# Copyright 2019 Kyoto University (Hirofumi Inaguma)
# Apache 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
"""Transformer text translation model (pytorch)."""
import logging
import math
from argparse import Namespace
import numpy as np
import torch
from espnet.nets.e2e_asr_common import end_detect
from espnet.nets.e2e_mt_common import ErrorCalculator
from espnet.nets.mt_interface import MTInterface
from espnet.nets.pytorch_backend.e2e_mt import Reporter
from espnet.nets.pytorch_backend.nets_utils import (
get_subsample,
make_pad_mask,
th_accuracy,
to_device,
)
from espnet.nets.pytorch_backend.transformer.add_sos_eos import add_sos_eos
from espnet.nets.pytorch_backend.transformer.argument import ( # noqa: H301
add_arguments_transformer_common,
)
from espnet.nets.pytorch_backend.transformer.attention import MultiHeadedAttention
from espnet.nets.pytorch_backend.transformer.decoder import Decoder
from espnet.nets.pytorch_backend.transformer.encoder import Encoder
from espnet.nets.pytorch_backend.transformer.initializer import initialize
from espnet.nets.pytorch_backend.transformer.label_smoothing_loss import ( # noqa: H301
LabelSmoothingLoss,
)
from espnet.nets.pytorch_backend.transformer.mask import subsequent_mask, target_mask
from espnet.nets.pytorch_backend.transformer.plot import PlotAttentionReport
from espnet.utils.fill_missing_args import fill_missing_args
[docs]class E2E(MTInterface, torch.nn.Module):
"""E2E module.
:param int idim: dimension of inputs
:param int odim: dimension of outputs
:param Namespace args: argument Namespace containing options
"""
[docs] @staticmethod
def add_arguments(parser):
"""Add arguments."""
group = parser.add_argument_group("transformer model setting")
group = add_arguments_transformer_common(group)
return parser
@property
def attention_plot_class(self):
"""Return PlotAttentionReport."""
return PlotAttentionReport
def __init__(self, idim, odim, args, ignore_id=-1):
"""Construct an E2E object.
:param int idim: dimension of inputs
:param int odim: dimension of outputs
:param Namespace args: argument Namespace containing options
"""
torch.nn.Module.__init__(self)
# fill missing arguments for compatibility
args = fill_missing_args(args, self.add_arguments)
if args.transformer_attn_dropout_rate is None:
args.transformer_attn_dropout_rate = args.dropout_rate
self.encoder = Encoder(
idim=idim,
selfattention_layer_type=args.transformer_encoder_selfattn_layer_type,
attention_dim=args.adim,
attention_heads=args.aheads,
conv_wshare=args.wshare,
conv_kernel_length=args.ldconv_encoder_kernel_length,
conv_usebias=args.ldconv_usebias,
linear_units=args.eunits,
num_blocks=args.elayers,
input_layer="embed",
dropout_rate=args.dropout_rate,
positional_dropout_rate=args.dropout_rate,
attention_dropout_rate=args.transformer_attn_dropout_rate,
)
self.decoder = Decoder(
odim=odim,
selfattention_layer_type=args.transformer_decoder_selfattn_layer_type,
attention_dim=args.adim,
attention_heads=args.aheads,
conv_wshare=args.wshare,
conv_kernel_length=args.ldconv_decoder_kernel_length,
conv_usebias=args.ldconv_usebias,
linear_units=args.dunits,
num_blocks=args.dlayers,
dropout_rate=args.dropout_rate,
positional_dropout_rate=args.dropout_rate,
self_attention_dropout_rate=args.transformer_attn_dropout_rate,
src_attention_dropout_rate=args.transformer_attn_dropout_rate,
)
self.pad = 0 # use <blank> for padding
self.sos = odim - 1
self.eos = odim - 1
self.odim = odim
self.ignore_id = ignore_id
self.subsample = get_subsample(args, mode="mt", arch="transformer")
self.reporter = Reporter()
# tie source and target emeddings
if args.tie_src_tgt_embedding:
if idim != odim:
raise ValueError(
"When using tie_src_tgt_embedding, idim and odim must be equal."
)
self.encoder.embed[0].weight = self.decoder.embed[0].weight
# tie emeddings and the classfier
if args.tie_classifier:
self.decoder.output_layer.weight = self.decoder.embed[0].weight
self.criterion = LabelSmoothingLoss(
self.odim,
self.ignore_id,
args.lsm_weight,
args.transformer_length_normalized_loss,
)
self.normalize_length = args.transformer_length_normalized_loss # for PPL
self.reset_parameters(args)
self.adim = args.adim
self.error_calculator = ErrorCalculator(
args.char_list, args.sym_space, args.sym_blank, args.report_bleu
)
self.rnnlm = None
# multilingual MT related
self.multilingual = args.multilingual
[docs] def reset_parameters(self, args):
"""Initialize parameters."""
initialize(self, args.transformer_init)
torch.nn.init.normal_(self.encoder.embed[0].weight, mean=0, std=args.adim**-0.5)
torch.nn.init.constant_(self.encoder.embed[0].weight[self.pad], 0)
torch.nn.init.normal_(self.decoder.embed[0].weight, mean=0, std=args.adim**-0.5)
torch.nn.init.constant_(self.decoder.embed[0].weight[self.pad], 0)
[docs] def forward(self, xs_pad, ilens, ys_pad):
"""E2E forward.
:param torch.Tensor xs_pad: batch of padded source sequences (B, Tmax)
:param torch.Tensor ilens: batch of lengths of source sequences (B)
:param torch.Tensor ys_pad: batch of padded target sequences (B, Lmax)
:rtype: torch.Tensor
:return: attention loss value
:rtype: torch.Tensor
:return: accuracy in attention decoder
:rtype: float
"""
# 1. forward encoder
xs_pad = xs_pad[:, : max(ilens)] # for data parallel
src_mask = (~make_pad_mask(ilens.tolist())).to(xs_pad.device).unsqueeze(-2)
xs_pad, ys_pad = self.target_forcing(xs_pad, ys_pad)
hs_pad, hs_mask = self.encoder(xs_pad, src_mask)
# 2. forward decoder
ys_in_pad, ys_out_pad = add_sos_eos(ys_pad, self.sos, self.eos, self.ignore_id)
ys_mask = target_mask(ys_in_pad, self.ignore_id)
pred_pad, pred_mask = self.decoder(ys_in_pad, ys_mask, hs_pad, hs_mask)
# 3. compute attention loss
self.loss = self.criterion(pred_pad, ys_out_pad)
self.acc = th_accuracy(
pred_pad.view(-1, self.odim), ys_out_pad, ignore_label=self.ignore_id
)
# 4. compute corpus-level bleu in a mini-batch
if self.training:
self.bleu = None
else:
ys_hat = pred_pad.argmax(dim=-1)
self.bleu = self.error_calculator(ys_hat.cpu(), ys_pad.cpu())
loss_data = float(self.loss)
if self.normalize_length:
self.ppl = np.exp(loss_data)
else:
batch_size = ys_out_pad.size(0)
ys_out_pad = ys_out_pad.view(-1)
ignore = ys_out_pad == self.ignore_id # (B*T,)
total_n_tokens = len(ys_out_pad) - ignore.sum().item()
self.ppl = np.exp(loss_data * batch_size / total_n_tokens)
if not math.isnan(loss_data):
self.reporter.report(loss_data, self.acc, self.ppl, self.bleu)
else:
logging.warning("loss (=%f) is not correct", loss_data)
return self.loss
[docs] def scorers(self):
"""Scorers."""
return dict(decoder=self.decoder)
[docs] def encode(self, xs):
"""Encode source sentences."""
self.eval()
xs = torch.as_tensor(xs).unsqueeze(0)
enc_output, _ = self.encoder(xs, None)
return enc_output.squeeze(0)
[docs] def target_forcing(self, xs_pad, ys_pad=None, tgt_lang=None):
"""Prepend target language IDs to source sentences for multilingual MT.
These tags are prepended in source/target sentences as pre-processing.
:param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax)
:return: source text without language IDs
:rtype: torch.Tensor
:return: target text without language IDs
:rtype: torch.Tensor
:return: target language IDs
:rtype: torch.Tensor (B, 1)
"""
if self.multilingual:
xs_pad = xs_pad[:, 1:] # remove source language IDs here
if ys_pad is not None:
# remove language ID in the beginning
lang_ids = ys_pad[:, 0].unsqueeze(1)
ys_pad = ys_pad[:, 1:]
elif tgt_lang is not None:
lang_ids = xs_pad.new_zeros(xs_pad.size(0), 1).fill_(tgt_lang)
else:
raise ValueError("Set ys_pad or tgt_lang.")
# prepend target language ID to source sentences
xs_pad = torch.cat([lang_ids, xs_pad], dim=1)
return xs_pad, ys_pad
[docs] def translate(self, x, trans_args, char_list=None):
"""Translate source text.
:param list x: input source text feature (T,)
:param Namespace trans_args: argment Namespace contraining options
:param list char_list: list of characters
:return: N-best decoding results
:rtype: list
"""
self.eval() # NOTE: this is important because self.encode() is not used
assert isinstance(x, list)
# make a utt list (1) to use the same interface for encoder
if self.multilingual:
x = to_device(
self, torch.from_numpy(np.fromiter(map(int, x[0][1:]), dtype=np.int64))
)
else:
x = to_device(
self, torch.from_numpy(np.fromiter(map(int, x[0]), dtype=np.int64))
)
logging.info("input lengths: " + str(x.size(0)))
xs_pad = x.unsqueeze(0)
tgt_lang = None
if trans_args.tgt_lang:
tgt_lang = char_list.index(trans_args.tgt_lang)
xs_pad, _ = self.target_forcing(xs_pad, tgt_lang=tgt_lang)
h, _ = self.encoder(xs_pad, None)
logging.info("encoder output lengths: " + str(h.size(1)))
# search parms
beam = trans_args.beam_size
penalty = trans_args.penalty
if trans_args.maxlenratio == 0:
maxlen = h.size(1)
else:
# maxlen >= 1
maxlen = max(1, int(trans_args.maxlenratio * h.size(1)))
minlen = int(trans_args.minlenratio * h.size(1))
logging.info("max output length: " + str(maxlen))
logging.info("min output length: " + str(minlen))
# initialize hypothesis
hyp = {"score": 0.0, "yseq": [self.sos]}
hyps = [hyp]
ended_hyps = []
for i in range(maxlen):
logging.debug("position " + str(i))
# batchfy
ys = h.new_zeros((len(hyps), i + 1), dtype=torch.int64)
for j, hyp in enumerate(hyps):
ys[j, :] = torch.tensor(hyp["yseq"])
ys_mask = subsequent_mask(i + 1).unsqueeze(0).to(h.device)
local_scores = self.decoder.forward_one_step(
ys, ys_mask, h.repeat([len(hyps), 1, 1])
)[0]
hyps_best_kept = []
for j, hyp in enumerate(hyps):
local_best_scores, local_best_ids = torch.topk(
local_scores[j : j + 1], beam, dim=1
)
for j in range(beam):
new_hyp = {}
new_hyp["score"] = hyp["score"] + float(local_best_scores[0, j])
new_hyp["yseq"] = [0] * (1 + len(hyp["yseq"]))
new_hyp["yseq"][: len(hyp["yseq"])] = hyp["yseq"]
new_hyp["yseq"][len(hyp["yseq"])] = int(local_best_ids[0, j])
# will be (2 x beam) hyps at most
hyps_best_kept.append(new_hyp)
hyps_best_kept = sorted(
hyps_best_kept, key=lambda x: x["score"], reverse=True
)[:beam]
# sort and get nbest
hyps = hyps_best_kept
logging.debug("number of pruned hypothes: " + str(len(hyps)))
if char_list is not None:
logging.debug(
"best hypo: "
+ "".join([char_list[int(x)] for x in hyps[0]["yseq"][1:]])
)
# add eos in the final loop to avoid that there are no ended hyps
if i == maxlen - 1:
logging.info("adding <eos> in the last position in the loop")
for hyp in hyps:
hyp["yseq"].append(self.eos)
# add ended hypothes to a final list, and removed them from current hypothes
# (this will be a probmlem, number of hyps < beam)
remained_hyps = []
for hyp in hyps:
if hyp["yseq"][-1] == self.eos:
# only store the sequence that has more than minlen outputs
# also add penalty
if len(hyp["yseq"]) > minlen:
hyp["score"] += (i + 1) * penalty
ended_hyps.append(hyp)
else:
remained_hyps.append(hyp)
# end detection
if end_detect(ended_hyps, i) and trans_args.maxlenratio == 0.0:
logging.info("end detected at %d", i)
break
hyps = remained_hyps
if len(hyps) > 0:
logging.debug("remeined hypothes: " + str(len(hyps)))
else:
logging.info("no hypothesis. Finish decoding.")
break
if char_list is not None:
for hyp in hyps:
logging.debug(
"hypo: " + "".join([char_list[int(x)] for x in hyp["yseq"][1:]])
)
logging.debug("number of ended hypothes: " + str(len(ended_hyps)))
nbest_hyps = sorted(ended_hyps, key=lambda x: x["score"], reverse=True)[
: min(len(ended_hyps), trans_args.nbest)
]
# check number of hypotheis
if len(nbest_hyps) == 0:
logging.warning(
"there is no N-best results, perform translation "
"again with smaller minlenratio."
)
# should copy becasuse Namespace will be overwritten globally
trans_args = Namespace(**vars(trans_args))
trans_args.minlenratio = max(0.0, trans_args.minlenratio - 0.1)
return self.translate(x, trans_args, char_list)
logging.info("total log probability: " + str(nbest_hyps[0]["score"]))
logging.info(
"normalized log probability: "
+ str(nbest_hyps[0]["score"] / len(nbest_hyps[0]["yseq"]))
)
return nbest_hyps
[docs] def calculate_all_attentions(self, xs_pad, ilens, ys_pad):
"""E2E attention calculation.
:param torch.Tensor xs_pad: batch of padded input sequences (B, Tmax)
:param torch.Tensor ilens: batch of lengths of input sequences (B)
:param torch.Tensor ys_pad: batch of padded token id sequence tensor (B, Lmax)
:return: attention weights (B, H, Lmax, Tmax)
:rtype: float ndarray
"""
self.eval()
with torch.no_grad():
self.forward(xs_pad, ilens, ys_pad)
ret = dict()
for name, m in self.named_modules():
if isinstance(m, MultiHeadedAttention) and m.attn is not None:
ret[name] = m.attn.cpu().numpy()
self.train()
return ret