分析下面代码的作用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 torch.nn.utils.rnn import PackedSequence, pack_padded_sequence, pad_packed_sequence
import modules.utils as utils
from modules.caption_model import CaptionModel
def sort_pack_padded_sequence(input, lengths):
sorted_lengths, indices = torch.sort(lengths, descending=True)
tmp = pack_padded_sequence(input[indices], sorted_lengths.cpu(), batch_first=True)
inv_ix = indices.clone()
inv_ix[indices] = torch.arange(0, len(indices)).type_as(inv_ix)
return tmp, inv_ix
def pad_unsort_packed_sequence(input, inv_ix):
tmp, _ = pad_packed_sequence(input, batch_first=True)
tmp = tmp[inv_ix]
return tmp
def pack_wrapper(module, att_feats, att_masks):
if att_masks is not None:
packed, inv_ix = sort_pack_padded_sequence(att_feats, att_masks.data.long().sum(1))
return pad_unsort_packed_sequence(PackedSequence(module(packed[0]), packed[1]), inv_ix)
else:
return module(att_feats)
class AttModel(CaptionModel):
def __init__(self, args, tokenizer):
super(AttModel, self).__init__()
self.args = args
self.tokenizer = tokenizer
self.vocab_size = len(tokenizer.idx2token)
self.input_encoding_size = args.d_model
self.rnn_size = args.d_ff
self.num_layers = args.num_layers
self.drop_prob_lm = args.drop_prob_lm
self.max_seq_length = args.max_seq_length
self.att_feat_size = args.d_vf
self.att_hid_size = args.d_model
self.bos_idx = args.bos_idx
self.eos_idx = args.eos_idx
self.pad_idx = args.pad_idx
self.use_bn = args.use_bn
self.embed = lambda x: x
self.fc_embed = lambda x: x
self.att_embed = nn.Sequential(*(
((nn.BatchNorm1d(self.att_feat_size),) if self.use_bn else ()) +
(nn.Linear(self.att_feat_size, self.input_encoding_size),
nn.ReLU(),
nn.Dropout(self.drop_prob_lm)) +
((nn.BatchNorm1d(self.input_encoding_size),) if self.use_bn == 2 else ())))
def clip_att(self, att_feats, att_masks):
# Clip the length of att_masks and att_feats to the maximum length
if att_masks is not None:
max_len = att_masks.data.long().sum(1).max()
att_feats = att_feats[:, :max_len].contiguous()
att_masks = att_masks[:, :max_len].contiguous()
return att_feats, att_masks
def _prepare_feature(self, fc_feats, att_feats, att_masks):
att_feats, att_masks = self.clip_att(att_feats, att_masks)
# embed fc and att feats
fc_feats = self.fc_embed(fc_feats)
att_feats = pack_wrapper(self.att_embed, att_feats, att_masks)
# Project the attention feats first to reduce memory and computation comsumptions.
p_att_feats = self.ctx2att(att_feats)
return fc_feats, att_feats, p_att_feats, att_masks
def get_logprobs_state(self, it, fc_feats, att_feats, p_att_feats, att_masks, state, output_logsoftmax=1):
# 'it' contains a word index
xt = self.embed(it)
output, state = self.core(xt, fc_feats, att_feats, p_att_feats, state, att_masks)
if output_logsoftmax:
logprobs = F.log_softmax(self.logit(output), dim=1)
else:
logprobs = self.logit(output)
return logprobs, state
def _sample_beam(self, fc_feats, att_feats, att_masks=None, opt={}):
beam_size = opt.get('beam_size', 10)
group_size = opt.get('group_size', 1)
sample_n = opt.get('sample_n', 10)
# when sample_n == beam_size then each beam is a sample.
assert sample_n == 1 or sample_n == beam_size // group_size, 'when beam search, sample_n == 1 or beam search'
batch_size = fc_feats.size(0)
p_fc_feats, p_att_feats, pp_att_feats, p_att_masks = self._prepare_feature(fc_feats, att_feats, att_masks)
assert beam_size <= self.vocab_size + 1, 'lets assume this for now, otherwise this corner case causes a few headaches down the road. can be dealt with in future if needed'
seq = fc_feats.new_full((batch_size * sample_n, self.max_seq_length), self.pad_idx, dtype=torch.long)
seqLogprobs = fc_feats.new_zeros(batch_size * sample_n, self.max_seq_length, self.vocab_size + 1)
# lets process every image independently for now, for simplicity
self.done_beams = [[] for _ in range(batch_size)]
state = self.init_hidden(batch_size)
# first step, feed bos
it = fc_feats.new_full([batch_size], self.bos_idx, dtype=torch.long)
logprobs, state = self.get_logprobs_state(it, p_fc_feats, p_att_feats, pp_att_feats, p_att_masks, state)
p_fc_feats, p_att_feats, pp_att_feats, p_att_masks = utils.repeat_tensors(beam_size,
[p_fc_feats, p_att_feats,
pp_att_feats, p_att_masks]
)
self.done_beams = self.beam_search(state, logprobs, p_fc_feats, p_att_feats, pp_att_feats, p_att_masks, opt=opt)
for k in range(batch_size):
if sample_n == beam_size:
for _n in range(sample_n):
seq_len = self.done_beams[k][_n]['seq'].shape[0]
seq[k * sample_n + _n, :seq_len] = self.done_beams[k][_n]['seq']
seqLogprobs[k * sample_n + _n, :seq_len] = self.done_beams[k][_n]['logps']
else:
seq_len = self.done_beams[k][0]['seq'].shape[0]
seq[k, :seq_len] = self.done_beams[k][0]['seq'] # the first beam has highest cumulative score
seqLogprobs[k, :seq_len] = self.done_beams[k][0]['logps']
# return the samples and their log likelihoods
return seq, seqLogprobs
def _sample(self, fc_feats, att_feats, att_masks=None, update_opts={}):
opt = self.args.__dict__
opt.update(**update_opts)
sample_method = opt.get('sample_method', 'greedy')
beam_size = opt.get('beam_size', 1)
temperature = opt.get('temperature', 1.0)
sample_n = int(opt.get('sample_n', 1))
group_size = opt.get('group_size', 1)
output_logsoftmax = opt.get('output_logsoftmax', 1)
decoding_constraint = opt.get('decoding_constraint', 0)
block_trigrams = opt.get('block_trigrams', 0)
if beam_size > 1 and sample_method in ['greedy', 'beam_search']:
return self._sample_beam(fc_feats, att_feats, att_masks, opt)
if group_size > 1:
return self._diverse_sample(fc_feats, att_feats, att_masks, opt)
batch_size = fc_feats.size(0)
state = self.init_hidden(batch_size * sample_n)
p_fc_feats, p_att_feats, pp_att_feats, p_att_masks = self._prepare_feature(fc_feats, att_feats, att_masks)
if sample_n > 1:
p_fc_feats, p_att_feats, pp_att_feats, p_att_masks = utils.repeat_tensors(sample_n,
[p_fc_feats, p_att_feats,
pp_att_feats, p_att_masks]
)
trigrams = [] # will be a list of batch_size dictionaries
seq = fc_feats.new_full((batch_size * sample_n, self.max_seq_length), self.pad_idx, dtype=torch.long)
seqLogprobs = fc_feats.new_zeros(batch_size * sample_n, self.max_seq_length, self.vocab_size + 1)
for t in range(self.max_seq_length + 1):
if t == 0: # input <bos>
it = fc_feats.new_full([batch_size * sample_n], self.bos_idx, dtype=torch.long)
logprobs, state = self.get_logprobs_state(it, p_fc_feats, p_att_feats, pp_att_feats, p_att_masks, state,
output_logsoftmax=output_logsoftmax)
if decoding_constraint and t > 0:
tmp = logprobs.new_zeros(logprobs.size())
tmp.scatter_(1, seq[:, t - 1].data.unsqueeze(1), float('-inf'))
logprobs = logprobs + tmp
# Mess with trigrams
# Copy from https://github.com/lukemelas/image-paragraph-captioning
if block_trigrams and t >= 3:
# Store trigram generated at last step
prev_two_batch = seq[:, t - 3:t - 1]
for i in range(batch_size): # = seq.size(0)
prev_two = (prev_two_batch[i][0].item(), prev_two_batch[i][1].item())
current = seq[i][t - 1]
if t == 3: # initialize
trigrams.append({prev_two: [current]}) # {LongTensor: list containing 1 int}
elif t > 3:
if prev_two in trigrams[i]: # add to list
trigrams[i][prev_two].append(current)
else: # create list
trigrams[i][prev_two] = [current]
# Block used trigrams at next step
prev_two_batch = seq[:, t - 2:t]
mask = torch.zeros(logprobs.size(), requires_grad=False).cuda() # batch_size x vocab_size
for i in range(batch_size):
prev_two = (prev_two_batch[i][0].item(), prev_two_batch[i][1].item())
if prev_two in trigrams[i]:
for j in trigrams[i][prev_two]:
mask[i, j] += 1
# Apply mask to log probs
# logprobs = logprobs - (mask * 1e9)
alpha = 2.0 # = 4
logprobs = logprobs + (mask * -0.693 * alpha) # ln(1/2) * alpha (alpha -> infty works best)
# sample the next word
if t == self.max_seq_length: # skip if we achieve maximum length
break
it, sampleLogprobs = self.sample_next_word(logprobs, sample_method, temperature)
# stop when all finished
if t == 0:
unfinished = it != self.eos_idx
else:
it[~unfinished] = self.pad_idx # This allows eos_idx not being overwritten to 0
logprobs = logprobs * unfinished.unsqueeze(1).float()
unfinished = unfinished * (it != self.eos_idx)
seq[:, t] = it
seqLogprobs[:, t] = logprobs
# quit loop if all sequences have finished
if unfinished.sum() == 0:
break
return seq, seqLogprobs
def _diverse_sample(self, fc_feats, att_feats, att_masks=None, opt={}):
sample_method = opt.get('sample_method', 'greedy')
beam_size = opt.get('beam_size', 1)
temperature = opt.get('temperature', 1.0)
group_size = opt.get('group_size', 1)
diversity_lambda = opt.get('diversity_lambda', 0.5)
decoding_constraint = opt.get('decoding_constraint', 0)
block_trigrams = opt.get('block_trigrams', 0)
batch_size = fc_feats.size(0)
state = self.init_hidden(batch_size)
p_fc_feats, p_att_feats, pp_att_feats, p_att_masks = self._prepare_feature(fc_feats, att_feats, att_masks)
trigrams_table = [[] for _ in range(group_size)] # will be a list of batch_size dictionaries
seq_table = [fc_feats.new_full((batch_size, self.max_seq_length), self.pad_idx, dtype=torch.long) for _ in
range(group_size)]
seqLogprobs_table = [fc_feats.new_zeros(batch_size, self.max_seq_length) for _ in range(group_size)]
state_table = [self.init_hidden(batch_size) for _ in range(group_size)]
for tt in range(self.max_seq_length + group_size):
for divm in range(group_size):
t = tt - divm
seq = seq_table[divm]
seqLogprobs = seqLogprobs_table[divm]
trigrams = trigrams_table[divm]
if t >= 0 and t <= self.max_seq_length - 1:
if t == 0: # input <bos>
it = fc_feats.new_full([batch_size], self.bos_idx, dtype=torch.long)
else:
it = seq[:, t - 1] # changed
logprobs, state_table[divm] = self.get_logprobs_state(it, p_fc_feats, p_att_feats, pp_att_feats,
p_att_masks, state_table[divm]) # changed
logprobs = F.log_softmax(logprobs / temperature, dim=-1)
# Add diversity
if divm > 0:
unaug_logprobs = logprobs.clone()
for prev_choice in range(divm):
prev_decisions = seq_table[prev_choice][:, t]
logprobs[:, prev_decisions] = logprobs[:, prev_decisions] - diversity_lambda
if decoding_constraint and t > 0:
tmp = logprobs.new_zeros(logprobs.size())
tmp.scatter_(1, seq[:, t - 1].data.unsqueeze(1), float('-inf'))
logprobs = logprobs + tmp
# Mess with trigrams
if block_trigrams and t >= 3:
# Store trigram generated at last step
prev_two_batch = seq[:, t - 3:t - 1]
for i in range(batch_size): # = seq.size(0)
prev_two = (prev_two_batch[i][0].item(), prev_two_batch[i][1].item())
current = seq[i][t - 1]
if t == 3: # initialize
trigrams.append({prev_two: [current]}) # {LongTensor: list containing 1 int}
elif t > 3:
if prev_two in trigrams[i]: # add to list
trigrams[i][prev_two].append(current)
else: # create list
trigrams[i][prev_two] = [current]
# Block used trigrams at next step
prev_two_batch = seq[:, t - 2:t]
mask = torch.zeros(logprobs.size(), requires_grad=False).cuda() # batch_size x vocab_size
for i in range(batch_size):
prev_two = (prev_two_batch[i][0].item(), prev_two_batch[i][1].item())
if prev_two in trigrams[i]:
for j in trigrams[i][prev_two]:
mask[i, j] += 1
# Apply mask to log probs
# logprobs = logprobs - (mask * 1e9)
alpha = 2.0 # = 4
logprobs = logprobs + (mask * -0.693 * alpha) # ln(1/2) * alpha (alpha -> infty works best)
it, sampleLogprobs = self.sample_next_word(logprobs, sample_method, 1)
# stop when all finished
if t == 0:
unfinished = it != self.eos_idx
else:
unfinished = seq[:, t - 1] != self.pad_idx & seq[:, t - 1] != self.eos_idx
it[~unfinished] = self.pad_idx
unfinished = unfinished & (it != self.eos_idx) # changed
seq[:, t] = it
seqLogprobs[:, t] = sampleLogprobs.view(-1)
return torch.stack(seq_table, 1).reshape(batch_size * group_size, -1), torch.stack(seqLogprobs_table,
1).reshape(
batch_size * group_size, -1)
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