def _init_clusters(self):
"""Initialization of clusters.
Returns:
Tuple with following elements:
cluster_centers: a Tensor for storing cluster centers
cluster_counts: a Tensor for storing counts of points assigned to this
cluster. This is used by mini-batch training.
"""
init = self._initial_clusters
if init == RANDOM_INIT:
clusters_init = self._init_clusters_random()
elif init == KMEANS_PLUS_PLUS_INIT:
# Points from only the first shard are used for initializing centers.
# TODO(ands): Use all points.
inp = self._inputs[0]
if self._distance_metric == COSINE_DISTANCE:
inp = nn_impl.l2_normalize(inp, dim=1)
clusters_init = gen_clustering_ops.kmeans_plus_plus_initialization(
inp, self._num_clusters, self._random_seed,
self._kmeans_plus_plus_num_retries)
elif callable(init):
clusters_init = init(self._inputs, self._num_clusters)
elif not isinstance(init, str):
clusters_init = init
else:
assert False, 'Unsupported init passed to Kmeans %s' % str(init)
if self._distance_metric == COSINE_DISTANCE and clusters_init is not None:
clusters_init = nn_impl.l2_normalize(clusters_init, dim=1)
clusters_init = clusters_init if clusters_init is not None else []
# TODO(agarwal): Locally cache cluster_centers on the worker to avoid
# copying them each step.
cluster_centers = variables.Variable(clusters_init,
name='clusters',
validate_shape=False)
if self._use_mini_batch and self._mini_batch_steps_per_iteration > 1:
# Copy of cluster centers actively updated each step according to
# mini-batch update rule.
cluster_centers_updated = variables.Variable(clusters_init,
name='clusters_updated',
validate_shape=False)
# How many steps till we copy the updated clusters to cluster_centers.
update_in_steps = variables.Variable(self._mini_batch_steps_per_iteration,
dtype=dtypes.int64,
name='update_in_steps')
# Count of points assigned to cluster_centers_updated.
cluster_counts = variables.Variable(array_ops.zeros([self._num_clusters],
dtype=dtypes.int64))
else:
cluster_centers_updated = cluster_centers
update_in_steps = None
cluster_counts = (variables.Variable(array_ops.ones([self._num_clusters],
dtype=dtypes.int64))
if self._use_mini_batch else None)
return (cluster_centers, cluster_counts,
cluster_centers_updated, update_in_steps)
def _f():
# Note that there is a race condition here, so we do a best effort
# updates here. We reset update_in_steps first so that other workers
# don't duplicate the updates. Also we update cluster_center_vars
# before resetting total_counts to avoid large updates to
# cluster_centers_updated based on partially updated
# cluster_center_vars.
with ops.control_dependencies([
state_ops.assign(update_in_steps,
self._mini_batch_steps_per_iteration - 1)
]):
with ops.colocate_with(
cluster_centers_updated, ignore_existing=True):
if self._distance_metric == COSINE_DISTANCE:
cluster_centers = nn_impl.l2_normalize(
cluster_centers_updated, dim=1)
else:
cluster_centers = cluster_centers_updated
with ops.colocate_with(cluster_centers_var, ignore_existing=True):
with ops.control_dependencies(
[state_ops.assign(cluster_centers_var, cluster_centers)]):
with ops.colocate_with(None, ignore_existing=True):
with ops.control_dependencies([
state_ops.assign(total_counts,
array_ops.zeros_like(total_counts))
]):
return array_ops.identity(update_in_steps)
def _init_clusters(self):
"""Initialization of clusters.
Returns:
Tuple with following elements:
cluster_centers: a Tensor for storing cluster centers
cluster_counts: a Tensor for storing counts of points assigned to this
cluster. This is used by mini-batch training.
"""
init = self._initial_clusters
if init == RANDOM_INIT:
clusters_init = self._init_clusters_random()
elif init == KMEANS_PLUS_PLUS_INIT:
# Points from only the first shard are used for initializing centers.
# TODO(ands): Use all points.
clusters_init = gen_clustering_ops.kmeans_plus_plus_initialization(
self._inputs[0], self._num_clusters, self._random_seed,
self._kmeans_plus_plus_num_retries)
elif callable(init):
clusters_init = init(self._inputs, self._num_clusters)
elif not isinstance(init, str):
clusters_init = init
else:
assert False, 'Unsupported init passed to Kmeans %s' % str(init)
if self._distance_metric == COSINE_DISTANCE and clusters_init is not None:
clusters_init = nn_impl.l2_normalize(clusters_init, dim=1)
clusters_init = clusters_init if clusters_init is not None else []
cluster_centers = variables.Variable(
clusters_init, name='clusters', validate_shape=False)
cluster_counts = (variables.Variable(
array_ops.ones(
[self._num_clusters], dtype=dtypes.int64)) if self._use_mini_batch
else None)
return cluster_centers, cluster_counts
def _l2_normalize_data(cls, inputs):
"""Normalized the input data."""
output = []
for inp in inputs:
with ops.colocate_with(inp):
output.append(nn_impl.l2_normalize(inp, dim=1))
return output
def _full_batch_training_op(self, inputs, cluster_idx_list, cluster_centers):
"""Creates an op for training for full batch case.
Args:
inputs: list of input Tensors.
cluster_idx_list: A vector (or list of vectors). Each element in the
vector corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
cluster_centers: Tensor Ref of cluster centers.
Returns:
An op for doing an update of mini-batch k-means.
"""
cluster_sums = []
cluster_counts = []
epsilon = constant_op.constant(1e-6, dtype=inputs[0].dtype)
for inp, cluster_idx in zip(inputs, cluster_idx_list):
with ops.colocate_with(inp):
cluster_sums.append(
math_ops.unsorted_segment_sum(inp, cluster_idx, self._num_clusters))
cluster_counts.append(
math_ops.unsorted_segment_sum(
array_ops.reshape(
array_ops.ones(
array_ops.reshape(array_ops.shape(inp)[0], [-1])),
[-1, 1]), cluster_idx, self._num_clusters))
with ops.colocate_with(cluster_centers):
new_clusters_centers = math_ops.add_n(cluster_sums) / (math_ops.cast(
math_ops.add_n(cluster_counts), cluster_sums[0].dtype) + epsilon)
if self._clusters_l2_normalized():
new_clusters_centers = nn_impl.l2_normalize(new_clusters_centers, dim=1)
return state_ops.assign(cluster_centers, new_clusters_centers)
def _sample_random():
"""Returns a random point as a cluster center."""
# By assumption the batch is reshuffled and _sample_random is always
# called for i=0. Hence, we simply return the first point.
new_center = array_ops.reshape(first_shard[0], [1, -1])
if self._distance_metric == COSINE_DISTANCE:
new_center = nn_impl.l2_normalize(new_center, dim=1)
return new_center
def _initialize_clusters(self,
cluster_centers,
cluster_centers_initialized,
cluster_centers_updated):
"""Returns an op to initialize the cluster centers."""
init = self._initial_clusters
if init == RANDOM_INIT:
clusters_init = self._init_clusters_random()
elif init == KMEANS_PLUS_PLUS_INIT:
# Points from only the first shard are used for initializing centers.
# TODO(ands): Use all points.
inp = self._inputs[0]
if self._distance_metric == COSINE_DISTANCE:
inp = nn_impl.l2_normalize(inp, dim=1)
clusters_init = gen_clustering_ops.kmeans_plus_plus_initialization(
inp, self._num_clusters, self._random_seed,
self._kmeans_plus_plus_num_retries)
elif callable(init):
clusters_init = init(self._inputs, self._num_clusters)
elif not isinstance(init, str):
clusters_init = init
else:
assert False, 'Unsupported init passed to Kmeans %s' % str(init)
if self._distance_metric == COSINE_DISTANCE and clusters_init is not None:
clusters_init = nn_impl.l2_normalize(clusters_init, dim=1)
with ops.colocate_with(cluster_centers_initialized):
initialized = control_flow_ops.with_dependencies(
[clusters_init],
array_ops.identity(cluster_centers_initialized))
with ops.colocate_with(cluster_centers):
assign_centers = state_ops.assign(cluster_centers, clusters_init,
validate_shape=False)
if cluster_centers_updated != cluster_centers:
assign_centers = control_flow_ops.group(
assign_centers,
state_ops.assign(cluster_centers_updated, clusters_init,
validate_shape=False))
assign_centers = control_flow_ops.with_dependencies(
[assign_centers],
state_ops.assign(cluster_centers_initialized, True))
return control_flow_ops.cond(initialized,
control_flow_ops.no_op,
lambda: assign_centers).op
def testL2NormalizeDimArray(self): x_shape = [20, 7, 3] np.random.seed(1) x_np = np.random.random_sample(x_shape).astype(np.float32) dim = [1, 2] y_np = self._l2Normalize(x_np, dim) x_tf = constant_op.constant(x_np, name="x") y_tf = nn_impl.l2_normalize(x_tf, dim) self.assertAllClose(y_np, self.evaluate(y_tf))
def _kmeans_plus_plus(self):
# Points from only the first shard are used for initializing centers.
# TODO(ands): Use all points.
inp = self._inputs[0]
if self._distance_metric == COSINE_DISTANCE:
inp = nn_impl.l2_normalize(inp, dim=1)
return gen_clustering_ops.kmeans_plus_plus_initialization(
inp, math_ops.cast(self._num_remaining, dtypes.int64), self._seed,
self._kmeans_plus_plus_num_retries)
def testL2Normalize(self):
x_shape = [20, 7, 3]
np.random.seed(1)
x_np = np.random.random_sample(x_shape).astype(np.float32)
for dim in range(len(x_shape)):
y_np = self._l2Normalize(x_np, dim)
with self.test_session():
x_tf = constant_op.constant(x_np, name="x")
y_tf = nn_impl.l2_normalize(x_tf, dim)
self.assertAllClose(y_np, y_tf.eval())
def testL2NormalizeGradient(self):
x_shape = [20, 7, 3]
np.random.seed(1)
x_np = np.random.random_sample(x_shape).astype(np.float64)
for dim in range(len(x_shape)):
with self.test_session():
x_tf = constant_op.constant(x_np, name="x")
y_tf = nn_impl.l2_normalize(x_tf, dim)
err = gradient_checker.compute_gradient_error(x_tf, x_shape, y_tf,
x_shape)
print("L2Normalize gradient err = %g " % err)
self.assertLess(err, 1e-4)
def training_graph(self):
"""Generate a training graph for kmeans algorithm.
Returns:
A tuple consisting of:
all_scores: A matrix (or list of matrices) of dimensions (num_input,
num_clusters) where the value is the distance of an input vector and a
cluster center.
cluster_idx: A vector (or list of vectors). Each element in the vector
corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
scores: Similar to cluster_idx but specifies the distance to the
assigned cluster instead.
cluster_centers_initialized: scalar indicating whether clusters have been
initialized.
init_op: an op to initialize the clusters.
training_op: an op that runs an iteration of training.
"""
# Implementation of kmeans.
inputs = self._inputs
(cluster_centers_var,
cluster_centers_initialized,
total_counts,
cluster_centers_updated,
update_in_steps) = self._create_variables()
init_op = self._initialize_clusters(cluster_centers_var,
cluster_centers_initialized,
cluster_centers_updated)
cluster_centers = cluster_centers_var
if self._distance_metric == COSINE_DISTANCE:
inputs = self._l2_normalize_data(inputs)
if not self._clusters_l2_normalized():
cluster_centers = nn_impl.l2_normalize(cluster_centers, dim=1)
all_scores, scores, cluster_idx = self._infer_graph(inputs, cluster_centers)
if self._use_mini_batch:
sync_updates_op = self._mini_batch_sync_updates_op(
update_in_steps,
cluster_centers_var, cluster_centers_updated,
total_counts)
assert sync_updates_op is not None
with ops.control_dependencies([sync_updates_op]):
training_op = self._mini_batch_training_op(
inputs, cluster_idx, cluster_centers_updated, total_counts)
else:
assert cluster_centers == cluster_centers_var
training_op = self._full_batch_training_op(inputs, cluster_idx,
cluster_centers_var)
return (all_scores, cluster_idx, scores,
cluster_centers_initialized, init_op, training_op)
def _compute_cosine_distance(cls, inputs, clusters, inputs_normalized=True):
"""Computes cosine distance between each input and each cluster center.
Args:
inputs: list of input Tensor.
clusters: cluster Tensor
inputs_normalized: if True, it assumes that inp and clusters are
normalized and computes the dot product which is equivalent to the cosine
distance. Else it L2 normalizes the inputs first.
Returns:
list of Tensors, where each element corresponds to each element in inp.
The value is the distance of each row to all the cluster centers.
"""
output = []
if not inputs_normalized:
with ops.colocate_with(clusters):
clusters = nn_impl.l2_normalize(clusters, dim=1)
for inp in inputs:
with ops.colocate_with(inp):
if not inputs_normalized:
inp = nn_impl.l2_normalize(inp, dim=1)
output.append(1 - math_ops.matmul(inp, clusters, transpose_b=True))
return output
def _add_new_centers(self):
"""Adds some centers and returns the number of centers remaining."""
new_centers = self._choose_initial_centers()
if self._distance_metric == COSINE_DISTANCE:
new_centers = nn_impl.l2_normalize(new_centers, dim=1)
# If cluster_centers is empty, it doesn't have the right shape for concat.
all_centers = control_flow_ops.cond(
math_ops.equal(self._num_selected, 0), lambda: new_centers,
lambda: array_ops.concat([self._cluster_centers, new_centers], 0))
# TODO(ccolby): De-dupe all_centers?
a = state_ops.assign(
self._cluster_centers, all_centers, validate_shape=False)
if self._cluster_centers_updated is not self._cluster_centers:
a = state_ops.assign(
self._cluster_centers_updated, a, validate_shape=False)
return self._num_clusters - array_ops.shape(a)[0]
def _sample_kmc2_chain():
"""Returns previous centers as well as a new center sampled using k-MC2.
"""
# Extract the subset from the underlying batch.
start = i * self._kmc2_chain_length
end = start + self._kmc2_chain_length
subset = first_shard[start:end]
# Compute the distances from points in the subset to previous centers.
_, distances = gen_clustering_ops.nearest_neighbors(
subset, self._cluster_centers, 1)
# Sample index of new center using k-MC2 Markov chain.
new_center_index = gen_clustering_ops.kmc2_chain_initialization(
array_ops.squeeze(distances), self._random_seed)
# Extract actual new center.
newly_sampled_center = array_ops.reshape(subset[new_center_index],
[1, -1])
# Return concatenation with previously sampled centers.
if self._distance_metric == COSINE_DISTANCE:
newly_sampled_center = nn_impl.l2_normalize(
newly_sampled_center, dim=1)
return array_ops.concat([self._cluster_centers, newly_sampled_center],
0)
def _infer_graph(self, inputs, clusters):
"""Maps input to closest cluster and the score.
Args:
inputs: list of input Tensors.
clusters: Tensor of cluster centers.
Returns:
List of tuple, where each value in tuple corresponds to a value in inp.
The tuple has following three elements:
all_scores: distance of each input to each cluster center.
score: distance of each input to closest cluster center.
cluster_idx: index of cluster center closest to the corresponding input.
"""
assert isinstance(inputs, list)
# Pairwise distances are used only by transform(). In all other cases, this
# sub-graph is not evaluated.
scores = self._distance_graph(inputs, clusters, self._distance_metric)
output = []
if (self._distance_metric == COSINE_DISTANCE and
not self._clusters_l2_normalized()):
# The cosine distance between normalized vectors x and y is the same as
# 2 * squared_euclidian_distance. We are using this fact and reusing the
# nearest_neighbors op.
# TODO(ands): Support COSINE distance in nearest_neighbors and remove
# this.
with ops.colocate_with(clusters):
clusters = nn_impl.l2_normalize(clusters, dim=1)
for inp, score in zip(inputs, scores):
with ops.colocate_with(inp):
(indices,
distances) = gen_clustering_ops.nearest_neighbors(inp, clusters, 1)
if self._distance_metric == COSINE_DISTANCE:
distances *= 0.5
output.append(
(score, array_ops.squeeze(distances), array_ops.squeeze(indices)))
return zip(*output)
def _infer_graph(self, inputs, clusters):
"""Maps input to closest cluster and the score.
Args:
inputs: list of input Tensors.
clusters: Tensor of cluster centers.
Returns:
List of tuple, where each value in tuple corresponds to a value in inp.
The tuple has following three elements:
all_scores: distance of each input to each cluster center.
score: distance of each input to closest cluster center.
cluster_idx: index of cluster center closest to the corresponding input.
"""
assert isinstance(inputs, list)
# Pairwise distances are used only by transform(). In all other cases, this
# sub-graph is not evaluated.
scores = self._distance_graph(inputs, clusters, self._distance_metric)
output = []
if (self._distance_metric == COSINE_DISTANCE
and not self._clusters_l2_normalized()):
# The cosine distance between normalized vectors x and y is the same as
# 2 * squared_euclidian_distance. We are using this fact and reusing the
# nearest_neighbors op.
# TODO(ands): Support COSINE distance in nearest_neighbors and remove
# this.
with ops.colocate_with(clusters):
clusters = nn_impl.l2_normalize(clusters, dim=1)
for inp, score in zip(inputs, scores):
with ops.colocate_with(inp):
(indices, distances) = gen_clustering_ops.nearest_neighbors(
inp, clusters, 1)
if self._distance_metric == COSINE_DISTANCE:
distances *= 0.5
output.append((score, array_ops.squeeze(distances),
array_ops.squeeze(indices)))
return zip(*output)
def _full_batch_training_op(self, inputs, cluster_idx_list,
cluster_centers):
"""Creates an op for training for full batch case.
Args:
inputs: list of input Tensors.
cluster_idx_list: A vector (or list of vectors). Each element in the
vector corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
cluster_centers: Tensor Ref of cluster centers.
Returns:
An op for doing an update of mini-batch k-means.
"""
cluster_sums = []
cluster_counts = []
epsilon = constant_op.constant(1e-6, dtype=inputs[0].dtype)
for inp, cluster_idx in zip(inputs, cluster_idx_list):
with ops.colocate_with(inp):
cluster_sums.append(
math_ops.unsorted_segment_sum(inp, cluster_idx,
self._num_clusters))
cluster_counts.append(
math_ops.unsorted_segment_sum(
array_ops.reshape(
array_ops.ones(
array_ops.reshape(
array_ops.shape(inp)[0], [-1])), [-1, 1]),
cluster_idx, self._num_clusters))
with ops.colocate_with(cluster_centers):
new_clusters_centers = math_ops.add_n(cluster_sums) / (
math_ops.cast(math_ops.add_n(cluster_counts),
cluster_sums[0].dtype) + epsilon)
if self._clusters_l2_normalized():
new_clusters_centers = nn_impl.l2_normalize(
new_clusters_centers, dim=1)
return state_ops.assign(cluster_centers, new_clusters_centers)
def training_graph(self):
"""Generate a training graph for kmeans algorithm.
Returns:
A tuple consisting of:
all_scores: A matrix (or list of matrices) of dimensions (num_input,
num_clusters) where the value is the distance of an input vector and a
cluster center.
cluster_idx: A vector (or list of vectors). Each element in the vector
corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
scores: Similar to cluster_idx but specifies the distance to the
assigned cluster instead.
training_op: an op that runs an iteration of training.
"""
# Implementation of kmeans.
inputs = self._inputs
cluster_centers_var, total_counts = self._init_clusters()
cluster_centers = cluster_centers_var
if self._distance_metric == COSINE_DISTANCE:
inputs = self._l2_normalize_data(inputs)
if not self._clusters_l2_normalized():
cluster_centers = nn_impl.l2_normalize(cluster_centers, dim=1)
all_scores, scores, cluster_idx = self._infer_graph(
inputs, cluster_centers)
if self._use_mini_batch:
training_op = self._mini_batch_training_op(inputs, cluster_idx,
cluster_centers,
cluster_centers_var,
total_counts)
else:
assert cluster_centers == cluster_centers_var
training_op = self._full_batch_training_op(inputs, cluster_idx,
cluster_centers_var)
return all_scores, cluster_idx, scores, training_op
def training_graph(self):
"""Generate a training graph for kmeans algorithm.
Returns:
A tuple consisting of:
all_scores: A matrix (or list of matrices) of dimensions (num_input,
num_clusters) where the value is the distance of an input vector and a
cluster center.
cluster_idx: A vector (or list of vectors). Each element in the vector
corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
scores: Similar to cluster_idx but specifies the distance to the
assigned cluster instead.
training_op: an op that runs an iteration of training.
"""
# Implementation of kmeans.
inputs = self._inputs
cluster_centers_var, total_counts = self._init_clusters()
cluster_centers = cluster_centers_var
if self._distance_metric == COSINE_DISTANCE:
inputs = self._l2_normalize_data(inputs)
if not self._clusters_l2_normalized():
cluster_centers = nn_impl.l2_normalize(cluster_centers, dim=1)
all_scores, scores, cluster_idx = self._infer_graph(inputs, cluster_centers)
if self._use_mini_batch:
training_op = self._mini_batch_training_op(inputs, cluster_idx,
cluster_centers,
cluster_centers_var,
total_counts)
else:
assert cluster_centers == cluster_centers_var
training_op = self._full_batch_training_op(inputs, cluster_idx,
cluster_centers_var)
return all_scores, cluster_idx, scores, training_op
def call(self, inputs, training=None):
if self.lr_mul == 1.0:
W = self.coeff * self.kernel
else:
@custom_gradient
def lr_multiplier(x):
y = array_ops.identity(x)
def grad(dy):
return dy * self.lr_mul
return y, grad
W = lr_multiplier(self.coeff * self.kernel)
training = self._get_training_value(training)
# Update singular vector by power iteration
W_T = array_ops.transpose(W)
u = array_ops.identity(self.u)
for i in range(self.power_iter):
v = nn_impl.l2_normalize(math_ops.matmul(u, W)) # 1 x filters
u = nn_impl.l2_normalize(math_ops.matmul(v, W_T))
# Spectral Normalization
sigma_W = math_ops.matmul(math_ops.matmul(u, W),
array_ops.transpose(v))
# Backprop doesn't need in power iteration
sigma_W = array_ops.stop_gradient(sigma_W)
W_bar = W / array_ops.squeeze(sigma_W)
# Assign new singular vector
training_value = tf_utils.constant_value(training)
if training_value is not False:
def u_update():
def true_branch():
return self._assign_singular_vector(self.u, u)
def false_branch():
return self.u
return tf_utils.smart_cond(training, true_branch, false_branch)
self.add_update(u_update)
# normal Dense using W_bar
inputs = ops.convert_to_tensor(inputs)
rank = common_shapes.rank(inputs)
if rank > 2:
# Broadcasting is required for the inputs.
outputs = standard_ops.tensordot(inputs, W_bar, [[rank - 1], [0]])
# Reshape the output back to the original ndim of the input.
if not context.executing_eagerly():
shape = inputs.shape.as_list()
output_shape = shape[:-1] + [self.units]
outputs.set_shape(output_shape)
else:
inputs = math_ops.cast(inputs, self._compute_dtype)
outputs = math_ops.mat_mul(inputs, W_bar)
if self.use_bias:
outputs = nn.bias_add(outputs, self.bias)
if self.activation is not None:
return self.activation(outputs) # pylint: disable=not-callable
return outputs
def _normalize(self, weight, name):
output_size = weight.get_shape().as_list()[1]
g = vs.get_variable(name, [output_size], dtype=weight.dtype)
return nn_impl.l2_normalize(weight, dim=0) * g
def __householder_rotation(self, x):
u = nn_impl.l2_normalize(self.__e1 - self._loc, axis=-1)
z = x - 2 * math_ops.reduce_sum(x * u, axis=-1, keepdims=True) * u
return z
def training_graph(self):
"""Generate a training graph for kmeans algorithm.
This returns, among other things, an op that chooses initial centers
(init_op), a boolean variable that is set to True when the initial centers
are chosen (cluster_centers_initialized), and an op to perform either an
entire Lloyd iteration or a mini-batch of a Lloyd iteration (training_op).
The caller should use these components as follows. A single worker should
execute init_op multiple times until cluster_centers_initialized becomes
True. Then multiple workers may execute training_op any number of times.
Returns:
A tuple consisting of:
all_scores: A matrix (or list of matrices) of dimensions (num_input,
num_clusters) where the value is the distance of an input vector and a
cluster center.
cluster_idx: A vector (or list of vectors). Each element in the vector
corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
scores: Similar to cluster_idx but specifies the distance to the
assigned cluster instead.
cluster_centers_initialized: scalar indicating whether clusters have been
initialized.
init_op: an op to initialize the clusters.
training_op: an op that runs an iteration of training.
"""
# Implementation of kmeans.
if (isinstance(self._initial_clusters, str)
or callable(self._initial_clusters)):
initial_clusters = self._initial_clusters
num_clusters = ops.convert_to_tensor(self._num_clusters)
else:
initial_clusters = ops.convert_to_tensor(self._initial_clusters)
num_clusters = array_ops.shape(initial_clusters)[0]
inputs = self._inputs
(cluster_centers_var, cluster_centers_initialized, total_counts,
cluster_centers_updated,
update_in_steps) = self._create_variables(num_clusters)
init_op = _InitializeClustersOpFactory(
self._inputs, num_clusters, initial_clusters,
self._distance_metric, self._random_seed,
self._kmeans_plus_plus_num_retries, self._kmc2_chain_length,
cluster_centers_var, cluster_centers_updated,
cluster_centers_initialized).op()
cluster_centers = cluster_centers_var
if self._distance_metric == COSINE_DISTANCE:
inputs = self._l2_normalize_data(inputs)
if not self._clusters_l2_normalized():
cluster_centers = nn_impl.l2_normalize(cluster_centers, dim=1)
all_scores, scores, cluster_idx = self._infer_graph(
inputs, cluster_centers)
if self._use_mini_batch:
sync_updates_op = self._mini_batch_sync_updates_op(
update_in_steps, cluster_centers_var, cluster_centers_updated,
total_counts)
assert sync_updates_op is not None
with ops.control_dependencies([sync_updates_op]):
training_op = self._mini_batch_training_op(
inputs, cluster_idx, cluster_centers_updated, total_counts)
else:
assert cluster_centers == cluster_centers_var
training_op = self._full_batch_training_op(inputs, num_clusters,
cluster_idx,
cluster_centers_var)
return (all_scores, cluster_idx, scores, cluster_centers_initialized,
init_op, training_op)
def _compute_weights(self):
"""Generate weights by combining the direction of weight vector
with it's norm """
with variable_scope.variable_scope('compute_weights'):
self.layer.W = nn_impl.l2_normalize(
self.layer.v, axis=self.norm_axes) * self.layer.g
def _compute_weights(self):
"""Generate weights by combining the direction of weight vector
with its norm """
with name_scope('compute_weights'):
self.layer.kernel = nn_impl.l2_normalize(
self.layer.v, axis=self.kernel_norm_axes) * self.layer.g
def training_graph(self):
"""Generate a training graph for kmeans algorithm.
This returns, among other things, an op that chooses initial centers
(init_op), a boolean variable that is set to True when the initial centers
are chosen (cluster_centers_initialized), and an op to perform either an
entire Lloyd iteration or a mini-batch of a Lloyd iteration (training_op).
The caller should use these components as follows. A single worker should
execute init_op multiple times until cluster_centers_initialized becomes
True. Then multiple workers may execute training_op any number of times.
Returns:
A tuple consisting of:
all_scores: A matrix (or list of matrices) of dimensions (num_input,
num_clusters) where the value is the distance of an input vector and a
cluster center.
cluster_idx: A vector (or list of vectors). Each element in the vector
corresponds to an input row in 'inp' and specifies the cluster id
corresponding to the input.
scores: Similar to cluster_idx but specifies the distance to the
assigned cluster instead.
cluster_centers_initialized: scalar indicating whether clusters have been
initialized.
init_op: an op to initialize the clusters.
training_op: an op that runs an iteration of training.
"""
# Implementation of kmeans.
if (isinstance(self._initial_clusters, str) or
callable(self._initial_clusters)):
initial_clusters = self._initial_clusters
num_clusters = ops.convert_to_tensor(self._num_clusters)
else:
initial_clusters = ops.convert_to_tensor(self._initial_clusters)
num_clusters = array_ops.shape(initial_clusters)[0]
inputs = self._inputs
(cluster_centers_var, cluster_centers_initialized, total_counts,
cluster_centers_updated,
update_in_steps) = self._create_variables(num_clusters)
init_op = _InitializeClustersOpFactory(
self._inputs, num_clusters, initial_clusters, self._distance_metric,
self._random_seed, self._kmeans_plus_plus_num_retries,
self._kmc2_chain_length, cluster_centers_var, cluster_centers_updated,
cluster_centers_initialized).op()
cluster_centers = cluster_centers_var
if self._distance_metric == COSINE_DISTANCE:
inputs = self._l2_normalize_data(inputs)
if not self._clusters_l2_normalized():
cluster_centers = nn_impl.l2_normalize(cluster_centers, dim=1)
all_scores, scores, cluster_idx = self._infer_graph(inputs, cluster_centers)
if self._use_mini_batch:
sync_updates_op = self._mini_batch_sync_updates_op(
update_in_steps, cluster_centers_var, cluster_centers_updated,
total_counts)
assert sync_updates_op is not None
with ops.control_dependencies([sync_updates_op]):
training_op = self._mini_batch_training_op(
inputs, cluster_idx, cluster_centers_updated, total_counts)
else:
assert cluster_centers == cluster_centers_var
training_op = self._full_batch_training_op(
inputs, num_clusters, cluster_idx, cluster_centers_var)
return (all_scores, cluster_idx, scores, cluster_centers_initialized,
init_op, training_op)
def _sample_n(self, n, seed=0):
return nn_impl.l2_normalize(random_ops.random_normal(
shape=array_ops.concat(([n], [self._dim + 1]), 0),
dtype=self.dtype,
seed=seed),
axis=-1)
def cosine_similarity(tensor: Tensor) -> Tensor:
""" Calculates the cosine similarity of a 2D array, with l2 normalization. """
l2_normalize(tensor, axis=1)
return matmul(tensor, transpose(tensor))
def build(self, input_shape):
input_shape = tensor_shape.TensorShape(
input_shape) # get the input shape
if self.data_format == 'channels_first': # judge the organize method of input_shape
channel_axis = 1
else:
channel_axis = -1
if input_shape.dims[channel_axis].value is None:
raise ValueError(
'The channel dimension of the inputs should be defined. Found `None`.'
)
input_dim = int(input_shape[channel_axis]) # get input dimension
kernel_shape = self.kernel_size + (input_dim, self.filters
) # define kernel_shape
kernel = self.add_weight(name='kernel',
shape=kernel_shape,
initializer=self.kernel_initializer,
regularizer=self.kernel_regularizer,
constraint=self.kernel_constraint,
trainable=True,
dtype=self.dtype)
# weight normalization
if self.weight_norm:
self.g = self.add_weight(name='wn/g',
shape=(self.filters, ),
initializer=tf.ones_initializer(),
trainable=True,
dtype=kernel.dtype)
self.kernel = tf.reshape(
self.g, [1, 1, self.filters]) * nn_impl.l2_normalize(
kernel, [0, 1])
else:
self.kernel = kernel
if self.use_bias:
self.bias = self.add_weight(name='bias',
shape=(self.filters, ),
initializer=self.bias_initializer,
regularizer=self.bias_regularizer,
constraint=self.bias_constraint,
trainable=True,
dtype=self.dtype)
else:
self.bias = None
self.input_spec = InputSpec(ndim=self.rank + 2,
axes={channel_axis: input_dim})
if self.padding == 'causal':
op_padding = 'valid'
else:
op_padding = self.padding
if not isinstance(op_padding, (list, tuple)):
op_padding = op_padding.upper()
self._convolution_op = nn_ops.Convolution(
input_shape,
filter_shape=self.kernel.get_shape(),
dilation_rate=self.dilation_rate,
strides=self.strides,
padding=op_padding,
data_format=conv_utils.convert_data_format(self.data_format,
self.rank + 2))
self.built = True
def call(self, inputs, training=None):
if self.lr_mul == 1.0:
kernel = self.coeff * self.kernel
else:
@custom_gradient
def lr_multiplier(x):
y = array_ops.identity(x)
def grad(dy):
return dy * self.lr_mul
return y, grad
kernel = lr_multiplier(self.coeff * self.kernel)
training = self._get_training_value(training)
# Update singular vector by power iteration
if self.data_format == 'channels_first':
W_T = array_ops.reshape(kernel, (self.filters, -1))
W = array_ops.transpose(W_T)
else:
W = array_ops.reshape(kernel, (-1, self.filters))
W_T = array_ops.transpose(W)
u = array_ops.identity(self.u)
for i in range(self.power_iter):
v = nn_impl.l2_normalize(math_ops.matmul(u, W)) # 1 x filters
u = nn_impl.l2_normalize(math_ops.matmul(v, W_T))
# Spectral Normalization
sigma_W = math_ops.matmul(math_ops.matmul(u, W),
array_ops.transpose(v))
# Backprop doesn't need in power iteration
sigma_W = array_ops.stop_gradient(sigma_W)
W_bar = kernel / array_ops.squeeze(sigma_W)
# Assign new singular vector
training_value = tf_utils.constant_value(training)
if training_value is not False:
def u_update():
def true_branch():
return self._assign_singular_vector(self.u, u)
def false_branch():
return self.u
return tf_utils.smart_cond(training, true_branch, false_branch)
self.add_update(u_update)
# normal convolution using W_bar
outputs = self._convolution_op(inputs, W_bar)
if self.use_bias:
if self.data_format == 'channels_first':
if self.rank == 1:
# nn.bias_add does not accept a 1D input tensor.
bias = array_ops.reshape(self.bias, (1, self.filters, 1))
outputs += bias
else:
outputs = nn.bias_add(outputs,
self.bias,
data_format='NCHW')
else:
outputs = nn.bias_add(outputs, self.bias, data_format='NHWC')
if self.activation is not None:
return self.activation(outputs)
return outputs