def call(self, inputs):
if len(inputs) == 3:
X, A, I = inputs
if K.ndim(I) == 2:
I = I[:, 0]
else:
X, A = inputs
I = None
# Check if the layer is operating in batch mode (X and A have rank 3)
batch_mode = K.ndim(X) == 3
# Compute cluster assignment matrix
S = self.mlp(X)
# MinCut regularization
A_pooled = ops.matmul_at_b_a(S, A)
num = tf.linalg.trace(A_pooled)
D = ops.degree_matrix(A)
den = tf.linalg.trace(ops.matmul_at_b_a(S, D)) + K.epsilon()
cut_loss = -(num / den)
if batch_mode:
cut_loss = K.mean(cut_loss)
self.add_loss(cut_loss)
# Orthogonality regularization
SS = ops.modal_dot(S, S, transpose_a=True)
I_S = tf.eye(self.k, dtype=SS.dtype)
ortho_loss = tf.norm(
SS / tf.norm(SS, axis=(-1, -2), keepdims=True) -
I_S / tf.norm(I_S),
axis=(-1, -2),
)
if batch_mode:
ortho_loss = K.mean(ortho_loss)
self.add_loss(ortho_loss)
# Pooling
X_pooled = ops.modal_dot(S, X, transpose_a=True)
A_pooled = tf.linalg.set_diag(
A_pooled, tf.zeros(K.shape(A_pooled)[:-1],
dtype=A_pooled.dtype)) # Remove diagonal
A_pooled = ops.normalize_A(A_pooled)
output = [X_pooled, A_pooled]
if I is not None:
I_mean = tf.math.segment_mean(I, I)
I_pooled = ops.repeat(I_mean, tf.ones_like(I_mean) * self.k)
output.append(I_pooled)
if self.return_mask:
output.append(S)
return output
def segment_top_k(x, i, ratio):
"""
Returns indices to get the top K values in x segment-wise, according to
the segments defined in I. K is not fixed, but it is defined as a ratio of
the number of elements in each segment.
:param x: a rank 1 Tensor;
:param i: a rank 1 Tensor with segment IDs for x;
:param ratio: float, ratio of elements to keep for each segment;
:return: a rank 1 Tensor containing the indices to get the top K values of
each segment in x.
"""
i = tf.cast(i, tf.int32)
n = tf.shape(i)[0]
n_nodes = tf.math.segment_sum(tf.ones_like(i), i)
batch_size = tf.shape(n_nodes)[0]
n_nodes_max = tf.reduce_max(n_nodes)
cumulative_n_nodes = tf.concat(
(tf.zeros(1, dtype=n_nodes.dtype), tf.cumsum(n_nodes)[:-1]), 0
)
index = tf.range(n)
index = (index - tf.gather(cumulative_n_nodes, i)) + (i * n_nodes_max)
dense_x = tf.zeros(batch_size * n_nodes_max, dtype=x.dtype) - 1e20
dense_x = tf.tensor_scatter_nd_update(dense_x, index[:, None], x)
dense_x = tf.reshape(dense_x, (batch_size, n_nodes_max))
perm = tf.argsort(dense_x, direction="DESCENDING")
perm = perm + cumulative_n_nodes[:, None]
perm = tf.reshape(perm, (-1,))
k = tf.cast(tf.math.ceil(ratio * tf.cast(n_nodes, tf.float32)), i.dtype)
# This costs more memory
# to_rep = tf.tile(tf.constant([1., 0.]), (batch_size,))
# rep_times = tf.reshape(tf.concat((k[:, None], (n_nodes_max - k)[:, None]), -1), (-1,))
# mask = ops.repeat(to_rep, rep_times)
# perm = tf.boolean_mask(perm, mask)
# This is slower
r_range = tf.ragged.range(k).flat_values
r_delta = ops.repeat(tf.range(batch_size) * n_nodes_max, k)
mask = r_range + r_delta
perm = tf.gather(perm, mask)
return perm
def call(self, inputs):
# Note that I is useless, because thee layer cannot be used in graph
# batch mode.
if len(inputs) == 3:
X, A, I = inputs
else:
X, A = inputs
I = None
N = K.shape(A)[-1]
# Check if the layer is operating in batch mode (X and A have rank 3)
mode = ops.autodetect_mode(A, X)
self.reduce_loss = mode in (ops._modes['M'], ops._modes['B'])
# Get normalized adjacency
if K.is_sparse(A):
I_ = tf.sparse.eye(N, dtype=A.dtype)
A_ = tf.sparse.add(A, I_)
else:
I_ = tf.eye(N, dtype=A.dtype)
A_ = A + I_
fltr = ops.normalize_A(A_)
# Node embeddings
Z = K.dot(X, self.kernel_emb)
Z = ops.filter_dot(fltr, Z)
if self.activation is not None:
Z = self.activation(Z)
# Compute cluster assignment matrix
S = K.dot(X, self.kernel_pool)
S = ops.filter_dot(fltr, S)
S = activations.softmax(S, axis=-1) # softmax applied row-wise
# Link prediction loss
S_gram = ops.matmul_A_BT(S, S)
if K.is_sparse(A):
LP_loss = tf.sparse.add(A, -S_gram) # A/tf.norm(A) - S_gram/tf.norm(S_gram)
else:
LP_loss = A - S_gram
LP_loss = tf.norm(LP_loss, axis=(-1, -2))
if self.reduce_loss:
LP_loss = K.mean(LP_loss)
self.add_loss(LP_loss)
# Entropy loss
entr = tf.negative(tf.reduce_sum(tf.multiply(S, K.log(S + K.epsilon())), axis=-1))
entr_loss = K.mean(entr, axis=-1)
if self.reduce_loss:
entr_loss = K.mean(entr_loss)
self.add_loss(entr_loss)
# Pooling
X_pooled = ops.matmul_AT_B(S, Z)
A_pooled = ops.matmul_AT_B_A(S, A)
if K.ndim(A_pooled) == 3:
self.mixed_mode = True
output = [X_pooled, A_pooled]
if I is not None:
I_mean = tf.segment_mean(I, I)
I_pooled = ops.repeat(I_mean, tf.ones_like(I_mean) * self.k)
output.append(I_pooled)
if self.return_mask:
output.append(S)
return output
def call(self, inputs):
# Note that I is useless, because thee layer cannot be used in graph
# batch mode.
if len(inputs) == 3:
X, A, I = inputs
else:
X, A = inputs
I = None
# Check if the layer is operating in batch mode (X and A have rank 3)
batch_mode = K.ndim(A) == 3
# Optionally compute hidden layer
if self.h is None:
Hid = X
else:
Hid = K.dot(X, self.kernel_in)
if self.use_bias:
Hid = K.bias_add(Hid, self.bias_in)
if self.activation is not None:
Hid = self.activation(Hid)
# Compute cluster assignment matrix
S = K.dot(Hid, self.kernel_out)
if self.use_bias:
S = K.bias_add(S, self.bias_out)
S = activations.softmax(S, axis=-1) # Apply softmax to get cluster assignments
# MinCut regularization
A_pooled = ops.matmul_AT_B_A(S, A)
num = tf.trace(A_pooled)
D = ops.degree_matrix(A)
den = tf.trace(ops.matmul_AT_B_A(S, D))
cut_loss = -(num / den)
if batch_mode:
cut_loss = K.mean(cut_loss)
self.add_loss(cut_loss)
# Orthogonality regularization
SS = ops.matmul_AT_B(S, S)
I_S = tf.eye(self.k)
ortho_loss = tf.norm(
SS / tf.norm(SS, axis=(-1, -2)) - I_S / tf.norm(I_S), axis=(-1, -2)
)
if batch_mode:
ortho_loss = K.mean(cut_loss)
self.add_loss(ortho_loss)
# Pooling
X_pooled = ops.matmul_AT_B(S, X)
A_pooled = tf.linalg.set_diag(A_pooled, tf.zeros(K.shape(A_pooled)[:-1])) # Remove diagonal
A_pooled = ops.normalize_A(A_pooled)
output = [X_pooled, A_pooled]
if I is not None:
I_mean = tf.segment_mean(I, I)
I_pooled = ops.repeat(I_mean, tf.ones_like(I_mean) * self.k)
output.append(I_pooled)
if self.return_mask:
output.append(S)
return output
def reduce_index(self, i, s, **kwargs):
i_mean = tf.math.segment_mean(i, i)
i_pool = ops.repeat(i_mean, tf.ones_like(i_mean) * self.k)
return i_pool
