt.max(w[0]))
depconv_min.append(tt.min(w[0]))
# plt.figure(figsize=(20,20))
# plt.imshow(my_unfold(w[0], -1))
# plt.colorbar()
# plt.show()
# plt.clf()
conv_info = [conv_norm, conv_max, conv_min]
depconv_info = [depconv_norm, depconv_max, depconv_min]
return conv_info, depconv_info
def test_R2X(self):
"""Test to ensure R2X for higher components is larger."""
tensor = tl.tensor(np.random.rand(12, 10, 15))
arr = [find_R2X(tensor, perform_decomposition(tensor, i)) for i in range(1, 8)]
for j in range(len(arr) - 1):
self.assertTrue(arr[j] < arr[j + 1])
# confirm R2X is >= 0 and <=1
self.assertGreaterEqual(tl.min(arr), 0)
self.assertLessEqual(tl.max(arr), 1)
def test_pad_by_zeros():
"""Test that if we pad a tensor by zeros, then it doesn't change.
This failed for TensorFlow at some point.
"""
rng = check_random_state(1234)
rank = 3
I = 25
J = 15
K = 30
weights, factors, projections = random_parafac2(shapes=[(J, K)] * I,
rank=rank,
random_state=rng)
constructed_tensor = parafac2_to_tensor((weights, factors, projections))
padded_tensor = _pad_by_zeros(constructed_tensor)
assert_(tl.max(tl.abs(constructed_tensor - padded_tensor)) < 1e-10)
def test_partial_tucker():
"""Test for the Partial Tucker decomposition"""
rng = check_random_state(1234)
tol_norm_2 = 10e-3
tol_max_abs = 10e-1
tensor = tl.tensor(rng.random_sample((3, 4, 3)))
modes = [1, 2]
for svd_func in tl.SVD_FUNS:
if tl.get_backend() == 'tensorflow_graph' and svd_func == 'numpy_svd':
continue # TODO(craymichael)
core, factors = partial_tucker(tensor,
modes,
rank=None,
n_iter_max=200,
svd=svd_func,
verbose=True)
reconstructed_tensor = multi_mode_dot(core, factors, modes=modes)
norm_rec = tl.to_numpy(tl.norm(reconstructed_tensor, 2))
norm_tensor = tl.to_numpy(tl.norm(tensor, 2))
assert_((norm_rec - norm_tensor) / norm_rec < tol_norm_2)
# Test the max abs difference between the reconstruction and the tensor
assert_(
tl.to_numpy(tl.max(tl.abs(norm_rec - norm_tensor))) < tol_max_abs)
# Test the shape of the core and factors
ranks = [3, 1]
core, factors = partial_tucker(tensor,
modes=modes,
rank=ranks,
n_iter_max=100,
svd=svd_func,
verbose=1)
for i, rank in enumerate(ranks):
assert_equal(
factors[i].shape, (tensor.shape[i + 1], ranks[i]),
err_msg="factors[{}].shape={}, expected {} (svd=\"{}\")".
format(i, factors[i].shape, (tensor.shape[i + 1], ranks[i]),
svd_func))
assert_equal(core.shape, [tensor.shape[0]] + ranks,
err_msg="Core.shape={}, "
"expected {} (svd=\"{}\")".format(
core.shape, [tensor.shape[0]] + ranks, svd_func))
def gcp(X, R, type='normal', func=None, grad=None, lower=None,\
opt='lbfgsb', mask=None, maxiters=1000, \
init='random', printitn=10, state=None, factr=1e7, pgtol=1e-4, \
fsamp=None, gsamp=None, oversample=1.1, sampler='uniform', \
fsampler=None, rate=1e-3, decay=0.1, maxfails=1, epciters=1000, \
festtol=-math.inf, beta1=0.9, beta2=0.999, epsilon=1e-8):
"""Generalized CANDECOMP/PARAFAC (GCP) decomposition via all-at-once optimization (OPT) [1]
Computes a rank-'R' decomposition of 'tensor' such that::
tensor = [|weights; factors[0], ..., factors[-1] |].
GCP-OPT allows the use of a variety of statistically motivated loss functions
suited to the data held in a tensor (i.e. continuous, discrete, binary, etc)
Parameters
----------
X : ndarray
Tensor to factorize
**COMING SOON**
Sparse tensor support
R : int
Rank of decomposition (Number of components).
type : str,
Type of objective function used
Options include:
'normal' or 'gaussian' - Gaussian for real-valued data (DEFAULT)
'binary' or 'bernoulli-odds' - Bernoulli w/ odds link for binary data
'bernoulli-logit' - Bernoulli w/ logit link for binary data
'count' or 'poisson' - Poisson for count data
'poisson-log' - Poisson w/ log link for count data
'rayleigh' - Rayleigh distribution for real-valued data
'gamma' - Gamma distribution for non-negative real-valued data
**COMING SOON**:
'huber (DELTA) - Similar to Gaussian, for real-valued data
'negative-binomial (r)' - Negative binomial for count data
'beta (BETA)' - Beta divergence for non-negative real-valued data
'user-specified' - Customized objective function provided by user
func: lambda function
User specified custom objective function, eg. lambda x, m: (m-x)**2
grad: lambda function
User specified custom gradient function, eg. lambda x, m: 2*(m-x)
lower: 0 or -inf
Lower bound for custom objective/gradient
opt : str
Optimization method
Options include:
'lbfgsb' - Bound-constrained limited-memory BFGS
'sgd' - Stochastic gradient descent (SGD)
**COMING SOON**
'adam' - Momentum-based SGD method
'adagrad' - Adaptive gradient algorithm, well suited for sparse data
If 'tensor' is dense, all 4 options can be used, 'lbfgsb' by default.
**COMING SOON** - Sparse format support
If 'tensor' is sparse, only 'sgd', 'adam' and 'adagrad' can be used, 'adam' by
default.
Each method has specific parameters, see documentation
mask : ndarray
Specifies a mask, 0's for missing/incomplete entries, 1's elsewhere, with
the same shape as 'tensor'.
**COMING SOON** - Missing/incomplete data simulation.
maxiters : int
Maximum number of outer iterations, 1000 by default.
init : {'random', 'svd', cptensor}
Initialization for factor matrices, 'random' by default.
Options include:
'random' - random initialization from a uniform distribution on [0,1)
'svd' - initialize the `m`th factor matrix using the `rank` left
singular vectors of the `m`th unfolding of the input tensor.
cptensor - initialization provided by user. NOTE: weights are pulled
in the last factor and then the weights are set to "1" for
the output tensor.
Initializations all result in a cptensor where the weights are one.
printitn : int
Print every n iterations; 0 for no printing, 10 by default.
state : {None, int, np.random.RandomState}
Seed for reproducable random number generation
factr : float
(L-BFGS-B parameter)
Tolerance on the change of objective values. Defaults to 1e7.
pgtol : float
(L-BFGS-B parameter)
Projected gradient tolerance. Defaults to 1e-5
sampler : {uniform, stratified, semi-stratified}
Type of sampling to use for stochastic gradient (SGD/ADAM/ADAGRAD).
Defaults to 'uniform' for dense tensors.
Defaults to 'stratified' for sparse tensors.
Options include:
'uniform' - Uniform random sampling
**COMING SOON**
'stratified' - Stratified sampling, targets sparse data. Zero and
nonzero values sampled separately.
'semi-stratified' - Similar to stratified sampling, but is more
computationally efficient (See papers referenced).
gsamp : int
Number of samples for stochastic gradient (SGD/ADAM/ADAGRAD parameter).
Generally set to be O(sum(shape)*R).
**COMING SOON**
For stratified or semi-stratified, this may be two numbers:
- the number of nnz samples
- the number of zero samples.
If only one number is specified, then this value is used for both nnzs and
zeros (total number of samples is 2x specified value in this case).
fsampler : {'uniform', 'stratified', custom}
Type of sampling for estimating objective function (SGD/ADAM/ADAGRAD parameter).
Options include:
'uniform' - Uniform random sampling
**COMING SOON**
'stratified' - Stratified sampling, targets sparse data. Zero and
nonzero values sampled separately.
custom - User-defined sampler (lambda function). Custom option
is primarily useful in reusing sampled elements across
multiple tests.
fsamp : int
(SGD/ADAM/ADAGRAD parameter)
Number of samples to estimate objective function.
This should generally be somewhat large since we want this sample to generate a
reliable estimate of the true function value.
oversample : float
(Stratified sampling parameter)
Factor to oversample when implicitly sampling zeros in the sparse case.
Defaults to 1.1. Only adjust for very small tensors.
rate : float
(SGD/ADAM parameter)
Initial learning rate. Defaults to 1e-3.
decay : float
(SGD/ADAM parameter)
Amount to decrease learning rate when progress stagnates, i.e. no change in
objective function between epochs. Defaults to 0.1.
maxfails : int
(SGD/ADAM parameter)
Number of times to decrease the learning rate.
Defaults to 1, may be set to zero.
epciters : int
(SGD/ADAM parameter)
Iterations per epoch. Defaults to 1000.
festtol : float
(SGD/ADAM parameter)
Quit estimation of function if it goes below this level.
Defaults to -inf.
beta1 : float
(ADAM parameter) - generally doesn't need to be changed
Defaults to 0.9
beta2 : float
(ADAM parameter) - generally doesn't need to be changed
Defaults to 0.999
epsilon : float
(ADAM parameter) - generally doesn't need to be changed
Defaults to 1e-8
Returns
-------
Mfin : CPTensor
Canonical polyadic decomposition of input tensor X
Reference
---------
[1] D. Hong, T. G. Kolda, J. A. Duersch, Generalized Canonical
Polyadic Tensor Decomposition, SIAM Review, 62:133-163, 2020,
https://doi.org/10.1137/18M1203626
[2] T. G. Kolda, D. Hong, Stochastic Gradients for Large-Scale Tensor
Decomposition. SIAM J. Mathematics of Data Science, 2:1066-1095,
2020, https://doi.org/10.1137/19m1266265
"""
# Timer - Setup (outside optimization)
start_setup0 = time.perf_counter()
# Initial setup
nd = tl.ndim(X)
sz = tl.shape(X)
tsz = X.size
X_context = tl.context(X)
vecsz = 0
for i in range(nd):
# tsz *= sz[i]
vecsz += sz[i]
vecsz *= R
W = mask
# Random set-up
if state is not None:
state = tl.check_random_state(state)
# capture stats(nnzs, zeros, missing)
nnonnzeros = 0
X = tl.tensor_to_vec(X)
for i in X:
if i > 0:
nnonnzeros += 1
X = tl.reshape(X, sz)
nzeros = tsz - nnonnzeros
nmissing = 0
if W is not None:
W = tl.tensor_to_vec(W)
for i in range(tl.shape(W)[0]):
if W[i] > 0: nmissing += 1 # TODO: is this right??
W = tl.reshape(W, sz)
# Dictionary for storing important information regarding the decomposition problem
info = {}
info['tsz'] = tsz
info[
'nmissing'] = 0 # TODO: revisit once missing value functionality incorporated
info['nnonnzeros'] = nnonnzeros
info[
'nzeros'] = nzeros # TODO: revisit once missing value functionality incorporated
# Set up function, gradient, and bounds
fh, gh, lb = validate_type(type, X)
info['type'] = type
info['fh'] = fh
info['gh'] = gh
info['lb'] = lb
# initialize CP-tensor and make a copy to work with so as to have the starting guess
M0 = initialize_cp(X, R, init=init, random_state=state)
wghts0 = tl.copy(M0[0])
fcts0 = []
for i in range(nd):
f = tl.copy(M0[1][i])
fcts0.append(f)
M = CPTensor((wghts0, fcts0))
# Lambda weights are assumed to be all ones throughout, check initial guess satisfies assumption
if not tl.all(M[0]):
print("Initialization of CP tensor has failed (lambda weight(s) != 1.")
sys.exit(1)
# check optimization method
if validate_opt(opt):
print("Choose optimization method from: {lbfgsb, sgd}")
sys.exit(1)
use_stoc = False
if opt != 'lbfgsb':
use_stoc = True
info['opt'] = opt
# set up for stochastic optimization (e.g. sgd, adam, adagrad)
if use_stoc:
# set up fsampler, gsampler ---> uniform sampling only for now
# TODO : add stratified, semi-stratified and user-specified sampling options
if not sampler == "uniform":
print(
"Only uniform sampling currently supported for stochastic optimization."
)
sys.exit(1)
fsampler_type = sampler
gsampler_type = sampler
# setup fsampler
f_samp = fsamp
if f_samp == None:
upper = np.maximum(math.ceil(tsz / 10), 10 ^ 6)
f_samp = np.minimum(upper, tsz)
# set up lambda function/function handle for uniform sampling
fsampler = lambda: tl_sample_uniform(X, f_samp)
fsampler_str = "{} with {} samples".format(fsampler_type, f_samp)
# setup gsampler
g_samp = gsamp
if g_samp == None:
upper = np.maximum(1000, math.ceil(10 * tsz / maxiters))
g_samp = np.minimum(upper, tsz)
# setup lambda function/function handle for uniform sampling
gsampler = lambda: tl_sample_uniform(X, g_samp)
gsampler_str = "{} with {} samples".format(gsampler_type, g_samp)
# capture the info
info['fsampler'] = fsampler_str
info['gsampler'] = gsampler_str
info['fsamp'] = f_samp
info['gsamp'] = g_samp
time_setup0 = time.perf_counter() - start_setup0
# Welcome message
if printitn > 0:
print("GCP-OPT-{} (Generalized CP Tensor Decomposition)".format(opt))
print("------------------------------------------------")
print("Tensor size:\t\t\t\t{} ({} total entries)".format(sz, tsz))
if nmissing > 0:
print("Missing entries: {} ({})".format(nmissing,
100 * nmissing / tsz))
print("Generalized function type:\t{}".format(type))
print("Objective function:\t\t\t{}".format(
inspect.getsource(fh).strip()))
print("Gradient function:\t\t\t{}".format(
inspect.getsource(gh).strip()))
print("Lower bound of factors:\t\t{}".format(lb))
print("Optimization method:\t\t{}".format(opt))
if use_stoc:
print("Max iterations (epochs): {}".format(maxiters))
print("Iterations per epoch: {}".format(epciters))
print("Learning rate / decay / maxfails: {} {} {}".format(
rate, decay, maxfails))
print("Function Sampler: {}".format(fsampler_str))
print("Gradient Sampler: {}".format(gsampler_str))
else:
print("Max iterations:\t\t\t\t{}".format(maxiters))
print("Projected gradient tol:\t\t{}\n".format(pgtol))
# Make like a zombie and start decomposing
Mfin = None
# L-BFGS-B optimization
if opt == 'lbfgsb':
# Timer - Setup (inside optimization)
start_setup1 = time.perf_counter()
# set up bounds for l-bfgs-b if lb = 0
bounds = None
if lb == 0:
lb = tl.zeros(tsz)
ub = math.inf * tl.ones(tsz)
fcn = lambda x: tl_gcp_fg(vec2factors(x, sz, R, X_context), X, fh, gh)
m = factors2vec(M[1])
# capture params for l-bfgs-b
lbfgsb_params = {}
lbfgsb_params['x0'] = factors2vec(M0.factors)
lbfgsb_params['printEvery'] = printitn
lbfgsb_params['maxIts'] = maxiters
lbfgsb_params['maxTotalIts'] = maxiters * 10
lbfgsb_params['factr'] = factr
lbfgsb_params['pgtol'] = pgtol
time_setup1 = time.perf_counter() - start_setup1
if printitn > 0:
print("Begin main loop")
# Timer - Main operation
start_main = time.perf_counter()
x, f, info_dict = fmin_l_bfgs_b(fcn, m, approx_grad=False, bounds=None, \
pgtol=pgtol, factr=factr, maxiter=maxiters)
time_main = time.perf_counter() - start_main
# capture info
info['fcn'] = fcn
info['lbfgsbopts'] = lbfgsb_params
info['lbfgsbout'] = info_dict
info['finalf'] = f
if printitn > 0:
print("\nFinal objective: {}".format(f))
print("Setup time: {}".format(time_setup0 + time_setup1))
print("Main loop time: {}".format(time_main))
print("Outer iterations:"
) # TODO: access this value (see manpage for fmin_l_bfgs_b)
print("Total iterations: {}".format(info_dict['nit']))
print("L-BFGS-B exit message: {} ({})".format(
info_dict['task'], info_dict['warnflag']))
Mfin = vec2factors(x, sz, R, X_context)
# Stochastic optimization
else:
# Timer - Setup (inside optimization)
start_setup1 = time.perf_counter()
if opt == "adam" or opt == "adagrad":
print("{} not currently supported".format(opt))
sys.exit(1)
# prepare for sgd
# initialize moments
m = []
v = []
# Extract samples for estimating function value (i.e. call fsampler), these never change
fsubs, fvals, fwgts = fsampler()
# Compute initial estimated function value
fest = tl_gcp_fg_est(M, fh, gh, fsubs, fvals, fwgts, True, False,
False, False)
# Set up loop variables
nfails = 0
titers = 0
M_weights = tl.copy(M[0])
M_factors = []
for k in range(nd):
M_factors.append(tl.copy(M[1][k]))
Msave = CPTensor(
(M_weights, M_factors)) # save a copy of the initial model
msave = m
vsave = v
fest_prev = fest[0]
# Tracing the progress in function value by epoch
fest_trace = tl.zeros(maxiters + 1)
step_trace = tl.zeros(maxiters + 1)
time_trace = tl.zeros(maxiters + 1)
fest_trace[0] = fest[0]
# Print status
if printitn > 0:
print("Begin main loop")
print("Initial f-est: {}".format(fest[0]))
time_setup1 = time.perf_counter() - start_setup1
start_main = time.perf_counter()
time_trace[0] = time.perf_counter() - start_setup0
# Main loop - outer iteration
for nepoch in range(maxiters):
step = (decay**nfails) * rate
# Main loop - inner iteration
for iter in range(epciters):
# Tracking iterations
titers = titers + 1
# Select subset for stochastic gradient (i.e. call gsampler)
gsubs, gvals, gwts = gsampler()
# Compute gradients for each mode
Gest = tl_gcp_fg_est(M, fh, gh, gsubs, gvals, gwts, False,
True, False, False)
# Check for inf gradient
for g in Gest[0]:
g_max = tl.max(g)
g_min = tl.min(g)
if math.isinf(g_max) or math.isinf(g_min):
print(
"Infinite gradient encountered! (epoch = {}, iter = {})"
.format(nepoch, iter))
# TODO : add functionality for ADAM and ADAGRAD optimization
# Take gradient step
for k in range(nd):
M.factors[k] = M.factors[k] - step * Gest[0][k]
# Estimate objective (i.e. call tl_gcp_fg_est)
fest = tl_gcp_fg_est(M, fh, gh, fsubs, fvals, fwgts, True, False,
False, False)
# Save trace (fest & step)
fest_trace[nepoch + 1] = fest[0]
step_trace[nepoch + 1] = step
# Check convergence condition
failed_epoch = False
if fest[0] > fest_prev:
failed_epoch = True
if failed_epoch:
nfails += 1
festtol_test = False
if fest[0] < festtol:
festtol_test = True
# Reporting
if printitn > 0 and (nepoch % printitn == 0 or failed_epoch
or festtol_test):
print("Epoch {}: f-est = {}, step = {}".format(
nepoch, fest[0], step),
end='')
if failed_epoch:
print(
", nfails = {} (resetting to solution from last epoch)"
.format(nfails))
print("")
# Rectify failed epoch or save current solution
if failed_epoch:
M = Msave
m = msave
v = vsave
fest[0] = fest_prev
titers = titers - epciters
else:
Msave = CPTensor((tl.copy(M.weights), tl.copy(M.factors)))
msave = m
vsave = v
fest_prev = fest[0]
time_trace[nepoch] = time.perf_counter() - start_setup0
if (nfails > maxfails) or festtol_test:
break
Mfin = M
time_main = time.perf_counter() - start_main
# capture info
info['fest_trace'] = fest_trace
info['step_trace'] = step_trace
info['time_trace'] = time_trace
info['nepoch'] = nepoch
# Report end of main loop
if printitn > 0:
print("End Main Loop")
print("")
print("Final f-east: {}".format(fest[0]))
print("Setup time: {0:0.6f}".format(time_setup0 + time_setup1))
print("Main loop time: {0:0.6f}".format(time_main))
print("Total iterations: {}".format(nepoch * epciters))
# Wrap up / capture remaining info
info['mainTime'] = time_main
info['setupTime0'] = time_setup0
info['setupTime1'] = time_setup1
info['setupTime'] = time_setup0 + time_setup1
return Mfin
def test_non_negative_parafac_hals():
"""Test for non-negative PARAFAC HALS
TODO: more rigorous test
"""
tol_norm_2 = 10e-1
tol_max_abs = 1
rng = tl.check_random_state(1234)
tensor = tl.tensor(rng.random_sample((3, 3, 3)) + 1)
res = parafac(tensor, rank=3, n_iter_max=120)
nn_res = non_negative_parafac_hals(tensor,
rank=3,
n_iter_max=100,
tol=10e-4,
init='svd',
verbose=0)
# Make sure all components are positive
_, nn_factors = nn_res
for factor in nn_factors:
assert_(tl.all(factor >= 0))
reconstructed_tensor = tl.cp_to_tensor(res)
nn_reconstructed_tensor = tl.cp_to_tensor(nn_res)
error = tl.norm(reconstructed_tensor - nn_reconstructed_tensor, 2)
error /= tl.norm(reconstructed_tensor, 2)
assert_(error < tol_norm_2, 'norm 2 of reconstruction higher than tol')
# Test the max abs difference between the reconstruction and the tensor
assert_(
tl.max(tl.abs(reconstructed_tensor - nn_reconstructed_tensor)) <
tol_max_abs, 'abs norm of reconstruction error higher than tol')
# Test fixing mode 0 or 1 with given init
fixed_tensor = random_cp((3, 3, 3), rank=2)
for factor in fixed_tensor[1]:
factor = tl.abs(factor)
rec_svd_fixed_mode_0 = non_negative_parafac_hals(tensor,
rank=2,
n_iter_max=2,
init=fixed_tensor,
fixed_modes=[0])
rec_svd_fixed_mode_1 = non_negative_parafac_hals(tensor,
rank=2,
n_iter_max=2,
init=fixed_tensor,
fixed_modes=[1])
# Check if modified after 2 iterations
assert_array_equal(
rec_svd_fixed_mode_0.factors[0],
fixed_tensor.factors[0],
err_msg='Fixed mode 0 was modified in candecomp_parafac')
assert_array_equal(
rec_svd_fixed_mode_1.factors[1],
fixed_tensor.factors[1],
err_msg='Fixed mode 1 was modified in candecomp_parafac')
res_svd = non_negative_parafac_hals(tensor,
rank=3,
n_iter_max=100,
tol=10e-4,
init='svd')
res_random = non_negative_parafac_hals(tensor,
rank=3,
n_iter_max=100,
tol=10e-4,
init='random',
verbose=0)
rec_svd = tl.cp_to_tensor(res_svd)
rec_random = tl.cp_to_tensor(res_random)
error = tl.norm(rec_svd - rec_random, 2)
error /= tl.norm(rec_svd, 2)
assert_(error < tol_norm_2,
'norm 2 of difference between svd and random init too high')
assert_(
tl.max(tl.abs(rec_svd - rec_random)) < tol_max_abs,
'abs norm of difference between svd and random init too high')
# Regression test: used wrong variable for convergence checking
# Used mttkrp*factor instead of mttkrp*factors[-1], which resulted in
# error when mode 2 was not constrained and erroneous convergence checking
# when mode 2 was constrained.
tensor = tl.tensor(rng.random_sample((3, 3, 3)) + 1)
nn_estimate, errs = non_negative_parafac_hals(tensor,
rank=2,
n_iter_max=2,
tol=1e-10,
init='svd',
verbose=0,
nn_modes={
0,
},
return_errors=True)
def hals_nnls(UtM,
UtU,
V=None,
n_iter_max=500,
tol=10e-8,
sparsity_coefficient=None,
normalize=False,
nonzero_rows=False,
exact=False):
"""
Non Negative Least Squares (NNLS)
Computes an approximate solution of a nonnegative least
squares problem (NNLS) with an exact block-coordinate descent scheme.
M is m by n, U is m by r, V is r by n.
All matrices are nonnegative componentwise.
This algorithm is defined in [1], as an accelerated version of the HALS algorithm.
It features two accelerations: an early stop stopping criterion, and a
complexity averaging between precomputations and loops, so as to use large
precomputations several times.
This function is made for being used repetively inside an
outer-loop alternating algorithm, for instance for computing nonnegative
matrix Factorization or tensor factorization.
Parameters
----------
UtM: r-by-n array
Pre-computed product of the transposed of U and M, used in the update rule
UtU: r-by-r array
Pre-computed product of the transposed of U and U, used in the update rule
V: r-by-n initialization matrix (mutable)
Initialized V array
By default, is initialized with one non-zero entry per column
corresponding to the closest column of U of the corresponding column of M.
n_iter_max: Postivie integer
Upper bound on the number of iterations
Default: 500
tol : float in [0,1]
early stop criterion, while err_k > delta*err_0. Set small for
almost exact nnls solution, or larger (e.g. 1e-2) for inner loops
of a PARAFAC computation.
Default: 10e-8
sparsity_coefficient: float or None
The coefficient controling the sparisty level in the objective function.
If set to None, the problem is solved unconstrained.
Default: None
nonzero_rows: boolean
True if the lines of the V matrix can't be zero,
False if they can be zero
Default: False
exact: If it is True, the algorithm gives a results with high precision but it needs high computational cost.
If it is False, the algorithm gives an approximate solution
Default: False
Returns
-------
V: array
a r-by-n nonnegative matrix \approx argmin_{V >= 0} ||M-UV||_F^2
rec_error: float
number of loops authorized by the error stop criterion
iteration: integer
final number of update iteration performed
complexity_ratio: float
number of loops authorized by the stop criterion
Notes
-----
We solve the following problem :math:`\\min_{V >= 0} ||M-UV||_F^2`
The matrix V is updated linewise. The update rule for this resolution is::
.. math::
\\begin{equation}
V[k,:]_(j+1) = V[k,:]_(j) + (UtM[k,:] - UtU[k,:]\\times V_(j))/UtU[k,k]
\\end{equation}
with j the update iteration.
This problem can also be defined by adding a sparsity coefficient,
enhancing sparsity in the solution [2]. In this sparse version, the update rule becomes::
.. math::
\\begin{equation}
V[k,:]_(j+1) = V[k,:]_(j) + (UtM[k,:] - UtU[k,:]\\times V_(j) - sparsity_coefficient)/UtU[k,k]
\\end{equation}
References
----------
.. [1]: N. Gillis and F. Glineur, Accelerated Multiplicative Updates and
Hierarchical ALS Algorithms for Nonnegative Matrix Factorization,
Neural Computation 24 (4): 1085-1105, 2012.
.. [2] J. Eggert, and E. Korner. "Sparse coding and NMF."
2004 IEEE International Joint Conference on Neural Networks
(IEEE Cat. No. 04CH37541). Vol. 4. IEEE, 2004.
"""
rank, n_col_M = tl.shape(UtM)
if V is None: # checks if V is empty
V = tl.solve(UtU, UtM)
V = tl.clip(V, a_min=0, a_max=None)
# Scaling
scale = tl.sum(UtM * V) / tl.sum(UtU * tl.dot(V, tl.transpose(V)))
V = V * scale
if exact:
n_iter_max = 50000
tol = 10e-16
for iteration in range(n_iter_max):
rec_error = 0
for k in range(rank):
if UtU[k, k]:
if sparsity_coefficient is not None: # Modifying the function for sparsification
deltaV = tl.where(
(UtM[k, :] - tl.dot(UtU[k, :], V) -
sparsity_coefficient) / UtU[k, k] > -V[k, :],
(UtM[k, :] - tl.dot(UtU[k, :], V) -
sparsity_coefficient) / UtU[k, k], -V[k, :])
V = tl.index_update(V, tl.index[k, :], V[k, :] + deltaV)
else: # without sparsity
deltaV = tl.where(
(UtM[k, :] - tl.dot(UtU[k, :], V)) / UtU[k, k] >
-V[k, :],
(UtM[k, :] - tl.dot(UtU[k, :], V)) / UtU[k, k],
-V[k, :])
V = tl.index_update(V, tl.index[k, :], V[k, :] + deltaV)
rec_error = rec_error + tl.dot(deltaV, tl.transpose(deltaV))
# Safety procedure, if columns aren't allow to be zero
if nonzero_rows and tl.all(V[k, :] == 0):
V[k, :] = tl.eps(V.dtype) * tl.max(V)
elif nonzero_rows:
raise ValueError("Column " + str(k) +
" of U is zero with nonzero condition")
if normalize:
norm = tl.norm(V[k, :])
if norm != 0:
V[k, :] /= norm
else:
sqrt_n = 1 / n_col_M**(1 / 2)
V[k, :] = [sqrt_n for i in range(n_col_M)]
if iteration == 0:
rec_error0 = rec_error
numerator = tl.shape(V)[0] * tl.shape(V)[1] + tl.shape(V)[1] * rank
denominator = tl.shape(V)[0] * rank + tl.shape(V)[0]
complexity_ratio = 1 + (numerator / denominator)
if exact:
if rec_error < tol * rec_error0:
break
else:
if rec_error < tol * rec_error0 or iteration > 1 + 0.5 * complexity_ratio:
break
return V, rec_error, iteration, complexity_ratio
def unimodality_prox(tensor):
"""
This function projects each column of the input array on the set of arrays so that
x[1] <= x[2] <= x[j] >= x[j+1]... >= x[n]
is satisfied columnwise.
Parameters
----------
tensor : ndarray
Returns
-------
ndarray
A tensor of which columns' distribution are unimodal.
References
----------
.. [1]: Bro, R., & Sidiropoulos, N. D. (1998). Least squares algorithms under
unimodality and non‐negativity constraints. Journal of Chemometrics:
A Journal of the Chemometrics Society, 12(4), 223-247.
"""
if tl.ndim(tensor) == 1:
tensor = tl.vec_to_tensor(tensor, [tl.shape(tensor)[0], 1])
elif tl.ndim(tensor) > 2:
raise ValueError(
"Unimodality prox doesn't support an input which has more than 2 dimensions."
)
tensor_unimodal = tl.copy(tensor)
monotone_increasing = tl.tensor(monotonicity_prox(tensor),
**tl.context(tensor))
monotone_decreasing = tl.tensor(monotonicity_prox(tensor, decreasing=True),
**tl.context(tensor))
# Next line finds mutual peak points
values = tl.tensor(
tl.to_numpy((tensor - monotone_decreasing >= 0)) * tl.to_numpy(
(tensor - monotone_increasing >= 0)), **tl.context(tensor))
sum_inc = tl.where(values == 1,
tl.cumsum(tl.abs(tensor - monotone_increasing), axis=0),
tl.tensor(0, **tl.context(tensor)))
sum_inc = tl.where(values == 1,
sum_inc - tl.abs(tensor - monotone_increasing),
tl.tensor(0, **tl.context(tensor)))
sum_dec = tl.where(
tl.flip(values, axis=0) == 1,
tl.cumsum(tl.abs(
tl.flip(tensor, axis=0) - tl.flip(monotone_decreasing, axis=0)),
axis=0), tl.tensor(0, **tl.context(tensor)))
sum_dec = tl.where(
tl.flip(values, axis=0) == 1, sum_dec -
tl.abs(tl.flip(tensor, axis=0) - tl.flip(monotone_decreasing, axis=0)),
tl.tensor(0, **tl.context(tensor)))
difference = tl.where(values == 1, sum_inc + tl.flip(sum_dec, axis=0),
tl.max(sum_inc + tl.flip(sum_dec, axis=0)))
min_indice = tl.argmin(tl.tensor(difference), axis=0)
for i in range(len(min_indice)):
tensor_unimodal = tl.index_update(
tensor_unimodal, tl.index[:int(min_indice[i]), i],
monotone_increasing[:int(min_indice[i]), i])
tensor_unimodal = tl.index_update(
tensor_unimodal, tl.index[int(min_indice[i] + 1):, i],
monotone_decreasing[int(min_indice[i] + 1):, i])
return tensor_unimodal
def proximal_operator(tensor,
non_negative=None,
l1_reg=None,
l2_reg=None,
l2_square_reg=None,
unimodality=None,
normalize=None,
simplex=None,
normalized_sparsity=None,
soft_sparsity=None,
smoothness=None,
monotonicity=None,
hard_sparsity=None,
n_const=1,
order=0):
"""
Proximal operator solves a convex optimization problem. Let f be a
convex proper lower-semicontinuous function, the proximal operator of f is :math:`\\argmin_x(f(x) + 1/2||x - v||_2^2)`.
This operator can be used to solve constrained optimization problems as a generalization to projections on convex sets.
Therefore, proximal gradients are used for constrained tensor decomposition problems in the literature.
Parameters
----------
tensor : ndarray
non_negative : bool or dictionary
This constraint is clipping negative values to '0'. If it is True non-negative constraint is applied to all modes.
l1_reg : float or list or dictionary, optional
l2_reg : float or list or dictionary, optional
l2_square_reg : float or list or dictionary, optional
unimodality : bool or dictionary, optional
If it is True unimodality constraint is applied to all modes.
normalize : bool or dictionary, optional
This constraint divides all the values by maximum value of the input array. If it is True normalize constraint
is applied to all modes.
simplex : float or list or dictionary, optional
normalized_sparsity : float or list or dictionary, optional
soft_sparsity : float or list or dictionary, optional
smoothness : float or list or dictionary, optional
monotonicity : bool or dictionary, optional
hard_sparsity : float or list or dictionary, optional
n_const : int
Number of constraints. If it is None, function returns input tensor.
Default : 1
order : int
Specifies which constraint to implement if several constraints are selected as input
Default : 0
Returns
-------
tensor : updated tensor according to the selected constraint, which is the solution of the optimization problem above.
If constraint is None, function returns the same tensor.
References
----------
.. [1]: Moreau, J. J. (1962). Fonctions convexes duales et points proximaux dans un espace hilbertien.
Comptes rendus hebdomadaires des séances de l'Académie des sciences, 255, 2897-2899.
.. [2]: Parikh, N., & Boyd, S. (2014). Proximal algorithms.
Foundations and Trends in optimization, 1(3), 127-239.
"""
if n_const is None:
return tensor
constraint, parameter = validate_constraints(
non_negative=non_negative,
l1_reg=l1_reg,
l2_reg=l2_reg,
l2_square_reg=l2_square_reg,
unimodality=unimodality,
normalize=normalize,
simplex=simplex,
normalized_sparsity=normalized_sparsity,
soft_sparsity=soft_sparsity,
smoothness=smoothness,
monotonicity=monotonicity,
hard_sparsity=hard_sparsity,
n_const=n_const,
order=order)
if constraint is None:
return tensor
elif constraint == 'non_negative':
return tl.clip(tensor, 0, tl.max(tensor))
elif constraint == 'l1_reg':
return soft_thresholding(tensor, parameter)
elif constraint == 'l2_reg':
return l2_prox(tensor, parameter)
elif constraint == 'l2_square_reg':
return l2_square_prox(tensor, parameter)
elif constraint == 'unimodality':
return unimodality_prox(tensor)
elif constraint == 'normalize':
return tensor / tl.max(tensor)
elif constraint == 'simplex':
return simplex_prox(tensor, parameter)
elif constraint == 'normalized_sparsity':
return normalized_sparsity_prox(tensor, parameter)
elif constraint == 'soft_sparsity':
return soft_sparsity_prox(tensor, parameter)
elif constraint == 'smoothness':
return smoothness_prox(tensor, parameter)
elif constraint == 'monotonicity':
return monotonicity_prox(tensor)
elif constraint == 'hard_sparsity':
return hard_thresholding(tensor, parameter)
def active_set_nnls(Utm, UtU, x=None, n_iter_max=100, tol=10e-8):
"""
Active set algorithm for non-negative least square solution.
Computes an approximate non-negative solution for Ux=m linear system.
Parameters
----------
Utm : vectorized ndarray
Pre-computed product of the transposed of U and m
UtU : ndarray
Pre-computed Kronecker product of the transposed of U and U
x : init
Default: None
n_iter_max : int
Maximum number of iteration
Default: 100
tol : float
Early stopping criterion
Returns
-------
x : ndarray
Notes
-----
This function solves following problem:
.. math::
\\begin{equation}
\\min_{x} ||Ux - m||^2
\\end{equation}
According to [1], non-negativity-constrained least square estimation problem becomes:
.. math::
\\begin{equation}
x' = (Utm) - (UTU)\\times x
\\end{equation}
Reference
----------
[1] : Bro, R., & De Jong, S. (1997). A fast non‐negativity‐constrained
least squares algorithm. Journal of Chemometrics: A Journal of
the Chemometrics Society, 11(5), 393-401.
"""
if tl.get_backend() == 'tensorflow':
raise ValueError(
"Active set is not supported with the tensorflow backend. Consider using fista method with tensorflow."
)
if x is None:
x_vec = tl.zeros(tl.shape(UtU)[1], **tl.context(UtU))
else:
x_vec = tl.base.tensor_to_vec(x)
x_gradient = Utm - tl.dot(UtU, x_vec)
passive_set = x_vec > 0
active_set = x_vec <= 0
support_vec = tl.zeros(tl.shape(x_vec), **tl.context(x_vec))
for iteration in range(n_iter_max):
if iteration > 0 or tl.all(x_vec == 0):
indice = tl.argmax(x_gradient)
passive_set = tl.index_update(passive_set, tl.index[indice], True)
active_set = tl.index_update(active_set, tl.index[indice], False)
# To avoid singularity error when initial x exists
try:
passive_solution = tl.solve(UtU[passive_set, :][:, passive_set],
Utm[passive_set])
indice_list = []
for i in range(tl.shape(support_vec)[0]):
if passive_set[i]:
indice_list.append(i)
support_vec = tl.index_update(
support_vec, tl.index[int(i)],
passive_solution[len(indice_list) - 1])
else:
support_vec = tl.index_update(support_vec,
tl.index[int(i)], 0)
# Start from zeros if solve is not achieved
except:
x_vec = tl.zeros(tl.shape(UtU)[1])
support_vec = tl.zeros(tl.shape(x_vec), **tl.context(x_vec))
passive_set = x_vec > 0
active_set = x_vec <= 0
if tl.any(active_set):
indice = tl.argmax(x_gradient)
passive_set = tl.index_update(passive_set, tl.index[indice],
True)
active_set = tl.index_update(active_set, tl.index[indice],
False)
passive_solution = tl.solve(UtU[passive_set, :][:, passive_set],
Utm[passive_set])
indice_list = []
for i in range(tl.shape(support_vec)[0]):
if passive_set[i]:
indice_list.append(i)
support_vec = tl.index_update(
support_vec, tl.index[int(i)],
passive_solution[len(indice_list) - 1])
else:
support_vec = tl.index_update(support_vec,
tl.index[int(i)], 0)
# update support vector if it is necessary
if tl.min(support_vec[passive_set]) <= 0:
for i in range(len(passive_set)):
alpha = tl.min(
x_vec[passive_set][support_vec[passive_set] <= 0] /
(x_vec[passive_set][support_vec[passive_set] <= 0] -
support_vec[passive_set][support_vec[passive_set] <= 0]))
update = alpha * (support_vec - x_vec)
x_vec = x_vec + update
passive_set = x_vec > 0
active_set = x_vec <= 0
passive_solution = tl.solve(
UtU[passive_set, :][:, passive_set], Utm[passive_set])
indice_list = []
for i in range(tl.shape(support_vec)[0]):
if passive_set[i]:
indice_list.append(i)
support_vec = tl.index_update(
support_vec, tl.index[int(i)],
passive_solution[len(indice_list) - 1])
else:
support_vec = tl.index_update(support_vec,
tl.index[int(i)], 0)
if tl.any(passive_set) != True or tl.min(
support_vec[passive_set]) > 0:
break
# set x to s
x_vec = tl.clip(support_vec, 0, tl.max(support_vec))
# gradient update
x_gradient = Utm - tl.dot(UtU, x_vec)
if tl.any(active_set) != True or tl.max(x_gradient[active_set]) <= tol:
break
return x_vec
