def upsampling_tpu_compatible(data, scale):
"""Nearest neighbor upsampling TPU-compatible implementation.
This implementation is TPU compatible as opposed to
tf.image.resize_nearest_neighbor().
Args:
data: A 4D float32 tensor of shape [batch, height, width, channels].
scale: An integer multiple to scale resolution of input data.
Returns:
A 4D float32 tensor of shape [batch, height*scale, width*scale, channels].
"""
with tf.name_scope('upsampling_tpu_compatible'):
if data.get_shape().is_fully_defined():
bs, height, width, _ = [s.value for s in data.get_shape()]
else:
shape = tf.shape(data)
bs, height, width = shape[0], shape[1], shape[2]
channels = data.get_shape().as_list()[3]
# Use reshape to quickly upsample the input. The nearest pixel is selected
# implicitly via broadcasting.
data = tf.reshape(data, [bs, height, 1, width, 1, channels]) * tf.ones(
[1, 1, scale, 1, scale, 1], dtype=data.dtype)
return tf.reshape(data, [bs, height * scale, width * scale, channels])
def pad_to_fixed_size(data, pad_value, output_shape):
"""Pad data to a fixed length at the first dimension.
Args:
data: Tensor to be padded to output_shape.
pad_value: A constant value assigned to the paddings.
output_shape: The output shape of a 2D tensor.
Returns:
The Padded tensor with output_shape [max_num_instances, dimension].
"""
max_num_instances = output_shape[0]
dimension = output_shape[1]
data = tf.reshape(data, [-1, dimension])
num_instances = tf.shape(data)[0]
assert_length = tf.Assert(tf.less_equal(num_instances, max_num_instances),
[num_instances])
with tf.control_dependencies([assert_length]):
pad_length = max_num_instances - num_instances
paddings = pad_value * tf.ones([pad_length, dimension])
padded_data = tf.concat([data, paddings], axis=0)
padded_data = tf.reshape(padded_data, output_shape)
return padded_data
def parser(record):
"""function used to parse tfrecord."""
record_spec = {
"input": tf.FixedLenFeature([seq_len], tf.int64),
"target": tf.FixedLenFeature([seq_len], tf.int64),
"seg_id": tf.FixedLenFeature([seq_len], tf.int64),
"label": tf.FixedLenFeature([1], tf.int64),
"is_masked": tf.FixedLenFeature([seq_len], tf.int64),
}
# retrieve serialized example
example = tf.parse_single_example(
serialized=record,
features=record_spec)
inputs = example.pop("input")
target = example.pop("target")
is_masked = tf.cast(example.pop("is_masked"), tf.bool)
non_reuse_len = seq_len - reuse_len
assert perm_size <= reuse_len and perm_size <= non_reuse_len
perm_mask_0, target_0, target_mask_0, input_k_0, input_q_0 = _local_perm(
inputs[:reuse_len],
target[:reuse_len],
is_masked[:reuse_len],
perm_size,
reuse_len)
perm_mask_1, target_1, target_mask_1, input_k_1, input_q_1 = _local_perm(
inputs[reuse_len:],
target[reuse_len:],
is_masked[reuse_len:],
perm_size,
non_reuse_len)
perm_mask_0 = tf.concat([perm_mask_0, tf.ones([reuse_len, non_reuse_len])],
axis=1)
perm_mask_1 = tf.concat([tf.zeros([non_reuse_len, reuse_len]), perm_mask_1],
axis=1)
perm_mask = tf.concat([perm_mask_0, perm_mask_1], axis=0)
target = tf.concat([target_0, target_1], axis=0)
target_mask = tf.concat([target_mask_0, target_mask_1], axis=0)
input_k = tf.concat([input_k_0, input_k_1], axis=0)
input_q = tf.concat([input_q_0, input_q_1], axis=0)
if num_predict is not None:
indices = tf.range(seq_len, dtype=tf.int64)
bool_target_mask = tf.cast(target_mask, tf.bool)
indices = tf.boolean_mask(indices, bool_target_mask)
##### extra padding due to CLS/SEP introduced after prepro
actual_num_predict = tf.shape(indices)[0]
pad_len = num_predict - actual_num_predict
##### target_mapping
target_mapping = tf.one_hot(indices, seq_len, dtype=tf.float32)
paddings = tf.zeros([pad_len, seq_len], dtype=target_mapping.dtype)
target_mapping = tf.concat([target_mapping, paddings], axis=0)
example["target_mapping"] = tf.reshape(target_mapping,
[num_predict, seq_len])
##### target
target = tf.boolean_mask(target, bool_target_mask)
paddings = tf.zeros([pad_len], dtype=target.dtype)
target = tf.concat([target, paddings], axis=0)
example["target"] = tf.reshape(target, [num_predict])
##### target mask
target_mask = tf.concat(
[tf.ones([actual_num_predict], dtype=tf.float32),
tf.zeros([pad_len], dtype=tf.float32)],
axis=0)
example["target_mask"] = tf.reshape(target_mask, [num_predict])
else:
example["target"] = tf.reshape(target, [seq_len])
example["target_mask"] = tf.reshape(target_mask, [seq_len])
# reshape back to fixed shape
example["perm_mask"] = tf.reshape(perm_mask, [seq_len, seq_len])
example["input_k"] = tf.reshape(input_k, [seq_len])
example["input_q"] = tf.reshape(input_q, [seq_len])
_convert_example(example, use_bfloat16)
for k, v in example.items():
tf.logging.info("%s: %s", k, v)
return example
def _local_perm(inputs, targets, is_masked, perm_size, seq_len):
"""
Sample a permutation of the factorization order, and create an
attention mask accordingly.
Args:
inputs: int64 Tensor in shape [seq_len], input ids.
targets: int64 Tensor in shape [seq_len], target ids.
is_masked: bool Tensor in shape [seq_len]. True means being selected
for partial prediction.
perm_size: the length of longest permutation. Could be set to be reuse_len.
Should not be larger than reuse_len or there will be data leaks.
seq_len: int, sequence length.
"""
# Generate permutation indices
index = tf.range(seq_len, dtype=tf.int64)
index = tf.transpose(tf.reshape(index, [-1, perm_size]))
index = tf.random_shuffle(index)
index = tf.reshape(tf.transpose(index), [-1])
# `perm_mask` and `target_mask`
# non-functional tokens
non_func_tokens = tf.logical_not(tf.logical_or(
tf.equal(inputs, SEP_ID),
tf.equal(inputs, CLS_ID)))
non_mask_tokens = tf.logical_and(tf.logical_not(is_masked), non_func_tokens)
masked_or_func_tokens = tf.logical_not(non_mask_tokens)
# Set the permutation indices of non-masked (& non-funcional) tokens to the
# smallest index (-1):
# (1) they can be seen by all other positions
# (2) they cannot see masked positions, so there won"t be information leak
smallest_index = -tf.ones([seq_len], dtype=tf.int64)
rev_index = tf.where(non_mask_tokens, smallest_index, index)
# Create `target_mask`: non-funcional and maksed tokens
# 1: use mask as input and have loss
# 0: use token (or [SEP], [CLS]) as input and do not have loss
target_tokens = tf.logical_and(masked_or_func_tokens, non_func_tokens)
target_mask = tf.cast(target_tokens, tf.float32)
# Create `perm_mask`
# `target_tokens` cannot see themselves
self_rev_index = tf.where(target_tokens, rev_index, rev_index + 1)
# 1: cannot attend if i <= j and j is not non-masked (masked_or_func_tokens)
# 0: can attend if i > j or j is non-masked
perm_mask = tf.logical_and(
self_rev_index[:, None] <= rev_index[None, :],
masked_or_func_tokens)
perm_mask = tf.cast(perm_mask, tf.float32)
# new target: [next token] for LM and [curr token] (self) for PLM
new_targets = tf.concat([inputs[0: 1], targets[: -1]],
axis=0)
# construct inputs_k
inputs_k = inputs
# construct inputs_q
inputs_q = target_mask
return perm_mask, new_targets, target_mask, inputs_k, inputs_q