def pg_loss_with_log_probs(log_probs,
advantages,
rank=None,
batched=False,
sequence_length=None,
average_across_batch=True,
average_across_timesteps=False,
average_across_remaining=False,
sum_over_batch=False,
sum_over_timesteps=True,
sum_over_remaining=True,
time_major=False):
"""Policy gradient loss with log probs of actions.
`pg_loss = reduce( advantages * -log_probs )`,
where `advantages` does not back-propagate gradients.
All arguments except :attr:`log_probs` are the same as
:func:`pg_loss_with_logits`.
Args:
log_probs: Log probabilities of shape
`[(batch_size,) max_time, ..., d_rank]` and dtype `float32`
or `float64`. The rank of the Tensor is specified
with :attr:`rank`.
The batch dimension exists only if :attr:`batched` is `True`.
The batch and time dimensions are exchanged, i.e.,
`[max_time, batch_size, ...]` if :attr:`time_major` is `True`.
advantages: Tensor of shape
`[(batch_size,) max_time, d_3, ..., d_rank]` and
dtype `float32` or `float64`.
The batch dimension exists only if `batched` is `True`.
The batch and time dimensions
are exchanged if `time_major` is `True`.
rank (int, optional): The rank of :attr:`log_probs`.
If `None` (default), rank is automatically inferred from
`log_probs` or `advantages`. If the inference fails,
`rank` is set to 1 if `batched``==False`,
and set to 2 if `batched``==True`.
batched (bool): `True` if the inputs are batched.
sequence_length (optional): A Tensor of shape `[batch_size]`.
Time steps beyond the respective sequence lengths will have zero
losses. Used if :attr:`batched` is `True`.
average_across_timesteps (bool): If set, average the loss across
the time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
average_across_batch (bool): If set, average the loss across the
batch dimension. Must not set `average_across_batch`'
and `sum_over_batch` at the same time.
Ignored if `batched` is `False`.
average_across_remaining (bool): If set, average the sequence across the
remaining dimensions. Must not set `average_across_remaining`'
and `sum_over_remaining` at the same time. Ignored if
no more dimensions other than the batch and time dimensions.
sum_over_timesteps (bool): If set, sum the loss across the
time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
sum_over_batch (bool): If set, sum the loss across the
batch dimension. Must not set `average_across_batch`
and `sum_over_batch` at the same time.
Ignored if `batched` is `False`.
sum_over_remaining (bool): If set, sum the loss across the
remaining dimension. Must not set `average_across_remaining`
and `sum_over_remaining` at the same time. Ignored if
no more dimensions other than the batch and time dimensions.
time_major (bool): The shape format of the inputs. If `True`,
:attr:`log_probs` and :attr:`advantages` must have shape
`[max_time, batch_size, ...]`. If `False` (default),
they must have shape `[batch_size, max_time, ...]`.
Ignored if :attr:`batched` is `False`.
Returns:
A Tensor containing the loss to minimize, whose rank depends on the
reduce arguments. For example, the batch dimension is reduced if
either :attr:`average_across_batch` or :attr:`sum_over_batch` is
`True`, which decreases the rank of output tensor by 1.
"""
advantages = tf.stop_gradient(advantages)
losses = -log_probs * advantages
if rank is None:
rank = get_rank(log_probs) or get_rank(advantages)
if rank is None:
rank = 2 if batched else 1
if batched:
losses = mask_and_reduce(
losses,
sequence_length,
rank=rank,
average_across_batch=average_across_batch,
average_across_timesteps=average_across_timesteps,
average_across_remaining=average_across_remaining,
sum_over_batch=sum_over_batch,
sum_over_timesteps=sum_over_timesteps,
sum_over_remaining=sum_over_remaining,
time_major=time_major)
elif rank > 1:
if average_across_remaining and sum_over_remaining:
raise ValueError("Only one of `average_across_remaining` and "
"`sum_over_remaining` can be set.")
if average_across_remaining:
losses = tf.reduce_mean(losses, axis=list(range(1, rank)))
elif sum_over_remaining:
losses = tf.reduce_sum(losses, axis=list(range(1, rank)))
if not batched:
if average_across_timesteps and sum_over_timesteps:
raise ValueError("Only one of `average_across_timesteps` and "
"`sum_over_timesteps` can be set.")
if average_across_timesteps:
losses = tf.reduce_mean(losses, axis=0)
elif sum_over_timesteps:
losses = tf.reduce_sum(losses, axis=0)
return losses
def sequence_sparse_softmax_cross_entropy(labels,
logits,
sequence_length,
average_across_batch=True,
average_across_timesteps=False,
sum_over_batch=False,
sum_over_timesteps=True,
time_major=False,
name=None):
"""Computes sparse softmax cross entropy for each time step of sequence
predictions.
Args:
labels: Target class indexes. I.e., classes are mutually exclusive
(each entry is in exactly one class).
- If :attr:`time_major` is `False` (default), this must be\
a Tensor of shape `[batch_size, max_time]`.
- If `time_major` is `True`, this must be a Tensor of shape\
`[max_time, batch_size].`
logits: Unscaled log probabilities. This must have the shape of
`[max_time, batch_size, num_classes]` or
`[batch_size, max_time, num_classes]` according to
the value of `time_major`.
sequence_length: A Tensor of shape `[batch_size]`. Time steps beyond
the respective sequence lengths will have zero losses.
average_across_timesteps (bool): If set, average the loss across
the time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
average_across_batch (bool): If set, average the loss across the
batch dimension. Must not set `average_across_batch`'
and `sum_over_batch` at the same time.
sum_over_timesteps (bool): If set, sum the loss across the
time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
sum_over_batch (bool): If set, sum the loss across the
batch dimension. Must not set `average_across_batch`
and `sum_over_batch` at the same time.
time_major (bool): The shape format of the inputs. If `True`,
:attr:`labels` and :attr:`logits` must have shape
`[max_time, batch_size, ...]`. If `False`
(default), they must have shape `[batch_size, max_time, ...]`.
name (str, optional): A name for the operation.
Returns:
A Tensor containing the loss, of rank 0, 1, or 2 depending on the
arguments :attr:`{average_across}/{sum_over}_{timesteps}/{batch}`.
For example:
- If :attr:`sum_over_timesteps` and :attr:`average_across_batch` \
are `True` (default), the return Tensor is of rank 0.
- If :attr:`average_across_batch` is `True` and other arguments are \
`False`, the return Tensor is of shape `[max_time]`.
Example:
.. code-block:: python
embedder = WordEmbedder(vocab_size=data.vocab.size)
decoder = BasicRNNDecoder(vocab_size=data.vocab.size)
outputs, _, _ = decoder(
decoding_strategy='train_greedy',
inputs=embedder(data_batch['text_ids']),
sequence_length=data_batch['length']-1)
loss = sequence_sparse_softmax_cross_entropy(
labels=data_batch['text_ids'][:, 1:],
logits=outputs.logits,
sequence_length=data_batch['length']-1)
"""
with tf.name_scope(name, "sequence_sparse_softmax_cross_entropy"):
losses = tf.nn.sparse_softmax_cross_entropy_with_logits(
labels=labels, logits=logits)
losses = mask_and_reduce(
losses,
sequence_length,
rank=2,
average_across_batch=average_across_batch,
average_across_timesteps=average_across_timesteps,
sum_over_batch=sum_over_batch,
sum_over_timesteps=sum_over_timesteps,
time_major=time_major)
return losses
def sequence_softmax_cross_entropy(labels,
logits,
sequence_length,
average_across_batch=True,
average_across_timesteps=False,
sum_over_batch=False,
sum_over_timesteps=True,
time_major=False,
stop_gradient_to_label=False,
name=None):
"""Computes softmax cross entropy for each time step of sequence
predictions.
Args:
labels: Target class distributions.
- If :attr:`time_major` is `False` (default), this must be a\
Tensor of shape `[batch_size, max_time, num_classes]`.
- If `time_major` is `True`, this must be a Tensor of shape\
`[max_time, batch_size, num_classes]`.
Each row of `labels` should be a valid probability
distribution, otherwise, the computation of the gradient will be
incorrect.
logits: Unscaled log probabilities. This must have the shape of
`[max_time, batch_size, num_classes]` or
`[batch_size, max_time, num_classes]` according to
the value of `time_major`.
sequence_length: A Tensor of shape `[batch_size]`. Time steps beyond
the respective sequence lengths will have zero losses.
average_across_timesteps (bool): If set, average the loss across
the time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
average_across_batch (bool): If set, average the loss across the
batch dimension. Must not set `average_across_batch`'
and `sum_over_batch` at the same time.
sum_over_timesteps (bool): If set, sum the loss across the
time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
sum_over_batch (bool): If set, sum the loss across the
batch dimension. Must not set `average_across_batch`
and `sum_over_batch` at the same time.
time_major (bool): The shape format of the inputs. If `True`,
:attr:`labels` and :attr:`logits` must have shape
`[max_time, batch_size, ...]`. If `False`
(default), they must have shape `[batch_size, max_time, ...]`.
stop_gradient_to_label (bool): If set, gradient propagation to
:attr:`labels` will be disabled.
name (str, optional): A name for the operation.
Returns:
A Tensor containing the loss, of rank 0, 1, or 2 depending on the
arguments :attr:`{average_across}/{sum_over}_{timesteps}/{batch}`.
For example:
- If :attr:`sum_over_timesteps` and :attr:`average_across_batch` \
are `True` (default), the return Tensor is of rank 0.
- If :attr:`average_across_batch` is `True` and other arguments are \
`False`, the return Tensor is of shape `[max_time]`.
"""
with tf.name_scope(name, "sequence_softmax_cross_entropy"):
if stop_gradient_to_label:
labels = tf.stop_gradient(labels)
losses = tf.nn.softmax_cross_entropy_with_logits_v2(
labels=labels, logits=logits)
losses = mask_and_reduce(
losses,
sequence_length,
rank=2,
average_across_batch=average_across_batch,
average_across_timesteps=average_across_timesteps,
sum_over_batch=sum_over_batch,
sum_over_timesteps=sum_over_timesteps,
time_major=time_major)
return losses
def sequence_entropy_with_logits(logits,
rank=None,
sequence_length=None,
average_across_batch=True,
average_across_timesteps=False,
average_across_remaining=False,
sum_over_batch=False,
sum_over_timesteps=True,
sum_over_remaining=True,
time_major=False):
"""Shannon entropy given logits.
Args:
logits: Unscaled log probabilities of shape
`[batch_size, max_time, d_3, ..., d_{rank-1}, distribution_dim]`
and of dtype `float32` or `float64`.
The rank of the tensor is optionally specified by the argument
:attr:`rank`.
The tensor is considered as having `[batch_size, .., d_{rank-1}]`
elements, each of which has a distribution of length `d_rank`
(i.e., `distribution_dim`). So the last dimension is always
summed out to compute the entropy.
The batch and time dimensions are exchanged if :attr:`time_major`
is `True`.
rank (int, optional): The rank of :attr:`logits`.
If `None` (default), `rank` is inferred automatically from
`logits`. If the inference fails, `rank` is
set to 3, i.e., assuming `logits` is of shape
`[batch_size, max_time, distribution_dim]`
sequence_length (optional): A Tensor of shape `[batch_size]`.
Time steps beyond the respective sequence lengths are
counted into the entropy.
average_across_timesteps (bool): If set, average the entropy across
the time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
average_across_batch (bool): If set, average the entropy across the
batch dimension. Must not set `average_across_batch`'
and `sum_over_batch` at the same time.
average_across_remaining (bool): If set, average the entropy across the
remaining dimensions. Must not set `average_across_remaining`'
and `sum_over_remaining` at the same time.
Used only when :attr:`logits` has rank >= 4.
sum_over_timesteps (bool): If set, sum the entropy across the
time dimension. Must not set `average_across_timesteps`
and `sum_over_timesteps` at the same time.
sum_over_batch (bool): If set, sum the entropy across the
batch dimension. Must not set `average_across_batch`
and `sum_over_batch` at the same time.
sum_over_remaining (bool): If set, sum the entropy across the
remaining dimension. Must not set `average_across_remaining`
and `sum_over_remaining` at the same time.
Used only when :attr:`logits` has rank >= 4.
time_major (bool): The shape format of the inputs. If `True`,
:attr:`logits` must have shape `[max_time, batch_size, ...]`.
If `False` (default), it must have shape
`[batch_size, max_time, ...]`.
Returns:
A Tensor containing the shannon entropy. The dimensionality of the
Tensor depends on the configuration of reduction arguments. For
example, if batch, time, and remaining dimensions are all reduced (by
either sum or average), the returned Tensor is a scalar Tensor.
"""
entropy = _get_entropy(logits)
if rank is None:
rank = get_rank(logits)
if rank is None:
rank = 3
rank -= 1 # reduced last dimension
entropy = mask_and_reduce(
entropy,
sequence_length,
rank=rank,
average_across_batch=average_across_batch,
average_across_timesteps=average_across_timesteps,
average_across_remaining=average_across_remaining,
sum_over_batch=sum_over_batch,
sum_over_timesteps=sum_over_timesteps,
sum_over_remaining=sum_over_remaining,
time_major=time_major)
return entropy