# coding=utf-8
# Copyright 2018 Google AI, Google Brain and Carnegie Mellon University Authors and the HuggingFace Inc. team.
# Copyright (c) 2018, NVIDIA CORPORATION. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" TF 2.0 Transformer XL model.
"""
import warnings
from dataclasses import dataclass
from typing import List, Optional, Tuple
import tensorflow as tf
from .configuration_transfo_xl import TransfoXLConfig
from .file_utils import ModelOutput, add_code_sample_docstrings, add_start_docstrings, add_start_docstrings_to_callable
from .modeling_tf_transfo_xl_utilities import TFAdaptiveSoftmaxMask
from .modeling_tf_utils import TFPreTrainedModel, get_initializer, keras_serializable, shape_list
from .tokenization_utils import BatchEncoding
from .utils import logging
logger = logging.get_logger(__name__)
_CONFIG_FOR_DOC = "TransfoXLConfig"
_TOKENIZER_FOR_DOC = "TransfoXLTokenizer"
TF_TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_LIST = [
"transfo-xl-wt103",
# See all Transformer XL models at https://huggingface.co/models?filter=transfo-xl
]
class TFPositionalEmbedding(tf.keras.layers.Layer):
def __init__(self, demb, **kwargs):
super().__init__(**kwargs)
self.inv_freq = 1 / (10000 ** (tf.range(0, demb, 2.0) / demb))
def call(self, pos_seq, bsz=None):
sinusoid_inp = tf.einsum("i,j->ij", pos_seq, self.inv_freq)
pos_emb = tf.concat([tf.sin(sinusoid_inp), tf.cos(sinusoid_inp)], -1)
if bsz is not None:
return tf.tile(pos_emb[:, None, :], [1, bsz, 1])
else:
return pos_emb[:, None, :]
class TFPositionwiseFF(tf.keras.layers.Layer):
def __init__(self, d_model, d_inner, dropout, pre_lnorm=False, layer_norm_epsilon=1e-5, init_std=0.02, **kwargs):
super().__init__(**kwargs)
self.d_model = d_model
self.d_inner = d_inner
self.dropout = dropout
self.layer_1 = tf.keras.layers.Dense(
d_inner, kernel_initializer=get_initializer(init_std), activation=tf.nn.relu, name="CoreNet_._0"
)
self.drop_1 = tf.keras.layers.Dropout(dropout)
self.layer_2 = tf.keras.layers.Dense(d_model, kernel_initializer=get_initializer(init_std), name="CoreNet_._3")
self.drop_2 = tf.keras.layers.Dropout(dropout)
self.layer_norm = tf.keras.layers.LayerNormalization(epsilon=layer_norm_epsilon, name="layer_norm")
self.pre_lnorm = pre_lnorm
def call(self, inp, training=False):
if self.pre_lnorm:
# layer normalization + positionwise feed-forward
core_out = self.layer_norm(inp)
core_out = self.layer_1(core_out)
core_out = self.drop_1(core_out, training=training)
core_out = self.layer_2(core_out)
core_out = self.drop_2(core_out, training=training)
# residual connection
output = core_out + inp
else:
# positionwise feed-forward
core_out = self.layer_1(inp)
core_out = self.drop_1(core_out, training=training)
core_out = self.layer_2(core_out)
core_out = self.drop_2(core_out, training=training)
# residual connection + layer normalization
output = self.layer_norm(inp + core_out)
return output
class TFRelPartialLearnableMultiHeadAttn(tf.keras.layers.Layer):
def __init__(
self,
n_head,
d_model,
d_head,
dropout,
dropatt=0.0,
pre_lnorm=False,
r_r_bias=None,
r_w_bias=None,
layer_norm_epsilon=1e-5,
init_std=0.02,
output_attentions=False,
**kwargs
):
super().__init__(**kwargs)
self.n_head = n_head
self.d_model = d_model
self.d_head = d_head
self.dropout = dropout
self.output_attentions = output_attentions
self.qkv_net = tf.keras.layers.Dense(
3 * n_head * d_head, kernel_initializer=get_initializer(init_std), use_bias=False, name="qkv_net"
)
self.drop = tf.keras.layers.Dropout(dropout)
self.dropatt = tf.keras.layers.Dropout(dropatt)
self.o_net = tf.keras.layers.Dense(
d_model, kernel_initializer=get_initializer(init_std), use_bias=False, name="o_net"
)
self.layer_norm = tf.keras.layers.LayerNormalization(epsilon=layer_norm_epsilon, name="layer_norm")
self.scale = 1 / (d_head ** 0.5)
self.pre_lnorm = pre_lnorm
if r_r_bias is not None and r_w_bias is not None: # Biases are shared
self.r_r_bias = r_r_bias
self.r_w_bias = r_w_bias
else:
self.r_r_bias = None
self.r_w_bias = None
self.r_net = tf.keras.layers.Dense(
self.n_head * self.d_head, kernel_initializer=get_initializer(init_std), use_bias=False, name="r_net"
)
def build(self, input_shape):
if self.r_r_bias is None or self.r_w_bias is None: # Biases are not shared
self.r_r_bias = self.add_weight(
shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_r_bias"
)
self.r_w_bias = self.add_weight(
shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_w_bias"
)
super().build(input_shape)
def _rel_shift(self, x):
x_size = shape_list(x)
x = tf.pad(x, [[0, 0], [1, 0], [0, 0], [0, 0]])
x = tf.reshape(x, [x_size[1] + 1, x_size[0], x_size[2], x_size[3]])
x = tf.slice(x, [1, 0, 0, 0], [-1, -1, -1, -1])
x = tf.reshape(x, x_size)
return x
def call(self, w, r, attn_mask, mems, head_mask, output_attentions, training=False):
qlen, rlen, bsz = shape_list(w)[0], shape_list(r)[0], shape_list(w)[1]
if mems is not None:
cat = tf.concat([mems, w], 0)
if self.pre_lnorm:
w_heads = self.qkv_net(self.layer_norm(cat))
else:
w_heads = self.qkv_net(cat)
r_head_k = self.r_net(r)
w_head_q, w_head_k, w_head_v = tf.split(w_heads, 3, axis=-1)
w_head_q = w_head_q[-qlen:]
else:
if self.pre_lnorm:
w_heads = self.qkv_net(self.layer_norm(w))
else:
w_heads = self.qkv_net(w)
r_head_k = self.r_net(r)
w_head_q, w_head_k, w_head_v = tf.split(w_heads, 3, axis=-1)
klen = shape_list(w_head_k)[0]
w_head_q = tf.reshape(w_head_q, (qlen, bsz, self.n_head, self.d_head)) # qlen x bsz x n_head x d_head
w_head_k = tf.reshape(w_head_k, (klen, bsz, self.n_head, self.d_head)) # qlen x bsz x n_head x d_head
w_head_v = tf.reshape(w_head_v, (klen, bsz, self.n_head, self.d_head)) # qlen x bsz x n_head x d_head
r_head_k = tf.reshape(r_head_k, (rlen, self.n_head, self.d_head)) # qlen x n_head x d_head
# compute attention score
rw_head_q = w_head_q + self.r_w_bias # qlen x bsz x n_head x d_head
AC = tf.einsum("ibnd,jbnd->ijbn", rw_head_q, w_head_k) # qlen x klen x bsz x n_head
rr_head_q = w_head_q + self.r_r_bias
BD = tf.einsum("ibnd,jnd->ijbn", rr_head_q, r_head_k) # qlen x klen x bsz x n_head
BD = self._rel_shift(BD)
# [qlen x klen x bsz x n_head]
attn_score = AC + BD
attn_score = attn_score * self.scale
# compute attention probability
if attn_mask is not None:
attn_mask_t = attn_mask[:, :, None, None]
attn_score = attn_score * (1 - attn_mask_t) - 1e30 * attn_mask_t
# [qlen x klen x bsz x n_head]
attn_prob = tf.nn.softmax(attn_score, axis=1)
attn_prob = self.dropatt(attn_prob, training=training)
# Mask heads if we want to
if head_mask is not None:
attn_prob = attn_prob * head_mask
# compute attention vector
attn_vec = tf.einsum("ijbn,jbnd->ibnd", attn_prob, w_head_v)
# [qlen x bsz x n_head x d_head]
attn_vec_sizes = shape_list(attn_vec)
attn_vec = tf.reshape(attn_vec, (attn_vec_sizes[0], attn_vec_sizes[1], self.n_head * self.d_head))
# linear projection
attn_out = self.o_net(attn_vec)
attn_out = self.drop(attn_out, training=training)
if self.pre_lnorm:
# residual connection
outputs = [w + attn_out]
else:
# residual connection + layer normalization
outputs = [self.layer_norm(w + attn_out)]
if output_attentions:
outputs.append(attn_prob)
return outputs
class TFRelPartialLearnableDecoderLayer(tf.keras.layers.Layer):
def __init__(
self,
n_head,
d_model,
d_head,
d_inner,
dropout,
dropatt=0.0,
pre_lnorm=False,
r_w_bias=None,
r_r_bias=None,
layer_norm_epsilon=1e-5,
init_std=0.02,
output_attentions=False,
**kwargs
):
super().__init__(**kwargs)
self.dec_attn = TFRelPartialLearnableMultiHeadAttn(
n_head,
d_model,
d_head,
dropout,
dropatt=dropatt,
pre_lnorm=pre_lnorm,
r_w_bias=r_w_bias,
r_r_bias=r_r_bias,
init_std=init_std,
layer_norm_epsilon=layer_norm_epsilon,
output_attentions=output_attentions,
name="dec_attn",
)
self.pos_ff = TFPositionwiseFF(
d_model,
d_inner,
dropout,
pre_lnorm=pre_lnorm,
init_std=init_std,
layer_norm_epsilon=layer_norm_epsilon,
name="pos_ff",
)
def call(self, dec_inp, r, dec_attn_mask, mems, head_mask, output_attentions, training=False):
attn_outputs = self.dec_attn(dec_inp, r, dec_attn_mask, mems, head_mask, output_attentions, training=training)
ff_output = self.pos_ff(attn_outputs[0], training=training)
outputs = [ff_output] + attn_outputs[1:]
return outputs
class TFAdaptiveEmbedding(tf.keras.layers.Layer):
def __init__(self, n_token, d_embed, d_proj, cutoffs, div_val=1, init_std=0.02, sample_softmax=False, **kwargs):
super().__init__(**kwargs)
self.n_token = n_token
self.d_embed = d_embed
self.init_std = init_std
self.cutoffs = cutoffs + [n_token]
self.div_val = div_val
self.d_proj = d_proj
self.emb_scale = d_proj ** 0.5
self.cutoff_ends = [0] + self.cutoffs
self.emb_layers = []
self.emb_projs = []
if div_val == 1:
raise NotImplementedError # Removed these to avoid maintaining dead code - They are not used in our pretrained checkpoint
else:
for i in range(len(self.cutoffs)):
l_idx, r_idx = self.cutoff_ends[i], self.cutoff_ends[i + 1]
d_emb_i = d_embed // (div_val ** i)
self.emb_layers.append(
tf.keras.layers.Embedding(
r_idx - l_idx,
d_emb_i,
embeddings_initializer=get_initializer(init_std),
name="emb_layers_._{}".format(i),
)
)
def build(self, input_shape):
for i in range(len(self.cutoffs)):
d_emb_i = self.d_embed // (self.div_val ** i)
self.emb_projs.append(
self.add_weight(
shape=(d_emb_i, self.d_proj),
initializer=get_initializer(self.init_std),
trainable=True,
name="emb_projs_._{}".format(i),
)
)
super().build(input_shape)
def call(self, inp):
if self.div_val == 1:
raise NotImplementedError # Removed these to avoid maintaining dead code - They are not used in our pretrained checkpoint
else:
inp_flat = tf.reshape(inp, (-1,))
emb_flat = tf.zeros([shape_list(inp_flat)[0], self.d_proj])
for i in range(len(self.cutoffs)):
l_idx, r_idx = self.cutoff_ends[i], self.cutoff_ends[i + 1]
mask_i = (inp_flat >= l_idx) & (inp_flat < r_idx)
inp_i = tf.boolean_mask(inp_flat, mask_i) - l_idx
emb_i = self.emb_layers[i](inp_i)
emb_i = tf.einsum("id,de->ie", emb_i, self.emb_projs[i])
mask_idx = tf.cast(tf.where(mask_i), dtype=tf.int64)
emb_flat += tf.scatter_nd(mask_idx, emb_i, tf.cast(shape_list(emb_flat), dtype=tf.int64))
embed_shape = shape_list(inp) + [self.d_proj]
embed = tf.reshape(emb_flat, embed_shape)
embed *= self.emb_scale
return embed
@keras_serializable
class TFTransfoXLMainLayer(tf.keras.layers.Layer):
config_class = TransfoXLConfig
def __init__(self, config, **kwargs):
super().__init__(**kwargs)
self.output_hidden_states = config.output_hidden_states
self.output_attentions = config.output_attentions
self.return_dict = config.use_return_dict
self.n_token = config.vocab_size
self.d_embed = config.d_embed
self.d_model = config.d_model
self.n_head = config.n_head
self.d_head = config.d_head
self.untie_r = config.untie_r
self.word_emb = TFAdaptiveEmbedding(
config.vocab_size,
config.d_embed,
config.d_model,
config.cutoffs,
div_val=config.div_val,
init_std=config.init_std,
name="word_emb",
)
self.drop = tf.keras.layers.Dropout(config.dropout)
self.n_layer = config.n_layer
self.mem_len = config.mem_len
self.attn_type = config.attn_type
self.layers = []
if config.attn_type == 0: # the default attention
for i in range(config.n_layer):
self.layers.append(
TFRelPartialLearnableDecoderLayer(
config.n_head,
config.d_model,
config.d_head,
config.d_inner,
config.dropout,
dropatt=config.dropatt,
pre_lnorm=config.pre_lnorm,
r_w_bias=None if self.untie_r else self.r_w_bias,
r_r_bias=None if self.untie_r else self.r_r_bias,
layer_norm_epsilon=config.layer_norm_epsilon,
init_std=config.init_std,
output_attentions=self.output_attentions,
name="layers_._{}".format(i),
)
)
else: # learnable embeddings and absolute embeddings
raise NotImplementedError # Removed these to avoid maintaining dead code - They are not used in our pretrained checkpoint
self.same_length = config.same_length
self.clamp_len = config.clamp_len
if self.attn_type == 0: # default attention
self.pos_emb = TFPositionalEmbedding(self.d_model, name="pos_emb")
else: # learnable embeddings and absolute embeddings
raise NotImplementedError # Removed these to avoid maintaining dead code - They are not used in our pretrained checkpoint
def build(self, input_shape):
if not self.untie_r:
self.r_w_bias = self.add_weight(
shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_w_bias"
)
self.r_r_bias = self.add_weight(
shape=(self.n_head, self.d_head), initializer="zeros", trainable=True, name="r_r_bias"
)
super().build(input_shape)
def get_input_embeddings(self):
return self.word_emb
def set_input_embeddings(self, value):
raise NotImplementedError
def _resize_token_embeddings(self, new_num_tokens):
return self.word_emb
def backward_compatible(self):
self.sample_softmax = -1
def reset_memory_length(self, mem_len):
self.mem_len = mem_len
def _prune_heads(self, heads):
raise NotImplementedError
def init_mems(self, bsz):
if self.mem_len > 0:
mems = []
for i in range(self.n_layer):
empty = tf.zeros([self.mem_len, bsz, self.d_model])
mems.append(empty)
return mems
else:
return None
def _update_mems(self, hids, mems, mlen, qlen):
# does not deal with None
if mems is None:
return None
# mems is not None
assert len(hids) == len(mems), "len(hids) != len(mems)"
# There are `mlen + qlen` steps that can be cached into mems
new_mems = []
end_idx = mlen + max(0, qlen)
beg_idx = max(0, end_idx - self.mem_len)
for i in range(len(hids)):
cat = tf.concat([mems[i], hids[i]], axis=0)
tf.stop_gradient(cat)
new_mems.append(cat[beg_idx:end_idx])
return new_mems
def call(
self,
inputs,
mems=None,
head_mask=None,
inputs_embeds=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
training=False,
):
if isinstance(inputs, (tuple, list)):
input_ids = inputs[0]
mems = inputs[1] if len(inputs) > 1 else mems
head_mask = inputs[2] if len(inputs) > 2 else head_mask
inputs_embeds = inputs[3] if len(inputs) > 3 else inputs_embeds
output_attentions = inputs[4] if len(inputs) > 4 else output_attentions
output_hidden_states = inputs[5] if len(inputs) > 5 else output_hidden_states
return_dict = inputs[6] if len(inputs) > 6 else return_dict
assert len(inputs) <= 7, "Too many inputs."
elif isinstance(inputs, (dict, BatchEncoding)):
input_ids = inputs.get("input_ids")
mems = inputs.get("mems", mems)
head_mask = inputs.get("head_mask", head_mask)
inputs_embeds = inputs.get("inputs_embeds", inputs_embeds)
output_attentions = inputs.get("output_attentions", output_attentions)
output_hidden_states = inputs.get("output_hidden_states", output_hidden_states)
return_dict = inputs.get("return_dict", return_dict)
assert len(inputs) <= 7, "Too many inputs."
else:
input_ids = inputs
output_attentions = output_attentions if output_attentions is not None else self.output_attentions
output_hidden_states = output_hidden_states if output_hidden_states is not None else self.output_hidden_states
return_dict = return_dict if return_dict is not None else self.return_dict
# the original code for Transformer-XL used shapes [len, bsz] but we want a unified interface in the library
# so we transpose here from shape [bsz, len] to shape [len, bsz]
if input_ids is not None and inputs_embeds is not None:
raise ValueError("You cannot specify both input_ids and inputs_embeds at the same time")
elif input_ids is not None:
input_ids = tf.transpose(input_ids, perm=(1, 0))
qlen, bsz = shape_list(input_ids)
elif inputs_embeds is not None:
inputs_embeds = tf.transpose(inputs_embeds, perm=(1, 0, 2))
qlen, bsz = shape_list(inputs_embeds)[:2]
else:
raise ValueError("You have to specify either input_ids or inputs_embeds")
if mems is None:
mems = self.init_mems(bsz)
# Prepare head mask if needed
# 1.0 in head_mask indicate we keep the head
# attention_probs has shape bsz x n_heads x N x N
# input head_mask has shape [num_heads] or [num_hidden_layers x num_heads] (a head_mask for each layer)
# and head_mask is converted to shape [num_hidden_layers x qlen x klen x bsz x n_head]
if head_mask is not None:
raise NotImplementedError
else:
head_mask = [None] * self.n_layer
if inputs_embeds is not None:
word_emb = inputs_embeds
else:
word_emb = self.word_emb(input_ids)
mlen = shape_list(mems[0])[0] if mems is not None else 0
klen = mlen + qlen
attn_mask = tf.ones([qlen, qlen])
mask_u = tf.linalg.band_part(attn_mask, 0, -1)
mask_dia = tf.linalg.band_part(attn_mask, 0, 0)
attn_mask_pad = tf.zeros([qlen, mlen])
dec_attn_mask = tf.concat([attn_mask_pad, mask_u - mask_dia], 1)
if self.same_length:
mask_l = tf.linalg.band_part(attn_mask, -1, 0)
dec_attn_mask = tf.concat([dec_attn_mask[:, :qlen] + mask_l - mask_dia, dec_attn_mask[:, qlen:]], 1)
# ::: PyTorch masking code for reference :::
# if self.same_length:
# all_ones = word_emb.new_ones((qlen, klen), dtype=torch.uint8)
# mask_len = klen - self.mem_len
# if mask_len > 0:
# mask_shift_len = qlen - mask_len
# else:
# mask_shift_len = qlen
# dec_attn_mask = (torch.triu(all_ones, 1+mlen)
# + torch.tril(all_ones, -mask_shift_len))[:, :, None] # -1
# else:
# dec_attn_mask = torch.triu(
# word_emb.new_ones((qlen, klen), dtype=torch.uint8), diagonal=1+mlen)[:,:,None]
hids = []
attentions = [] if output_attentions else None
if self.attn_type == 0: # default
pos_seq = tf.range(klen - 1, -1, -1.0)
if self.clamp_len > 0:
pos_seq = tf.minimum(pos_seq, self.clamp_len)
pos_emb = self.pos_emb(pos_seq)
core_out = self.drop(word_emb, training=training)
pos_emb = self.drop(pos_emb, training=training)
for i, layer in enumerate(self.layers):
hids.append(core_out)
mems_i = None if mems is None else mems[i]
layer_outputs = layer(
core_out,
pos_emb,
dec_attn_mask,
mems_i,
head_mask[i],
output_attentions,
training=training,
)
core_out = layer_outputs[0]
if output_attentions:
attentions.append(layer_outputs[1])
else: # learnable embeddings and absolute embeddings
raise NotImplementedError # Removed these to avoid maintaining dead code - They are not used in our pretrained checkpoint
core_out = self.drop(core_out, training=training)
new_mems = self._update_mems(hids, mems, mlen, qlen)
# We transpose back here to shape [bsz, len, hidden_dim]
core_out = tf.transpose(core_out, perm=(1, 0, 2))
if output_hidden_states:
# Add last layer and transpose to library standard shape [bsz, len, hidden_dim]
hids.append(core_out)
hids = tuple(tf.transpose(t, perm=(1, 0, 2)) for t in hids)
else:
hids = None
if output_attentions:
# Transpose to library standard shape [bsz, n_heads, query_seq_len, key_seq_len]
attentions = tuple(tf.transpose(t, perm=(2, 3, 0, 1)) for t in attentions)
if not return_dict:
return tuple(v for v in [core_out, new_mems, hids, attentions] if v is not None)
return TFTransfoXLModelOutput(
last_hidden_state=core_out,
mems=new_mems,
hidden_states=hids,
attentions=attentions,
)
class TFTransfoXLPreTrainedModel(TFPreTrainedModel):
"""An abstract class to handle weights initialization and
a simple interface for downloading and loading pretrained models.
"""
config_class = TransfoXLConfig
base_model_prefix = "transformer"
[docs]@dataclass
class TFTransfoXLModelOutput(ModelOutput):
"""
Base class for model's outputs that may also contain a past key/values (to speed up sequential decoding).
Args:
last_hidden_state (:obj:`tf.Tensor` of shape :obj:`(batch_size, sequence_length, hidden_size)`):
Sequence of hidden-states at the output of the last layer of the model.
mems (:obj:`List[tf.Tensor]` of length :obj:`config.n_layers`):
Contains pre-computed hidden-states (key and values in the attention blocks).
Can be used (see `mems` input) to speed up sequential decoding. The token ids which have their past given to this model
should not be passed as input ids as they have already been computed.
hidden_states (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_hidden_states=True`` is passed or when ``config.output_hidden_states=True``):
Tuple of :obj:`tf.Tensor` (one for the output of the embeddings + one for the output of each layer)
of shape :obj:`(batch_size, sequence_length, hidden_size)`.
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
attentions (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_attentions=True`` is passed or when ``config.output_attentions=True``):
Tuple of :obj:`tf.Tensor` (one for each layer) of shape
:obj:`(batch_size, num_heads, sequence_length, sequence_length)`.
Attentions weights after the attention softmax, used to compute the weighted average in the self-attention
heads.
"""
last_hidden_state: tf.Tensor = None
mems: List[tf.Tensor] = None
hidden_states: Optional[Tuple[tf.Tensor]] = None
attentions: Optional[Tuple[tf.Tensor]] = None
[docs]@dataclass
class TFTransfoXLLMHeadModelOutput(ModelOutput):
"""
Base class for model's outputs that may also contain a past key/values (to speed up sequential decoding).
Args:
losses (:obj:`tf.Tensor` of shape `(batch_size, sequence_length-1)`, `optional`, returned when ``labels`` is provided)
Language modeling losses (not reduced).
prediction_scores (:obj:`tf.Tensor` of shape :obj:`(batch_size, sequence_length, config.vocab_size)`):
Prediction scores of the language modeling head (scores for each vocabulary token after SoftMax).
mems (:obj:`List[tf.Tensor]` of length :obj:`config.n_layers`):
Contains pre-computed hidden-states (key and values in the attention blocks).
Can be used (see `mems` input) to speed up sequential decoding. The token ids which have their past given to this model
should not be passed as input ids as they have already been computed.
hidden_states (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_hidden_states=True`` is passed or when ``config.output_hidden_states=True``):
Tuple of :obj:`tf.Tensor` (one for the output of the embeddings + one for the output of each layer)
of shape :obj:`(batch_size, sequence_length, hidden_size)`.
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
attentions (:obj:`tuple(tf.Tensor)`, `optional`, returned when ``output_attentions=True`` is passed or when ``config.output_attentions=True``):
Tuple of :obj:`tf.Tensor` (one for each layer) of shape
:obj:`(batch_size, num_heads, sequence_length, sequence_length)`.
Attentions weights after the attention softmax, used to compute the weighted average in the self-attention
heads.
"""
prediction_scores: tf.Tensor = None
mems: List[tf.Tensor] = None
hidden_states: Optional[Tuple[tf.Tensor]] = None
attentions: Optional[Tuple[tf.Tensor]] = None
TRANSFO_XL_START_DOCSTRING = r"""
.. note::
TF 2.0 models accepts two formats as inputs:
- having all inputs as keyword arguments (like PyTorch models), or
- having all inputs as a list, tuple or dict in the first positional arguments.
This second option is useful when using :obj:`tf.keras.Model.fit()` method which currently requires having
all the tensors in the first argument of the model call function: :obj:`model(inputs)`.
If you choose this second option, there are three possibilities you can use to gather all the input Tensors
in the first positional argument :
- a single Tensor with input_ids only and nothing else: :obj:`model(inputs_ids)`
- a list of varying length with one or several input Tensors IN THE ORDER given in the docstring:
:obj:`model([input_ids, attention_mask])` or :obj:`model([input_ids, attention_mask, token_type_ids])`
- a dictionary with one or several input Tensors associated to the input names given in the docstring:
:obj:`model({'input_ids': input_ids, 'token_type_ids': token_type_ids})`
Parameters:
config (:class:`~transformers.TransfoXLConfig`): Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the configuration.
Check out the :meth:`~transformers.PreTrainedModel.from_pretrained` method to load the model weights.
"""
TRANSFO_XL_INPUTS_DOCSTRING = r"""
Args:
input_ids (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, sequence_length)`):
Indices of input sequence tokens in the vocabulary.
Indices can be obtained using :class:`transformers.TransfoXLTokenizer`.
See :func:`transformers.PreTrainedTokenizer.encode` and
:func:`transformers.PreTrainedTokenizer.__call__` for details.
`What are input IDs? <../glossary.html#input-ids>`__
mems (:obj:`List[tf.Tensor]` of length :obj:`config.n_layers`):
Contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
(see `mems` output below). Can be used to speed up sequential decoding. The token ids which have their mems
given to this model should not be passed as input ids as they have already been computed.
head_mask (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(num_heads,)` or :obj:`(num_layers, num_heads)`, `optional`):
Mask to nullify selected heads of the self-attention modules.
Mask values selected in ``[0, 1]``:
:obj:`1` indicates the head is **not masked**, :obj:`0` indicates the head is **masked**.
inputs_embeds (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, sequence_length, hidden_size)`, `optional`):
Optionally, instead of passing :obj:`input_ids` you can choose to directly pass an embedded representation.
This is useful if you want more control over how to convert `input_ids` indices into associated vectors
than the model's internal embedding lookup matrix.
output_attentions (:obj:`bool`, `optional`):
If set to ``True``, the attentions tensors of all attention layers are returned. See ``attentions`` under returned tensors for more detail.
output_hidden_states (:obj:`bool`, `optional`):
If set to ``True``, the hidden states of all layers are returned. See ``hidden_states`` under returned tensors for more detail.
return_dict (:obj:`bool`, `optional`):
If set to ``True``, the model will return a :class:`~transformers.file_utils.ModelOutput` instead of a
plain tuple.
"""
[docs]@add_start_docstrings(
"The bare Bert Model transformer outputing raw hidden-states without any specific head on top.",
TRANSFO_XL_START_DOCSTRING,
)
class TFTransfoXLModel(TFTransfoXLPreTrainedModel):
def __init__(self, config, *inputs, **kwargs):
super().__init__(config, *inputs, **kwargs)
self.transformer = TFTransfoXLMainLayer(config, name="transformer")
[docs] @add_start_docstrings_to_callable(TRANSFO_XL_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="transfo-xl-wt103",
output_type=TFTransfoXLModelOutput,
config_class=_CONFIG_FOR_DOC,
)
def call(self, inputs, **kwargs):
outputs = self.transformer(inputs, **kwargs)
return outputs
class TFTransfoXLMHead(tf.keras.layers.Layer):
def __init__(self, config, input_embeddings, **kwargs):
super().__init__(**kwargs)
self.vocab_size = config.vocab_size
# The output weights are the same as the input embeddings, but there is
# an output-only bias for each token.
self.input_embeddings = input_embeddings
def build(self, input_shape):
self.bias = self.add_weight(shape=(self.vocab_size,), initializer="zeros", trainable=True, name="bias")
super().build(input_shape)
def call(self, hidden_states):
hidden_states = self.input_embeddings(hidden_states, mode="linear")
hidden_states = hidden_states + self.bias
return hidden_states
[docs]@add_start_docstrings(
"""The Transformer-XL Model with a language modeling head on top
(adaptive softmax with weights tied to the adaptive input embeddings)""",
TRANSFO_XL_START_DOCSTRING,
)
class TFTransfoXLLMHeadModel(TFTransfoXLPreTrainedModel):
def __init__(self, config):
super().__init__(config)
self.transformer = TFTransfoXLMainLayer(config, name="transformer")
self.sample_softmax = config.sample_softmax
assert (
self.sample_softmax <= 0
), "Sampling from the softmax is not implemented yet. Please look at issue: #3310: https://github.com/huggingface/transformers/issues/3310"
self.crit = TFAdaptiveSoftmaxMask(
config.vocab_size, config.d_embed, config.d_model, config.cutoffs, div_val=config.div_val, name="crit"
)
[docs] def get_output_embeddings(self):
"""Double-check if you are using adaptive softmax."""
if len(self.crit.out_layers) > 0:
return self.crit.out_layers[-1]
return None
def reset_length(self, tgt_len, ext_len, mem_len):
warnings.warn(
"The method `reset_length` is deprecated and will be removed in a future version, use `reset_memory_length` instead.",
FutureWarning,
)
self.transformer.reset_memory_length(mem_len)
def reset_memory_length(self, mem_len):
self.transformer.reset_memory_length(mem_len)
def init_mems(self, bsz):
return self.transformer.init_mems(bsz)
[docs] @add_start_docstrings_to_callable(TRANSFO_XL_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="transfo-xl-wt103",
output_type=TFTransfoXLLMHeadModelOutput,
config_class=_CONFIG_FOR_DOC,
)
def call(
self,
inputs,
mems=None,
head_mask=None,
inputs_embeds=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
labels=None,
training=False,
):
if isinstance(inputs, (tuple, list)):
input_ids = inputs[0]
mems = inputs[1] if len(inputs) > 1 else mems
head_mask = inputs[2] if len(inputs) > 2 else head_mask
inputs_embeds = inputs[3] if len(inputs) > 3 else inputs_embeds
output_attentions = inputs[4] if len(inputs) > 4 else output_attentions
output_hidden_states = inputs[5] if len(inputs) > 5 else output_hidden_states
return_dict = inputs[6] if len(inputs) > 6 else return_dict
labels = inputs[7] if len(inputs) > 7 else labels
assert len(inputs) <= 8, "Too many inputs."
elif isinstance(inputs, (BatchEncoding, dict)):
input_ids = inputs.get("input_ids")
mems = inputs.get("mems", mems)
head_mask = inputs.get("head_mask", head_mask)
inputs_embeds = inputs.get("inputs_embeds", inputs_embeds)
output_attentions = inputs.get("output_attentions", output_attentions)
output_hidden_states = inputs.get("output_hidden_states", output_hidden_states)
return_dict = inputs.get("return_dict", return_dict)
labels = inputs.get("labels", labels)
assert len(inputs) <= 8, "Too many inputs."
else:
input_ids = inputs
return_dict = return_dict if return_dict is not None else self.transformer.return_dict
if input_ids is not None:
bsz, tgt_len = shape_list(input_ids)[:2]
else:
bsz, tgt_len = shape_list(inputs_embeds)[:2]
transformer_outputs = self.transformer(
input_ids,
mems,
head_mask,
inputs_embeds,
output_attentions,
output_hidden_states,
return_dict,
training=training,
)
last_hidden = transformer_outputs[0]
pred_hid = last_hidden[:, -tgt_len:]
softmax_output = self.crit(pred_hid, labels, training=training)
if not return_dict:
return (softmax_output,) + transformer_outputs[1:]
return TFTransfoXLLMHeadModelOutput(
prediction_scores=softmax_output,
mems=transformer_outputs.mems,
hidden_states=transformer_outputs.hidden_states,
attentions=transformer_outputs.attentions,
)