# 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.
""" PyTorch XLNet model.
"""
from __future__ import absolute_import, division, print_function, unicode_literals
import json
import logging
import math
import os
import sys
from io import open
import torch
from torch import nn
from torch.nn import functional as F
from torch.nn import CrossEntropyLoss, MSELoss
from .modeling_utils import (CONFIG_NAME, WEIGHTS_NAME, PretrainedConfig, PreTrainedModel,
SequenceSummary, PoolerAnswerClass, PoolerEndLogits, PoolerStartLogits,
add_start_docstrings)
logger = logging.getLogger(__name__)
XLNET_PRETRAINED_MODEL_ARCHIVE_MAP = {
'xlnet-base-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/xlnet-base-cased-pytorch_model.bin",
'xlnet-large-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/xlnet-large-cased-pytorch_model.bin",
}
XLNET_PRETRAINED_CONFIG_ARCHIVE_MAP = {
'xlnet-base-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/xlnet-base-cased-config.json",
'xlnet-large-cased': "https://s3.amazonaws.com/models.huggingface.co/bert/xlnet-large-cased-config.json",
}
def build_tf_xlnet_to_pytorch_map(model, config, tf_weights=None):
""" A map of modules from TF to PyTorch.
I use a map to keep the PyTorch model as
identical to the original PyTorch model as possible.
"""
tf_to_pt_map = {}
if hasattr(model, 'transformer'):
if hasattr(model, 'lm_loss'):
# We will load also the output bias
tf_to_pt_map['model/lm_loss/bias'] = model.lm_loss.bias
if hasattr(model, 'sequence_summary') and 'model/sequnece_summary/summary/kernel' in tf_weights:
# We will load also the sequence summary
tf_to_pt_map['model/sequnece_summary/summary/kernel'] = model.sequence_summary.summary.weight
tf_to_pt_map['model/sequnece_summary/summary/bias'] = model.sequence_summary.summary.bias
if hasattr(model, 'logits_proj') and config.finetuning_task is not None \
and 'model/regression_{}/logit/kernel'.format(config.finetuning_task) in tf_weights:
tf_to_pt_map['model/regression_{}/logit/kernel'.format(config.finetuning_task)] = model.logits_proj.weight
tf_to_pt_map['model/regression_{}/logit/bias'.format(config.finetuning_task)] = model.logits_proj.bias
# Now load the rest of the transformer
model = model.transformer
# Embeddings and output
tf_to_pt_map.update({'model/transformer/word_embedding/lookup_table': model.word_embedding.weight,
'model/transformer/mask_emb/mask_emb': model.mask_emb})
# Transformer blocks
for i, b in enumerate(model.layer):
layer_str = "model/transformer/layer_%d/" % i
tf_to_pt_map.update({
layer_str + "rel_attn/LayerNorm/gamma": b.rel_attn.layer_norm.weight,
layer_str + "rel_attn/LayerNorm/beta": b.rel_attn.layer_norm.bias,
layer_str + "rel_attn/o/kernel": b.rel_attn.o,
layer_str + "rel_attn/q/kernel": b.rel_attn.q,
layer_str + "rel_attn/k/kernel": b.rel_attn.k,
layer_str + "rel_attn/r/kernel": b.rel_attn.r,
layer_str + "rel_attn/v/kernel": b.rel_attn.v,
layer_str + "ff/LayerNorm/gamma": b.ff.layer_norm.weight,
layer_str + "ff/LayerNorm/beta": b.ff.layer_norm.bias,
layer_str + "ff/layer_1/kernel": b.ff.layer_1.weight,
layer_str + "ff/layer_1/bias": b.ff.layer_1.bias,
layer_str + "ff/layer_2/kernel": b.ff.layer_2.weight,
layer_str + "ff/layer_2/bias": b.ff.layer_2.bias,
})
# Relative positioning biases
if config.untie_r:
r_r_list = []
r_w_list = []
r_s_list = []
seg_embed_list = []
for b in model.layer:
r_r_list.append(b.rel_attn.r_r_bias)
r_w_list.append(b.rel_attn.r_w_bias)
r_s_list.append(b.rel_attn.r_s_bias)
seg_embed_list.append(b.rel_attn.seg_embed)
else:
r_r_list = [model.r_r_bias]
r_w_list = [model.r_w_bias]
r_s_list = [model.r_s_bias]
seg_embed_list = [model.seg_embed]
tf_to_pt_map.update({
'model/transformer/r_r_bias': r_r_list,
'model/transformer/r_w_bias': r_w_list,
'model/transformer/r_s_bias': r_s_list,
'model/transformer/seg_embed': seg_embed_list})
return tf_to_pt_map
def load_tf_weights_in_xlnet(model, config, tf_path):
""" Load tf checkpoints in a pytorch model
"""
try:
import numpy as np
import tensorflow as tf
except ImportError:
logger.error("Loading a TensorFlow models in PyTorch, requires TensorFlow to be installed. Please see "
"https://www.tensorflow.org/install/ for installation instructions.")
raise
# Load weights from TF model
init_vars = tf.train.list_variables(tf_path)
tf_weights = {}
for name, shape in init_vars:
logger.info("Loading TF weight {} with shape {}".format(name, shape))
array = tf.train.load_variable(tf_path, name)
tf_weights[name] = array
# Build TF to PyTorch weights loading map
tf_to_pt_map = build_tf_xlnet_to_pytorch_map(model, config, tf_weights)
for name, pointer in tf_to_pt_map.items():
logger.info("Importing {}".format(name))
if name not in tf_weights:
logger.info("{} not in tf pre-trained weights, skipping".format(name))
continue
array = tf_weights[name]
# adam_v and adam_m are variables used in AdamWeightDecayOptimizer to calculated m and v
# which are not required for using pretrained model
if 'kernel' in name and ('ff' in name or 'summary' in name or 'logit' in name):
logger.info("Transposing")
array = np.transpose(array)
if isinstance(pointer, list):
# Here we will split the TF weigths
assert len(pointer) == array.shape[0]
for i, p_i in enumerate(pointer):
arr_i = array[i, ...]
try:
assert p_i.shape == arr_i.shape
except AssertionError as e:
e.args += (p_i.shape, arr_i.shape)
raise
logger.info("Initialize PyTorch weight {} for layer {}".format(name, i))
p_i.data = torch.from_numpy(arr_i)
else:
try:
assert pointer.shape == array.shape
except AssertionError as e:
e.args += (pointer.shape, array.shape)
raise
logger.info("Initialize PyTorch weight {}".format(name))
pointer.data = torch.from_numpy(array)
tf_weights.pop(name, None)
tf_weights.pop(name + '/Adam', None)
tf_weights.pop(name + '/Adam_1', None)
logger.info("Weights not copied to PyTorch model: {}".format(', '.join(tf_weights.keys())))
return model
def gelu(x):
""" Implementation of the gelu activation function.
XLNet is using OpenAI GPT's gelu (not exactly the same as BERT)
Also see https://arxiv.org/abs/1606.08415
"""
cdf = 0.5 * (1.0 + torch.tanh(math.sqrt(2 / math.pi) * (x + 0.044715 * torch.pow(x, 3))))
return x * cdf
def swish(x):
return x * torch.sigmoid(x)
ACT2FN = {"gelu": gelu, "relu": torch.nn.functional.relu, "swish": swish}
class XLNetConfig(PretrainedConfig):
"""Configuration class to store the configuration of a ``XLNetModel``.
Args:
vocab_size_or_config_json_file: Vocabulary size of ``inputs_ids`` in ``XLNetModel``.
d_model: Size of the encoder layers and the pooler layer.
n_layer: Number of hidden layers in the Transformer encoder.
n_head: Number of attention heads for each attention layer in
the Transformer encoder.
d_inner: The size of the "intermediate" (i.e., feed-forward)
layer in the Transformer encoder.
ff_activation: The non-linear activation function (function or string) in the
encoder and pooler. If string, "gelu", "relu" and "swish" are supported.
untie_r: untie relative position biases
attn_type: 'bi' for XLNet, 'uni' for Transformer-XL
dropout: The dropout probabilitiy for all fully connected
layers in the embeddings, encoder, and pooler.
dropatt: The dropout ratio for the attention
probabilities.
initializer_range: The sttdev of the truncated_normal_initializer for
initializing all weight matrices.
layer_norm_eps: The epsilon used by LayerNorm.
dropout: float, dropout rate.
dropatt: float, dropout rate on attention probabilities.
init: str, the initialization scheme, either "normal" or "uniform".
init_range: float, initialize the parameters with a uniform distribution
in [-init_range, init_range]. Only effective when init="uniform".
init_std: float, initialize the parameters with a normal distribution
with mean 0 and stddev init_std. Only effective when init="normal".
mem_len: int, the number of tokens to cache.
reuse_len: int, the number of tokens in the currect batch to be cached
and reused in the future.
bi_data: bool, whether to use bidirectional input pipeline.
Usually set to True during pretraining and False during finetuning.
clamp_len: int, clamp all relative distances larger than clamp_len.
-1 means no clamping.
same_length: bool, whether to use the same attention length for each token.
finetuning_task: name of the glue task on which the model was fine-tuned if any
"""
pretrained_config_archive_map = XLNET_PRETRAINED_CONFIG_ARCHIVE_MAP
def __init__(self,
vocab_size_or_config_json_file=32000,
d_model=1024,
n_layer=24,
n_head=16,
d_inner=4096,
ff_activation="gelu",
untie_r=True,
attn_type="bi",
initializer_range=0.02,
layer_norm_eps=1e-12,
dropout=0.1,
mem_len=None,
reuse_len=None,
bi_data=False,
clamp_len=-1,
same_length=False,
finetuning_task=None,
num_labels=2,
summary_type='last',
summary_use_proj=True,
summary_activation='tanh',
summary_last_dropout=0.1,
start_n_top=5,
end_n_top=5,
**kwargs):
"""Constructs XLNetConfig.
"""
super(XLNetConfig, self).__init__(**kwargs)
if isinstance(vocab_size_or_config_json_file, str) or (sys.version_info[0] == 2
and isinstance(vocab_size_or_config_json_file, unicode)):
with open(vocab_size_or_config_json_file, "r", encoding='utf-8') as reader:
json_config = json.loads(reader.read())
for key, value in json_config.items():
self.__dict__[key] = value
elif isinstance(vocab_size_or_config_json_file, int):
self.n_token = vocab_size_or_config_json_file
self.d_model = d_model
self.n_layer = n_layer
self.n_head = n_head
assert d_model % n_head == 0
self.d_head = d_model // n_head
self.ff_activation = ff_activation
self.d_inner = d_inner
self.untie_r = untie_r
self.attn_type = attn_type
self.initializer_range = initializer_range
self.layer_norm_eps = layer_norm_eps
self.dropout = dropout
self.mem_len = mem_len
self.reuse_len = reuse_len
self.bi_data = bi_data
self.clamp_len = clamp_len
self.same_length = same_length
self.finetuning_task = finetuning_task
self.num_labels = num_labels
self.summary_type = summary_type
self.summary_use_proj = summary_use_proj
self.summary_activation = summary_activation
self.summary_last_dropout = summary_last_dropout
self.start_n_top = start_n_top
self.end_n_top = end_n_top
else:
raise ValueError("First argument must be either a vocabulary size (int)"
"or the path to a pretrained model config file (str)")
@property
def max_position_embeddings(self):
return -1
@property
def vocab_size(self):
return self.n_token
@vocab_size.setter
def vocab_size(self, value):
self.n_token = value
@property
def hidden_size(self):
return self.d_model
@property
def num_attention_heads(self):
return self.n_head
@property
def num_hidden_layers(self):
return self.n_layer
try:
from apex.normalization.fused_layer_norm import FusedLayerNorm as XLNetLayerNorm
except (ImportError, AttributeError) as e:
logger.info("Better speed can be achieved with apex installed from https://www.github.com/nvidia/apex .")
class XLNetLayerNorm(nn.Module):
def __init__(self, d_model, eps=1e-12):
"""Construct a layernorm module in the TF style (epsilon inside the square root).
"""
super(XLNetLayerNorm, self).__init__()
self.weight = nn.Parameter(torch.ones(d_model))
self.bias = nn.Parameter(torch.zeros(d_model))
self.variance_epsilon = eps
def forward(self, x):
u = x.mean(-1, keepdim=True)
s = (x - u).pow(2).mean(-1, keepdim=True)
x = (x - u) / torch.sqrt(s + self.variance_epsilon)
return self.weight * x + self.bias
class XLNetRelativeAttention(nn.Module):
def __init__(self, config):
super(XLNetRelativeAttention, self).__init__()
self.output_attentions = config.output_attentions
if config.d_model % config.n_head != 0:
raise ValueError(
"The hidden size (%d) is not a multiple of the number of attention "
"heads (%d)" % (config.d_model, config.n_head))
self.n_head = config.n_head
self.d_head = config.d_head
self.d_model = config.d_model
self.scale = 1 / (config.d_head ** 0.5)
self.q = nn.Parameter(torch.FloatTensor(config.d_model, self.n_head, self.d_head))
self.k = nn.Parameter(torch.FloatTensor(config.d_model, self.n_head, self.d_head))
self.v = nn.Parameter(torch.FloatTensor(config.d_model, self.n_head, self.d_head))
self.o = nn.Parameter(torch.FloatTensor(config.d_model, self.n_head, self.d_head))
self.r = nn.Parameter(torch.FloatTensor(config.d_model, self.n_head, self.d_head))
self.r_r_bias = nn.Parameter(torch.FloatTensor(self.n_head, self.d_head))
self.r_s_bias = nn.Parameter(torch.FloatTensor(self.n_head, self.d_head))
self.r_w_bias = nn.Parameter(torch.FloatTensor(self.n_head, self.d_head))
self.seg_embed = nn.Parameter(torch.FloatTensor(2, self.n_head, self.d_head))
self.layer_norm = XLNetLayerNorm(config.d_model, eps=config.layer_norm_eps)
self.dropout = nn.Dropout(config.dropout)
def prune_heads(self, heads):
raise NotImplementedError
@staticmethod
def rel_shift(x, klen=-1):
"""perform relative shift to form the relative attention score."""
x_size = x.shape
x = x.reshape(x_size[1], x_size[0], x_size[2], x_size[3])
x = x[1:, ...]
x = x.reshape(x_size[0], x_size[1] - 1, x_size[2], x_size[3])
# x = x[:, 0:klen, :, :]
x = torch.index_select(x, 1, torch.arange(klen, device=x.device, dtype=torch.long))
return x
def rel_attn_core(self, q_head, k_head_h, v_head_h, k_head_r, seg_mat=None, attn_mask=None, head_mask=None):
"""Core relative positional attention operations."""
# content based attention score
ac = torch.einsum('ibnd,jbnd->ijbn', q_head + self.r_w_bias, k_head_h)
# position based attention score
bd = torch.einsum('ibnd,jbnd->ijbn', q_head + self.r_r_bias, k_head_r)
bd = self.rel_shift(bd, klen=ac.shape[1])
# segment based attention score
if seg_mat is None:
ef = 0
else:
ef = torch.einsum('ibnd,snd->ibns', q_head + self.r_s_bias, self.seg_embed)
ef = torch.einsum('ijbs,ibns->ijbn', seg_mat, ef)
# merge attention scores and perform masking
attn_score = (ac + bd + ef) * self.scale
if attn_mask is not None:
# attn_score = attn_score * (1 - attn_mask) - 1e30 * attn_mask
attn_score = attn_score - 1e30 * attn_mask
# attention probability
attn_prob = F.softmax(attn_score, dim=1)
attn_prob = self.dropout(attn_prob)
# Mask heads if we want to
if head_mask is not None:
attn_prob = attn_prob * head_mask
# attention output
attn_vec = torch.einsum('ijbn,jbnd->ibnd', attn_prob, v_head_h)
if self.output_attentions:
return attn_vec, attn_prob
return attn_vec
def post_attention(self, h, attn_vec, residual=True):
"""Post-attention processing."""
# post-attention projection (back to `d_model`)
attn_out = torch.einsum('ibnd,hnd->ibh', attn_vec, self.o)
attn_out = self.dropout(attn_out)
if residual:
attn_out = attn_out + h
output = self.layer_norm(attn_out)
return output
def forward(self, h, g,
attn_mask_h, attn_mask_g,
r, seg_mat,
mems=None, target_mapping=None, head_mask=None):
if g is not None:
###### Two-stream attention with relative positional encoding.
# content based attention score
if mems is not None and mems.dim() > 1:
cat = torch.cat([mems, h], dim=0)
else:
cat = h
# content-based key head
k_head_h = torch.einsum('ibh,hnd->ibnd', cat, self.k)
# content-based value head
v_head_h = torch.einsum('ibh,hnd->ibnd', cat, self.v)
# position-based key head
k_head_r = torch.einsum('ibh,hnd->ibnd', r, self.r)
##### h-stream
# content-stream query head
q_head_h = torch.einsum('ibh,hnd->ibnd', h, self.q)
# core attention ops
attn_vec_h = self.rel_attn_core(
q_head_h, k_head_h, v_head_h, k_head_r, seg_mat=seg_mat, attn_mask=attn_mask_h, head_mask=head_mask)
if self.output_attentions:
attn_vec_h, attn_prob_h = attn_vec_h
# post processing
output_h = self.post_attention(h, attn_vec_h)
##### g-stream
# query-stream query head
q_head_g = torch.einsum('ibh,hnd->ibnd', g, self.q)
# core attention ops
if target_mapping is not None:
q_head_g = torch.einsum('mbnd,mlb->lbnd', q_head_g, target_mapping)
attn_vec_g = self.rel_attn_core(
q_head_g, k_head_h, v_head_h, k_head_r, seg_mat=seg_mat, attn_mask=attn_mask_g, head_mask=head_mask)
if self.output_attentions:
attn_vec_g, attn_prob_g = attn_vec_g
attn_vec_g = torch.einsum('lbnd,mlb->mbnd', attn_vec_g, target_mapping)
else:
attn_vec_g = self.rel_attn_core(
q_head_g, k_head_h, v_head_h, k_head_r, seg_mat=seg_mat, attn_mask=attn_mask_g, head_mask=head_mask)
if self.output_attentions:
attn_vec_g, attn_prob_g = attn_vec_g
# post processing
output_g = self.post_attention(g, attn_vec_g)
if self.output_attentions:
attn_prob = attn_prob_h, attn_prob_g
else:
###### Multi-head attention with relative positional encoding
if mems is not None and mems.dim() > 1:
cat = torch.cat([mems, h], dim=0)
else:
cat = h
# content heads
q_head_h = torch.einsum('ibh,hnd->ibnd', h, self.q)
k_head_h = torch.einsum('ibh,hnd->ibnd', cat, self.k)
v_head_h = torch.einsum('ibh,hnd->ibnd', cat, self.v)
# positional heads
k_head_r = torch.einsum('ibh,hnd->ibnd', r, self.r)
# core attention ops
attn_vec = self.rel_attn_core(
q_head_h, k_head_h, v_head_h, k_head_r, seg_mat=seg_mat, attn_mask=attn_mask_h, head_mask=head_mask)
if self.output_attentions:
attn_vec, attn_prob = attn_vec
# post processing
output_h = self.post_attention(h, attn_vec)
output_g = None
outputs = (output_h, output_g)
if self.output_attentions:
outputs = outputs + (attn_prob,)
return outputs
class XLNetFeedForward(nn.Module):
def __init__(self, config):
super(XLNetFeedForward, self).__init__()
self.layer_norm = XLNetLayerNorm(config.d_model, eps=config.layer_norm_eps)
self.layer_1 = nn.Linear(config.d_model, config.d_inner)
self.layer_2 = nn.Linear(config.d_inner, config.d_model)
self.dropout = nn.Dropout(config.dropout)
if isinstance(config.ff_activation, str) or \
(sys.version_info[0] == 2 and isinstance(config.ff_activation, unicode)):
self.activation_function = ACT2FN[config.ff_activation]
else:
self.activation_function = config.ff_activation
def forward(self, inp):
output = inp
output = self.layer_1(output)
output = self.activation_function(output)
output = self.dropout(output)
output = self.layer_2(output)
output = self.dropout(output)
output = self.layer_norm(output + inp)
return output
class XLNetLayer(nn.Module):
def __init__(self, config):
super(XLNetLayer, self).__init__()
self.rel_attn = XLNetRelativeAttention(config)
self.ff = XLNetFeedForward(config)
self.dropout = nn.Dropout(config.dropout)
def forward(self, output_h, output_g,
attn_mask_h, attn_mask_g,
r, seg_mat, mems=None, target_mapping=None, head_mask=None):
outputs = self.rel_attn(output_h, output_g, attn_mask_h, attn_mask_g,
r, seg_mat, mems=mems, target_mapping=target_mapping,
head_mask=head_mask)
output_h, output_g = outputs[:2]
if output_g is not None:
output_g = self.ff(output_g)
output_h = self.ff(output_h)
outputs = (output_h, output_g) + outputs[2:] # Add again attentions if there are there
return outputs
class XLNetPreTrainedModel(PreTrainedModel):
""" An abstract class to handle weights initialization and
a simple interface for dowloading and loading pretrained models.
"""
config_class = XLNetConfig
pretrained_model_archive_map = XLNET_PRETRAINED_MODEL_ARCHIVE_MAP
load_tf_weights = load_tf_weights_in_xlnet
base_model_prefix = "transformer"
def __init__(self, *inputs, **kwargs):
super(XLNetPreTrainedModel, self).__init__(*inputs, **kwargs)
def init_weights(self, module):
""" Initialize the weights.
"""
if isinstance(module, (nn.Linear, nn.Embedding)):
# Slightly different from the TF version which uses truncated_normal for initialization
# cf https://github.com/pytorch/pytorch/pull/5617
module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
if isinstance(module, nn.Linear) and module.bias is not None:
module.bias.data.zero_()
elif isinstance(module, XLNetLayerNorm):
module.bias.data.zero_()
module.weight.data.fill_(1.0)
elif isinstance(module, XLNetRelativeAttention):
for param in [module.q, module.k, module.v, module.o, module.r,
module.r_r_bias, module.r_s_bias, module.r_w_bias,
module.seg_embed]:
param.data.normal_(mean=0.0, std=self.config.initializer_range)
elif isinstance(module, XLNetModel):
module.mask_emb.data.normal_(mean=0.0, std=self.config.initializer_range)
XLNET_START_DOCSTRING = r""" The XLNet model was proposed in
`XLNet: Generalized Autoregressive Pretraining for Language Understanding`_
by Zhilin Yang*, Zihang Dai*, Yiming Yang, Jaime Carbonell, Ruslan Salakhutdinov, Quoc V. Le.
XLnet is an extension of the Transformer-XL model pre-trained using an autoregressive method
to learn bidirectional contexts by maximizing the expected likelihood over all permutations
of the input sequence factorization order.
The specific attention pattern can be controlled at training and test time using the `perm_mask` input.
Do to the difficulty of training a fully auto-regressive model over various factorization order,
XLNet is pretrained using only a sub-set of the output tokens as target which are selected
with the `target_mapping` input.
To use XLNet for sequential decoding (i.e. not in fully bi-directional setting), use the `perm_mask` and
`target_mapping` inputs to control the attention span and outputs (see examples in `examples/run_generation.py`)
This model is a PyTorch `torch.nn.Module`_ sub-class. Use it as a regular PyTorch Module and
refer to the PyTorch documentation for all matter related to general usage and behavior.
.. _`XLNet: Generalized Autoregressive Pretraining for Language Understanding`:
http://arxiv.org/abs/1906.08237
.. _`torch.nn.Module`:
https://pytorch.org/docs/stable/nn.html#module
Parameters:
config (:class:`~pytorch_transformers.XLNetConfig`): 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:`~pytorch_transformers.PreTrainedModel.from_pretrained` method to load the model weights.
"""
XLNET_INPUTS_DOCSTRING = r"""
Inputs:
**input_ids**: ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
Indices of input sequence tokens in the vocabulary.
XLNet is a model with relative position embeddings so you can either pad the inputs on
the right or on the left.
Indices can be obtained using :class:`pytorch_transformers.XLNetTokenizer`.
See :func:`pytorch_transformers.PreTrainedTokenizer.encode` and
:func:`pytorch_transformers.PreTrainedTokenizer.convert_tokens_to_ids` for details.
**token_type_ids**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
A parallel sequence of tokens (can be used to indicate various portions of the inputs).
The embeddings from these tokens will be summed with the respective token embeddings.
Indices are selected in the vocabulary (unlike BERT which has a specific vocabulary for segment indices).
**attention_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length)``:
Mask to avoid performing attention on padding token indices.
Mask values selected in ``[0, 1]``:
``1`` for tokens that are NOT MASKED, ``0`` for MASKED tokens.
**input_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length)``:
Mask to avoid performing attention on padding token indices.
Negative of `attention_mask`, i.e. with 0 for real tokens and 1 for padding.
Kept for compatibility with the original code base.
You can only uses one of `input_mask` and `attention_mask`
Mask values selected in ``[0, 1]``:
``1`` for tokens that are MASKED, ``0`` for tokens that are NOT MASKED.
**mems**: (`optional`)
list of ``torch.FloatTensor`` (one for each layer):
that 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 and attend to longer context.
**perm_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, sequence_length)``:
Mask to indicate the attention pattern for each input token with values selected in ``[0, 1]``:
If ``perm_mask[k, i, j] = 0``, i attend to j in batch k;
if ``perm_mask[k, i, j] = 1``, i does not attend to j in batch k.
If None, each token attends to all the others (full bidirectional attention).
Only used during pretraining (to define factorization order) or for sequential decoding (generation).
**target_mapping**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, num_predict, sequence_length)``:
Mask to indicate the output tokens to use.
If ``target_mapping[k, i, j] = 1``, the i-th predict in batch k is on the j-th token.
Only used during pretraining for partial prediction or for sequential decoding (generation).
**head_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(num_heads,)`` or ``(num_layers, num_heads)``:
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**.
"""
@add_start_docstrings("The bare XLNet Model transformer outputing raw hidden-states without any specific head on top.",
XLNET_START_DOCSTRING, XLNET_INPUTS_DOCSTRING)
class XLNetModel(XLNetPreTrainedModel):
r"""
Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:
**last_hidden_state**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, hidden_size)``
Sequence of hidden-states at the last layer of the model.
**mems**:
list of ``torch.FloatTensor`` (one for each layer):
that contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
(see `mems` input above). Can be used to speed up sequential decoding and attend to longer context.
**hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)
list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)
of shape ``(batch_size, sequence_length, hidden_size)``:
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
**attentions**: (`optional`, returned when ``config.output_attentions=True``)
list of ``torch.FloatTensor`` (one for each layer) of shape ``(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.
Examples::
tokenizer = XLNetTokenizer.from_pretrained('xlnet-large-cased')
model = XLNetModel.from_pretrained('xlnet-large-cased')
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute")).unsqueeze(0) # Batch size 1
outputs = model(input_ids)
last_hidden_states = outputs[0] # The last hidden-state is the first element of the output tuple
"""
def __init__(self, config):
super(XLNetModel, self).__init__(config)
self.output_attentions = config.output_attentions
self.output_hidden_states = config.output_hidden_states
self.mem_len = config.mem_len
self.reuse_len = config.reuse_len
self.d_model = config.d_model
self.same_length = config.same_length
self.attn_type = config.attn_type
self.bi_data = config.bi_data
self.clamp_len = config.clamp_len
self.n_layer = config.n_layer
self.word_embedding = nn.Embedding(config.n_token, config.d_model)
self.mask_emb = nn.Parameter(torch.FloatTensor(1, 1, config.d_model))
self.layer = nn.ModuleList([XLNetLayer(config) for _ in range(config.n_layer)])
self.dropout = nn.Dropout(config.dropout)
self.apply(self.init_weights)
def _resize_token_embeddings(self, new_num_tokens):
self.word_embedding = self._get_resized_embeddings(self.word_embedding, new_num_tokens)
return self.word_embedding
def _prune_heads(self, heads_to_prune):
raise NotImplementedError
def create_mask(self, qlen, mlen):
"""
Creates causal attention mask. Float mask where 1.0 indicates masked, 0.0 indicates not-masked.
Args:
qlen: TODO Lysandre didn't fill
mlen: TODO Lysandre didn't fill
::
same_length=False: same_length=True:
<mlen > < qlen > <mlen > < qlen >
^ [0 0 0 0 0 1 1 1 1] [0 0 0 0 0 1 1 1 1]
[0 0 0 0 0 0 1 1 1] [1 0 0 0 0 0 1 1 1]
qlen [0 0 0 0 0 0 0 1 1] [1 1 0 0 0 0 0 1 1]
[0 0 0 0 0 0 0 0 1] [1 1 1 0 0 0 0 0 1]
v [0 0 0 0 0 0 0 0 0] [1 1 1 1 0 0 0 0 0]
"""
attn_mask = torch.ones([qlen, qlen])
mask_up = torch.triu(attn_mask, diagonal=1)
attn_mask_pad = torch.zeros([qlen, mlen])
ret = torch.cat([attn_mask_pad, mask_up], dim=1)
if self.same_length:
mask_lo = torch.tril(attn_mask, diagonal=-1)
ret = torch.cat([ret[:, :qlen] + mask_lo, ret[:, qlen:]], dim=1)
ret = ret.to(next(self.parameters()))
return ret
def cache_mem(self, curr_out, prev_mem):
"""cache hidden states into memory."""
if self.mem_len is None or self.mem_len == 0:
return None
else:
if self.reuse_len is not None and self.reuse_len > 0:
curr_out = curr_out[:self.reuse_len]
if prev_mem is None:
new_mem = curr_out[-self.mem_len:]
else:
new_mem = torch.cat([prev_mem, curr_out], dim=0)[-self.mem_len:]
return new_mem.detach()
@staticmethod
def positional_embedding(pos_seq, inv_freq, bsz=None):
sinusoid_inp = torch.einsum('i,d->id', pos_seq, inv_freq)
pos_emb = torch.cat([torch.sin(sinusoid_inp), torch.cos(sinusoid_inp)], dim=-1)
pos_emb = pos_emb[:, None, :]
if bsz is not None:
pos_emb = pos_emb.expand(-1, bsz, -1)
return pos_emb
def relative_positional_encoding(self, qlen, klen, bsz=None):
"""create relative positional encoding."""
freq_seq = torch.arange(0, self.d_model, 2.0, dtype=torch.float)
inv_freq = 1 / torch.pow(10000, (freq_seq / self.d_model))
if self.attn_type == 'bi':
# beg, end = klen - 1, -qlen
beg, end = klen, -qlen
elif self.attn_type == 'uni':
# beg, end = klen - 1, -1
beg, end = klen, -1
else:
raise ValueError('Unknown `attn_type` {}.'.format(self.attn_type))
if self.bi_data:
fwd_pos_seq = torch.arange(beg, end, -1.0, dtype=torch.float)
bwd_pos_seq = torch.arange(-beg, -end, 1.0, dtype=torch.float)
if self.clamp_len > 0:
fwd_pos_seq = fwd_pos_seq.clamp(-self.clamp_len, self.clamp_len)
bwd_pos_seq = bwd_pos_seq.clamp(-self.clamp_len, self.clamp_len)
if bsz is not None:
fwd_pos_emb = self.positional_embedding(fwd_pos_seq, inv_freq, bsz//2)
bwd_pos_emb = self.positional_embedding(bwd_pos_seq, inv_freq, bsz//2)
else:
fwd_pos_emb = self.positional_embedding(fwd_pos_seq, inv_freq)
bwd_pos_emb = self.positional_embedding(bwd_pos_seq, inv_freq)
pos_emb = torch.cat([fwd_pos_emb, bwd_pos_emb], dim=1)
else:
fwd_pos_seq = torch.arange(beg, end, -1.0)
if self.clamp_len > 0:
fwd_pos_seq = fwd_pos_seq.clamp(-self.clamp_len, self.clamp_len)
pos_emb = self.positional_embedding(fwd_pos_seq, inv_freq, bsz)
pos_emb = pos_emb.to(next(self.parameters()))
return pos_emb
def forward(self, input_ids, token_type_ids=None, input_mask=None, attention_mask=None,
mems=None, perm_mask=None, target_mapping=None, head_mask=None):
# the original code for XLNet uses shapes [len, bsz] with the batch dimension at the end
# but we want a unified interface in the library with the batch size on the first dimension
# so we move here the first dimension (batch) to the end
input_ids = input_ids.transpose(0, 1).contiguous()
token_type_ids = token_type_ids.transpose(0, 1).contiguous() if token_type_ids is not None else None
input_mask = input_mask.transpose(0, 1).contiguous() if input_mask is not None else None
attention_mask = attention_mask.transpose(0, 1).contiguous() if attention_mask is not None else None
perm_mask = perm_mask.permute(1, 2, 0).contiguous() if perm_mask is not None else None
target_mapping = target_mapping.permute(1, 2, 0).contiguous() if target_mapping is not None else None
qlen, bsz = input_ids.shape[0], input_ids.shape[1]
mlen = mems[0].shape[0] if mems is not None else 0
klen = mlen + qlen
dtype_float = next(self.parameters()).dtype
device = next(self.parameters()).device
##### Attention mask
# causal attention mask
if self.attn_type == 'uni':
attn_mask = self.create_mask(qlen, mlen)
attn_mask = attn_mask[:, :, None, None]
elif self.attn_type == 'bi':
attn_mask = None
else:
raise ValueError('Unsupported attention type: {}'.format(self.attn_type))
# data mask: input mask & perm mask
assert input_mask is None or attention_mask is None, "You can only use one of input_mask (uses 1 for padding) "
"or attention_mask (uses 0 for padding, added for compatbility with BERT). Please choose one."
if input_mask is None and attention_mask is not None:
input_mask = 1.0 - attention_mask
if input_mask is not None and perm_mask is not None:
data_mask = input_mask[None] + perm_mask
elif input_mask is not None and perm_mask is None:
data_mask = input_mask[None]
elif input_mask is None and perm_mask is not None:
data_mask = perm_mask
else:
data_mask = None
if data_mask is not None:
# all mems can be attended to
mems_mask = torch.zeros([data_mask.shape[0], mlen, bsz]).to(data_mask)
data_mask = torch.cat([mems_mask, data_mask], dim=1)
if attn_mask is None:
attn_mask = data_mask[:, :, :, None]
else:
attn_mask += data_mask[:, :, :, None]
if attn_mask is not None:
attn_mask = (attn_mask > 0).to(dtype_float)
if attn_mask is not None:
non_tgt_mask = -torch.eye(qlen).to(attn_mask)
non_tgt_mask = torch.cat([torch.zeros([qlen, mlen]).to(attn_mask), non_tgt_mask], dim=-1)
non_tgt_mask = ((attn_mask + non_tgt_mask[:, :, None, None]) > 0).to(attn_mask)
else:
non_tgt_mask = None
##### Word embeddings and prepare h & g hidden states
word_emb_k = self.word_embedding(input_ids)
output_h = self.dropout(word_emb_k)
if target_mapping is not None:
word_emb_q = self.mask_emb.expand(target_mapping.shape[0], bsz, -1)
# else: # We removed the inp_q input which was same as target mapping
# inp_q_ext = inp_q[:, :, None]
# word_emb_q = inp_q_ext * self.mask_emb + (1 - inp_q_ext) * word_emb_k
output_g = self.dropout(word_emb_q)
else:
output_g = None
##### Segment embedding
if token_type_ids is not None:
# Convert `token_type_ids` to one-hot `seg_mat`
mem_pad = torch.zeros([mlen, bsz], dtype=torch.long, device=device)
cat_ids = torch.cat([mem_pad, token_type_ids], dim=0)
# `1` indicates not in the same segment [qlen x klen x bsz]
seg_mat = (token_type_ids[:, None] != cat_ids[None, :]).long()
seg_mat = F.one_hot(seg_mat, num_classes=2).to(dtype_float)
else:
seg_mat = None
##### Positional encoding
pos_emb = self.relative_positional_encoding(qlen, klen, bsz=bsz)
pos_emb = self.dropout(pos_emb)
# 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:
if head_mask.dim() == 1:
head_mask = head_mask.unsqueeze(0).unsqueeze(0).unsqueeze(0).unsqueeze(0)
head_mask = head_mask.expand(self.n_layer, -1, -1, -1, -1)
elif head_mask.dim() == 2:
head_mask = head_mask.unsqueeze(1).unsqueeze(1).unsqueeze(1)
head_mask = head_mask.to(dtype=next(self.parameters()).dtype) # switch to fload if need + fp16 compatibility
else:
head_mask = [None] * self.n_layer
new_mems = ()
if mems is None:
mems = [None] * len(self.layer)
attentions = []
hidden_states = []
for i, layer_module in enumerate(self.layer):
# cache new mems
new_mems = new_mems + (self.cache_mem(output_h, mems[i]),)
if self.output_hidden_states:
hidden_states.append((output_h, output_g) if output_g is not None else output_h)
outputs = layer_module(output_h, output_g, attn_mask_h=non_tgt_mask, attn_mask_g=attn_mask,
r=pos_emb, seg_mat=seg_mat, mems=mems[i], target_mapping=target_mapping,
head_mask=head_mask[i])
output_h, output_g = outputs[:2]
if self.output_attentions:
attentions.append(outputs[2])
# Add last hidden state
if self.output_hidden_states:
hidden_states.append((output_h, output_g) if output_g is not None else output_h)
output = self.dropout(output_g if output_g is not None else output_h)
# Prepare outputs, we transpose back here to shape [bsz, len, hidden_dim] (cf. beginning of forward() method)
outputs = (output.permute(1, 0, 2).contiguous(), new_mems)
if self.output_hidden_states:
if output_g is not None:
hidden_states = tuple(h.permute(1, 0, 2).contiguous() for hs in hidden_states for h in hs)
else:
hidden_states = tuple(hs.permute(1, 0, 2).contiguous() for hs in hidden_states)
outputs = outputs + (hidden_states,)
if self.output_attentions:
attentions = tuple(t.permute(2, 3, 0, 1).contiguous() for t in attentions)
outputs = outputs + (attentions,)
return outputs # outputs, new_mems, (hidden_states), (attentions)
@add_start_docstrings("""XLNet Model with a language modeling head on top
(linear layer with weights tied to the input embeddings). """,
XLNET_START_DOCSTRING, XLNET_INPUTS_DOCSTRING)
class XLNetLMHeadModel(XLNetPreTrainedModel):
r"""
**labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
Labels for language modeling.
Note that the labels **are shifted** inside the model, i.e. you can set ``lm_labels = input_ids``
Indices are selected in ``[-1, 0, ..., config.vocab_size]``
All labels set to ``-1`` are ignored (masked), the loss is only
computed for labels in ``[0, ..., config.vocab_size]``
Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:
**loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:
Language modeling loss.
**prediction_scores**: ``torch.FloatTensor`` of shape ``(batch_size, sequence_length, config.vocab_size)``
Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).
**mems**:
list of ``torch.FloatTensor`` (one for each layer):
that contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
(see `mems` input above). Can be used to speed up sequential decoding and attend to longer context.
**hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)
list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)
of shape ``(batch_size, sequence_length, hidden_size)``:
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
**attentions**: (`optional`, returned when ``config.output_attentions=True``)
list of ``torch.FloatTensor`` (one for each layer) of shape ``(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.
Examples::
tokenizer = XLNetTokenizer.from_pretrained('xlnet-large-cased')
model = XLNetLMHeadModel.from_pretrained('xlnet-large-cased')
# We show how to setup inputs to predict a next token using a bi-directional context.
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is very <mask>")).unsqueeze(0) # We will predict the masked token
perm_mask = torch.zeros((1, input_ids.shape[1], input_ids.shape[1]), dtype=torch.float)
perm_mask[:, :, -1] = 1.0 # Previous tokens don't see last token
target_mapping = torch.zeros((1, 1, input_ids.shape[1]), dtype=torch.float) # Shape [1, 1, seq_length] => let's predict one token
target_mapping[0, 0, -1] = 1.0 # Our first (and only) prediction will be the last token of the sequence (the masked token)
outputs = model(input_ids, perm_mask=perm_mask, target_mapping=target_mapping)
next_token_logits = outputs[0] # Output has shape [target_mapping.size(0), target_mapping.size(1), config.vocab_size]
"""
def __init__(self, config):
super(XLNetLMHeadModel, self).__init__(config)
self.attn_type = config.attn_type
self.same_length = config.same_length
self.transformer = XLNetModel(config)
self.lm_loss = nn.Linear(config.d_model, config.n_token, bias=True)
self.apply(self.init_weights)
self.tie_weights()
def tie_weights(self):
""" Make sure we are sharing the embeddings
"""
self._tie_or_clone_weights(self.lm_loss, self.transformer.word_embedding)
def forward(self, input_ids, token_type_ids=None, input_mask=None, attention_mask=None,
mems=None, perm_mask=None, target_mapping=None,
labels=None, head_mask=None):
transformer_outputs = self.transformer(input_ids, token_type_ids=token_type_ids,
input_mask=input_mask, attention_mask=attention_mask,
mems=mems, perm_mask=perm_mask, target_mapping=target_mapping,
head_mask=head_mask)
logits = self.lm_loss(transformer_outputs[0])
outputs = (logits,) + transformer_outputs[1:] # Keep mems, hidden states, attentions if there are in it
if labels is not None:
# Flatten the tokens
loss_fct = CrossEntropyLoss(ignore_index=-1)
loss = loss_fct(logits.view(-1, logits.size(-1)),
labels.view(-1))
outputs = (loss,) + outputs
return outputs # return (loss), logits, mems, (hidden states), (attentions)
@add_start_docstrings("""XLNet Model with a sequence classification/regression head on top (a linear layer on top of
the pooled output) e.g. for GLUE tasks. """,
XLNET_START_DOCSTRING, XLNET_INPUTS_DOCSTRING)
class XLNetForSequenceClassification(XLNetPreTrainedModel):
r"""
**labels**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
Labels for computing the sequence classification/regression loss.
Indices should be in ``[0, ..., config.num_labels - 1]``.
If ``config.num_labels == 1`` a regression loss is computed (Mean-Square loss),
If ``config.num_labels > 1`` a classification loss is computed (Cross-Entropy).
Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:
**loss**: (`optional`, returned when ``labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:
Classification (or regression if config.num_labels==1) loss.
**logits**: ``torch.FloatTensor`` of shape ``(batch_size, config.num_labels)``
Classification (or regression if config.num_labels==1) scores (before SoftMax).
**mems**:
list of ``torch.FloatTensor`` (one for each layer):
that contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
(see `mems` input above). Can be used to speed up sequential decoding and attend to longer context.
**hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)
list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)
of shape ``(batch_size, sequence_length, hidden_size)``:
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
**attentions**: (`optional`, returned when ``config.output_attentions=True``)
list of ``torch.FloatTensor`` (one for each layer) of shape ``(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.
Examples::
tokenizer = XLNetTokenizer.from_pretrained('xlnet-large-cased')
model = XLNetForSequenceClassification.from_pretrained('xlnet-large-cased')
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute")).unsqueeze(0) # Batch size 1
labels = torch.tensor([1]).unsqueeze(0) # Batch size 1
outputs = model(input_ids, labels=labels)
loss, logits = outputs[:2]
"""
def __init__(self, config):
super(XLNetForSequenceClassification, self).__init__(config)
self.num_labels = config.num_labels
self.dropout = nn.Dropout(config.lstm_dropout)
self.transformer = XLNetModel(config)
self.sequence_summary = SequenceSummary(config)
self.logits_proj = nn.Linear(config.lstm_hidden_size*2, self.config.num_labels)
self.W=[]
self.gru=[]
for i in range(config.lstm_layers):
self.W.append(nn.Linear(config.lstm_hidden_size*2, config.lstm_hidden_size*2))
self.gru.append(nn.GRU(config.hidden_size if i==0 else config.lstm_hidden_size*4, config.lstm_hidden_size,num_layers=1,bidirectional=True,batch_first=True).cuda() )
self.W=nn.ModuleList(self.W)
self.gru=nn.ModuleList(self.gru)
self.apply(self.init_weights)
def forward(self, input_ids, token_type_ids=None, input_mask=None, attention_mask=None,
mems=None, perm_mask=None, target_mapping=None,
labels=None, head_mask=None):
flat_input_ids = input_ids.view(-1, input_ids.size(-1))
flat_token_type_ids = token_type_ids.view(-1, token_type_ids.size(-1)) if token_type_ids is not None else None
flat_input_mask = input_mask.view(-1, token_type_ids.size(-1)) if input_mask is not None else None
flat_attention_mask = attention_mask.view(-1, attention_mask.size(-1)) if attention_mask is not None else None
flat_mems = mems.view(-1, mems.size(-1)) if mems is not None else None
flat_perm_mask = perm_mask.view(-1, perm_mask.size(-1)) if perm_mask is not None else None
flat_target_mapping = target_mapping.view(-1, target_mapping.size(-1)) if target_mapping is not None else None
flat_head_mask = head_mask.view(-1, head_mask.size(-1)) if head_mask is not None else None
transformer_outputs = self.transformer(flat_input_ids, token_type_ids=flat_token_type_ids,
input_mask=flat_input_mask, attention_mask=flat_attention_mask,
mems=flat_mems, perm_mask=flat_perm_mask, target_mapping=flat_target_mapping,
head_mask=flat_head_mask)
output = transformer_outputs[0][:,-1,:]
output = output.reshape(input_ids.size(0),input_ids.size(1),-1)
for w,gru in zip(self.W,self.gru):
try:
gru.flatten_parameters()
except:
pass
output, hidden = gru(output)
output = self.dropout(output)
hidden=hidden.permute(1,0,2).reshape(input_ids.size(0),-1).contiguous()
logits = self.logits_proj(hidden)
outputs = logits # Keep mems, hidden states, attentions if there are in it
if labels is not None:
if self.num_labels == 1:
# We are doing regression
loss_fct = MSELoss()
loss = loss_fct(logits.view(-1), labels.view(-1))
else:
loss_fct = CrossEntropyLoss()
loss = loss_fct(logits.view(-1, self.num_labels), labels.view(-1))
outputs = loss
else:
outputs = nn.functional.softmax(outputs,-1)
return outputs # return (loss), logits, mems, (hidden states), (attentions)
@add_start_docstrings("""XLNet Model with a span classification head on top for extractive question-answering tasks like SQuAD (a linear layers on top of
the hidden-states output to compute `span start logits` and `span end logits`). """,
XLNET_START_DOCSTRING, XLNET_INPUTS_DOCSTRING)
class XLNetForQuestionAnswering(XLNetPreTrainedModel):
r"""
**start_positions**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
Labels for position (index) of the start of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (`sequence_length`).
Position outside of the sequence are not taken into account for computing the loss.
**end_positions**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
Labels for position (index) of the end of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (`sequence_length`).
Position outside of the sequence are not taken into account for computing the loss.
**is_impossible**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
Labels whether a question has an answer or no answer (SQuAD 2.0)
**cls_index**: (`optional`) ``torch.LongTensor`` of shape ``(batch_size,)``:
Labels for position (index) of the classification token to use as input for computing plausibility of the answer.
**p_mask**: (`optional`) ``torch.FloatTensor`` of shape ``(batch_size, sequence_length)``:
Optional mask of tokens which can't be in answers (e.g. [CLS], [PAD], ...).
1.0 means token should be masked. 0.0 mean token is not masked.
Outputs: `Tuple` comprising various elements depending on the configuration (config) and inputs:
**loss**: (`optional`, returned if both ``start_positions`` and ``end_positions`` are provided) ``torch.FloatTensor`` of shape ``(1,)``:
Classification loss as the sum of start token, end token (and is_impossible if provided) classification losses.
**start_top_log_probs**: (`optional`, returned if ``start_positions`` or ``end_positions`` is not provided)
``torch.FloatTensor`` of shape ``(batch_size, config.start_n_top)``
Log probabilities for the top config.start_n_top start token possibilities (beam-search).
**start_top_index**: (`optional`, returned if ``start_positions`` or ``end_positions`` is not provided)
``torch.LongTensor`` of shape ``(batch_size, config.start_n_top)``
Indices for the top config.start_n_top start token possibilities (beam-search).
**end_top_log_probs**: (`optional`, returned if ``start_positions`` or ``end_positions`` is not provided)
``torch.FloatTensor`` of shape ``(batch_size, config.start_n_top * config.end_n_top)``
Log probabilities for the top ``config.start_n_top * config.end_n_top`` end token possibilities (beam-search).
**end_top_index**: (`optional`, returned if ``start_positions`` or ``end_positions`` is not provided)
``torch.LongTensor`` of shape ``(batch_size, config.start_n_top * config.end_n_top)``
Indices for the top ``config.start_n_top * config.end_n_top`` end token possibilities (beam-search).
**cls_logits**: (`optional`, returned if ``start_positions`` or ``end_positions`` is not provided)
``torch.FloatTensor`` of shape ``(batch_size,)``
Log probabilities for the ``is_impossible`` label of the answers.
**mems**:
list of ``torch.FloatTensor`` (one for each layer):
that contains pre-computed hidden-states (key and values in the attention blocks) as computed by the model
(see `mems` input above). Can be used to speed up sequential decoding and attend to longer context.
**hidden_states**: (`optional`, returned when ``config.output_hidden_states=True``)
list of ``torch.FloatTensor`` (one for the output of each layer + the output of the embeddings)
of shape ``(batch_size, sequence_length, hidden_size)``:
Hidden-states of the model at the output of each layer plus the initial embedding outputs.
**attentions**: (`optional`, returned when ``config.output_attentions=True``)
list of ``torch.FloatTensor`` (one for each layer) of shape ``(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.
Examples::
tokenizer = XLMTokenizer.from_pretrained('xlm-mlm-en-2048')
model = XLMForQuestionAnswering.from_pretrained('xlnet-large-cased')
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute")).unsqueeze(0) # Batch size 1
start_positions = torch.tensor([1])
end_positions = torch.tensor([3])
outputs = model(input_ids, start_positions=start_positions, end_positions=end_positions)
loss, start_scores, end_scores = outputs[:2]
"""
def __init__(self, config):
super(XLNetForQuestionAnswering, self).__init__(config)
self.start_n_top = config.start_n_top
self.end_n_top = config.end_n_top
self.transformer = XLNetModel(config)
self.start_logits = PoolerStartLogits(config)
self.end_logits = PoolerEndLogits(config)
self.answer_class = PoolerAnswerClass(config)
self.apply(self.init_weights)
def forward(self, input_ids, token_type_ids=None, input_mask=None, attention_mask=None,
mems=None, perm_mask=None, target_mapping=None,
start_positions=None, end_positions=None, cls_index=None, is_impossible=None, p_mask=None,
head_mask=None):
transformer_outputs = self.transformer(input_ids, token_type_ids=token_type_ids,
input_mask=input_mask, attention_mask=attention_mask,
mems=mems, perm_mask=perm_mask, target_mapping=target_mapping,
head_mask=head_mask)
hidden_states = transformer_outputs[0]
start_logits = self.start_logits(hidden_states, p_mask=p_mask)
outputs = transformer_outputs[1:] # Keep mems, hidden states, attentions if there are in it
if start_positions is not None and end_positions is not None:
# If we are on multi-GPU, let's remove the dimension added by batch splitting
for x in (start_positions, end_positions, cls_index, is_impossible):
if x is not None and x.dim() > 1:
x.squeeze_(-1)
# during training, compute the end logits based on the ground truth of the start position
end_logits = self.end_logits(hidden_states, start_positions=start_positions, p_mask=p_mask)
loss_fct = CrossEntropyLoss()
start_loss = loss_fct(start_logits, start_positions)
end_loss = loss_fct(end_logits, end_positions)
total_loss = (start_loss + end_loss) / 2
if cls_index is not None and is_impossible is not None:
# Predict answerability from the representation of CLS and START
cls_logits = self.answer_class(hidden_states, start_positions=start_positions, cls_index=cls_index)
loss_fct_cls = nn.BCEWithLogitsLoss()
cls_loss = loss_fct_cls(cls_logits, is_impossible)
# note(zhiliny): by default multiply the loss by 0.5 so that the scale is comparable to start_loss and end_loss
total_loss += cls_loss * 0.5
outputs = (total_loss,) + outputs
else:
# during inference, compute the end logits based on beam search
bsz, slen, hsz = hidden_states.size()
start_log_probs = F.softmax(start_logits, dim=-1) # shape (bsz, slen)
start_top_log_probs, start_top_index = torch.topk(start_log_probs, self.start_n_top, dim=-1) # shape (bsz, start_n_top)
start_top_index_exp = start_top_index.unsqueeze(-1).expand(-1, -1, hsz) # shape (bsz, start_n_top, hsz)
start_states = torch.gather(hidden_states, -2, start_top_index_exp) # shape (bsz, start_n_top, hsz)
start_states = start_states.unsqueeze(1).expand(-1, slen, -1, -1) # shape (bsz, slen, start_n_top, hsz)
hidden_states_expanded = hidden_states.unsqueeze(2).expand_as(start_states) # shape (bsz, slen, start_n_top, hsz)
p_mask = p_mask.unsqueeze(-1) if p_mask is not None else None
end_logits = self.end_logits(hidden_states_expanded, start_states=start_states, p_mask=p_mask)
end_log_probs = F.softmax(end_logits, dim=1) # shape (bsz, slen, start_n_top)
end_top_log_probs, end_top_index = torch.topk(end_log_probs, self.end_n_top, dim=1) # shape (bsz, end_n_top, start_n_top)
end_top_log_probs = end_top_log_probs.view(-1, self.start_n_top * self.end_n_top)
end_top_index = end_top_index.view(-1, self.start_n_top * self.end_n_top)
start_states = torch.einsum("blh,bl->bh", hidden_states, start_log_probs) # get the representation of START as weighted sum of hidden states
cls_logits = self.answer_class(hidden_states, start_states=start_states, cls_index=cls_index) # Shape (batch size,): one single `cls_logits` for each sample
outputs = (start_top_log_probs, start_top_index, end_top_log_probs, end_top_index, cls_logits) + outputs
# return start_top_log_probs, start_top_index, end_top_log_probs, end_top_index, cls_logits
# or (if labels are provided) (total_loss,)
return outputs
