def _mtf_model_fn(self, features, mesh):
self._original_features = features
hparams = self._hparams
def import_feature(key):
return self._import_feature(features, mesh, key)
targets = import_feature("targets")
if self.autoregressive:
inputs = mtf.shift(targets,
offset=1,
dim=self.length_dim,
wrap=False)
else:
inputs = import_feature("inputs")
# TODO(noam): options for bert-style masking here?
sequence_id = import_feature("targets_segmentation")
model = self.model()
logits, loss = model.call_simple(inputs=inputs,
targets=targets,
compute_loss=True,
mode=hparams.mode,
variable_dtype=self.variable_dtype,
sequence_id=sequence_id)
return logits, loss
def _mtf_model_fn(self, features, mesh):
self._original_features = features
hparams = self._hparams
def import_feature(key):
return self._import_feature(features, mesh, key)
targets = import_feature("targets")
sequence_id = import_feature("targets_segmentation")
position = import_feature("targets_position")
if self.autoregressive:
inputs = mtf.shift(targets,
offset=1,
dim=self.length_dim,
wrap=False)
if position is not None:
# first input in later sequences should be 0
inputs *= mtf.to_int32(mtf.not_equal(position, 0))
else:
inputs = import_feature("inputs")
# TODO(noam): options for bert-style masking here?
model = self.model()
logits, loss = model.call_simple(inputs=inputs,
targets=targets,
compute_loss=True,
mode=hparams.mode,
variable_dtype=self.variable_dtype,
sequence_id=sequence_id,
position=position)
return logits, loss
def _mtf_model_fn(self, features, mesh):
self._original_features = features
hparams = self._hparams
def import_feature(key):
return self._import_feature(features, mesh, key)
targets = import_feature("targets")
sequence_id = import_feature("targets_segmentation")
if hparams.use_global_position_in_packed_sequence:
position = None
else:
position = import_feature("targets_position")
if self.autoregressive:
inputs = mtf.shift(targets,
offset=1,
dim=self.length_dim,
wrap=False)
# We should have a 0 at the beginning of each sequence rather than the
# shifted EOS (1) from the previous sequence.
inputs -= mtf.to_int32(mtf.equal(inputs, 1))
else:
inputs = import_feature("inputs")
# TODO(noam): options for bert-style masking here?
model = self.model()
logits, loss = model.call_simple(inputs=inputs,
targets=targets,
compute_loss=True,
mode=hparams.mode,
variable_dtype=self.variable_dtype,
sequence_id=sequence_id,
position=position)
return logits, loss
def call_simple(self,
inputs,
targets,
compute_loss,
mode=tf.estimator.ModeKeys.TRAIN,
variable_dtype=mtf.VariableDType(tf.float32),
encoder_sequence_id=None,
decoder_sequence_id=None):
"""Compute logits based on inputs (all positions in parallel).
This is called during training and evaluation.
Args:
inputs: an int32 Tensor with shape [<batch_dims>, length_dim]
targets: an optional int32 Tensor with shape [<batch_dims>, length_dim]
compute_loss: a boolean
mode: a tf.estimator.ModeKeys
variable_dtype: a mtf.VariableDType
encoder_sequence_id: an optional Tensor
decoder_sequence_id: an optional Tensor
Returns:
logits: a Tensor with shape [<batch_dims>, output_vocab_dim]
loss: an optional Scalar (if compute_loss=True)
"""
shared_params = self._shared_params(inputs.mesh, variable_dtype)
encoder_output, encoder_loss = self.encoder.call_simple(
inputs,
None,
compute_loss,
mode=mode,
variable_dtype=variable_dtype,
sequence_id=encoder_sequence_id,
shared_params=shared_params)
encoder_output = mtf.layers.rename_length_to_memory_length(
encoder_output)
if encoder_sequence_id is not None:
encoder_sequence_id = mtf.layers.rename_length_to_memory_length(
encoder_sequence_id)
length_dim = targets.shape.dims[-1]
shifted_targets = mtf.shift(targets,
offset=1,
dim=length_dim,
wrap=False)
logits, loss = self.decoder.call_simple(
shifted_targets,
targets,
compute_loss,
mode=mode,
variable_dtype=variable_dtype,
sequence_id=decoder_sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
shared_params=shared_params)
if loss is not None and encoder_loss is not None:
loss += encoder_loss
return logits, loss
def halo_reduce(x, blocks_dim, block_size_dim, halo_size, wrap=True):
"""Reduce each block with the margins of adjacent blocks.
Get left and right blocks_dim and sum overlap along block_size_dim.
Only supports halo size smaller than block_size/2
Args:
x: a Tensor.
blocks_dim: a Dimension in x.shape
block_size_dim: a Dimension in x.shape
halo_size: an integer
wrap: a boolean
Returns:
a Tensor with the same shape as x, other than in block_size_dim, whose
size is increased by 2*halo_size.
"""
if halo_size == 0:
return x
block_size = block_size_dim.size
assert halo_size <= block_size // 2
left_margin = mtf.slice(x, 0, 2 * halo_size, block_size_dim.name)
right_margin = mtf.slice(x, block_size_dim.size - 2 * halo_size,
2 * halo_size, block_size_dim.name)
center = mtf.slice(x, 2 * halo_size, block_size_dim.size - 4 * halo_size,
block_size_dim.name)
# Perform halo exchange sum margins
left = mtf.shift(right_margin, 1, blocks_dim, wrap) + left_margin
right = mtf.shift(left_margin, -1, blocks_dim, wrap) + right_margin
# Recompose block
left = mtf.pad(left, [0, block_size_dim.size - 2 * halo_size],
block_size_dim.name)
right = mtf.pad(right, [block_size_dim.size - 2 * halo_size, 0],
block_size_dim.name)
center = mtf.pad(center, [2 * halo_size, 2 * halo_size],
block_size_dim.name)
x = left + center + right
return x
def model_fn(mtf_features):
"""The kind of function we need for mtf.serialize_training_step.
Args:
mtf_features: a dictionary
Returns:
a dictionary
"""
targets = mtf_features["targets"]
if model_type == "lm":
_, _, length_dim = targets.shape
inputs = mtf.shift(targets,
offset=1,
dim=length_dim,
wrap=False)
else:
inputs = mtf_features["inputs"]
if isinstance(transformer_model, transformer.Unitransformer):
position_kwargs = dict(
sequence_id=mtf_features.get("targets_segmentation",
None),
position=mtf_features.get("targets_position", None),
)
elif isinstance(transformer_model, transformer.Bitransformer
) or model_type == "bi_student_teacher":
position_kwargs = dict(
encoder_sequence_id=mtf_features.get(
"inputs_segmentation", None),
decoder_sequence_id=mtf_features.get(
"targets_segmentation", None),
encoder_position=mtf_features.get(
"inputs_position", None),
decoder_position=mtf_features.get(
"targets_position", None),
)
else:
raise ValueError("unrecognized class")
logits, loss = transformer_model.call_simple(
inputs=inputs,
targets=targets,
compute_loss=True,
mode=mode,
variable_dtype=get_variable_dtype(),
**position_kwargs)
if num_microbatches > 1:
loss /= float(num_microbatches)
del logits
return {"loss": loss}
def causal_depthwise_conv(x, context, kernel_size=3):
"""Causal depthwise convolution."""
def scale_var(shift_distance):
return mtf.get_variable(
context.mesh,
"conv_%s" % shift_distance,
mtf.Shape(context.model.ensemble_dims + x.shape.dims[-1:]),
initializer=tf.constant_initializer(0.5 if shift_distance ==
0 else 0.5 / kernel_size),
dtype=context.variable_dtype)
ret = x * scale_var(0)
for shift_distance in range(1, kernel_size):
x = mtf.shift(x, 1, context.length_dim, wrap=False)
ret += x * scale_var(shift_distance)
return ret
def _mtf_model_fn(self, features, mesh):
self._original_features = features
features = copy.copy(features)
hparams = self._hparams
targets = tf.to_int32(features["targets"])
if len(targets.get_shape()) > 2:
tf.logging.info("targets = %s" % targets)
targets = tf.squeeze(targets, [2, 3])
# pad targets to max_length
def pad_to_length(x):
extra_length = self.length_dim.size - tf.shape(x)[1]
x = tf.pad(x, [[0, 0], [0, extra_length]])
x = tf.reshape(x, [hparams.batch_size, self.length_dim.size])
return x
targets = pad_to_length(targets)
targets = self._import_to_batch_by_length(targets, "targets", mesh)
for key in [
"targets_segmentation", "targets_position",
"inputs_segmentation", "inputs_position"
]:
if key in features:
features[key] = pad_to_length(features[key])
if hparams.decoder_type == "autoregressive":
shifted_targets = mtf.shift(targets,
offset=1,
dim=self.length_dim,
wrap=False)
else:
raise ValueError("unknown hparams.decoder_type = %s" %
hparams.decoder_type)
model = self.model()
logits, loss = model.call_simple(inputs=shifted_targets,
targets=targets,
compute_loss=True,
mode=hparams.mode,
variable_dtype=self.variable_dtype)
# mesh_shape=hparams.mesh_shape,
# layout=hparams.layout,
return logits, loss
def body_fn(position, ids, *states):
"""One step in the decode loop."""
nonlocal sampling_keep_top_k
context = mtf_transformer.transformer.Context(
model=None,
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
variable_dtype=variable_dtype,
mode="incremental",
position=position,
position_is_default=True,
states=states,
new_states=[],
initial_position=position,
sequence_id=None,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
shared_params=shared_params,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=read_priority,
inputs=ids,
encoder_inputs=encoder_inputs) if not slow_sampling else None
with tf.variable_scope("gpt2", reuse=tf.AUTO_REUSE):
logits, _, _ = gpt2.model({"inputs": ids},
other_features,
params,
inputs.mesh,
variable_dtype=variable_dtype,
context=context)
# By default, do top_k sampling of 0.9
if sampling_keep_top_k == -2:
sampling_keep_top_k = int(logits.shape[-1].size * 0.1)
if sampling_keep_top_k != -1:
if sampling_keep_top_k <= 0:
raise ValueError(
"sampling_keep_top_k must either be -1 or positive.")
k_largest = mtf.nth_largest_element(
logits,
n=sampling_keep_top_k,
reduced_dim=other_features["vocab_dim"])
logits = mtf.where(mtf.less_equal(logits, k_largest),
mtf.ones_like(logits) * -1e6, logits)
ids_this_step = mtf.sample_with_temperature(
logits, other_features["vocab_dim"], temperature)
if slow_sampling:
ids_this_step = mtf.shift(ids_this_step,
offset=1,
dim=length_dim,
wrap=False)
else:
ids_this_step = mtf.reshape(ids_this_step, (batch_dims))
one_hot = mtf.one_hot(position, length_dim, dtype=tf.int32)
one_new_id = ids_this_step * one_hot
new_ids = (1 - one_hot) * ids + one_new_id
new_position = position + 1
ret = [new_position, new_ids]
if context is not None:
ret += context.new_states
return ret
def call_simple(self,
inputs,
targets,
compute_loss,
attributes=None,
mode=tf.estimator.ModeKeys.TRAIN,
variable_dtype=mtf.VariableDType(tf.float32),
sequence_id=None,
subsequence_id=None,
position=None,
encoder_output=None,
encoder_sequence_id=None,
encoder_inputs=None,
shared_params=None,
layer_outputs=None,
encoder_layer_outputs=None,
z=None):
"""Compute logits based on inputs (all positions in parallel).
This is called during training and evaluation.
Args:
inputs: an int32 Tensor with shape [<batch_dims>, length_dim] For training
autoregressive models this should be equal to mtf.shift(targets,
offset=1, dim=length_dim, wrap=False)
targets: an optional int32 Tensor with shape [<batch_dims>, length_dim]
compute_loss: a boolean
attributes: an (optional?) int32 Tensor with shape [<batch_dims>, length_dim] ([<batch_dims>])
mode: a tf.estimator.ModeKeys
variable_dtype: a mtf.VariableDType
sequence_id: an optional Tensor
subsequence_id: an optional Tensor
position: an optional Tensor
encoder_output: an optional Tensor
encoder_sequence_id: an optional Tensor
encoder_inputs: an optional Tensor
shared_params: an optional dictionary
layer_outputs: an optional list to append Tensor layer activations to
encoder_layer_outputs: optional - readonly list of tensor activations when
decoding, one per each input layer + the embedding layer
Returns:
logits: a Tensor with shape [<batch_dims>, output_vocab_dim]
loss: an optional Scalar (if compute_loss=True)
"""
batch_dims = inputs.shape.dims[:-1]
length_dim = inputs.shape.dims[-1]
length_range = mtf.range(inputs.mesh, length_dim, dtype=tf.int32)
if not self.positional_embedding:
# To make relative attention faster, we drop the information about the
# position in the subsequence. The relative attention code then
# assumes that the positions are given by index in the tensor,
# which still leads to the correct computation of relative position.
position = None
if position is None:
position_is_default = True
position = length_range
else:
position_is_default = False
if self.input_full_attention:
# The inputs part of each sequence can fully attend within itself.
full_attention_region = delimited_lm_inputs_mask(targets)
# We can include one additional position to the right - the position
# where the final EOS of the inputs is read and the first target token
# is predicted.
full_attention_region = mtf.logical_or(
full_attention_region,
mtf.shift(full_attention_region,
offset=1,
dim=length_dim,
wrap=False))
# We set read_priority and write_priority to 0 in the full-attention
# region and equal to the position elsewhere.
read_priority = write_priority = length_range * mtf.cast(
mtf.logical_not(full_attention_region), tf.int32)
elif self.autoregressive:
# Vanilla autoregressive model - each position can see previous positions.
read_priority = write_priority = length_range
else:
read_priority = write_priority = None
context = Context(model=self,
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
variable_dtype=variable_dtype,
mode=mode,
losses=[] if compute_loss else None,
sequence_id=sequence_id,
subsequence_id=subsequence_id,
position=position,
position_is_default=position_is_default,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
shared_params=shared_params,
layer_outputs=layer_outputs,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=read_priority,
inputs=inputs,
encoder_inputs=encoder_inputs)
with tf.variable_scope(self.name):
logits = self._call_internal(context,
inputs,
targets,
attributes,
z=z)
if compute_loss:
loss = mtf.add_n(context.losses)
else:
loss = None
return logits, loss
def _mtf_model_fn(self, features, mesh):
self._original_features = features
features = copy.copy(features)
hparams = self._hparams
extra_losses = []
targets = tf.to_int32(features["targets"])
mode = getattr(hparams, "mode", tf.estimator.ModeKeys.TRAIN)
is_training = mode == tf.estimator.ModeKeys.TRAIN
if len(targets.get_shape()) > 2:
tf.logging.info("targets = %s" % targets)
targets = tf.squeeze(targets, [2, 3])
# pad targets to max_length
def pad_to_max_length(x):
extra_length = hparams.max_length - tf.shape(x)[1]
x = tf.pad(x, [[0, 0], [0, extra_length]])
x = tf.reshape(x, [hparams.batch_size, hparams.max_length])
return x
targets = pad_to_max_length(targets)
targets = self._import_to_batch_by_length(targets, "targets", mesh, hparams)
for key in ["targets_segmentation", "targets_position",
"inputs_segmentation", "inputs_position"]:
if key in features:
features[key] = pad_to_max_length(features[key])
if hparams.decoder_type == "autoregressive":
shifted_targets = mtf.shift(
targets, offset=1, dim=self.length_dim, wrap=False)
elif hparams.decoder_type == "denoising":
shifted_targets = self._noisy_targets(targets, extra_losses)
else:
raise ValueError(
"unknown hparams.decoder_type = %s" % hparams.decoder_type)
if "targets_segmentation" in features:
# "Packed" dataset - keep the examples from seeing each other.
targets_segmentation = self._import_to_batch_by_length(
features["targets_segmentation"], "targets_segmentation",
mesh, hparams)
targets_position = self._import_to_batch_by_length(
features["targets_position"], "targets_position",
mesh, hparams)
decoder_self_attention_mask = mtf.layers.attention_mask_same_segment(
targets_segmentation, dtype=self.activation_dtype)
if hparams.decoder_type == "autoregressive":
decoder_self_attention_mask += mtf.layers.attention_mask_autoregressive(
targets_position, dtype=self.activation_dtype)
else:
targets_position = mtf.range(mesh, self.length_dim, dtype=tf.int32)
if hparams.decoder_type == "autoregressive":
decoder_self_attention_mask = mtf.layers.attention_mask_autoregressive(
targets_position, dtype=self.activation_dtype)
else:
decoder_self_attention_mask = None
def layer_prepostprocess_dropout(x):
return mtf.dropout(
x, is_training, keep_prob=1.0 - hparams.layer_prepostprocess_dropout,
noise_shape=mtf.Shape(self.batch_dims + [self.model_dim]))
(inputs_embedding_var,
targets_embedding_var,
softmax_var,
positional_embedding_var) = self._embedding_and_softmax_vars(mesh)
if hparams.transformer_type == "decoder":
encoder_output = None
encoder_decoder_attention_mask = None
else:
inputs = tf.squeeze(tf.to_int32(features["inputs"]), [2, 3])
inputs = pad_to_max_length(inputs)
inputs = self._import_to_batch_by_length(inputs, "inputs", mesh, hparams)
if "inputs_segmentation" in features:
# "Packed" dataset - keep the examples from seeing each other.
inputs_segmentation = self._import_to_batch_by_length(
features["inputs_segmentation"], "inputs_segmentation",
mesh, hparams)
inputs_position = self._import_to_batch_by_length(
features["inputs_position"], "inputs_position",
mesh, hparams)
encoder_self_attention_mask = (
mtf.layers.attention_mask_same_segment(
inputs_segmentation, dtype=self.activation_dtype))
else:
inputs_position = mtf.range(mesh, self.length_dim, dtype=tf.int32)
encoder_self_attention_mask = (
mtf.layers.attention_mask_ignore_padding(
inputs, dtype=self.activation_dtype))
x = (mtf.gather(inputs_embedding_var, inputs, self.inputs_vocab_dim) +
mtf.gather(positional_embedding_var, inputs_position,
self.max_length_dim))
x = layer_prepostprocess_dropout(x)
with tf.variable_scope("encoder"):
x = self._layer_stack(x,
hparams.encoder_layers,
self_attention_mask=encoder_self_attention_mask,
losses=extra_losses)
if hparams.transformer_type == "encdec":
if "inputs_segmentation" in features:
encoder_decoder_attention_mask = (
mtf.layers.attention_mask_same_segment(
targets_segmentation, inputs_segmentation,
dtype=self.activation_dtype))
else:
encoder_decoder_attention_mask = encoder_self_attention_mask
encoder_output = mtf.rename_dimension(
x, self.length_dim.name, self.memory_length_dim.name)
if hparams.transformer_type != "encoder":
# DECODER
x = (mtf.gather(
targets_embedding_var, shifted_targets, self.targets_vocab_dim) +
mtf.gather(
positional_embedding_var, targets_position, self.max_length_dim))
x = layer_prepostprocess_dropout(x)
with tf.variable_scope("decoder"):
x = self._layer_stack(
x,
hparams.decoder_layers,
encoder_output=encoder_output,
self_attention_mask=decoder_self_attention_mask,
encdec_attention_mask=encoder_decoder_attention_mask,
losses=extra_losses)
if (hparams.reshape_logits_hack and
hparams.mode == tf.estimator.ModeKeys.TRAIN):
# For some reason, the logits computation is extremely slow on TPU
# in some cases where the batch size per core is 1. Reshape the logits
# and the targets to double the batch size and halve the length.
# TODO(noam): file a bug.
old_dims = self.batch_dims + [self.length_dim]
new_dims = self.batch_dims[:-1] + [
mtf.Dimension(self.batch_dims[-1].name,
self.batch_dims[-1].size * 2),
mtf.Dimension(self.length_dim.name, self.length_dim.size // 2)]
x = mtf.reshape(x, new_dims + [self.model_dim])
targets = mtf.reshape(targets, new_dims)
logits = mtf.matmul(x, softmax_var)
if hparams.mode == tf.estimator.ModeKeys.TRAIN:
logits = mtf.layers.multiplicative_jitter(logits, epsilon=1e-2)
off_value = hparams.label_smoothing / self._targets_vocab_size
on_value = 1.0 - hparams.label_smoothing + off_value
soft_targets = mtf.one_hot(
targets, self.targets_vocab_dim, on_value=on_value, off_value=off_value,
dtype=self.activation_dtype)
loss = mtf.layers.softmax_cross_entropy_with_logits(
logits, soft_targets, self.targets_vocab_dim)
weights = mtf.layers.weights_nonzero(targets, dtype=self.activation_dtype)
loss = mtf.reduce_mean(loss * weights)
for l in extra_losses:
loss += l
if (hparams.reshape_logits_hack and
hparams.mode == tf.estimator.ModeKeys.TRAIN):
logits = mtf.reshape(logits, old_dims + [self.targets_vocab_dim])
logits = mtf.to_float(logits)
return logits, loss
def logits_and_loss(mtf_features):
"""Compute logits and loss.
Args:
mtf_features: a dictionary
Returns:
logits: a mtf.Tensor
loss: a mtf.Tensor
"""
if model_type == "lm": # TOTRY Adapt that to our case
if "inputs" in mtf_features:
mtf_features = _dynamic_text2self(mtf_features)
_, _, length_dim = mtf_features["targets"].shape
inputs = mtf.shift(mtf_features["targets"],
offset=1,
dim=length_dim,
wrap=False)
else:
inputs = mtf_features["inputs"]
if attribute_embedding:
attributes = mtf_features["attribute"]
else:
attributes = None
if control_codes:
codeprefixedtargets = mtf_features["codeprefixedtargets"]
else:
codeprefixedtargets = None
if isinstance(transformer_model, transformer.Unitransformer):
position_kwargs = dict(
sequence_id=mtf_features.get("targets_segmentation", None),
position=mtf_features.get("targets_position", None),
)
elif isinstance(transformer_model, transformer.Bitransformer
) or model_type == "bi_student_teacher":
if control_codes:
position_kwargs = dict(
encoder_sequence_id=mtf_features.get(
"inputs_segmentation", None),
decoder_sequence_id=mtf_features.get(
"codeprefixedtargets_segmentation", None),
decoder_subsequence_id=mtf_features.get(
"codeprefixedtargets_subsegmentation", None),
encoder_position=mtf_features.get(
"inputs_position", None),
decoder_position=mtf_features.get(
"codeprefixedtargets_position", None),
)
else:
position_kwargs = dict(
encoder_sequence_id=mtf_features.get(
"inputs_segmentation", None),
decoder_sequence_id=mtf_features.get(
"targets_segmentation", None),
decoder_subsequence_id=mtf_features.get(
"targets_subsegmentation", None),
encoder_position=mtf_features.get(
"inputs_position", None),
decoder_position=mtf_features.get(
"targets_position", None),
)
else:
raise ValueError("unrecognized class")
if isinstance(transformer_model, Bitransformer_ll):
if cycle_consistency_loss:
logits_ae, l_ae = transformer_model.call_simple(
inputs=inputs,
targets=mtf_features["targets"],
compute_loss=True,
attributes=attributes,
codeprefixedtargets=codeprefixedtargets,
mode=mode,
variable_dtype=get_variable_dtype(),
**position_kwargs)
if has_partial_sequences:
controlcodes = mtf_features["controlcode"]
else:
controlcodes = None
with gin.config_scope('training'):
mtf_samples = transformer_model.decode(
inputs,
attributes=attributes,
controlcodes=controlcodes,
has_partial_sequences=has_partial_sequences,
remove_partial_sequences=remove_partial_sequences,
variable_dtype=get_variable_dtype())
# mtf_samples = mtf.anonymize(mtf_samples)
outputs = mtf_samples
logits_cycle, l_cycle = transformer_model.call_simple(
inputs=outputs,
targets=mtf_features["targets"],
compute_loss=True,
attributes=attributes,
codeprefixedtargets=codeprefixedtargets,
mode=mode,
variable_dtype=get_variable_dtype(),
**position_kwargs)
loss_ae_cycle = lambda_ae * l_ae + lambda_cycle * l_cycle
return logits_cycle, loss_ae_cycle
else:
return transformer_model.call_simple(
inputs=inputs,
targets=mtf_features["targets"],
compute_loss=True,
attributes=attributes,
codeprefixedtargets=codeprefixedtargets,
mode=mode,
variable_dtype=get_variable_dtype(),
**position_kwargs)
else:
return transformer_model.call_simple(
inputs=inputs,
targets=mtf_features["targets"],
compute_loss=True,
mode=mode,
variable_dtype=get_variable_dtype(),
num_microbatches=num_microbatches,
**position_kwargs)
def sample_autoregressive(self,
partial_sequences,
dst_attributes=None,
stop_at_token=1,
max_steps=None,
temperature=0.0,
variable_dtype=mtf.VariableDType(tf.float32),
encoder_output=None,
encoder_sequence_id=None,
encoder_inputs=None,
shared_params=None,
has_partial_sequences=True,
encoder_layer_outputs=None,
never_end=False,
remove_partial_sequences=False,
sampling_keep_top_k=-1,
z=None):
"""Sample randomly one token at a time.
The partial_sequences represent partial sequences to be continued. The
first tokens of each sequence are nonzero representing the given partial
sequences and the last tokens of each sequence are zeros, representing what
needs to be filled in.
If there are no partial sequences (you want to sample from the beginning),
then pass partial_sequences=mtf.zeros(mesh, shape, dtype=tf.int32) and
has_partial_sequences=False (so we can skip computation).
The dst_attributes represents the destination attributes in which we want to generate sequences.
Args:
partial_sequences: an int32 Tensor with shape [<batch_dims>, length_dim]
dst_attribute: an int32 Tensor with shape [<batch_dims>, length_dim] ([<batch_dims>])
stop_at_token: an optional integer eos id. Stop when we produce it.
max_steps: an optional integer, the max number of steps to decode.
temperature: an optional floating point value between 0.0 and 1.0 0.0
means argmax, 1.0 means sample according to predicted distribution.
variable_dtype: a mtf.VariableDType
encoder_output: an optional Tensor
encoder_sequence_id: an optional Tensor
encoder_inputs: an optional Tensor
shared_params: an optional dictionary
has_partial_sequences: a boolean
encoder_layer_outputs: optional - readonly list of tensor activations when
decoding, one per each input layer + the embedding layer
never_end: a boolean - if set, then avoid generating stop_at_token
remove_partial_sequences: a boolean - whether to remove the partial
sequences from the output
sampling_keep_top_k: an integer - if not -1, only sample from the top k
logits.
Returns:
a Tensor with shape [<batch_dims>, length_dim]
"""
if not self.autoregressive:
raise ValueError("must be autoregressive")
inputs = partial_sequences
attributes = dst_attributes
batch_dims = inputs.shape.dims[:-1]
length_dim = inputs.shape.dims[-1]
initial_position = mtf.reduce_sum(mtf.to_int32(mtf.not_equal(
inputs, 0)),
reduced_dim=length_dim)
sequence_id = 1 if encoder_sequence_id is not None else None
length_range = mtf.range(inputs.mesh, length_dim, tf.int32)
if self.input_full_attention:
read_priority = write_priority = length_range * mtf.to_int32(
mtf.greater(length_range, initial_position))
else:
read_priority = write_priority = length_range
context_first_part = Context(
model=self,
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
variable_dtype=variable_dtype,
mode="first_part",
position=length_range,
position_is_default=True,
new_states=[],
initial_position=initial_position,
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=[],
shared_params=shared_params,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=read_priority,
inputs=inputs,
encoder_inputs=encoder_inputs)
shifted_inputs = mtf.shift(inputs,
offset=1,
dim=length_dim,
wrap=False)
with tf.variable_scope(self.name):
logits = self._call_internal(context_first_part,
shifted_inputs,
attributes=attributes,
z=z)
del logits
constant_states = context_first_part.constant_states
if not has_partial_sequences:
initial_states = [
mtf.zeros_like(t) for t in context_first_part.new_states
]
partial_sequences_eos_count = 0
else:
initial_states = context_first_part.new_states
partial_sequences_eos_count = mtf.reduce_sum(
mtf.to_int32(mtf.equal(partial_sequences, stop_at_token)),
reduced_dim=length_dim)
def cond_fn(position, ids, *unused_states):
"""Should we run another loop iteration."""
past_end = mtf.greater_equal(position, length_dim.size)
if max_steps:
past_end = mtf.logical_or(
past_end,
mtf.greater_equal(position - initial_position, max_steps))
is_done = past_end
if stop_at_token is not None:
eos_count = mtf.reduce_sum(mtf.to_int32(
mtf.equal(ids, stop_at_token)),
reduced_dim=length_dim)
has_additional_eos = mtf.greater(eos_count,
partial_sequences_eos_count)
is_done = mtf.logical_or(is_done, has_additional_eos)
all_done = mtf.reduce_all(is_done)
return mtf.logical_not(all_done)
def body_fn(position, ids, *states):
"""One step in the decode loop."""
inputs_this_step = mtf.gather(ids, position - 1, length_dim)
if self.attribute_embedding:
attributes_this_step = mtf.gather(attributes, position - 1,
length_dim)
else:
attributes_this_step = None
# raise ValueError("inputs_this_step shape=%s , ids shape=%s, position - 1 shape=%s, length_dim=%s" % (inputs_this_step.shape, ids.shape, (position - 1).shape, length_dim))
context_incremental = Context(
model=self,
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
variable_dtype=variable_dtype,
mode="incremental",
position=position,
states=states,
new_states=[],
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=constant_states,
shared_params=shared_params,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=position,
inputs=inputs_this_step,
encoder_inputs=encoder_inputs)
with tf.variable_scope(self.name, reuse=True):
logits = self._call_internal(context_incremental,
inputs_this_step,
attributes=attributes_this_step,
z=z)
if never_end:
logits += mtf.one_hot(mtf.constant(logits.mesh,
stop_at_token,
dtype=tf.int32),
self.output_vocab_dim,
on_value=-1e9,
off_value=0.0,
dtype=logits.dtype)
# TBD whether this should be before or after never_end:
# Note for adding top_p sampling in the future, in other code bases, the
# option to apply temperature is done before the top-k truncation. This
# implementation does this in the opposite order. For top-k this doesn't
# matter, but for top_p it will.
if sampling_keep_top_k != -1:
if sampling_keep_top_k <= 0:
raise ValueError(
"sampling_keep_top_k must either be -1 or positive.")
k_largest = mtf.nth_largest_element(
logits,
n=sampling_keep_top_k,
reduced_dim=self.output_vocab_dim)
logits = mtf.where(mtf.less_equal(logits, k_largest),
mtf.ones_like(logits) * -1e6, logits)
ids_this_step = mtf.sample_with_temperature(
logits, self.output_vocab_dim, temperature)
new_position = position + 1
new_ids = ids + ids_this_step * mtf.one_hot(
position, length_dim, dtype=tf.int32)
return [new_position, new_ids] + context_incremental.new_states
while_loop_inputs = [initial_position, inputs] + initial_states
final_position, outputs = mtf.while_loop(cond_fn, body_fn,
while_loop_inputs)[:2]
del final_position
if has_partial_sequences and remove_partial_sequences:
# remove partial sequences from outputs
partial_length = mtf.reduce_sum(mtf.to_int32(
mtf.not_equal(partial_sequences, 0)),
reduced_dim=length_dim)
outputs = mtf.dynamic_shift(outputs,
-partial_length,
length_dim,
wrap=False)
return outputs
def gradient_based_subword_tokenization(x,
length_dim,
max_subword_length=4,
downsample=None,
use_offsets=False,
consider_chars_as_blocks=False,
use_block_pos_embedding=False,
share_block_kernel=False,
memory_embeddings=0,
context=None,
block_mixing_mode=None,
activation="softmax",
downsample_function="mean"):
"""Implements GBSWT from Charformer.
Args:
x: a Tensor containing length_dim
length_dim: a Dimension
max_subword_length: integer
downsample: integer.
use_offsets: boolean.
consider_chars_as_blocks: boolean.
use_block_pos_embedding: boolean.
share_block_kernel: boolean.
memory_embeddings: integer.
context: Context.
block_mixing_mode: Str for block mixing.
activation: Str for block ranking.
downsample_function: Str, supports mean/linformer for now.
Returns:
a Tensor with the same shape as x.
Raises:
ValueError: if channels or depth don't match.
"""
# don't use this for now.
del max_subword_length
del memory_embeddings
all_blocks = []
all_scores = []
tf.logging.info("GSW block layer")
def _tile(x, n, tile_dim):
# Simple tile function in MTF.
return mtf.concat([x] * n, tile_dim.name)
def _repeat(x, n, repeat_dim):
# repeat function in MTF
tmp_dim = mtf.Dimension("tmp", 1)
expand_shape = mtf.Shape(x.shape.dims + [tmp_dim])
x = mtf.reshape(x, expand_shape)
x = _tile(x, n, tmp_dim)
output_shape = []
for dim in x.shape.dims:
if dim.name == "tmp":
continue
if dim.name == repeat_dim.name:
dim = mtf.Dimension(dim.name, dim.size * n)
output_shape.append(dim)
output_shape = mtf.Shape(output_shape)
x = mtf.reshape(x, output_shape)
return x
def _combined_dim(dims):
return mtf.Dimension(dims[0].name, mtf.Shape(dims).size)
# compute all subword blocks
# TODO(yitay): handle offsets to get all blocks
if activation == "sigtanh":
# one score for sigmoid
tmp_dim = mtf.Dimension("block_score", 2)
else:
tmp_dim = mtf.Dimension("block_score", 1)
model_dim = x.shape[-1]
subword_blocks_width = [2, 3, 4]
if consider_chars_as_blocks:
subword_blocks_width += [1]
if share_block_kernel:
block_kernel_shape = mtf.Shape([model_dim, tmp_dim])
block_kernel = mtf.get_variable(x.mesh,
"block_kernel",
block_kernel_shape,
initializer=None,
dtype=context.variable_dtype)
else:
block_kernel = None
for subword_len in subword_blocks_width:
if use_block_pos_embedding:
# this is turn off by default. It is meant to support cases like
# parameterized pooling or other features.
block_len_dim = mtf.Dimension(length_dim.name, subword_len)
# TODO(vqtran): Consider other positional embeddings.
block_pos_emb = sinusoid_positional_embedding_weights(
context.mesh, block_len_dim, x.shape[-1],
context.variable_dtype.activation_dtype)
block_pos_emb = _repeat(
block_pos_emb, math.ceil(length_dim.size / float(subword_len)),
block_len_dim)
if use_offsets:
offset_space = subword_len
else:
offset_space = 1
for offsets in range(offset_space):
if offsets > 0:
xoff = mtf.shift(x, offsets, length_dim, wrap=False)
if use_block_pos_embedding:
block_pos_emb = mtf.shift(block_pos_emb,
offsets,
block_pos_emb.shape[-2],
wrap=False)
else:
xoff = x
tf.logging.info("SW len=%d offset=%d", subword_len, offsets)
if length_dim.size % subword_len != 0:
tf.logging.info("Not divisible by length")
# add extra padding tokens
pad_amt = int(subword_len) - int(length_dim.size % subword_len)
kp = mtf.pad(xoff, [0, pad_amt], length_dim.name)
else:
kp = xoff
if use_block_pos_embedding:
kp += block_pos_emb
bx = mtf.pool_tensor_1d(
kp,
pool_dim=kp.shape.get_dim_by_name("length"),
reduce_fn=mtf.reduce_mean,
pool_size=int(subword_len))
block_score = mtf.layers.dense(bx, [tmp_dim],
use_bias=False,
name="bx",
reduced_dims=[model_dim],
variable_dtype=None,
kernel_weights=block_kernel)
expand_bx = _repeat(bx, subword_len, length_dim)
expand_scores = _repeat(block_score, subword_len, length_dim)
if offsets > 0:
# add offset.
expand_bx = mtf.pad(expand_bx, [offsets, 0], length_dim.name)
expand_scores = mtf.pad(expand_scores, [offsets, 0],
length_dim.name)
new_len = expand_bx.shape.get_dim_by_name(length_dim.name)
if new_len.size < length_dim.size:
pad_amt = new_len.size - length_dim.size
expand_bx = mtf.pad(expand_bx, [0, pad_amt], length_dim.name)
expand_scores = mtf.pad(expand_scores, [0, pad_amt],
length_dim.name)
elif new_len.size > length_dim.size:
expand_bx = mtf.slice(expand_bx, 0, length_dim.size,
length_dim.name)
expand_scores = mtf.slice(expand_scores, 0, length_dim.size,
length_dim.name)
new_tmp_dim = mtf.Dimension("extra_dim", 1)
expand_shape = mtf.Shape(expand_bx.shape.dims + [new_tmp_dim])
expand_scores_shape = mtf.Shape(expand_scores.shape.dims +
[new_tmp_dim])
expand_bx = mtf.reshape(expand_bx, expand_shape)
expand_scores = mtf.reshape(expand_scores, expand_scores_shape)
all_blocks.append(expand_bx)
all_scores.append(expand_scores)
all_blocks = mtf.concat(all_blocks, new_tmp_dim.name)
all_scores = mtf.concat(all_scores, new_tmp_dim.name)
tf.logging.info(all_blocks)
new_tmp_dim = all_blocks.shape.get_dim_by_name("extra_dim")
combined_dim = _combined_dim([new_tmp_dim, tmp_dim])
block_net_shape = all_scores.shape - tmp_dim - new_tmp_dim + combined_dim
block_net = mtf.reshape(all_scores, block_net_shape)
if block_mixing_mode == "score_attention":
tf.logging.info("Using score attention")
att = mtf.einsum([block_net, block_net], reduced_dims=[new_tmp_dim])
tf.logging.info(block_net)
att = mtf.softmax(att, reduced_dim=att.shape[-1])
block_net = mtf.einsum([att, block_net], output_shape=block_net.shape)
tf.logging.info(block_net)
if activation == "softmax":
block_net = mtf.softmax(block_net, reduced_dim=new_tmp_dim)
elif activation == "tanh":
tf.logging.info("Using tanh")
block_net = mtf.tanh(block_net)
all_blocks = block_net * all_blocks
all_blocks = mtf.reduce_sum(all_blocks, reduced_dim=new_tmp_dim)
output = all_blocks
if downsample:
output_length = output.shape.get_dim_by_name("length")
if output_length.size % int(downsample) != 0:
pad_amt = int(downsample) - int(
output_length.size % int(downsample))
output = mtf.pad(output, [0, pad_amt], output_length.name)
if downsample_function == "mean":
output = mtf.pool_tensor_1d(
output,
pool_dim=output.shape.get_dim_by_name("length"),
reduce_fn=mtf.reduce_mean,
pool_size=int(downsample))
else:
raise ValueError("Downsampling function not implemeneted.")
return output
def beam_search(self,
inputs,
decode_length,
dst_attributes=None,
variable_dtype=mtf.VariableDType(tf.float32),
encoder_output=None,
encoder_sequence_id=None,
encoder_inputs=None,
alpha=0.6,
shared_params=None,
encoder_layer_outputs=None,
z=None):
"""Beam search.
Args:
inputs: an int32 zero-Tensor with shape [<batch_dims>, beam_dim,
length_dim].#
decode_length: an int32 mtf scalar. Maximum decode length.
attributes: an int32 zero-Tensor with shape [<batch_dims>, beam_dim, length_dim]
([<batch_dims>]
[<batch_dims>, beam_dim]).
variable_dtype: a mtf.VariableDType
encoder_output: an optional Tensor
encoder_sequence_id: an optional Tensor
encoder_inputs: an optional Tensor
alpha: a floating point value (length bonus)
shared_params: an optional dictionary
encoder_layer_outputs: optional - readonly list of tensor activations when
decoding, one per each input layer + the embedding layer
Returns:
a Tensor with shape [<batch_dims>, beam_dim, length_dim]
"""
attributes = dst_attributes
if not self.autoregressive:
raise ValueError("must be autoregressive")
batch_dims = inputs.shape.dims[:-2]
if len(batch_dims) != 1:
raise NotImplementedError(
"beam search supports exactly one batch dimension.")
beam_dim = inputs.shape.dims[-2]
length_dim = inputs.shape.dims[-1]
length_range = mtf.range(inputs.mesh, length_dim, tf.int32)
initial_position = mtf.reduce_sum(mtf.to_int32(mtf.not_equal(
inputs, 0)),
reduced_dim=length_dim)
sequence_id = 1 if encoder_sequence_id is not None else None
if self.input_full_attention:
# This only makes sense in the case of beam search with given partial
# sequences, which is not yet implemented.
# TODO(noam): implement
raise NotImplementedError(
"Beam search for language models not yet implemented")
else:
read_priority = write_priority = length_range
context_first_part = Context(
model=self,
mesh=inputs.mesh,
batch_dims=batch_dims + [beam_dim],
length_dim=length_dim,
variable_dtype=variable_dtype,
mode="first_part",
position=length_range,
position_is_default=True,
new_states=[],
initial_position=initial_position,
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=[],
shared_params=shared_params,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=read_priority,
inputs=inputs,
encoder_inputs=encoder_inputs)
shifted_inputs = mtf.shift(inputs,
offset=1,
dim=length_dim,
wrap=False)
with tf.variable_scope(self.name):
logits = self._call_internal(context_first_part,
shifted_inputs,
attributes=attributes,
z=z)
del logits
# There are no partial targets.
# Replace initial states by zeros to avoid computing them.
initial_states = [
mtf.zeros_like(t) for t in context_first_part.new_states
]
constant_states = context_first_part.constant_states
def logits_fn(step_num, ids, states):
"""logits_fn for mtf.beam_search.beam_search()."""
inputs_this_step = mtf.gather(ids, step_num - 1, length_dim)
if self.attribute_embedding:
attributes_this_step = mtf.gather(attributes, step_num - 1,
length_dim)
else:
attributes_this_step = None
context_incremental = Context(
model=self,
mesh=inputs.mesh,
batch_dims=batch_dims + [beam_dim],
length_dim=length_dim,
variable_dtype=variable_dtype,
mode="incremental",
position=step_num,
states=states,
new_states=[],
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=constant_states,
shared_params=shared_params,
encoder_layer_outputs=encoder_layer_outputs,
write_priority=write_priority,
read_priority=step_num,
inputs=inputs_this_step,
encoder_inputs=encoder_inputs)
with tf.variable_scope(self.name, reuse=True):
logits = self._call_internal(context_incremental,
inputs_this_step,
attributes=attributes_this_step,
z=z)
return mtf.to_float(logits), context_incremental.new_states
beams, unused_scores = mtf.beam_search.beam_search(
logits_fn,
inputs,
alpha,
states=initial_states,
decode_length=decode_length,
use_tpu=True,
dtype=tf.float32,
mesh_shape=self.mesh_shape,
layout=self.layout)
return mtf.gather(beams, mtf.constant(inputs.mesh, 0, dtype=tf.int32),
beam_dim)
def my_model_fn(features, labels, mode, params=None, config=None):
"""Estimator model function.
Args:
features: input features dictionary
labels: ignored
mode: a tf.estimator.ModeKeys
params: something
config: something
Returns:
something
"""
del labels, config
global_step = tf.train.get_global_step()
if use_tpu:
ctx = params["context"]
num_hosts = ctx.num_hosts
host_placement_fn = ctx.tpu_host_placement_function
device_list = [
host_placement_fn(host_id=t) for t in range(num_hosts)
]
# TODO(ylc): Better estimation of replica cache size?
replica_cache_size = 300 * 1000000 # 300M per replica
# Worker 0 caches all the TPU binaries.
worker0_mem = replica_cache_size * ctx.num_replicas
devices_memeory_usage = [worker0_mem] + [0] * (num_hosts - 1)
var_placer = mtf.utils.BalancedVariablePlacer(
device_list, devices_memeory_usage)
mesh_devices = [""] * mesh_shape.size
mesh_impl = mtf.simd_mesh_impl.SimdMeshImpl(
mesh_shape, layout_rules, mesh_devices, ctx.device_assignment)
else:
var_placer = None
mesh_devices = [""] * mesh_shape.size
mesh_impl = mtf.placement_mesh_impl.PlacementMeshImpl(
mesh_shape, layout_rules, mesh_devices)
graph = mtf.Graph()
mesh = mtf.Mesh(graph, "my_mesh", var_placer)
def _import_feature(key):
"""Import a feature from the features dictionary into a mtf.Tensor.
Args:
key: a string
Returns:
a mtf.Tensor with dtype int32 and shape [batch_dim, length_dim]
"""
batch_dim = mtf.Dimension("batch", batch_size)
length_dim = mtf.Dimension("length", length)
mtf_shape = mtf.Shape([batch_dim, length_dim])
if key not in features:
return None
x = tf.to_int32(features[key])
if not use_tpu:
x = tf.Print(x, [x],
"import feature %s" % key,
summarize=1000,
first_n=1)
return mtf.import_fully_replicated(mesh, x, mtf_shape, name=key)
# PREDICT mode
if mode == tf.estimator.ModeKeys.PREDICT:
inputs = _import_feature("inputs")
if text2self:
mtf_samples = transformer_model.sample_autoregressive(
inputs,
variable_dtype=variable_dtype,
temperature=temperature)
else:
mtf_samples = transformer_model.decode(
inputs,
variable_dtype=variable_dtype,
beam_size=beam_size,
alpha=alpha,
temperature=temperature)
mtf_samples = mtf.anonymize(mtf_samples)
lowering = mtf.Lowering(graph, {mesh: mesh_impl},
autostack=autostack)
outputs = lowering.export_to_tf_tensor(mtf_samples)
predictions = {"outputs": outputs}
return tpu_estimator.TPUEstimatorSpec(
mode=tf.estimator.ModeKeys.PREDICT,
predictions=predictions,
prediction_hooks=[mtf.MtfRestoreHook(lowering)])
targets = _import_feature("targets")
anon_targets = mtf.anonymize(targets)
if text2self:
_, length_dim = targets.shape
inputs = mtf.shift(targets, offset=1, dim=length_dim, wrap=False)
else:
inputs = _import_feature("inputs")
if text2self:
position_kwargs = dict(
sequence_id=_import_feature("targets_segmentation"),
position=_import_feature("targets_position"),
)
else:
position_kwargs = dict(
encoder_sequence_id=_import_feature("inputs_segmentation"),
decoder_sequence_id=_import_feature("targets_segmentation"),
encoder_position=_import_feature("inputs_position"),
decoder_position=_import_feature("targets_position"),
)
logits, loss = transformer_model.call_simple(
inputs=inputs,
targets=targets,
compute_loss=True,
mode=mode,
variable_dtype=variable_dtype,
**position_kwargs)
if use_tpu and logits is not None:
logits = mtf.anonymize(logits)
# TRAIN mode
if mode == tf.estimator.ModeKeys.TRAIN:
var_grads = mtf.gradients(
[loss], [v.outputs[0] for v in graph.trainable_variables])
optimizer = mtf.optimize.AdafactorOptimizer()
update_ops = optimizer.apply_grads(var_grads,
graph.trainable_variables)
lowering = mtf.Lowering(graph, {mesh: mesh_impl}, autostack=autostack)
tf_loss = lowering.export_to_tf_tensor(loss)
tf_loss = tf.to_float(tf_loss)
if not use_tpu:
tf_loss = tf.Print(tf_loss,
[tf_loss, tf.train.get_global_step()],
"step, tf_loss")
if logits and mode != tf.estimator.ModeKeys.TRAIN:
tf_logits = lowering.export_to_tf_tensor(logits)
if mode == tf.estimator.ModeKeys.TRAIN:
tf_update_ops = [
lowering.lowered_operation(op) for op in update_ops
]
tf_update_ops.append(tf.assign_add(global_step, 1))
train_op = tf.group(tf_update_ops)
with mtf.utils.outside_all_rewrites():
# Copy master variables to slices. Must be called first.
restore_hook = mtf.MtfRestoreHook(lowering)
saver = tf.train.Saver(tf.global_variables(),
sharded=True,
max_to_keep=10,
keep_checkpoint_every_n_hours=2,
defer_build=False,
save_relative_paths=True)
tf.add_to_collection(tf.GraphKeys.SAVERS, saver)
saver_listener = mtf.MtfCheckpointSaverListener(lowering)
saver_hook = tf.train.CheckpointSaverHook(
model_dir,
save_steps=1000,
saver=saver,
listeners=[saver_listener])
if mode == tf.estimator.ModeKeys.TRAIN:
if use_tpu:
return tpu_estimator.TPUEstimatorSpec(
mode=tf.estimator.ModeKeys.TRAIN,
loss=tf_loss,
train_op=train_op,
training_hooks=[restore_hook, saver_hook])
else:
return tf.estimator.EstimatorSpec(
tf.estimator.ModeKeys.TRAIN,
loss=tf_loss,
train_op=train_op,
training_chief_hooks=[restore_hook, saver_hook])
elif mode == tf.estimator.ModeKeys.EVAL:
def padded_neg_log_perplexity(logits, labels):
weights = tf.to_float(tf.not_equal(labels, 0))
xent = tf.nn.sparse_softmax_cross_entropy_with_logits(
labels=labels, logits=logits)
return {
"neg_log_perplexity": tf.metrics.mean(-xent, weights)
}
labels = lowering.export_to_tf_tensor(anon_targets)
eval_metrics = (padded_neg_log_perplexity, [tf_logits, labels])
return tpu_estimator.TPUEstimatorSpec(
tf.estimator.ModeKeys.EVAL,
evaluation_hooks=[restore_hook],
loss=tf_loss,
eval_metrics=eval_metrics)
def sample_autoregressive(self,
partial_sequences,
stop_at_token=1,
max_steps=None,
temperature=1.0,
variable_dtype=mtf.VariableDType(tf.float32),
encoder_output=None,
encoder_sequence_id=None,
shared_params=None,
has_partial_sequences=True,
encoder_layer_outputs=None):
"""Sample randomly one token at a time.
The partial_sequences represent partial sequences to be continued. The
first tokens of each sequence are nonzero representing the given partial
sequences and the last tokens of each sequence are zeros, representing what
needs to be filled in.
If there are no partial sequences (you want to sample from the beginning),
then pass partial_sequences=mtf.zeros(mesh, shape, dtype=tf.int32) and
has_partial_sequences=False (so we can skip computation).
Args:
partial_sequences: an int32 Tensor with shape [<batch_dims>, length_dim]
stop_at_token: an optional integer eos id. Stop when we produce it.
max_steps: an optional integer
temperature: an optional floating point value between 0.0 and 1.0 0.0
means argmax, 1.0 means sample according to predicted distribution.
variable_dtype: a mtf.VariableDType
encoder_output: an optional Tensor
encoder_sequence_id: an optional Tensor
shared_params: an optional dictionary
has_partial_sequences: a boolean
encoder_layer_outputs: optional - readonly list of tensor activations when
decoding, one per each input layer + the embedding layer
Returns:
a Tensor with shape [<batch_dims>, length_dim]
"""
del max_steps # TODO(noam): implement
if not self.autoregressive:
raise ValueError("must be autoregressive")
inputs = partial_sequences
batch_dims = inputs.shape.dims[:-1]
length_dim = inputs.shape.dims[-1]
initial_position = mtf.reduce_sum(
mtf.to_int32(mtf.not_equal(inputs, 0)), reduced_dim=length_dim)
sequence_id = 1 if encoder_sequence_id is not None else None
context_first_part = Context(
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
model_dim=self.model_dim,
variable_dtype=variable_dtype,
mode="first_part",
autoregressive=self.autoregressive,
new_states=[],
initial_position=initial_position,
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=[],
shared_params=shared_params,
layout=self.layout,
mesh_shape=self.mesh_shape,
encoder_layer_outputs=encoder_layer_outputs)
shifted_inputs = mtf.shift(inputs, offset=1, dim=length_dim, wrap=False)
with tf.variable_scope(self.name):
logits = self._call_internal(context_first_part, shifted_inputs)
del logits
constant_states = context_first_part.constant_states
if not has_partial_sequences:
initial_states = [
mtf.zeros_like(t) for t in context_first_part.new_states]
else:
initial_states = context_first_part.new_states
def cond_fn(position, ids, *unused_states):
"""Should we run another loop iteration."""
past_end = mtf.greater_equal(position, length_dim.size)
is_done = past_end
if stop_at_token is not None:
has_eos = mtf.reduce_any(
mtf.equal(ids, stop_at_token), reduced_dim=length_dim)
is_done = mtf.logical_or(is_done, has_eos)
all_done = mtf.reduce_all(is_done)
return mtf.logical_not(all_done)
def body_fn(position, ids, *states):
"""One step in the decode loop."""
context_incremental = Context(
mesh=inputs.mesh,
batch_dims=batch_dims,
length_dim=length_dim,
model_dim=self.model_dim,
variable_dtype=variable_dtype,
mode="incremental",
autoregressive=self.autoregressive,
position=position,
states=states,
new_states=[],
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=constant_states,
shared_params=shared_params,
layout=self.layout,
mesh_shape=self.mesh_shape,
encoder_layer_outputs=encoder_layer_outputs)
inputs_this_step = mtf.gather(ids, position - 1, length_dim)
with tf.variable_scope(self.name, reuse=True):
logits = self._call_internal(context_incremental, inputs_this_step)
ids_this_step = mtf.sample_with_temperature(
logits, self.output_vocab_dim, temperature)
new_position = position + 1
new_ids = ids + ids_this_step * mtf.one_hot(
position, length_dim, dtype=tf.int32)
return [new_position, new_ids] + context_incremental.new_states
while_loop_inputs = [initial_position, inputs] + initial_states
final_position, outputs = mtf.while_loop(
cond_fn, body_fn, while_loop_inputs)[:2]
del final_position
return outputs
def my_model_fn(features, labels, mode, params=None, config=None):
"""Estimator model function.
Args:
features: input features dictionary
labels: ignored
mode: a tf.estimator.ModeKeys
params: something
config: something
Returns:
something
"""
del labels, config
global_step = tf.train.get_global_step()
if use_tpu:
ctx = params["context"]
num_hosts = ctx.num_hosts
host_placement_fn = ctx.tpu_host_placement_function
device_list = [
host_placement_fn(host_id=t) for t in range(num_hosts)
]
# TODO(ylc): Better estimation of replica cache size?
replica_cache_size = 300 * 1000000 # 300M per replica
# Worker 0 caches all the TPU binaries.
worker0_mem = replica_cache_size * ctx.num_replicas
devices_memeory_usage = [worker0_mem] + [0] * (num_hosts - 1)
var_placer = mtf.utils.BalancedVariablePlacer(
device_list, devices_memeory_usage)
mesh_devices = [""] * mesh_shape.size
physical_shape = list(
params["context"].device_assignment.topology.mesh_shape)
logical_to_physical = _logical_to_physical(physical_shape,
mesh_shape)
mesh_impl = mtf.simd_mesh_impl.SimdMeshImpl(
mesh_shape,
layout_rules,
mesh_devices,
ctx.device_assignment,
logical_to_physical=logical_to_physical)
else:
var_placer = None
mesh_devices = [""] * mesh_shape.size
mesh_impl = mtf.placement_mesh_impl.PlacementMeshImpl(
mesh_shape, layout_rules, mesh_devices)
graph = mtf.Graph()
mesh = mtf.Mesh(graph, "my_mesh", var_placer)
def _import_feature(key, allow_missing=False):
"""Import a feature from the features dictionary into a mtf.Tensor.
Args:
key: a string
allow_missing: a boolean
Returns:
a mtf.Tensor with dtype int32 and shape [batch_dim, length_dim]
"""
outer_batch_dim = mtf.Dimension("outer_batch", outer_batch_size)
batch_dim = mtf.Dimension("batch", batch_size // outer_batch_size)
length_dim = mtf.Dimension("length", sequence_length)
mtf_shape = mtf.Shape([outer_batch_dim, batch_dim, length_dim])
if key not in features:
if allow_missing:
return None
else:
raise ValueError("feature not found %s - features %s = " %
(key, features))
tf.logging.info("Import feature %s: %s" % (key, features[key]))
x = tf.to_int32(features[key])
x = tf.reshape(
x, [outer_batch_size, batch_size // outer_batch_size, -1])
if not use_tpu:
x = tf.Print(x, [x],
"import feature %s" % key,
summarize=1000,
first_n=1)
return mtf.import_fully_replicated(mesh, x, mtf_shape, name=key)
if mode == tf.estimator.ModeKeys.PREDICT:
inputs = _import_feature("inputs")
inputs = mtf.reshape(
inputs,
mtf.Shape([
mtf.Dimension("batch", batch_size),
mtf.Dimension("length", sequence_length)
]))
if isinstance(transformer_model, transformer.Unitransformer):
mtf_samples = transformer_model.sample_autoregressive(
inputs, variable_dtype=get_variable_dtype())
elif isinstance(transformer_model, transformer.Bitransformer):
mtf_samples = transformer_model.decode(
inputs, variable_dtype=get_variable_dtype())
else:
raise ValueError("unrecognized class")
mtf_samples = mtf.anonymize(mtf_samples)
lowering = mtf.Lowering(graph, {mesh: mesh_impl},
autostack=autostack)
outputs = lowering.export_to_tf_tensor(mtf_samples)
predictions = {"outputs": outputs}
return tpu_estimator.TPUEstimatorSpec(
mode=tf.estimator.ModeKeys.PREDICT,
predictions=predictions,
prediction_hooks=[mtf.MtfRestoreHook(lowering)])
targets = _import_feature("targets")
anon_targets = mtf.anonymize(targets)
if model_type == "lm":
_, length_dim = targets.shape
inputs = mtf.shift(targets, offset=1, dim=length_dim, wrap=False)
else:
inputs = _import_feature("inputs")
if mode == tf.estimator.ModeKeys.EVAL:
if isinstance(transformer_model, transformer.Unitransformer):
mtf_samples = transformer_model.sample_autoregressive(
inputs, variable_dtype=get_variable_dtype())
elif isinstance(transformer_model, transformer.Bitransformer):
mtf_samples = transformer_model.decode(
inputs, variable_dtype=get_variable_dtype())
else:
raise ValueError("unrecognized class")
mtf_samples = mtf.anonymize(mtf_samples)
lowering = mtf.Lowering(graph, {mesh: mesh_impl},
autostack=autostack)
outputs = lowering.export_to_tf_tensor(mtf_samples)
labels = lowering.export_to_tf_tensor(anon_targets)
restore_hook = mtf.MtfRestoreHook(lowering)
# metric_names becomes locally scoped if we simply assign
# ["padded_neg_log_perplexity"] to it conditioned on if it's None.
local_metric_names = metric_names or ["token_accuracy"]
def metric_fn(labels, outputs):
return get_metric_fns(local_metric_names, labels, outputs)
eval_metrics = (metric_fn, [labels, outputs])
return tpu_estimator.TPUEstimatorSpec(
tf.estimator.ModeKeys.EVAL,
# Unfortunately TPUEstimatorSpec requires us to provide a value for
# loss when in EVAL mode. Since we are sampling or decoding from the
# model, we don't have a loss to report.
loss=tf.constant(0.),
evaluation_hooks=[restore_hook],
eval_metrics=eval_metrics)
if isinstance(transformer_model, transformer.Unitransformer):
position_kwargs = dict(
sequence_id=_import_feature("targets_segmentation", True),
position=_import_feature("targets_position", True),
)
elif isinstance(transformer_model, transformer.Bitransformer):
position_kwargs = dict(
encoder_sequence_id=_import_feature("inputs_segmentation",
True),
decoder_sequence_id=_import_feature("targets_segmentation",
True),
encoder_position=_import_feature("inputs_position", True),
decoder_position=_import_feature("targets_position", True),
)
else:
raise ValueError("unrecognized class")
logits, loss = transformer_model.call_simple(
inputs=inputs,
targets=targets,
compute_loss=True,
mode=mode,
variable_dtype=get_variable_dtype(),
**position_kwargs)
if use_tpu and logits is not None:
logits = mtf.anonymize(logits)
# TRAIN mode
if mode == tf.estimator.ModeKeys.TRAIN:
var_grads = mtf.gradients(
[loss], [v.outputs[0] for v in graph.trainable_variables])
optimizer = mtf.optimize.AdafactorOptimizer(
learning_rate=learning_rate)
update_ops = optimizer.apply_grads(var_grads,
graph.trainable_variables)
lowering = mtf.Lowering(graph, {mesh: mesh_impl}, autostack=autostack)
tf_loss = lowering.export_to_tf_tensor(loss)
tf_loss = tf.to_float(tf_loss)
if not use_tpu:
tf_loss = tf.Print(tf_loss,
[tf_loss, tf.train.get_global_step()],
"step, tf_loss")
if mode == tf.estimator.ModeKeys.TRAIN:
tf_update_ops = [
lowering.lowered_operation(op) for op in update_ops
]
tf_update_ops.append(tf.assign_add(global_step, 1))
train_op = tf.group(tf_update_ops)
with mtf.utils.outside_all_rewrites():
# Copy master variables to slices. Must be called first.
restore_hook = mtf.MtfRestoreHook(lowering)
saver = tf.train.Saver(tf.global_variables(),
sharded=True,
max_to_keep=checkpoints_to_keep,
keep_checkpoint_every_n_hours=2,
defer_build=False,
save_relative_paths=True)
tf.add_to_collection(tf.GraphKeys.SAVERS, saver)
saver_listener = mtf.MtfCheckpointSaverListener(lowering)
saver_hook = tf.train.CheckpointSaverHook(
model_dir,
save_steps=save_steps,
saver=saver,
listeners=[saver_listener])
gin_config_saver_hook = gin.tf.GinConfigSaverHook(
model_dir, summarize_config=True)
if mode == tf.estimator.ModeKeys.TRAIN:
if use_tpu:
return tpu_estimator.TPUEstimatorSpec(
mode=tf.estimator.ModeKeys.TRAIN,
loss=tf_loss,
train_op=train_op,
training_hooks=[
restore_hook,
saver_hook,
gin_config_saver_hook,
])
else:
return tf.estimator.EstimatorSpec(
tf.estimator.ModeKeys.TRAIN,
loss=tf_loss,
train_op=train_op,
training_chief_hooks=[
restore_hook,
saver_hook,
gin_config_saver_hook,
])
def beam_search(self,
inputs,
decode_length,
variable_dtype=mtf.VariableDType(tf.float32),
encoder_output=None,
encoder_sequence_id=None,
alpha=0.6,
shared_params=None,
encoder_layer_outputs=None):
"""Beam search.
Args:
inputs: an int32 zero-Tensor with shape [<batch_dims>, beam_dim,
length_dim].
decode_length: an int32 mtf scalar. Maximum decode length.
variable_dtype: a mtf.VariableDType
encoder_output: an optional Tensor
encoder_sequence_id: an optional Tensor
alpha: a floating point value (length bonus)
shared_params: an optional dictionary
encoder_layer_outputs: optional - readonly list of tensor activations when
decoding, one per each input layer + the embedding layer
Returns:
a Tensor with shape [<batch_dims>, beam_dim, length_dim]
"""
if not self.autoregressive:
raise ValueError("must be autoregressive")
batch_dims = inputs.shape.dims[:-2]
if len(batch_dims) != 1:
raise NotImplementedError(
"beam search supports exactly one batch dimension.")
beam_dim = inputs.shape.dims[-2]
length_dim = inputs.shape.dims[-1]
initial_position = mtf.reduce_sum(
mtf.to_int32(mtf.not_equal(inputs, 0)), reduced_dim=length_dim)
sequence_id = 1 if encoder_sequence_id is not None else None
context_first_part = Context(
mesh=inputs.mesh,
batch_dims=batch_dims + [beam_dim],
length_dim=length_dim,
model_dim=self.model_dim,
variable_dtype=variable_dtype,
mode="first_part",
autoregressive=self.autoregressive,
new_states=[],
initial_position=initial_position,
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=[],
shared_params=shared_params,
layout=self.layout,
mesh_shape=self.mesh_shape,
encoder_layer_outputs=encoder_layer_outputs)
shifted_inputs = mtf.shift(inputs, offset=1, dim=length_dim, wrap=False)
with tf.variable_scope(self.name):
logits = self._call_internal(context_first_part, shifted_inputs)
del logits
# There are no partial targets.
# Replace initial states by zeros to avoid computing them.
initial_states = [mtf.zeros_like(t) for t in context_first_part.new_states]
constant_states = context_first_part.constant_states
def logits_fn(step_num, ids, states):
"""logits_fn for mtf.beam_search.beam_search()."""
context_incremental = Context(
mesh=inputs.mesh,
batch_dims=batch_dims + [beam_dim],
length_dim=length_dim,
model_dim=self.model_dim,
variable_dtype=variable_dtype,
mode="incremental",
autoregressive=self.autoregressive,
position=step_num,
states=states,
new_states=[],
sequence_id=sequence_id,
encoder_output=encoder_output,
encoder_sequence_id=encoder_sequence_id,
constant_states=constant_states,
shared_params=shared_params,
layout=self.layout,
mesh_shape=self.mesh_shape,
encoder_layer_outputs=encoder_layer_outputs)
inputs_this_step = mtf.gather(ids, step_num - 1, length_dim)
with tf.variable_scope(self.name, reuse=True):
logits = self._call_internal(context_incremental, inputs_this_step)
return mtf.to_float(logits), context_incremental.new_states
beams, unused_scores = mtf.beam_search.beam_search(
logits_fn,
inputs,
alpha,
states=initial_states,
decode_length=decode_length,
use_tpu=True,
dtype=tf.float32,
mesh_shape=self.mesh_shape,
layout=self.layout)
return mtf.gather(
beams, mtf.constant(inputs.mesh, 0, dtype=tf.int32), beam_dim)
def _mtf_model_fn(self, features, mesh):
self._original_features = features
features = copy.copy(features)
hparams = self._hparams
extra_losses = []
targets = tf.to_int32(features["targets"])
if len(targets.get_shape()) > 2:
tf.logging.info("targets = %s" % targets)
targets = tf.squeeze(targets, [2, 3])
# pad targets to max_length
def pad_to_max_length(x):
extra_length = hparams.max_length - tf.shape(x)[1]
x = tf.pad(x, [[0, 0], [0, extra_length]])
x = tf.reshape(x, [hparams.batch_size, hparams.max_length])
return x
targets = pad_to_max_length(targets)
targets = self._import_to_batch_by_length(targets, "targets", mesh, hparams)
for key in ["targets_segmentation", "targets_position",
"inputs_segmentation", "inputs_position"]:
if key in features:
features[key] = pad_to_max_length(features[key])
if hparams.decoder_type == "autoregressive":
shifted_targets = mtf.shift(
targets, offset=1, dim=self.length_dim, wrap=False)
elif hparams.decoder_type == "denoising":
shifted_targets = self._noisy_targets(targets, extra_losses)
else:
raise ValueError(
"unknown hparams.decoder_type = %s" % hparams.decoder_type)
if "targets_segmentation" in features:
# "Packed" dataset - keep the examples from seeing each other.
targets_segmentation = self._import_to_batch_by_length(
features["targets_segmentation"], "targets_segmentation",
mesh, hparams)
targets_position = self._import_to_batch_by_length(
features["targets_position"], "targets_position",
mesh, hparams)
decoder_self_attention_mask = mtf.layers.attention_mask_same_segment(
targets_segmentation, dtype=self.activation_dtype)
if hparams.decoder_type == "autoregressive":
decoder_self_attention_mask += mtf.layers.attention_mask_autoregressive(
targets_position, dtype=self.activation_dtype)
else:
targets_position = mtf.range(mesh, self.length_dim, dtype=tf.int32)
if hparams.decoder_type == "autoregressive":
decoder_self_attention_mask = mtf.layers.attention_mask_autoregressive(
targets_position, dtype=self.activation_dtype)
else:
decoder_self_attention_mask = None
def layer_prepostprocess_dropout(x):
return mtf.dropout(
x, keep_prob=1.0 - hparams.layer_prepostprocess_dropout,
noise_shape=mtf.Shape(self.batch_dims + [self.model_dim]))
(inputs_embedding_var,
targets_embedding_var,
softmax_var,
positional_embedding_var) = self._embedding_and_softmax_vars(mesh)
if hparams.transformer_type == "decoder":
encoder_output = None
encoder_decoder_attention_mask = None
else:
inputs = tf.squeeze(tf.to_int32(features["inputs"]), [2, 3])
inputs = pad_to_max_length(inputs)
inputs = self._import_to_batch_by_length(inputs, "inputs", mesh, hparams)
if "inputs_segmentation" in features:
# "Packed" dataset - keep the examples from seeing each other.
inputs_segmentation = self._import_to_batch_by_length(
features["inputs_segmentation"], "inputs_segmentation",
mesh, hparams)
inputs_position = self._import_to_batch_by_length(
features["inputs_position"], "inputs_position",
mesh, hparams)
encoder_self_attention_mask = (
mtf.layers.attention_mask_same_segment(
inputs_segmentation, dtype=self.activation_dtype))
else:
inputs_position = mtf.range(mesh, self.length_dim, dtype=tf.int32)
encoder_self_attention_mask = (
mtf.layers.attention_mask_ignore_padding(
inputs, dtype=self.activation_dtype))
x = (mtf.gather(inputs_embedding_var, inputs, self.inputs_vocab_dim) +
mtf.gather(positional_embedding_var, inputs_position,
self.max_length_dim))
x = layer_prepostprocess_dropout(x)
with tf.variable_scope("encoder"):
x = self._layer_stack(x,
hparams.encoder_layers,
self_attention_mask=encoder_self_attention_mask,
losses=extra_losses)
if hparams.transformer_type == "encdec":
if "inputs_segmentation" in features:
encoder_decoder_attention_mask = (
mtf.layers.attention_mask_same_segment(
targets_segmentation, inputs_segmentation,
dtype=self.activation_dtype))
else:
encoder_decoder_attention_mask = encoder_self_attention_mask
encoder_output = mtf.rename_dimension(
x, self.length_dim.name, self.memory_length_dim.name)
if hparams.transformer_type != "encoder":
# DECODER
x = (mtf.gather(
targets_embedding_var, shifted_targets, self.targets_vocab_dim) +
mtf.gather(
positional_embedding_var, targets_position, self.max_length_dim))
x = layer_prepostprocess_dropout(x)
with tf.variable_scope("decoder"):
x = self._layer_stack(
x,
hparams.decoder_layers,
encoder_output=encoder_output,
self_attention_mask=decoder_self_attention_mask,
encdec_attention_mask=encoder_decoder_attention_mask,
losses=extra_losses)
if (hparams.reshape_logits_hack and
hparams.mode == tf.estimator.ModeKeys.TRAIN):
# For some reason, the logits computation is extremely slow on TPU
# in some cases where the batch size per core is 1. Reshape the logits
# and the targets to double the batch size and halve the length.
# TODO(noam): file a bug.
old_dims = self.batch_dims + [self.length_dim]
new_dims = self.batch_dims[:-1] + [
mtf.Dimension(self.batch_dims[-1].name,
self.batch_dims[-1].size * 2),
mtf.Dimension(self.length_dim.name, self.length_dim.size // 2)]
x = mtf.reshape(x, new_dims + [self.model_dim])
targets = mtf.reshape(targets, new_dims)
logits = mtf.matmul(x, softmax_var)
if hparams.mode == tf.estimator.ModeKeys.TRAIN:
logits = mtf.layers.multiplicative_jitter(logits, epsilon=1e-2)
off_value = hparams.label_smoothing / self._targets_vocab_size
on_value = 1.0 - hparams.label_smoothing + off_value
soft_targets = mtf.one_hot(
targets, self.targets_vocab_dim, on_value=on_value, off_value=off_value,
dtype=self.activation_dtype)
loss = mtf.layers.softmax_cross_entropy_with_logits(
logits, soft_targets, self.targets_vocab_dim)
weights = mtf.layers.weights_nonzero(targets, dtype=self.activation_dtype)
loss = mtf.reduce_mean(loss * weights)
for l in extra_losses:
loss += l
if (hparams.reshape_logits_hack and
hparams.mode == tf.estimator.ModeKeys.TRAIN):
logits = mtf.reshape(logits, old_dims + [self.targets_vocab_dim])
logits = mtf.to_float(logits)
return logits, loss