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import torch
from . import losses
from ..utils.rewards import init_scorer, get_self_critical_reward
class LossWrapper(torch.nn.Module):
def __init__(self, model, opt):
super(LossWrapper, self).__init__()
self.opt = opt
self.model = model
if opt.label_smoothing > 0:
self.crit = losses.LabelSmoothing(smoothing=opt.label_smoothing)
else:
self.crit = losses.LanguageModelCriterion()
self.rl_crit = losses.RewardCriterion()
self.struc_crit = losses.StructureLosses(opt)
def forward(self, fc_feats, att_feats, labels, masks, att_masks, gts, gt_indices,
sc_flag, struc_flag):
opt = self.opt
out = {}
if struc_flag:
if opt.structure_loss_weight < 1:
lm_loss = self.crit(self.model(fc_feats, att_feats, labels[..., :-1], att_masks), labels[..., 1:], masks[..., 1:])
else:
lm_loss = torch.tensor(0).type_as(fc_feats)
if opt.structure_loss_weight > 0:
gen_result, sample_logprobs = self.model(fc_feats, att_feats, att_masks,
opt={'sample_method':opt.train_sample_method,
'beam_size':opt.train_beam_size,
'output_logsoftmax': opt.struc_use_logsoftmax or opt.structure_loss_type == 'softmax_margin'\
or not 'margin' in opt.structure_loss_type,
'sample_n': opt.train_sample_n},
mode='sample')
gts = [gts[_] for _ in gt_indices.tolist()]
struc_loss = self.struc_crit(sample_logprobs, gen_result, gts)
else:
struc_loss = {'loss': torch.tensor(0).type_as(fc_feats),
'reward': torch.tensor(0).type_as(fc_feats)}
loss = (1-opt.structure_loss_weight) * lm_loss + opt.structure_loss_weight * struc_loss['loss']
out['lm_loss'] = lm_loss
out['struc_loss'] = struc_loss['loss']
out['reward'] = struc_loss['reward']
elif not sc_flag:
loss = self.crit(self.model(fc_feats, att_feats, labels[..., :-1], att_masks), labels[..., 1:], masks[..., 1:])
else:
self.model.eval()
with torch.no_grad():
greedy_res, _ = self.model(fc_feats, att_feats, att_masks,
mode='sample',
opt={'sample_method': opt.sc_sample_method,
'beam_size': opt.sc_beam_size})
self.model.train()
gen_result, sample_logprobs = self.model(fc_feats, att_feats, att_masks,
opt={'sample_method':opt.train_sample_method,
'beam_size':opt.train_beam_size,
'sample_n': opt.train_sample_n},
mode='sample')
gts = [gts[_] for _ in gt_indices.tolist()]
reward = get_self_critical_reward(greedy_res, gts, gen_result, self.opt)
reward = torch.from_numpy(reward).to(sample_logprobs)
loss = self.rl_crit(sample_logprobs, gen_result.data, reward)
out['reward'] = reward[:,0].mean()
out['loss'] = loss
return out
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