# 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 Transformer XL model.
Adapted from https://github.com/kimiyoung/transformer-xl.
In particular https://github.com/kimiyoung/transformer-xl/blob/master/pytorch/mem_transformer.py
"""
from __future__ import absolute_import, division, print_function, unicode_literals
import os
import json
import math
import logging
import collections
import sys
from io import open
import torch
import torch.nn as nn
import torch.nn.functional as F
from torch.nn import CrossEntropyLoss
from torch.nn.parameter import Parameter
from .modeling_bert import BertLayerNorm as LayerNorm
from .modeling_transfo_xl_utilities import ProjectedAdaptiveLogSoftmax, sample_logits
from .modeling_utils import (PretrainedConfig, PreTrainedModel, add_start_docstrings)
logger = logging.getLogger(__name__)
TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_MAP = {
'transfo-xl-wt103': "https://s3.amazonaws.com/models.huggingface.co/bert/transfo-xl-wt103-pytorch_model.bin",
}
TRANSFO_XL_PRETRAINED_CONFIG_ARCHIVE_MAP = {
'transfo-xl-wt103': "https://s3.amazonaws.com/models.huggingface.co/bert/transfo-xl-wt103-config.json",
}
def build_tf_to_pytorch_map(model, config):
""" A map of modules from TF to PyTorch.
This time 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'):
# We are loading in a TransfoXLLMHeadModel => we will load also the Adaptive Softmax
tf_to_pt_map.update({
"transformer/adaptive_softmax/cutoff_0/cluster_W": model.crit.cluster_weight,
"transformer/adaptive_softmax/cutoff_0/cluster_b": model.crit.cluster_bias})
for i, (out_l, proj_l, tie_proj) in enumerate(zip(
model.crit.out_layers,
model.crit.out_projs,
config.tie_projs)):
layer_str = "transformer/adaptive_softmax/cutoff_%d/" % i
if config.tie_weight:
tf_to_pt_map.update({
layer_str + 'b': out_l.bias})
else:
raise NotImplementedError
# I don't think this is implemented in the TF code
tf_to_pt_map.update({
layer_str + 'lookup_table': out_l.weight,
layer_str + 'b': out_l.bias})
if not tie_proj:
tf_to_pt_map.update({
layer_str + 'proj': proj_l
})
# Now load the rest of the transformer
model = model.transformer
# Embeddings
for i, (embed_l, proj_l) in enumerate(zip(model.word_emb.emb_layers, model.word_emb.emb_projs)):
layer_str = "transformer/adaptive_embed/cutoff_%d/" % i
tf_to_pt_map.update({
layer_str + 'lookup_table': embed_l.weight,
layer_str + 'proj_W': proj_l
})
# Transformer blocks
for i, b in enumerate(model.layers):
layer_str = "transformer/layer_%d/" % i
tf_to_pt_map.update({
layer_str + "rel_attn/LayerNorm/gamma": b.dec_attn.layer_norm.weight,
layer_str + "rel_attn/LayerNorm/beta": b.dec_attn.layer_norm.bias,
layer_str + "rel_attn/o/kernel": b.dec_attn.o_net.weight,
layer_str + "rel_attn/qkv/kernel": b.dec_attn.qkv_net.weight,
layer_str + "rel_attn/r/kernel": b.dec_attn.r_net.weight,
layer_str + "ff/LayerNorm/gamma": b.pos_ff.layer_norm.weight,
layer_str + "ff/LayerNorm/beta": b.pos_ff.layer_norm.bias,
layer_str + "ff/layer_1/kernel": b.pos_ff.CoreNet[0].weight,
layer_str + "ff/layer_1/bias": b.pos_ff.CoreNet[0].bias,
layer_str + "ff/layer_2/kernel": b.pos_ff.CoreNet[3].weight,
layer_str + "ff/layer_2/bias": b.pos_ff.CoreNet[3].bias,
})
# Relative positioning biases
if config.untie_r:
r_r_list = []
r_w_list = []
for b in model.layers:
r_r_list.append(b.dec_attn.r_r_bias)
r_w_list.append(b.dec_attn.r_w_bias)
else:
r_r_list = [model.r_r_bias]
r_w_list = [model.r_w_bias]
tf_to_pt_map.update({
'transformer/r_r_bias': r_r_list,
'transformer/r_w_bias': r_w_list})
return tf_to_pt_map
def load_tf_weights_in_transfo_xl(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
# Build TF to PyTorch weights loading map
tf_to_pt_map = build_tf_to_pytorch_map(model, config)
# 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
for name, pointer in tf_to_pt_map.items():
assert name in tf_weights
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 or 'proj' in name:
array = np.transpose(array)
if ('r_r_bias' in name or 'r_w_bias' in name) and len(pointer) > 1:
# 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
class TransfoXLConfig(PretrainedConfig):
"""Configuration class to store the configuration of a `TransfoXLModel`.
Args:
vocab_size_or_config_json_file: Vocabulary size of `inputs_ids` in `TransfoXLModel` or a configuration json file.
cutoffs: cutoffs for the adaptive softmax
d_model: Dimensionality of the model's hidden states.
d_embed: Dimensionality of the embeddings
d_head: Dimensionality of the model's heads.
div_val: divident value for adapative input and softmax
pre_lnorm: apply LayerNorm to the input instead of the output
d_inner: Inner dimension in FF
n_layer: Number of hidden layers in the Transformer encoder.
n_head: Number of attention heads for each attention layer in
the Transformer encoder.
tgt_len: number of tokens to predict
ext_len: length of the extended context
mem_len: length of the retained previous heads
same_length: use the same attn length for all tokens
proj_share_all_but_first: True to share all but first projs, False not to share.
attn_type: attention type. 0 for Transformer-XL, 1 for Shaw et al, 2 for Vaswani et al, 3 for Al Rfou et al.
clamp_len: use the same pos embeddings after clamp_len
sample_softmax: number of samples in sampled softmax
adaptive: use adaptive softmax
tie_weight: tie the word embedding and softmax weights
dropout: The dropout probabilitiy for all fully connected
layers in the embeddings, encoder, and pooler.
dropatt: The dropout ratio for the attention probabilities.
untie_r: untie relative position biases
embd_pdrop: The dropout ratio for the embeddings.
init: parameter initializer to use
init_range: parameters initialized by U(-init_range, init_range).
proj_init_std: parameters initialized by N(0, init_std)
init_std: parameters initialized by N(0, init_std)
"""
pretrained_config_archive_map = TRANSFO_XL_PRETRAINED_CONFIG_ARCHIVE_MAP
def __init__(self,
vocab_size_or_config_json_file=267735,
cutoffs=[20000, 40000, 200000],
d_model=1024,
d_embed=1024,
n_head=16,
d_head=64,
d_inner=4096,
div_val=4,
pre_lnorm=False,
n_layer=18,
tgt_len=128,
ext_len=0,
mem_len=1600,
clamp_len=1000,
same_length=True,
proj_share_all_but_first=True,
attn_type=0,
sample_softmax=-1,
adaptive=True,
tie_weight=True,
dropout=0.1,
dropatt=0.0,
untie_r=True,
init="normal",
init_range=0.01,
proj_init_std=0.01,
init_std=0.02,
**kwargs):
"""Constructs TransfoXLConfig.
"""
super(TransfoXLConfig, 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.cutoffs = []
self.cutoffs.extend(cutoffs)
self.tie_weight = tie_weight
if proj_share_all_but_first:
self.tie_projs = [False] + [True] * len(self.cutoffs)
else:
self.tie_projs = [False] + [False] * len(self.cutoffs)
self.d_model = d_model
self.d_embed = d_embed
self.d_head = d_head
self.d_inner = d_inner
self.div_val = div_val
self.pre_lnorm = pre_lnorm
self.n_layer = n_layer
self.n_head = n_head
self.tgt_len = tgt_len
self.ext_len = ext_len
self.mem_len = mem_len
self.same_length = same_length
self.attn_type = attn_type
self.clamp_len = clamp_len
self.sample_softmax = sample_softmax
self.adaptive = adaptive
self.dropout = dropout
self.dropatt = dropatt
self.untie_r = untie_r
self.init = init
self.init_range = init_range
self.proj_init_std = proj_init_std
self.init_std = init_std
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 self.tgt_len + self.ext_len + self.mem_len
@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
class PositionalEmbedding(nn.Module):
def __init__(self, demb):
super(PositionalEmbedding, self).__init__()
self.demb = demb
inv_freq = 1 / (10000 ** (torch.arange(0.0, demb, 2.0) / demb))
self.register_buffer('inv_freq', inv_freq)
def forward(self, pos_seq, bsz=None):
sinusoid_inp = torch.ger(pos_seq, self.inv_freq)
pos_emb = torch.cat([sinusoid_inp.sin(), sinusoid_inp.cos()], dim=-1)
if bsz is not None:
return pos_emb[:,None,:].expand(-1, bsz, -1)
else:
return pos_emb[:,None,:]
class PositionwiseFF(nn.Module):
def __init__(self, d_model, d_inner, dropout, pre_lnorm=False):
super(PositionwiseFF, self).__init__()
self.d_model = d_model
self.d_inner = d_inner
self.dropout = dropout
self.CoreNet = nn.Sequential(
nn.Linear(d_model, d_inner), nn.ReLU(inplace=True),
nn.Dropout(dropout),
nn.Linear(d_inner, d_model),
nn.Dropout(dropout),
)
self.layer_norm = LayerNorm(d_model)
self.pre_lnorm = pre_lnorm
def forward(self, inp):
if self.pre_lnorm:
##### layer normalization + positionwise feed-forward
core_out = self.CoreNet(self.layer_norm(inp))
##### residual connection
output = core_out + inp
else:
##### positionwise feed-forward
core_out = self.CoreNet(inp)
##### residual connection + layer normalization
output = self.layer_norm(inp + core_out)
return output
class MultiHeadAttn(nn.Module):
def __init__(self, n_head, d_model, d_head, dropout, dropatt=0,
pre_lnorm=False, r_r_bias=None, r_w_bias=None, output_attentions=False):
super(MultiHeadAttn, self).__init__()
self.output_attentions = output_attentions
self.n_head = n_head
self.d_model = d_model
self.d_head = d_head
self.dropout = dropout
self.q_net = nn.Linear(d_model, n_head * d_head, bias=False)
self.kv_net = nn.Linear(d_model, 2 * n_head * d_head, bias=False)
self.drop = nn.Dropout(dropout)
self.dropatt = nn.Dropout(dropatt)
self.o_net = nn.Linear(n_head * d_head, d_model, bias=False)
self.layer_norm = LayerNorm(d_model)
self.scale = 1 / (d_head ** 0.5)
self.pre_lnorm = pre_lnorm
if r_r_bias is None or r_w_bias is None: # Biases are not shared
self.r_r_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))
else:
self.r_r_bias = r_r_bias
self.r_w_bias = r_w_bias
def forward(self, h, attn_mask=None, mems=None, head_mask=None):
##### multihead attention
# [hlen x bsz x n_head x d_head]
if mems is not None:
c = torch.cat([mems, h], 0)
else:
c = h
if self.pre_lnorm:
##### layer normalization
c = self.layer_norm(c)
head_q = self.q_net(h)
head_k, head_v = torch.chunk(self.kv_net(c), 2, -1)
head_q = head_q.view(h.size(0), h.size(1), self.n_head, self.d_head)
head_k = head_k.view(c.size(0), c.size(1), self.n_head, self.d_head)
head_v = head_v.view(c.size(0), c.size(1), self.n_head, self.d_head)
# [qlen x klen x bsz x n_head]
attn_score = torch.einsum('ibnd,jbnd->ijbn', (head_q, head_k))
attn_score.mul_(self.scale)
if attn_mask is not None and attn_mask.any().item():
if attn_mask.dim() == 2:
attn_score.masked_fill_(attn_mask[None,:,:,None], -float('inf'))
elif attn_mask.dim() == 3:
attn_score.masked_fill_(attn_mask[:,:,:,None], -float('inf'))
# [qlen x klen x bsz x n_head]
attn_prob = F.softmax(attn_score, dim=1)
attn_prob = self.dropatt(attn_prob)
# Mask heads if we want to
if head_mask is not None:
attn_prob = attn_prob * head_mask
# [qlen x klen x bsz x n_head] + [klen x bsz x n_head x d_head] -> [qlen x bsz x n_head x d_head]
attn_vec = torch.einsum('ijbn,jbnd->ibnd', (attn_prob, head_v))
attn_vec = attn_vec.contiguous().view(
attn_vec.size(0), attn_vec.size(1), self.n_head * self.d_head)
##### linear projection
attn_out = self.o_net(attn_vec)
attn_out = self.drop(attn_out)
if self.pre_lnorm:
##### residual connection
outputs = [h + attn_out]
else:
##### residual connection + layer normalization
outputs = [self.layer_norm(h + attn_out)]
if self.output_attentions:
outputs.append(attn_prob)
return outputs
class RelMultiHeadAttn(nn.Module):
def __init__(self, n_head, d_model, d_head, dropout, dropatt=0,
tgt_len=None, ext_len=None, mem_len=None, pre_lnorm=False,
r_r_bias=None, r_w_bias=None, output_attentions=False):
super(RelMultiHeadAttn, self).__init__()
self.output_attentions = output_attentions
self.n_head = n_head
self.d_model = d_model
self.d_head = d_head
self.dropout = dropout
self.qkv_net = nn.Linear(d_model, 3 * n_head * d_head, bias=False)
self.drop = nn.Dropout(dropout)
self.dropatt = nn.Dropout(dropatt)
self.o_net = nn.Linear(n_head * d_head, d_model, bias=False)
self.layer_norm = LayerNorm(d_model)
self.scale = 1 / (d_head ** 0.5)
self.pre_lnorm = pre_lnorm
if r_r_bias is None or r_w_bias is None: # Biases are not shared
self.r_r_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))
else:
self.r_r_bias = r_r_bias
self.r_w_bias = r_w_bias
def _parallelogram_mask(self, h, w, left=False):
mask = torch.ones((h, w)).byte()
m = min(h, w)
mask[:m,:m] = torch.triu(mask[:m,:m])
mask[-m:,-m:] = torch.tril(mask[-m:,-m:])
if left:
return mask
else:
return mask.flip(0)
def _shift(self, x, qlen, klen, mask, left=False):
if qlen > 1:
zero_pad = torch.zeros((x.size(0), qlen-1, x.size(2), x.size(3)),
device=x.device, dtype=x.dtype)
else:
zero_pad = torch.zeros(0, device=x.device, dtype=x.dtype)
if left:
mask = mask.flip(1)
x_padded = torch.cat([zero_pad, x], dim=1).expand(qlen, -1, -1, -1)
else:
x_padded = torch.cat([x, zero_pad], dim=1).expand(qlen, -1, -1, -1)
x = x_padded.masked_select(mask[:,:,None,None]) \
.view(qlen, klen, x.size(2), x.size(3))
return x
def _rel_shift(self, x, zero_triu=False):
zero_pad_shape = (x.size(0), 1) + x.size()[2:]
zero_pad = torch.zeros(zero_pad_shape, device=x.device, dtype=x.dtype)
x_padded = torch.cat([zero_pad, x], dim=1)
x_padded_shape = (x.size(1) + 1, x.size(0)) + x.size()[2:]
x_padded = x_padded.view(*x_padded_shape)
x = x_padded[1:].view_as(x)
if zero_triu:
ones = torch.ones((x.size(0), x.size(1)))
x = x * torch.tril(ones, x.size(1) - x.size(0))[:,:,None,None]
return x
def forward(self, w, r, attn_mask=None, mems=None):
raise NotImplementedError
class RelPartialLearnableMultiHeadAttn(RelMultiHeadAttn):
def __init__(self, *args, **kwargs):
super(RelPartialLearnableMultiHeadAttn, self).__init__(*args, **kwargs)
self.r_net = nn.Linear(self.d_model, self.n_head * self.d_head, bias=False)
def forward(self, w, r, attn_mask=None, mems=None, head_mask=None):
qlen, rlen, bsz = w.size(0), r.size(0), w.size(1)
if mems is not None:
cat = torch.cat([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 = torch.chunk(w_heads, 3, dim=-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 = torch.chunk(w_heads, 3, dim=-1)
klen = w_head_k.size(0)
w_head_q = w_head_q.view(qlen, bsz, self.n_head, self.d_head) # qlen x bsz x n_head x d_head
w_head_k = w_head_k.view(klen, bsz, self.n_head, self.d_head) # qlen x bsz x n_head x d_head
w_head_v = w_head_v.view(klen, bsz, self.n_head, self.d_head) # qlen x bsz x n_head x d_head
r_head_k = r_head_k.view(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 = torch.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 = torch.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.mul_(self.scale)
#### compute attention probability
if attn_mask is not None and attn_mask.any().item():
if attn_mask.dim() == 2:
attn_score = attn_score.float().masked_fill(
attn_mask[None,:,:,None], -1e30).type_as(attn_score)
elif attn_mask.dim() == 3:
attn_score = attn_score.float().masked_fill(
attn_mask[:,:,:,None], -1e30).type_as(attn_score)
# [qlen x klen x bsz x n_head]
attn_prob = F.softmax(attn_score, dim=1)
attn_prob = self.dropatt(attn_prob)
# Mask heads if we want to
if head_mask is not None:
attn_prob = attn_prob * head_mask
#### compute attention vector
attn_vec = torch.einsum('ijbn,jbnd->ibnd', (attn_prob, w_head_v))
# [qlen x bsz x n_head x d_head]
attn_vec = attn_vec.contiguous().view(
attn_vec.size(0), attn_vec.size(1), self.n_head * self.d_head)
##### linear projection
attn_out = self.o_net(attn_vec)
attn_out = self.drop(attn_out)
if self.pre_lnorm:
##### residual connection
outputs = [w + attn_out]
else:
##### residual connection + layer normalization
outputs = [self.layer_norm(w + attn_out)]
if self.output_attentions:
outputs.append(attn_prob)
return outputs
class RelLearnableMultiHeadAttn(RelMultiHeadAttn):
def __init__(self, *args, **kwargs):
super(RelLearnableMultiHeadAttn, self).__init__(*args, **kwargs)
def forward(self, w, r_emb, r_w_bias, r_bias, attn_mask=None, mems=None, head_mask=None):
# r_emb: [klen, n_head, d_head], used for term B
# r_w_bias: [n_head, d_head], used for term C
# r_bias: [klen, n_head], used for term D
qlen, bsz = w.size(0), w.size(1)
if mems is not None:
cat = torch.cat([mems, w], 0)
if self.pre_lnorm:
w_heads = self.qkv_net(self.layer_norm(cat))
else:
w_heads = self.qkv_net(cat)
w_head_q, w_head_k, w_head_v = torch.chunk(w_heads, 3, dim=-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)
w_head_q, w_head_k, w_head_v = torch.chunk(w_heads, 3, dim=-1)
klen = w_head_k.size(0)
w_head_q = w_head_q.view(qlen, bsz, self.n_head, self.d_head)
w_head_k = w_head_k.view(klen, bsz, self.n_head, self.d_head)
w_head_v = w_head_v.view(klen, bsz, self.n_head, self.d_head)
if klen > r_emb.size(0):
r_emb_pad = r_emb[0:1].expand(klen-r_emb.size(0), -1, -1)
r_emb = torch.cat([r_emb_pad, r_emb], 0)
r_bias_pad = r_bias[0:1].expand(klen-r_bias.size(0), -1)
r_bias = torch.cat([r_bias_pad, r_bias], 0)
else:
r_emb = r_emb[-klen:]
r_bias = r_bias[-klen:]
#### compute attention score
rw_head_q = w_head_q + r_w_bias[None] # qlen x bsz x n_head x d_head
AC = torch.einsum('ibnd,jbnd->ijbn', (rw_head_q, w_head_k)) # qlen x klen x bsz x n_head
B_ = torch.einsum('ibnd,jnd->ijbn', (w_head_q, r_emb)) # qlen x klen x bsz x n_head
D_ = r_bias[None, :, None] # 1 x klen x 1 x n_head
BD = self._rel_shift(B_ + D_)
# [qlen x klen x bsz x n_head]
attn_score = AC + BD
attn_score.mul_(self.scale)
#### compute attention probability
if attn_mask is not None and attn_mask.any().item():
if attn_mask.dim() == 2:
attn_score.masked_fill_(attn_mask[None,:,:,None], -float('inf'))
elif attn_mask.dim() == 3:
attn_score.masked_fill_(attn_mask[:,:,:,None], -float('inf'))
# [qlen x klen x bsz x n_head]
attn_prob = F.softmax(attn_score, dim=1)
attn_prob = self.dropatt(attn_prob)
if head_mask is not None:
attn_prob = attn_prob * head_mask
#### compute attention vector
attn_vec = torch.einsum('ijbn,jbnd->ibnd', (attn_prob, w_head_v))
# [qlen x bsz x n_head x d_head]
attn_vec = attn_vec.contiguous().view(
attn_vec.size(0), attn_vec.size(1), self.n_head * self.d_head)
##### linear projection
attn_out = self.o_net(attn_vec)
attn_out = self.drop(attn_out)
if self.pre_lnorm:
##### residual connection
outputs = [w + attn_out]
else:
##### residual connection + layer normalization
outputs = [self.layer_norm(w + attn_out)]
if self.output_attentions:
outputs.append(attn_prob)
return outputs
class DecoderLayer(nn.Module):
def __init__(self, n_head, d_model, d_head, d_inner, dropout, **kwargs):
super(DecoderLayer, self).__init__()
self.dec_attn = MultiHeadAttn(n_head, d_model, d_head, dropout, **kwargs)
self.pos_ff = PositionwiseFF(d_model, d_inner, dropout,
pre_lnorm=kwargs.get('pre_lnorm'))
def forward(self, dec_inp, dec_attn_mask=None, mems=None, head_mask=None):
attn_outputs = self.dec_attn(dec_inp, attn_mask=dec_attn_mask,
mems=mems, head_mask=head_mask)
ff_output = self.pos_ff(attn_outputs[0])
outputs = [ff_output] + attn_outputs[1:]
return outputs
class RelLearnableDecoderLayer(nn.Module):
def __init__(self, n_head, d_model, d_head, d_inner, dropout,
**kwargs):
super(RelLearnableDecoderLayer, self).__init__()
self.dec_attn = RelLearnableMultiHeadAttn(n_head, d_model, d_head, dropout,
**kwargs)
self.pos_ff = PositionwiseFF(d_model, d_inner, dropout,
pre_lnorm=kwargs.get('pre_lnorm'))
def forward(self, dec_inp, r_emb, r_w_bias, r_bias, dec_attn_mask=None, mems=None, head_mask=None):
attn_outputs = self.dec_attn(dec_inp, r_emb, r_w_bias, r_bias,
attn_mask=dec_attn_mask,
mems=mems, head_mask=head_mask)
ff_output = self.pos_ff(attn_outputs[0])
outputs = [ff_output] + attn_outputs[1:]
return outputs
class RelPartialLearnableDecoderLayer(nn.Module):
def __init__(self, n_head, d_model, d_head, d_inner, dropout,
**kwargs):
super(RelPartialLearnableDecoderLayer, self).__init__()
self.dec_attn = RelPartialLearnableMultiHeadAttn(n_head, d_model,
d_head, dropout, **kwargs)
self.pos_ff = PositionwiseFF(d_model, d_inner, dropout,
pre_lnorm=kwargs.get('pre_lnorm'))
def forward(self, dec_inp, r, dec_attn_mask=None, mems=None, head_mask=None):
attn_outputs = self.dec_attn(dec_inp, r,
attn_mask=dec_attn_mask,
mems=mems, head_mask=head_mask)
ff_output = self.pos_ff(attn_outputs[0])
outputs = [ff_output] + attn_outputs[1:]
return outputs
class AdaptiveEmbedding(nn.Module):
def __init__(self, n_token, d_embed, d_proj, cutoffs, div_val=1,
sample_softmax=False):
super(AdaptiveEmbedding, self).__init__()
self.n_token = n_token
self.d_embed = d_embed
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 = nn.ModuleList()
self.emb_projs = nn.ParameterList()
if div_val == 1:
self.emb_layers.append(
nn.Embedding(n_token, d_embed, sparse=sample_softmax>0)
)
if d_proj != d_embed:
self.emb_projs.append(nn.Parameter(torch.FloatTensor(d_proj, d_embed)))
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(nn.Embedding(r_idx-l_idx, d_emb_i))
self.emb_projs.append(nn.Parameter(torch.FloatTensor(d_proj, d_emb_i)))
def forward(self, inp):
if self.div_val == 1:
embed = self.emb_layers[0](inp)
if self.d_proj != self.d_embed:
embed = F.linear(embed, self.emb_projs[0])
else:
param = next(self.parameters())
inp_flat = inp.view(-1)
emb_flat = torch.zeros([inp_flat.size(0), self.d_proj],
dtype=param.dtype, device=param.device)
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)
indices_i = mask_i.nonzero().squeeze()
if indices_i.numel() == 0:
continue
inp_i = inp_flat.index_select(0, indices_i) - l_idx
emb_i = self.emb_layers[i](inp_i)
emb_i = F.linear(emb_i, self.emb_projs[i])
emb_flat.index_copy_(0, indices_i, emb_i)
embed_shape = inp.size() + (self.d_proj,)
embed = emb_flat.view(embed_shape)
embed.mul_(self.emb_scale)
return embed
class TransfoXLPreTrainedModel(PreTrainedModel):
""" An abstract class to handle weights initialization and
a simple interface for dowloading and loading pretrained models.
"""
config_class = TransfoXLConfig
pretrained_model_archive_map = TRANSFO_XL_PRETRAINED_MODEL_ARCHIVE_MAP
load_tf_weights = load_tf_weights_in_transfo_xl
base_model_prefix = "transformer"
def __init__(self, *inputs, **kwargs):
super(TransfoXLPreTrainedModel, self).__init__(*inputs, **kwargs)
def _init_weight(self, weight):
if self.config.init == 'uniform':
nn.init.uniform_(weight, -self.config.init_range, self.config.init_range)
elif self.config.init == 'normal':
nn.init.normal_(weight, 0.0, self.config.init_std)
def _init_bias(self, bias):
nn.init.constant_(bias, 0.0)
def init_weights(self, m):
""" Initialize the weights.
"""
classname = m.__class__.__name__
if classname.find('Linear') != -1:
if hasattr(m, 'weight') and m.weight is not None:
self._init_weight(m.weight)
if hasattr(m, 'bias') and m.bias is not None:
self._init_bias(m.bias)
elif classname.find('AdaptiveEmbedding') != -1:
if hasattr(m, 'emb_projs'):
for i in range(len(m.emb_projs)):
if m.emb_projs[i] is not None:
nn.init.normal_(m.emb_projs[i], 0.0, self.config.proj_init_std)
elif classname.find('Embedding') != -1:
if hasattr(m, 'weight'):
self._init_weight(m.weight)
elif classname.find('ProjectedAdaptiveLogSoftmax') != -1:
if hasattr(m, 'cluster_weight') and m.cluster_weight is not None:
self._init_weight(m.cluster_weight)
if hasattr(m, 'cluster_bias') and m.cluster_bias is not None:
self._init_bias(m.cluster_bias)
if hasattr(m, 'out_projs'):
for i in range(len(m.out_projs)):
if m.out_projs[i] is not None:
nn.init.normal_(m.out_projs[i], 0.0, self.config.proj_init_std)
elif classname.find('LayerNorm') != -1:
if hasattr(m, 'weight'):
nn.init.normal_(m.weight, 1.0, self.config.init_std)
if hasattr(m, 'bias') and m.bias is not None:
self._init_bias(m.bias)
else:
if hasattr(m, 'r_emb'):
self._init_weight(m.r_emb)
if hasattr(m, 'r_w_bias'):
self._init_weight(m.r_w_bias)
if hasattr(m, 'r_r_bias'):
self._init_weight(m.r_r_bias)
if hasattr(m, 'r_bias'):
self._init_bias(m.r_bias)
def set_num_special_tokens(self, num_special_tokens):
pass
TRANSFO_XL_START_DOCSTRING = r""" The Transformer-XL model was proposed in
`Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context`_
by Zihang Dai*, Zhilin Yang*, Yiming Yang, Jaime Carbonell, Quoc V. Le, Ruslan Salakhutdinov.
It's a causal (uni-directional) transformer with relative positioning (sinusoïdal) embeddings which can reuse
previously computed hidden-states to attend to longer context (memory).
This model also uses adaptive softmax inputs and outputs (tied).
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.
.. _`Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context`:
https://arxiv.org/abs/1901.02860
.. _`torch.nn.Module`:
https://pytorch.org/docs/stable/nn.html#module
Parameters:
config (:class:`~pytorch_transformers.TransfoXLConfig`): Model configuration class with all the parameters of the model.
"""
TRANSFO_XL_INPUTS_DOCSTRING = r"""
Inputs:
**input_ids**: ``torch.LongTensor`` of shape ``(batch_size, sequence_length)``:
Indices of input sequence tokens in the vocabulary.
Indices can be obtained using :class:`pytorch_transformers.TransfoXLTokenizer`.
See :func:`pytorch_transformers.PreTrainedTokenizer.encode` and
:func:`pytorch_transformers.PreTrainedTokenizer.convert_tokens_to_ids` for details.
**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.
**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 Bert Model transformer outputing raw hidden-states without any specific head on top.",
TRANSFO_XL_START_DOCSTRING, TRANSFO_XL_INPUTS_DOCSTRING)
class TransfoXLModel(TransfoXLPreTrainedModel):
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 = TransfoXLTokenizer.from_pretrained('transfo-xl-wt103')
model = TransfoXLModel.from_pretrained('transfo-xl-wt103')
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute")).unsqueeze(0) # Batch size 1
outputs = model(input_ids)
last_hidden_states, mems = outputs[:2]
"""
def __init__(self, config):
super(TransfoXLModel, self).__init__(config)
self.output_attentions = config.output_attentions
self.output_hidden_states = config.output_hidden_states
self.n_token = config.n_token
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.word_emb = AdaptiveEmbedding(config.n_token, config.d_embed, config.d_model, config.cutoffs,
div_val=config.div_val)
self.drop = nn.Dropout(config.dropout)
self.n_layer = config.n_layer
self.tgt_len = config.tgt_len
self.mem_len = config.mem_len
self.ext_len = config.ext_len
self.max_klen = config.tgt_len + config.ext_len + config.mem_len
self.attn_type = config.attn_type
if not config.untie_r:
self.r_w_bias = nn.Parameter(torch.FloatTensor(self.n_head, self.d_head))
self.r_r_bias = nn.Parameter(torch.FloatTensor(self.n_head, self.d_head))
self.layers = nn.ModuleList()
if config.attn_type == 0: # the default attention
for i in range(config.n_layer):
self.layers.append(
RelPartialLearnableDecoderLayer(
config.n_head, config.d_model, config.d_head, config.d_inner, config.dropout,
tgt_len=config.tgt_len, ext_len=config.ext_len, mem_len=config.mem_len,
dropatt=config.dropatt, pre_lnorm=config.pre_lnorm,
r_w_bias=None if config.untie_r else self.r_w_bias,
r_r_bias=None if config.untie_r else self.r_r_bias,
output_attentions=self.output_attentions)
)
elif config.attn_type == 1: # learnable embeddings
for i in range(config.n_layer):
self.layers.append(
RelLearnableDecoderLayer(
config.n_head, config.d_model, config.d_head, config.d_inner, config.dropout,
tgt_len=config.tgt_len, ext_len=config.ext_len, mem_len=config.mem_len,
dropatt=config.dropatt, pre_lnorm=config.pre_lnorm,
r_w_bias=None if config.untie_r else self.r_w_bias,
r_r_bias=None if config.untie_r else self.r_r_bias,
output_attentions=self.output_attentions)
)
elif config.attn_type in [2, 3]: # absolute embeddings
for i in range(config.n_layer):
self.layers.append(
DecoderLayer(
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 config.untie_r else self.r_w_bias,
r_r_bias=None if config.untie_r else self.r_r_bias,
output_attentions=self.output_attentions)
)
self.same_length = config.same_length
self.clamp_len = config.clamp_len
if self.attn_type == 0: # default attention
self.pos_emb = PositionalEmbedding(self.d_model)
elif self.attn_type == 1: # learnable
self.r_emb = nn.Parameter(torch.FloatTensor(
self.n_layer, self.max_klen, self.n_head, self.d_head))
self.r_bias = nn.Parameter(torch.FloatTensor(
self.n_layer, self.max_klen, self.n_head))
elif self.attn_type == 2: # absolute standard
self.pos_emb = PositionalEmbedding(self.d_model)
elif self.attn_type == 3: # absolute deeper SA
self.r_emb = nn.Parameter(torch.FloatTensor(
self.n_layer, self.max_klen, self.n_head, self.d_head))
self.apply(self.init_weights)
def _resize_token_embeddings(self, new_num_tokens):
return self.word_emb
def backward_compatible(self):
self.sample_softmax = -1
def reset_length(self, tgt_len, ext_len, mem_len):
self.tgt_len = tgt_len
self.mem_len = mem_len
self.ext_len = ext_len
def _prune_heads(self, heads):
logger.info("Head pruning is not implemented for Transformer-XL model")
pass
def init_mems(self, data):
if self.mem_len > 0:
mems = []
param = next(self.parameters())
for i in range(self.n_layer):
empty = torch.zeros(self.mem_len, data.size(1), self.config.d_model,
dtype=param.dtype, device=param.device)
mems.append(empty)
return mems
else:
return None
def _update_mems(self, hids, mems, qlen, mlen):
# 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
# For the next step, the last `ext_len` of the `qlen` tokens
# will be used as the extended context. Hence, we only cache
# the tokens from `mlen + qlen - self.ext_len - self.mem_len`
# to `mlen + qlen - self.ext_len`.
with torch.no_grad():
new_mems = []
end_idx = mlen + max(0, qlen - 0 - self.ext_len)
beg_idx = max(0, end_idx - self.mem_len)
for i in range(len(hids)):
cat = torch.cat([mems[i], hids[i]], dim=0)
new_mems.append(cat[beg_idx:end_idx].detach())
return new_mems
def _forward(self, dec_inp, mems=None, head_mask=None):
qlen, bsz = dec_inp.size()
# 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
word_emb = self.word_emb(dec_inp)
mlen = mems[0].size(0) if mems is not None else 0
klen = mlen + qlen
if self.same_length:
all_ones = word_emb.new_ones(qlen, klen)
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)).byte()[:, :, None] # -1
else:
dec_attn_mask = torch.triu(
word_emb.new_ones(qlen, klen), diagonal=1+mlen).byte()[:,:,None]
hids = []
attentions = []
if self.attn_type == 0: # default
pos_seq = torch.arange(klen-1, -1, -1.0, device=word_emb.device,
dtype=word_emb.dtype)
if self.clamp_len > 0:
pos_seq.clamp_(max=self.clamp_len)
pos_emb = self.pos_emb(pos_seq)
core_out = self.drop(word_emb)
pos_emb = self.drop(pos_emb)
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=dec_attn_mask,
mems=mems_i, head_mask=head_mask[i])
core_out = layer_outputs[0]
if self.output_attentions:
attentions.append(layer_outputs[1])
elif self.attn_type == 1: # learnable
core_out = self.drop(word_emb)
for i, layer in enumerate(self.layers):
hids.append(core_out)
if self.clamp_len > 0:
r_emb = self.r_emb[i][-self.clamp_len :]
r_bias = self.r_bias[i][-self.clamp_len :]
else:
r_emb, r_bias = self.r_emb[i], self.r_bias[i]
mems_i = None if mems is None else mems[i]
layer_outputs = layer(core_out, r_emb, self.r_w_bias[i],
r_bias, dec_attn_mask=dec_attn_mask,
mems=mems_i, head_mask=head_mask[i])
core_out = layer_outputs[0]
if self.output_attentions:
attentions.append(layer_outputs[1])
elif self.attn_type == 2: # absolute
pos_seq = torch.arange(klen - 1, -1, -1.0, device=word_emb.device,
dtype=word_emb.dtype)
if self.clamp_len > 0:
pos_seq.clamp_(max=self.clamp_len)
pos_emb = self.pos_emb(pos_seq)
core_out = self.drop(word_emb + pos_emb[-qlen:])
for i, layer in enumerate(self.layers):
hids.append(core_out)
mems_i = None if mems is None else mems[i]
if mems_i is not None and i == 0:
mems_i += pos_emb[:mlen]
layer_outputs = layer(core_out, dec_attn_mask=dec_attn_mask,
mems=mems_i, head_mask=head_mask[i])
core_out = layer_outputs[0]
if self.output_attentions:
attentions.append(layer_outputs[1])
elif self.attn_type == 3:
core_out = self.drop(word_emb)
for i, layer in enumerate(self.layers):
hids.append(core_out)
mems_i = None if mems is None else mems[i]
if mems_i is not None and mlen > 0:
cur_emb = self.r_emb[i][:-qlen]
cur_size = cur_emb.size(0)
if cur_size < mlen:
cur_emb_pad = cur_emb[0:1].expand(mlen-cur_size, -1, -1)
cur_emb = torch.cat([cur_emb_pad, cur_emb], 0)
else:
cur_emb = cur_emb[-mlen:]
mems_i += cur_emb.view(mlen, 1, -1)
core_out += self.r_emb[i][-qlen:].view(qlen, 1, -1)
layer_outputs = layer(core_out, dec_attn_mask=dec_attn_mask,
mems=mems_i, head_mask=head_mask[i])
core_out = layer_outputs[0]
if self.output_attentions:
attentions.append(layer_outputs[1])
core_out = self.drop(core_out)
new_mems = self._update_mems(hids, mems, mlen, qlen)
# We transpose back here to shape [bsz, len, hidden_dim]
outputs = [core_out.transpose(0, 1).contiguous(), new_mems]
if self.output_hidden_states:
# Add last layer and transpose to library standard shape [bsz, len, hidden_dim]
hids.append(core_out)
hids = list(t.transpose(0, 1).contiguous() for t in hids)
outputs.append(hids)
if self.output_attentions:
# Transpose to library standard shape [bsz, n_heads, query_seq_len, key_seq_len]
attentions = list(t.permute(2, 3, 0, 1).contiguous() for t in attentions)
outputs.append(attentions)
return outputs # last hidden state, new_mems, (all hidden states), (all attentions)
def forward(self, input_ids, mems=None, head_mask=None):
# 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]
input_ids = input_ids.transpose(0, 1).contiguous()
if mems is None:
mems = self.init_mems(input_ids)
outputs = self._forward(input_ids, mems=mems, head_mask=head_mask)
return outputs # last hidden state, new_mems, (all hidden states), (all attentions)
@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, TRANSFO_XL_INPUTS_DOCSTRING)
class TransfoXLLMHeadModel(TransfoXLPreTrainedModel):
r"""
**lm_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 ``lm_labels`` is provided) ``torch.FloatTensor`` of shape ``(1,)``:
Language modeling loss.
**prediction_scores**: ``None`` if ``lm_labels`` is provided else ``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).
We don't output them when the loss is computed to speedup adaptive softmax decoding.
**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 = TransfoXLTokenizer.from_pretrained('transfo-xl-wt103')
model = TransfoXLLMHeadModel.from_pretrained('transfo-xl-wt103')
input_ids = torch.tensor(tokenizer.encode("Hello, my dog is cute")).unsqueeze(0) # Batch size 1
outputs = model(input_ids)
prediction_scores, mems = outputs[:2]
"""
def __init__(self, config):
super(TransfoXLLMHeadModel, self).__init__(config)
self.transformer = TransfoXLModel(config)
self.sample_softmax = config.sample_softmax
# use sampled softmax
if config.sample_softmax > 0:
self.out_layer = nn.Linear(config.d_model, config.n_token)
self.sampler = LogUniformSampler(config.n_token, config.sample_softmax)
# use adaptive softmax (including standard softmax)
else:
self.crit = ProjectedAdaptiveLogSoftmax(config.n_token, config.d_embed, config.d_model,
config.cutoffs, div_val=config.div_val)
self.apply(self.init_weights)
self.tie_weights()
def tie_weights(self):
"""
Run this to be sure output and input (adaptive) softmax weights are tied
"""
# sampled softmax
if self.sample_softmax > 0:
if self.config.tie_weight:
self.out_layer.weight = self.transformer.word_emb.weight
# adaptive softmax (including standard softmax)
else:
if self.config.tie_weight:
for i in range(len(self.crit.out_layers)):
self._tie_or_clone_weights(self.crit.out_layers[i],
self.transformer.word_emb.emb_layers[i])
if self.config.tie_projs:
for i, tie_proj in enumerate(self.config.tie_projs):
if tie_proj and self.config.div_val == 1 and self.config.d_model != self.config.d_embed:
if self.config.torchscript:
self.crit.out_projs[i] = nn.Parameter(self.transformer.word_emb.emb_projs[0].clone())
else:
self.crit.out_projs[i] = self.transformer.word_emb.emb_projs[0]
elif tie_proj and self.config.div_val != 1:
if self.config.torchscript:
self.crit.out_projs[i] = nn.Parameter(self.transformer.word_emb.emb_projs[i].clone())
else:
self.crit.out_projs[i] = self.transformer.word_emb.emb_projs[i]
def reset_length(self, tgt_len, ext_len, mem_len):
self.transformer.reset_length(tgt_len, ext_len, mem_len)
def init_mems(self, data):
return self.transformer.init_mems(data)
def forward(self, input_ids, labels=None, mems=None, head_mask=None):
bsz = input_ids.size(0)
tgt_len = input_ids.size(1)
transformer_outputs = self.transformer(input_ids, mems=mems, head_mask=head_mask)
last_hidden = transformer_outputs[0]
pred_hid = last_hidden[:, -tgt_len:]
outputs = transformer_outputs[1:]
if self.sample_softmax > 0 and self.training:
assert self.config.tie_weight
logit = sample_logits(self.transformer.word_emb, self.out_layer.bias, labels, pred_hid, self.sampler)
softmax_output = -F.log_softmax(logit, -1)[:, :, 0]
outputs = [softmax_output] + outputs
if labels is not None:
# TODO: This is not implemented
raise NotImplementedError
else:
softmax_output = self.crit(pred_hid.view(-1, pred_hid.size(-1)), labels)
if labels is None:
softmax_output = softmax_output.view(bsz, tgt_len, -1)
outputs = [softmax_output] + outputs
else:
softmax_output = softmax_output.view(bsz, tgt_len)
outputs = [softmax_output, None] + outputs
return outputs # (loss), logits or None if labels is not None (speed up adaptive softmax), new_mems, (all hidden states), (all attentions)
