def _to_tensor_array(name, v, clear_after_read=None):
''' create TensorArray from v, of size batch.'''
ta = tf.TensorArray(v.dtype,
batch,
name=name,
clear_after_read=clear_after_read)
ta = ta.unstack(v)
return ta
def splice_layer(x, name, context):
'''
Splice a tensor along the last dimension with context.
e.g.:
t = [[[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]]
splice_tensor(t, [0, 1]) =
[[[1, 2, 3, 4, 5, 6],
[4, 5, 6, 7, 8, 9],
[7, 8, 9, 7, 8, 9]]]
Args:
tensor: a tf.Tensor with shape (B, T, D) a.k.a. (N, H, W)
context: a list of context offsets
Returns:
spliced tensor with shape (..., D * len(context))
'''
with tf.variable_scope(name):
input_shape = tf.shape(x)
B, T = input_shape[0], input_shape[1]
context_len = len(context)
array = tf.TensorArray(x.dtype, size=context_len)
for idx, offset in enumerate(context):
begin = offset
end = T + offset
if begin < 0:
begin = 0
sliced = x[:, begin:end, :]
tiled = tf.tile(x[:, 0:1, :], [1, abs(offset), 1])
final = tf.concat((tiled, sliced), axis=1)
else:
end = T
sliced = x[:, begin:end, :]
tiled = tf.tile(x[:, -1:, :], [1, abs(offset), 1])
final = tf.concat((sliced, tiled), axis=1)
array = array.write(idx, final)
spliced = array.stack()
spliced = tf.transpose(spliced, (1, 2, 0, 3))
spliced = tf.reshape(spliced, (B, T, -1))
return spliced
def _new_tensor_array(name, size, dtype=None):
''' create empty TensorArray which can store size elements.'''
return tf.TensorArray(dtype, size, name=name)