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# This file contains Transformer network
# Most of the code is copied from http://nlp.seas.harvard.edu/2018/04/03/attention.html
# The cfg name correspondance:
# N=num_layers
# d_model=input_encoding_size
# d_ff=rnn_size
# h is always 8
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import torch
import torch.nn as nn
import torch.nn.functional as F
#from . import utils
import copy
import math
import numpy as np
#from .CaptionModel import CaptionModel
#from .AttModel import sort_pack_padded_sequence, pad_unsort_packed_sequence, pack_wrapper, AttModel
from captioning.models.CaptionModel import CaptionModel
from captioning.models.AttModel import sort_pack_padded_sequence, pad_unsort_packed_sequence, pack_wrapper, AttModel
def repeat_tensors(n, x):
"""
For a tensor of size Bx..., we repeat it n times, and make it Bnx...
For collections, do nested repeat
"""
if torch.is_tensor(x):
x = x.unsqueeze(1) # Bx1x...
x = x.expand(-1, n, *([-1]*len(x.shape[2:]))) # Bxnx...
x = x.reshape(x.shape[0]*n, *x.shape[2:]) # Bnx...
elif type(x) is list or type(x) is tuple:
x = [repeat_tensors(n, _) for _ in x]
return x
class EncoderDecoder(nn.Module):
"""
A standard Encoder-Decoder architecture. Base for this and many
other models.
"""
def __init__(self, encoder, decoder, src_embed, tgt_embed, generator):
super(EncoderDecoder, self).__init__()
self.encoder = encoder
self.decoder = decoder
self.src_embed = src_embed
self.tgt_embed = tgt_embed
self.generator = generator
def forward(self, src, tgt, src_mask, tgt_mask):
"Take in and process masked src and target sequences."
return self.decode(self.encode(src, src_mask), src_mask,
tgt, tgt_mask)
def encode(self, src, src_mask):
return self.encoder(self.src_embed(src), src_mask)
def decode(self, memory, src_mask, tgt, tgt_mask):
return self.decoder(self.tgt_embed(tgt), memory, src_mask, tgt_mask)
class Generator(nn.Module):
"Define standard linear + softmax generation step."
def __init__(self, d_model, vocab):
super(Generator, self).__init__()
self.proj = nn.Linear(d_model, vocab)
def forward(self, x):
return F.log_softmax(self.proj(x), dim=-1)
def clones(module, N):
"Produce N identical layers."
return nn.ModuleList([copy.deepcopy(module) for _ in range(N)])
class Encoder(nn.Module):
"Core encoder is a stack of N layers"
def __init__(self, layer, N):
super(Encoder, self).__init__()
self.layers = clones(layer, N)
self.norm = LayerNorm(layer.size)
def forward(self, x, mask):
"Pass the input (and mask) through each layer in turn."
for layer in self.layers:
x = layer(x, mask)
return self.norm(x)
class LayerNorm(nn.Module):
"Construct a layernorm module (See citation for details)."
def __init__(self, features, eps=1e-6):
super(LayerNorm, self).__init__()
self.a_2 = nn.Parameter(torch.ones(features))
self.b_2 = nn.Parameter(torch.zeros(features))
self.eps = eps
def forward(self, x):
mean = x.mean(-1, keepdim=True)
std = x.std(-1, keepdim=True)
return self.a_2 * (x - mean) / (std + self.eps) + self.b_2
class SublayerConnection(nn.Module):
"""
A residual connection followed by a layer norm.
Note for code simplicity the norm is first as opposed to last.
"""
def __init__(self, size, dropout):
super(SublayerConnection, self).__init__()
self.norm = LayerNorm(size)
self.dropout = nn.Dropout(dropout)
def forward(self, x, sublayer):
"Apply residual connection to any sublayer with the same size."
return x + self.dropout(sublayer(self.norm(x)))
class EncoderLayer(nn.Module):
"Encoder is made up of self-attn and feed forward (defined below)"
def __init__(self, size, self_attn, feed_forward, dropout):
super(EncoderLayer, self).__init__()
self.self_attn = self_attn
self.feed_forward = feed_forward
self.sublayer = clones(SublayerConnection(size, dropout), 2)
self.size = size
def forward(self, x, mask):
"Follow Figure 1 (left) for connections."
x = self.sublayer[0](x, lambda x: self.self_attn(x, x, x, mask))
return self.sublayer[1](x, self.feed_forward)
class Decoder(nn.Module):
"Generic N layer decoder with masking."
def __init__(self, layer, N):
super(Decoder, self).__init__()
self.layers = clones(layer, N)
self.norm = LayerNorm(layer.size)
def forward(self, x, memory, src_mask, tgt_mask):
for layer in self.layers:
x = layer(x, memory, src_mask, tgt_mask)
return self.norm(x)
class DecoderLayer(nn.Module):
"Decoder is made of self-attn, src-attn, and feed forward (defined below)"
def __init__(self, size, self_attn, src_attn, feed_forward, dropout):
super(DecoderLayer, self).__init__()
self.size = size
self.self_attn = self_attn
self.src_attn = src_attn
self.feed_forward = feed_forward
self.sublayer = clones(SublayerConnection(size, dropout), 3)
def forward(self, x, memory, src_mask, tgt_mask):
"Follow Figure 1 (right) for connections."
m = memory
x = self.sublayer[0](x, lambda x: self.self_attn(x, x, x, tgt_mask))
x = self.sublayer[1](x, lambda x: self.src_attn(x, m, m, src_mask))
return self.sublayer[2](x, self.feed_forward)
def subsequent_mask(size):
"Mask out subsequent positions."
attn_shape = (1, size, size)
subsequent_mask = np.triu(np.ones(attn_shape), k=1).astype('uint8')
return torch.from_numpy(subsequent_mask) == 0
def attention(query, key, value, mask=None, dropout=None):
"Compute 'Scaled Dot Product Attention'"
d_k = query.size(-1)
scores = torch.matmul(query, key.transpose(-2, -1)) \
/ math.sqrt(d_k)
if mask is not None:
scores = scores.masked_fill(mask == 0, float('-inf'))
p_attn = F.softmax(scores, dim = -1)
if dropout is not None:
p_attn = dropout(p_attn)
return torch.matmul(p_attn, value), p_attn
class MultiHeadedAttention(nn.Module):
def __init__(self, h, d_model, dropout=0.1):
"Take in model size and number of heads."
super(MultiHeadedAttention, self).__init__()
assert d_model % h == 0
# We assume d_v always equals d_k
self.d_k = d_model // h
self.h = h
self.linears = clones(nn.Linear(d_model, d_model), 4)
self.attn = None
self.dropout = nn.Dropout(p=dropout)
def forward(self, query, key, value, mask=None):
"Implements Figure 2"
if mask is not None:
# Same mask applied to all h heads.
mask = mask.unsqueeze(1)
nbatches = query.size(0)
# 1) Do all the linear projections in batch from d_model => h x d_k
query, key, value = \
[l(x).view(nbatches, -1, self.h, self.d_k).transpose(1, 2)
for l, x in zip(self.linears, (query, key, value))]
# 2) Apply attention on all the projected vectors in batch.
x, self.attn = attention(query, key, value, mask=mask,
dropout=self.dropout)
# 3) "Concat" using a view and apply a final linear.
x = x.transpose(1, 2).contiguous() \
.view(nbatches, -1, self.h * self.d_k)
return self.linears[-1](x)
class PositionwiseFeedForward(nn.Module):
"Implements FFN equation."
def __init__(self, d_model, d_ff, dropout=0.1):
super(PositionwiseFeedForward, self).__init__()
self.w_1 = nn.Linear(d_model, d_ff)
self.w_2 = nn.Linear(d_ff, d_model)
self.dropout = nn.Dropout(dropout)
def forward(self, x):
return self.w_2(self.dropout(F.relu(self.w_1(x))))
class Embeddings(nn.Module):
def __init__(self, d_model, vocab):
super(Embeddings, self).__init__()
self.lut = nn.Embedding(vocab, d_model)
self.d_model = d_model
def forward(self, x):
return self.lut(x) * math.sqrt(self.d_model)
class PositionalEncoding(nn.Module):
"Implement the PE function."
def __init__(self, d_model, dropout, max_len=5000):
super(PositionalEncoding, self).__init__()
self.dropout = nn.Dropout(p=dropout)
# Compute the positional encodings once in log space.
pe = torch.zeros(max_len, d_model)
position = torch.arange(0, max_len).unsqueeze(1).float()
div_term = torch.exp(torch.arange(0, d_model, 2).float() *
-(math.log(10000.0) / d_model))
pe[:, 0::2] = torch.sin(position * div_term)
pe[:, 1::2] = torch.cos(position * div_term)
pe = pe.unsqueeze(0)
self.register_buffer('pe', pe)
def forward(self, x):
x = x + self.pe[:, :x.size(1)]
return self.dropout(x)
class TransformerModel(AttModel):
def make_model(self, src_vocab, tgt_vocab, N_enc=6, N_dec=6,
d_model=512, d_ff=2048, h=8, dropout=0.1):
"Helper: Construct a model from hyperparameters."
c = copy.deepcopy
attn = MultiHeadedAttention(h, d_model, dropout)
ff = PositionwiseFeedForward(d_model, d_ff, dropout)
position = PositionalEncoding(d_model, dropout)
model = EncoderDecoder(
Encoder(EncoderLayer(d_model, c(attn), c(ff), dropout), N_enc),
Decoder(DecoderLayer(d_model, c(attn), c(attn),
c(ff), dropout), N_dec),
lambda x:x, # nn.Sequential(Embeddings(d_model, src_vocab), c(position)),
nn.Sequential(Embeddings(d_model, tgt_vocab), c(position)),
Generator(d_model, tgt_vocab))
# This was important from their code.
# Initialize parameters with Glorot / fan_avg.
for p in model.parameters():
if p.dim() > 1:
nn.init.xavier_uniform_(p)
return model
def __init__(self, opt):
super(TransformerModel, self).__init__(opt)
self.opt = opt
# self.config = yaml.load(open(opt.config_file))
self.N_enc = getattr(opt, 'N_enc', opt.num_layers)
self.N_dec = getattr(opt, 'N_dec', opt.num_layers)
self.d_model = getattr(opt, 'd_model', opt.input_encoding_size)
self.d_ff = getattr(opt, 'd_ff', opt.rnn_size)
self.h = getattr(opt, 'num_att_heads', 8)
self.dropout = getattr(opt, 'dropout', 0.1)
delattr(self, 'att_embed')
self.att_embed = nn.Sequential(*(
((nn.BatchNorm1d(self.att_feat_size),) if self.use_bn else ())+
(nn.Linear(self.att_feat_size, self.d_model),
nn.ReLU(),
nn.Dropout(self.drop_prob_lm))+
((nn.BatchNorm1d(self.d_model),) if self.use_bn==2 else ())))
delattr(self, 'embed')
self.embed = lambda x : x
delattr(self, 'fc_embed')
self.fc_embed = lambda x : x
delattr(self, 'logit')
del self.ctx2att
tgt_vocab = self.vocab_size + 1
self.model = self.make_model(0, tgt_vocab,
N_enc=self.N_enc,
N_dec=self.N_dec,
d_model=self.d_model,
d_ff=self.d_ff,
h=self.h,
dropout=self.dropout)
def logit(self, x): # unsafe way
return self.model.generator.proj(x)
def init_hidden(self, bsz):
return []
def _prepare_feature(self, fc_feats, att_feats, att_masks):
att_feats, seq, att_masks, seq_mask = self._prepare_feature_forward(att_feats, att_masks)
memory = self.model.encode(att_feats, att_masks)
return fc_feats[...,:0], att_feats[...,:0], memory, att_masks
def _prepare_feature_forward(self, att_feats, att_masks=None, seq=None):
att_feats, att_masks = self.clip_att(att_feats, att_masks)
att_feats = pack_wrapper(self.att_embed, att_feats, att_masks)
if att_masks is None:
att_masks = att_feats.new_ones(att_feats.shape[:2], dtype=torch.long)
att_masks = att_masks.unsqueeze(-2)
if seq is not None:
# crop the last one
# seq = seq[:,:-1]
seq_mask = (seq.data != self.eos_idx) & (seq.data != self.pad_idx)
seq_mask[:,0] = 1 # bos
seq_mask = seq_mask.unsqueeze(-2)
seq_mask = seq_mask & subsequent_mask(seq.size(-1)).to(seq_mask)
seq_per_img = seq.shape[0] // att_feats.shape[0]
if seq_per_img > 1:
att_feats, att_masks = utils.repeat_tensors(seq_per_img,
[att_feats, att_masks]
)
else:
seq_mask = None
return att_feats, seq, att_masks, seq_mask
def _forward(self, fc_feats, att_feats, seq, att_masks=None):
if seq.ndim == 3: # B * seq_per_img * seq_len
seq = seq.reshape(-1, seq.shape[2])
att_feats, seq, att_masks, seq_mask = self._prepare_feature_forward(att_feats, att_masks, seq)
out = self.model(att_feats, seq, att_masks, seq_mask)
outputs = self.model.generator(out)
return outputs
# return torch.cat([_.unsqueeze(1) for _ in outputs], 1)
def core(self, it, fc_feats_ph, att_feats_ph, memory, state, mask):
"""
state = [ys.unsqueeze(0)]
"""
if len(state) == 0:
ys = it.unsqueeze(1)
else:
ys = torch.cat([state[0][0], it.unsqueeze(1)], dim=1)
out = self.model.decode(memory, mask,
ys,
subsequent_mask(ys.size(1))
.to(memory.device))
return out[:, -1], [ys.unsqueeze(0)]