def sparse_bool_mask(x, mask, axis=0):
# Only necessary if indices may have non-unique elements
indices = tf.boolean_mask(tf.range(tf.shape(x)[axis]), mask)
n_indices = tf.size(indices)
# Get indices for the axis
idx = x.indices[:, axis]
# Find where indices match the selection
eq = tf.equal(tf.expand_dims(idx, 1),
tf.cast(indices, tf.int64)) # TODO this has quadratic cost
# Mask for selected values
sel = tf.reduce_any(eq, axis=1)
# Selected values
values_new = tf.boolean_mask(x.values, sel, axis=0)
# New index value for selected elements
n_indices = tf.cast(n_indices, tf.int64)
idx_new = tf.reduce_sum(tf.cast(eq, tf.int64) * tf.range(n_indices),
axis=1)
idx_new = tf.boolean_mask(idx_new, sel, axis=0)
# New full indices tensor
indices_new = tf.boolean_mask(x.indices, sel, axis=0)
indices_new = tf.concat([
indices_new[:, :axis],
tf.expand_dims(idx_new, 1), indices_new[:, axis + 1:]
],
axis=1)
# New shape
shape_new = tf.concat(
[x.dense_shape[:axis], [n_indices], x.dense_shape[axis + 1:]], axis=0)
return tf.SparseTensor(indices_new, values_new, shape_new)
def call(self, inputs):
if len(inputs) == 3:
X, A, I = inputs
self.data_mode = 'graph'
else:
X, A = inputs
I = tf.zeros(tf.shape(X)[:1], dtype=tf.int32)
self.data_mode = 'single'
if K.ndim(I) == 2:
I = I[:, 0]
A_is_sparse = K.is_sparse(A)
# Get mask
y = K.dot(X, K.l2_normalize(self.kernel))
N = K.shape(X)[-2]
indices = ops.top_k(y[:, 0], I, self.ratio, self.top_k_var)
mask = tf.scatter_nd(tf.expand_dims(indices, 1), tf.ones_like(indices),
(N, ))
# Multiply X and y to make layer differentiable
features = X * self.gating_op(y)
axis = 0 if len(K.int_shape(
A)) == 2 else 1 # Cannot use negative axis in tf.boolean_mask
# Reduce X
X_pooled = tf.boolean_mask(features, mask, axis=axis)
# Compute A^2
if A_is_sparse:
A_dense = tf.sparse.to_dense(A)
else:
A_dense = A
A_squared = K.dot(A, A_dense)
# Reduce A
A_pooled = tf.boolean_mask(A_squared, mask, axis=axis)
A_pooled = tf.boolean_mask(A_pooled, mask, axis=axis + 1)
if A_is_sparse:
A_pooled = tf.contrib.layers.dense_to_sparse(A_pooled)
output = [X_pooled, A_pooled]
# Reduce I
if self.data_mode == 'graph':
I_pooled = tf.boolean_mask(I[:, None], mask)[:, 0]
output.append(I_pooled)
if self.return_mask:
output.append(mask)
return output
def upsampling_from_mask(inputs):
X_, A_, I_, M_ = inputs
S_ = tf.eye(tf.shape(M_)[0])
S_ = tf.boolean_mask(S_, M_)
S_t_ = tf.transpose(S_)
X_out_ = K.dot(S_t_, X_)
A_out_ = K.dot(K.transpose(K.dot(A_, S_)), S_)
I_out_ = K.dot(S_t_, K.cast(I_[:, None], tf.float32))[:, 0]
I_out_ = K.cast(I_out_, tf.int32)
return [X_out_, A_out_, I_out_]
def top_k(scores, I, ratio, top_k_var):
"""
Returns indices to get the top K values in `scores` segment-wise, with
segments defined by I. K is not fixed, but it is defined as a ratio of the
number of elements in each segment.
:param scores: a rank 1 tensor with scores;
:param I: a rank 1 tensor with segment IDs;
:param ratio: float, ratio of elements to keep for each segment;
:param top_k_var: a tf.Variable without shape validation (e.g.,
`tf.Variable(0.0, validate_shape=False)`);
:return: a rank 1 tensor containing the indices to get the top K values of
each segment in `scores`.
"""
num_nodes = tf.segment_sum(tf.ones_like(I),
I) # Number of nodes in each graph
cumsum = tf.cumsum(num_nodes) # Cumulative number of nodes (A, A+B, A+B+C)
cumsum_start = cumsum - num_nodes # Start index of each graph
n_graphs = tf.shape(num_nodes)[0] # Number of graphs in batch
max_n_nodes = tf.reduce_max(num_nodes) # Order of biggest graph in batch
batch_n_nodes = tf.shape(I)[0] # Number of overall nodes in batch
to_keep = tf.ceil(ratio * tf.cast(num_nodes, tf.float32))
to_keep = tf.cast(to_keep, tf.int32) # Nodes to keep in each graph
index = tf.range(batch_n_nodes)
index = (index - tf.gather(cumsum_start, I)) + (I * max_n_nodes)
y_min = tf.reduce_min(scores)
dense_y = tf.ones((n_graphs * max_n_nodes, ))
dense_y = dense_y * tf.cast(
y_min - 1, tf.float32
) # subtract 1 to ensure that filler values do not get picked
dense_y = tf.assign(
top_k_var, dense_y, validate_shape=False
) # top_k_var is a variable with unknown shape defined in the elsewhere
dense_y = tf.scatter_update(dense_y, index, scores)
dense_y = tf.reshape(dense_y, (n_graphs, max_n_nodes))
perm = tf.argsort(dense_y, direction='DESCENDING')
perm = perm + cumsum_start[:, None]
perm = tf.reshape(perm, (-1, ))
to_rep = tf.tile(tf.constant([1., 0.]), (n_graphs, ))
rep_times = tf.reshape(
tf.concat((to_keep[:, None], (max_n_nodes - to_keep)[:, None]), -1),
(-1, ))
mask = tf_repeat_1d(to_rep, rep_times)
perm = tf.boolean_mask(perm, mask)
return perm
def tf_repeat_1d(x, repeats):
"""
Repeats each value `x[i]` a number of times `repeats[i]`.
:param x: a rank 1 tensor;
:param repeats: a rank 1 tensor;
:return: a rank 1 tensor, of shape `(sum(repeats), )`.
"""
x = tf.expand_dims(x, 1)
max_repeats = tf.reduce_max(repeats)
tile_repeats = [1, max_repeats]
arr_tiled = tf.tile(x, tile_repeats)
mask = tf.less(tf.range(max_repeats), tf.expand_dims(repeats, 1))
result = tf.reshape(tf.boolean_mask(arr_tiled, mask), [-1])
return result
