# coding=utf-8
# Copyright 2018 The OpenAI Team Authors and 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 OpenAI GPT-2 model. """
from dataclasses import dataclass
from typing import List, Optional, Tuple
import tensorflow as tf
from .activations_tf import get_tf_activation
from .configuration_gpt2 import GPT2Config
from .file_utils import (
ModelOutput,
add_code_sample_docstrings,
add_start_docstrings,
add_start_docstrings_to_callable,
replace_return_docstrings,
)
from .modeling_tf_outputs import TFBaseModelOutputWithPast, TFCausalLMOutputWithPast
from .modeling_tf_utils import (
TFCausalLanguageModelingLoss,
TFConv1D,
TFPreTrainedModel,
TFSequenceSummary,
TFSharedEmbeddings,
get_initializer,
keras_serializable,
shape_list,
)
from .tokenization_utils import BatchEncoding
from .utils import logging
logger = logging.get_logger(__name__)
_CONFIG_FOR_DOC = "GPT2Config"
_TOKENIZER_FOR_DOC = "GPT2Tokenizer"
TF_GPT2_PRETRAINED_MODEL_ARCHIVE_LIST = [
"gpt2",
"gpt2-medium",
"gpt2-large",
"gpt2-xl",
"distilgpt2",
# See all GPT-2 models at https://huggingface.co/models?filter=gpt2
]
class TFAttention(tf.keras.layers.Layer):
def __init__(self, nx, n_ctx, config, scale=False, **kwargs):
super().__init__(**kwargs)
n_state = nx # in Attention: n_state=768 (nx=n_embd)
# [switch nx => n_state from Block to Attention to keep identical to TF implem]
assert n_state % config.n_head == 0
self.n_ctx = n_ctx
self.n_head = config.n_head
self.split_size = n_state
self.scale = scale
self.output_attentions = config.output_attentions
self.c_attn = TFConv1D(n_state * 3, nx, initializer_range=config.initializer_range, name="c_attn")
self.c_proj = TFConv1D(n_state, nx, initializer_range=config.initializer_range, name="c_proj")
self.attn_dropout = tf.keras.layers.Dropout(config.attn_pdrop)
self.resid_dropout = tf.keras.layers.Dropout(config.resid_pdrop)
self.pruned_heads = set()
def prune_heads(self, heads):
pass
@staticmethod
def causal_attention_mask(nd, ns, dtype):
"""1's in the lower triangle, counting from the lower right corner.
Same as tf.matrix_band_part(tf.ones([nd, ns]), -1, ns-nd), but doesn't produce garbage on TPUs.
"""
i = tf.range(nd)[:, None]
j = tf.range(ns)
m = i >= j - ns + nd
return tf.cast(m, dtype)
def _attn(self, q, k, v, attention_mask, head_mask, output_attentions, training=False):
# q, k, v have shape [batch, heads, sequence, features]
w = tf.matmul(q, k, transpose_b=True)
if self.scale:
dk = tf.cast(shape_list(k)[-1], tf.float32) # scale attention_scores
w = w / tf.math.sqrt(dk)
# w has shape [batch, heads, dst_sequence, src_sequence], where information flows from src to dst.
_, _, nd, ns = shape_list(w)
b = self.causal_attention_mask(nd, ns, dtype=w.dtype)
b = tf.reshape(b, [1, 1, nd, ns])
w = w * b - 1e4 * (1 - b)
if attention_mask is not None:
# Apply the attention mask
w = w + attention_mask
w = tf.nn.softmax(w, axis=-1)
w = self.attn_dropout(w, training=training)
# Mask heads if we want to
if head_mask is not None:
w = w * head_mask
outputs = [tf.matmul(w, v)]
if output_attentions:
outputs.append(w)
return outputs
def merge_heads(self, x):
x = tf.transpose(x, [0, 2, 1, 3])
x_shape = shape_list(x)
new_x_shape = x_shape[:-2] + [x_shape[-2] * x_shape[-1]]
return tf.reshape(x, new_x_shape)
def split_heads(self, x):
x_shape = shape_list(x)
new_x_shape = x_shape[:-1] + [self.n_head, x_shape[-1] // self.n_head]
x = tf.reshape(x, new_x_shape)
return tf.transpose(x, (0, 2, 1, 3)) # (batch, head, seq_length, head_features)
def call(self, x, layer_past, attention_mask, head_mask, use_cache, output_attentions, training=False):
x = self.c_attn(x)
query, key, value = tf.split(x, 3, axis=2)
query = self.split_heads(query)
key = self.split_heads(key)
value = self.split_heads(value)
if layer_past is not None:
past_key, past_value = tf.unstack(layer_past, axis=0)
key = tf.concat([past_key, key], axis=-2)
value = tf.concat([past_value, value], axis=-2)
# to cope with keras serialization
if use_cache:
present = tf.stack([key, value], axis=0)
else:
present = (None,)
attn_outputs = self._attn(query, key, value, attention_mask, head_mask, output_attentions, training=training)
a = attn_outputs[0]
a = self.merge_heads(a)
a = self.c_proj(a)
a = self.resid_dropout(a, training=training)
outputs = [a, present] + attn_outputs[1:]
return outputs # a, present, (attentions)
class TFMLP(tf.keras.layers.Layer):
def __init__(self, n_state, config, **kwargs):
super().__init__(**kwargs)
nx = config.n_embd
self.c_fc = TFConv1D(n_state, nx, initializer_range=config.initializer_range, name="c_fc")
self.c_proj = TFConv1D(nx, n_state, initializer_range=config.initializer_range, name="c_proj")
self.act = get_tf_activation("gelu")
self.dropout = tf.keras.layers.Dropout(config.resid_pdrop)
def call(self, x, training=False):
h = self.act(self.c_fc(x))
h2 = self.c_proj(h)
h2 = self.dropout(h2, training=training)
return h2
class TFBlock(tf.keras.layers.Layer):
def __init__(self, n_ctx, config, scale=False, **kwargs):
super().__init__(**kwargs)
nx = config.n_embd
inner_dim = config.n_inner if config.n_inner is not None else 4 * nx
self.ln_1 = tf.keras.layers.LayerNormalization(epsilon=config.layer_norm_epsilon, name="ln_1")
self.attn = TFAttention(nx, n_ctx, config, scale, name="attn")
self.ln_2 = tf.keras.layers.LayerNormalization(epsilon=config.layer_norm_epsilon, name="ln_2")
self.mlp = TFMLP(inner_dim, config, name="mlp")
def call(self, x, layer_past, attention_mask, head_mask, use_cache, output_attentions, training=False):
a = self.ln_1(x)
output_attn = self.attn(
a, layer_past, attention_mask, head_mask, use_cache, output_attentions, training=training
)
a = output_attn[0] # output_attn: a, present, (attentions)
x = x + a
m = self.ln_2(x)
m = self.mlp(m, training=training)
x = x + m
outputs = [x] + output_attn[1:]
return outputs # x, present, (attentions)
@keras_serializable
class TFGPT2MainLayer(tf.keras.layers.Layer):
config_class = GPT2Config
def __init__(self, config, *inputs, **kwargs):
super().__init__(*inputs, **kwargs)
self.output_attentions = config.output_attentions
self.output_hidden_states = config.output_hidden_states
self.use_cache = config.use_cache
self.return_dict = config.use_return_dict
self.num_hidden_layers = config.n_layer
self.vocab_size = config.vocab_size
self.n_embd = config.n_embd
self.wte = TFSharedEmbeddings(
config.vocab_size, config.hidden_size, initializer_range=config.initializer_range, name="wte"
)
self.wpe = tf.keras.layers.Embedding(
config.n_positions,
config.n_embd,
embeddings_initializer=get_initializer(config.initializer_range),
name="wpe",
)
self.drop = tf.keras.layers.Dropout(config.embd_pdrop)
self.h = [TFBlock(config.n_ctx, config, scale=True, name="h_._{}".format(i)) for i in range(config.n_layer)]
self.ln_f = tf.keras.layers.LayerNormalization(epsilon=config.layer_norm_epsilon, name="ln_f")
def get_input_embeddings(self):
return self.wte
def set_input_embeddings(self, value):
self.wte.weight = value
self.wte.vocab_size = self.wte.weight.shape[0]
def _prune_heads(self, heads_to_prune):
"""Prunes heads of the model.
heads_to_prune: dict of {layer_num: list of heads to prune in this layer}
"""
raise NotImplementedError
def call(
self,
inputs,
past=None,
attention_mask=None,
token_type_ids=None,
position_ids=None,
head_mask=None,
inputs_embeds=None,
use_cache=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
training=False,
):
if isinstance(inputs, (tuple, list)):
input_ids = inputs[0]
past = inputs[1] if len(inputs) > 1 else past
attention_mask = inputs[2] if len(inputs) > 2 else attention_mask
token_type_ids = inputs[3] if len(inputs) > 3 else token_type_ids
position_ids = inputs[4] if len(inputs) > 4 else position_ids
head_mask = inputs[5] if len(inputs) > 5 else head_mask
inputs_embeds = inputs[6] if len(inputs) > 6 else inputs_embeds
use_cache = inputs[7] if len(inputs) > 7 else use_cache
output_attentions = inputs[8] if len(inputs) > 8 else output_attentions
output_hidden_states = inputs[9] if len(inputs) > 9 else output_hidden_states
return_dict = inputs[10] if len(inputs) > 10 else return_dict
assert len(inputs) <= 11, "Too many inputs."
elif isinstance(inputs, (dict, BatchEncoding)):
input_ids = inputs.get("input_ids")
past = inputs.get("past", past)
attention_mask = inputs.get("attention_mask", attention_mask)
token_type_ids = inputs.get("token_type_ids", token_type_ids)
position_ids = inputs.get("position_ids", position_ids)
head_mask = inputs.get("head_mask", head_mask)
inputs_embeds = inputs.get("inputs_embeds", inputs_embeds)
use_cache = inputs.get("use_cache", use_cache)
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) <= 11, "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
use_cache = use_cache if use_cache is not None else self.use_cache
return_dict = return_dict if return_dict is not None else self.return_dict
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_shape = shape_list(input_ids)
input_ids = tf.reshape(input_ids, [-1, input_shape[-1]])
elif inputs_embeds is not None:
input_shape = shape_list(inputs_embeds)[:-1]
else:
raise ValueError("You have to specify either input_ids or inputs_embeds")
if past is None:
past_length = 0
past = [None] * len(self.h)
else:
past_length = shape_list(past[0][0])[-2]
if position_ids is None:
position_ids = tf.range(past_length, input_shape[-1] + past_length, dtype=tf.int32)[tf.newaxis, :]
if attention_mask is not None:
# We create a 3D attention mask from a 2D tensor mask.
# Sizes are [batch_size, 1, 1, to_seq_length]
# So we can broadcast to [batch_size, num_heads, from_seq_length, to_seq_length]
# this attention mask is more simple than the triangular masking of causal attention
# used in OpenAI GPT, we just need to prepare the broadcast dimension here.
attention_mask = attention_mask[:, tf.newaxis, tf.newaxis, :]
# Since attention_mask is 1.0 for positions we want to attend and 0.0 for
# masked positions, this operation will create a tensor which is 0.0 for
# positions we want to attend and -10000.0 for masked positions.
# Since we are adding it to the raw scores before the softmax, this is
# effectively the same as removing these entirely.
attention_mask = tf.cast(attention_mask, tf.float32)
attention_mask = (1.0 - attention_mask) * -10000.0
else:
attention_mask = None
# 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]
# and head_mask is converted to shape [num_hidden_layers x batch x num_heads x seq_length x seq_length]
if head_mask is not None:
raise NotImplementedError
else:
head_mask = [None] * self.num_hidden_layers
# head_mask = tf.constant([0] * self.num_hidden_layers)
position_ids = tf.reshape(position_ids, [-1, shape_list(position_ids)[-1]])
if inputs_embeds is None:
inputs_embeds = self.wte(input_ids, mode="embedding")
position_embeds = self.wpe(position_ids)
if token_type_ids is not None:
token_type_ids = tf.reshape(token_type_ids, [-1, shape_list(token_type_ids)[-1]])
token_type_embeds = self.wte(token_type_ids, mode="embedding")
else:
token_type_embeds = 0
hidden_states = inputs_embeds + position_embeds + token_type_embeds
hidden_states = self.drop(hidden_states, training=training)
output_shape = input_shape + [shape_list(hidden_states)[-1]]
presents = () if use_cache else None
all_attentions = () if output_attentions else None
all_hidden_states = () if output_hidden_states else None
for i, (block, layer_past) in enumerate(zip(self.h, past)):
if output_hidden_states:
all_hidden_states = all_hidden_states + (tf.reshape(hidden_states, output_shape),)
outputs = block(
hidden_states,
layer_past,
attention_mask,
head_mask[i],
use_cache,
output_attentions,
training=training,
)
hidden_states, present = outputs[:2]
if use_cache:
presents = presents + (present,)
if output_attentions:
all_attentions = all_attentions + (outputs[2],)
hidden_states = self.ln_f(hidden_states)
hidden_states = tf.reshape(hidden_states, output_shape)
# Add last hidden state
if output_hidden_states:
all_hidden_states = all_hidden_states + (hidden_states,)
if output_attentions:
# let the number of heads free (-1) so we can extract attention even after head pruning
attention_output_shape = input_shape[:-1] + [-1] + shape_list(all_attentions[0])[-2:]
all_attentions = tuple(tf.reshape(t, attention_output_shape) for t in all_attentions)
if not return_dict:
return tuple(v for v in [hidden_states, presents, all_hidden_states, all_attentions] if v is not None)
return TFBaseModelOutputWithPast(
last_hidden_state=hidden_states,
past_key_values=presents,
hidden_states=all_hidden_states,
attentions=all_attentions,
)
class TFGPT2PreTrainedModel(TFPreTrainedModel):
"""An abstract class to handle weights initialization and
a simple interface for downloading and loading pretrained models.
"""
config_class = GPT2Config
base_model_prefix = "transformer"
[docs]@dataclass
class TFGPT2DoubleHeadsModelOutput(ModelOutput):
"""
Base class for outputs of models predicting if two sentences are consecutive or not.
Args:
logits (:obj:`tf.Tensor` of shape :obj:`(batch_size, num_choices, sequence_length, config.vocab_size)`):
Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).
mc_logits (:obj:`tf.Tensor` of shape :obj:`(batch_size, num_choices)`):
Prediction scores of the multiple choice classification head (scores for each choice before SoftMax).
past_key_values (:obj:`List[tf.Tensor]`, `optional`, returned when ``use_cache=True`` is passed or when ``config.use_cache=True``):
List of :obj:`tf.Tensor` of length :obj:`config.n_layers`, with each tensor of shape
:obj:`(2, batch_size, num_heads, sequence_length, embed_size_per_head)`).
Contains pre-computed hidden-states (key and values in the attention blocks) that can be used (see
``past_key_values`` input) to speed up sequential decoding.
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.
"""
logits: tf.Tensor = None
mc_logits: tf.Tensor = None
past_key_values: Optional[List[tf.Tensor]] = None
hidden_states: Optional[Tuple[tf.Tensor]] = None
attentions: Optional[Tuple[tf.Tensor]] = None
GPT2_START_DOCSTRING = r"""
This model inherits from :class:`~transformers.TFPreTrainedModel`. Check the superclass documentation for the
generic methods the library implements for all its model (such as downloading or saving, resizing the input
embeddings, pruning heads etc.)
This model is also a `tf.keras.Model <https://www.tensorflow.org/api_docs/python/tf/keras/Model>`__ subclass.
Use it as a regular TF 2.0 Keras Model and refer to the TF 2.0 documentation for all matter related to general
usage and behavior.
.. 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 :meth:`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 :obj:`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.GPT2Config`): 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.
"""
GPT2_INPUTS_DOCSTRING = r"""
Args:
input_ids (:obj:`Numpy array` or :obj:`tf.Tensor` of shape :obj:`(batch_size, input_ids_length)`):
:obj:`input_ids_length` = ``sequence_length`` if ``past`` is ``None`` else ``past[0].shape[-2]``
(``sequence_length`` of input past key value states).
Indices of input sequence tokens in the vocabulary.
If :obj:`past` is used, only input IDs that do not have their past calculated should be passed as
``input_ids``.
Indices can be obtained using :class:`~transformers.GPT2Tokenizer`.
See :func:`transformers.PreTrainedTokenizer.__call__` and
:func:`transformers.PreTrainedTokenizer.encode` for details.
`What are input IDs? <../glossary.html#input-ids>`__
past (: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 :obj:`past` output below). Can be used 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.
attention_mask (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Mask to avoid performing attention on padding token indices.
Mask values selected in ``[0, 1]``:
- 1 for tokens that are **not masked**,
- 0 for tokens that are **maked**.
`What are attention masks? <../glossary.html#attention-mask>`__
token_type_ids (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Segment token indices to indicate first and second portions of the inputs.
Indices are selected in ``[0, 1]``:
- 0 corresponds to a `sentence A` token,
- 1 corresponds to a `sentence B` token.
`What are token type IDs? <../glossary.html#token-type-ids>`__
position_ids (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Indices of positions of each input sequence tokens in the position embeddings.
Selected in the range ``[0, config.max_position_embeddings - 1]``.
`What are position IDs? <../glossary.html#position-ids>`__
head_mask (:obj:`Numpy array` or :obj:`tf.Tensor` 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]``:
- 1 indicates the head is **not masked**,
- 0 indicates the head is **masked**.
inputs_embeds (:obj:`tf.Tensor` 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 :obj:`input_ids` indices into associated
vectors than the model's internal embedding lookup matrix.
output_attentions (:obj:`bool`, `optional`):
Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
tensors for more detail.
output_hidden_states (:obj:`bool`, `optional`):
Whether or not to return the hidden states of all layers. See ``hidden_states`` under returned tensors for
more detail.
return_dict (:obj:`bool`, `optional`):
Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.
training (:obj:`bool`, `optional`, defaults to :obj:`False`):
Whether or not to use the model in training mode (some modules like dropout modules have different
behaviors between training and evaluation).
"""
[docs]@add_start_docstrings(
"The bare GPT2 Model transformer outputing raw hidden-states without any specific head on top.",
GPT2_START_DOCSTRING,
)
class TFGPT2Model(TFGPT2PreTrainedModel):
def __init__(self, config, *inputs, **kwargs):
super().__init__(config, *inputs, **kwargs)
self.transformer = TFGPT2MainLayer(config, name="transformer")
[docs] @add_start_docstrings_to_callable(GPT2_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="gpt2",
output_type=TFBaseModelOutputWithPast,
config_class=_CONFIG_FOR_DOC,
)
def call(self, inputs, **kwargs):
outputs = self.transformer(inputs, **kwargs)
return outputs
[docs]@add_start_docstrings(
"""The GPT2 Model transformer with a language modeling head on top
(linear layer with weights tied to the input embeddings). """,
GPT2_START_DOCSTRING,
)
class TFGPT2LMHeadModel(TFGPT2PreTrainedModel, TFCausalLanguageModelingLoss):
def __init__(self, config, *inputs, **kwargs):
super().__init__(config, *inputs, **kwargs)
self.transformer = TFGPT2MainLayer(config, name="transformer")
def get_output_embeddings(self):
return self.transformer.wte
def prepare_inputs_for_generation(self, inputs, past, **kwargs):
# only last token for inputs_ids if past is defined in kwargs
if past:
inputs = tf.expand_dims(inputs[:, -1], -1)
return {"inputs": inputs, "past": past, "use_cache": kwargs["use_cache"]}
[docs] @add_start_docstrings_to_callable(GPT2_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="gpt2",
output_type=TFCausalLMOutputWithPast,
config_class=_CONFIG_FOR_DOC,
)
def call(
self,
inputs,
past=None,
attention_mask=None,
token_type_ids=None,
position_ids=None,
head_mask=None,
inputs_embeds=None,
use_cache=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
labels=None,
training=False,
):
r"""
labels (:obj:`tf.Tensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Labels for computing the cross entropy classification loss.
Indices should be in ``[0, ..., config.vocab_size - 1]``.
"""
return_dict = return_dict if return_dict is not None else self.transformer.return_dict
if isinstance(inputs, (tuple, list)):
labels = inputs[11] if len(inputs) > 11 else labels
if len(inputs) > 11:
inputs = inputs[:11]
elif isinstance(inputs, (dict, BatchEncoding)):
labels = inputs.pop("labels", labels)
transformer_outputs = self.transformer(
inputs,
past=past,
attention_mask=attention_mask,
token_type_ids=token_type_ids,
position_ids=position_ids,
head_mask=head_mask,
inputs_embeds=inputs_embeds,
use_cache=use_cache,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
training=training,
)
hidden_states = transformer_outputs[0]
logits = self.transformer.wte(hidden_states, mode="linear")
loss = None
if labels is not None:
# shift labels to the left and cut last logit token
logits = logits[:, :-1]
labels = labels[:, 1:]
loss = self.compute_loss(labels, logits)
if not return_dict:
output = (logits,) + transformer_outputs[1:]
return ((loss,) + output) if loss is not None else output
return TFCausalLMOutputWithPast(
loss=loss,
logits=logits,
past_key_values=transformer_outputs.past_key_values,
hidden_states=transformer_outputs.hidden_states,
attentions=transformer_outputs.attentions,
)
[docs]@add_start_docstrings(
"""The GPT2 Model transformer with a language modeling and a multiple-choice classification
head on top e.g. for RocStories/SWAG tasks. The two heads are two linear layers.
The language modeling head has its weights tied to the input embeddings,
the classification head takes as input the input of a specified classification token index in the input sequence).
""",
GPT2_START_DOCSTRING,
)
class TFGPT2DoubleHeadsModel(TFGPT2PreTrainedModel):
def __init__(self, config, *inputs, **kwargs):
super().__init__(config, *inputs, **kwargs)
config.num_labels = 1
self.transformer = TFGPT2MainLayer(config, name="transformer")
self.multiple_choice_head = TFSequenceSummary(
config, initializer_range=config.initializer_range, name="multiple_choice_head"
)
def get_output_embeddings(self):
return self.transformer.wte
[docs] @add_start_docstrings_to_callable(GPT2_INPUTS_DOCSTRING)
@replace_return_docstrings(output_type=TFGPT2DoubleHeadsModelOutput, config_class=_CONFIG_FOR_DOC)
def call(
self,
inputs,
past=None,
attention_mask=None,
token_type_ids=None,
position_ids=None,
head_mask=None,
inputs_embeds=None,
mc_token_ids=None,
use_cache=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
training=False,
):
r"""
mc_token_ids (:obj:`tf.Tensor` or :obj:`Numpy array` of shape :obj:`(batch_size, num_choices)`, `optional`, default to index of the last token of the input)
Index of the classification token in each input sequence.
Selected in the range ``[0, input_ids.size(-1) - 1[``.
Return:
Examples::
>>> import tensorflow as tf
>>> from transformers import GPT2Tokenizer, TFGPT2DoubleHeadsModel
>>> tokenizer = GPT2Tokenizer.from_pretrained('gpt2')
>>> model = TFGPT2DoubleHeadsModel.from_pretrained('gpt2')
>>> # Add a [CLS] to the vocabulary (we should train it also!)
>>> num_added_tokens = tokenizer.add_special_tokens({'cls_token': '[CLS]'})
>>> embedding_layer = model.resize_token_embeddings(len(tokenizer)) # Update the model embeddings with the new vocabulary size
>>> choices = ["Hello, my dog is cute [CLS]", "Hello, my cat is cute [CLS]"]
>>> encoded_choices = [tokenizer.encode(s) for s in choices]
>>> cls_token_location = [tokens.index(tokenizer.cls_token_id) for tokens in encoded_choices]
>>> input_ids = tf.constant(encoded_choices)[None, :] # Batch size: 1, number of choices: 2
>>> mc_token_ids = tf.constant([cls_token_location]) # Batch size: 1
>>> outputs = model(input_ids, mc_token_ids=mc_token_ids)
>>> lm_prediction_scores, mc_prediction_scores = outputs[:2]
"""
if isinstance(inputs, (tuple, list)):
input_ids = inputs[0]
past = inputs[1] if len(inputs) > 1 else past
attention_mask = inputs[2] if len(inputs) > 2 else attention_mask
token_type_ids = inputs[3] if len(inputs) > 3 else token_type_ids
position_ids = inputs[4] if len(inputs) > 4 else position_ids
head_mask = inputs[5] if len(inputs) > 5 else head_mask
inputs_embeds = inputs[6] if len(inputs) > 6 else inputs_embeds
mc_token_ids = inputs[7] if len(inputs) > 7 else mc_token_ids
use_cache = inputs[8] if len(inputs) > 8 else use_cache
output_attentions = inputs[9] if len(inputs) > 9 else output_attentions
output_hidden_states = inputs[10] if len(inputs) > 10 else output_hidden_states
return_dict = inputs[11] if len(inputs) > 11 else return_dict
assert len(inputs) <= 12, "Too many inputs."
elif isinstance(inputs, dict):
input_ids = inputs.get("input_ids")
past = inputs.get("past", past)
attention_mask = inputs.get("attention_mask", attention_mask)
token_type_ids = inputs.get("token_type_ids", token_type_ids)
position_ids = inputs.get("position_ids", position_ids)
head_mask = inputs.get("head_mask", head_mask)
inputs_embeds = inputs.get("inputs_embeds", inputs_embeds)
mc_token_ids = inputs.get("mc_token_ids", mc_token_ids)
use_cache = inputs.get("use_cache", use_cache)
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) <= 12, "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:
input_shapes = shape_list(input_ids)
else:
input_shapes = shape_list(inputs_embeds)[:-1]
seq_length = input_shapes[-1]
flat_input_ids = tf.reshape(input_ids, (-1, seq_length)) if input_ids is not None else None
flat_attention_mask = tf.reshape(attention_mask, (-1, seq_length)) if attention_mask is not None else None
flat_token_type_ids = tf.reshape(token_type_ids, (-1, seq_length)) if token_type_ids is not None else None
flat_position_ids = tf.reshape(position_ids, (-1, seq_length)) if position_ids is not None else None
transformer_outputs = self.transformer(
flat_input_ids,
past,
flat_attention_mask,
flat_token_type_ids,
flat_position_ids,
head_mask,
inputs_embeds,
use_cache,
output_attentions,
output_hidden_states,
return_dict=return_dict,
training=training,
)
hidden_states = transformer_outputs[0]
hidden_states = tf.reshape(hidden_states, input_shapes + shape_list(hidden_states)[-1:])
lm_logits = self.transformer.wte(hidden_states, mode="linear")
mc_logits = self.multiple_choice_head(hidden_states, mc_token_ids, training=training)
mc_logits = tf.squeeze(mc_logits, axis=-1)
if not return_dict:
return (lm_logits, mc_logits) + transformer_outputs[1:]
return TFGPT2DoubleHeadsModelOutput(
logits=lm_logits,
mc_logits=mc_logits,
past_key_values=transformer_outputs.past_key_values,
hidden_states=transformer_outputs.hidden_states,
attentions=transformer_outputs.attentions,
)