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.autograd import * from . import utils from .CaptionModel import CaptionModel class ShowTellModel(CaptionModel): def __init__(self, opt): super(ShowTellModel, self).__init__() self.vocab_size = opt.vocab_size self.input_encoding_size = opt.input_encoding_size self.rnn_type = opt.rnn_type self.rnn_size = opt.rnn_size self.num_layers = opt.num_layers self.drop_prob_lm = opt.drop_prob_lm self.seq_length = opt.seq_length self.fc_feat_size = opt.fc_feat_size self.ss_prob = 0.0 # Schedule sampling probability self.img_embed = nn.Linear(self.fc_feat_size, self.input_encoding_size) self.core = getattr(nn, self.rnn_type.upper())(self.input_encoding_size, self.rnn_size, self.num_layers, bias=False, dropout=self.drop_prob_lm) self.embed = nn.Embedding(self.vocab_size + 1, self.input_encoding_size) self.logit = nn.Linear(self.rnn_size, self.vocab_size + 1) self.dropout = nn.Dropout(self.drop_prob_lm) self.init_weights() def init_weights(self): initrange = 0.1 self.embed.weight.data.uniform_(-initrange, initrange) self.logit.bias.data.fill_(0) self.logit.weight.data.uniform_(-initrange, initrange) def init_hidden(self, bsz): weight = self.logit.weight if self.rnn_type == 'lstm': return (weight.new_zeros(self.num_layers, bsz, self.rnn_size), weight.new_zeros(self.num_layers, bsz, self.rnn_size)) else: return weight.new_zeros(self.num_layers, bsz, self.rnn_size) def _forward(self, fc_feats, att_feats, seq, att_masks=None): batch_size = fc_feats.size(0) seq_per_img = seq.shape[0] // batch_size state = self.init_hidden(batch_size*seq_per_img) outputs = [] if seq_per_img > 1: fc_feats = utils.repeat_tensors(seq_per_img, fc_feats) for i in range(seq.size(1) + 1): if i == 0: xt = self.img_embed(fc_feats) else: if self.training and i >= 2 and self.ss_prob > 0.0: # otherwiste no need to sample sample_prob = fc_feats.data.new(batch_size*seq_per_img).uniform_(0, 1) sample_mask = sample_prob < self.ss_prob if sample_mask.sum() == 0: it = seq[:, i-1].clone() else: sample_ind = sample_mask.nonzero().view(-1) it = seq[:, i-1].data.clone() #prob_prev = torch.exp(outputs[-1].data.index_select(0, sample_ind)) # fetch prev distribution: shape Nx(M+1) #it.index_copy_(0, sample_ind, torch.multinomial(prob_prev, 1).view(-1)) prob_prev = torch.exp(outputs[-1].data) # fetch prev distribution: shape Nx(M+1) it.index_copy_(0, sample_ind, torch.multinomial(prob_prev, 1).view(-1).index_select(0, sample_ind)) else: it = seq[:, i-1].clone() # break if all the sequences end if i >= 2 and seq[:, i-1].data.sum() == 0: break xt = self.embed(it) output, state = self.core(xt.unsqueeze(0), state) output = F.log_softmax(self.logit(self.dropout(output.squeeze(0))), dim=1) outputs.append(output) return torch.cat([_.unsqueeze(1) for _ in outputs[1:]], 1).contiguous() def get_logprobs_state(self, it, state): # 'it' contains a word index xt = self.embed(it) output, state = self.core(xt.unsqueeze(0), state) logprobs = F.log_softmax(self.logit(self.dropout(output.squeeze(0))), dim=1) return logprobs, state def _sample_beam(self, fc_feats, att_feats, att_masks=None, opt={}): beam_size = opt.get('beam_size', 10) batch_size = fc_feats.size(0) 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 = torch.LongTensor(self.seq_length, batch_size).zero_() seqLogprobs = torch.FloatTensor(self.seq_length, batch_size) # lets process every image independently for now, for simplicity self.done_beams = [[] for _ in range(batch_size)] for k in range(batch_size): state = self.init_hidden(beam_size) for t in range(2): if t == 0: xt = self.img_embed(fc_feats[k:k+1]).expand(beam_size, self.input_encoding_size) elif t == 1: # input it = fc_feats.data.new(beam_size).long().zero_() xt = self.embed(it) output, state = self.core(xt.unsqueeze(0), state) logprobs = F.log_softmax(self.logit(self.dropout(output.squeeze(0))), dim=1) self.done_beams[k] = self.beam_search(state, logprobs, opt=opt) seq[:, k] = self.done_beams[k][0]['seq'] # the first beam has highest cumulative score seqLogprobs[:, k] = self.done_beams[k][0]['logps'] # return the samples and their log likelihoods return seq.transpose(0, 1), seqLogprobs.transpose(0, 1) def _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) if beam_size > 1 and sample_method in ['greedy', 'beam_search']: return self.sample_beam(fc_feats, att_feats, opt) batch_size = fc_feats.size(0) state = self.init_hidden(batch_size) seq = fc_feats.new_zeros(batch_size, self.seq_length, dtype=torch.long) seqLogprobs = fc_feats.new_zeros(batch_size, self.seq_length) for t in range(self.seq_length + 2): if t == 0: xt = self.img_embed(fc_feats) else: if t == 1: # input it = fc_feats.data.new(batch_size).long().zero_() xt = self.embed(it) output, state = self.core(xt.unsqueeze(0), state) logprobs = F.log_softmax(self.logit(self.dropout(output.squeeze(0))), dim=1) # sample the next word if t == self.seq_length + 1: # skip if we achieve maximum length break if sample_method == 'greedy': sampleLogprobs, it = torch.max(logprobs.data, 1) it = it.view(-1).long() else: if temperature == 1.0: prob_prev = torch.exp(logprobs.data).cpu() # fetch prev distribution: shape Nx(M+1) else: # scale logprobs by temperature prob_prev = torch.exp(torch.div(logprobs.data, temperature)).cpu() it = torch.multinomial(prob_prev, 1).to(logprobs.device) sampleLogprobs = logprobs.gather(1, it) # gather the logprobs at sampled positions it = it.view(-1).long() # and flatten indices for downstream processing if t >= 1: # stop when all finished if t == 1: unfinished = it > 0 else: unfinished = unfinished & (it > 0) it = it * unfinished.type_as(it) seq[:,t-1] = it #seq[t] the input of t+2 time step seqLogprobs[:,t-1] = sampleLogprobs.view(-1) if unfinished.sum() == 0: break return seq, seqLogprobs