nmt.py

# Copyright 2017 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
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#
#     http://www.apache.org/licenses/LICENSE-2.0
#
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# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# limitations under the License.
# ==============================================================================
#
# Copyright (c) 2019, NVIDIA CORPORATION. All rights reserved.
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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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#     http://www.apache.org/licenses/LICENSE-2.0
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# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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"""TensorFlow NMT model implementation."""
from __future__ import print_function

import argparse
import os
import random
import sys
import subprocess

# import matplotlib.image as mpimg
import numpy as np
import time
import tensorflow as tf

import estimator
from utils import evaluation_utils
from utils import iterator_utils
from utils import misc_utils as utils
from utils import vocab_utils
from variable_mgr import constants

utils.check_tensorflow_version()

FLAGS = None


# LINT.IfChange
def add_arguments(parser):
  """Build ArgumentParser."""
  parser.register("type", "bool", lambda v: v.lower() == "true")

  # network
  parser.add_argument(
      "--num_units", type=int, default=1024, help="Network size.")
  parser.add_argument(
      "--num_layers", type=int, default=4, help="Network depth.")
  parser.add_argument("--num_encoder_layers", type=int, default=None,
                      help="Encoder depth, equal to num_layers if None.")
  parser.add_argument("--num_decoder_layers", type=int, default=None,
                      help="Decoder depth, equal to num_layers if None.")
  parser.add_argument(
      "--encoder_type",
      type=str,
      default="gnmt",
      help="""\
      uni | bi | gnmt.
      For bi, we build num_encoder_layers/2 bi-directional layers.
      For gnmt, we build 1 bi-directional layer, and (num_encoder_layers - 1)
        uni-directional layers.\
      """)
  parser.add_argument(
      "--residual",
      type="bool",
      nargs="?",
      const=True,
      default=True,
      help="Whether to add residual connections.")
  parser.add_argument("--time_major", type="bool", nargs="?", const=True,
                      default=True,
                      help="Whether to use time-major mode for dynamic RNN.")
  parser.add_argument("--num_embeddings_partitions", type=int, default=0,
                      help="Number of partitions for embedding vars.")

  # attention mechanisms
  parser.add_argument(
      "--attention",
      type=str,
      default="normed_bahdanau",
      help="""\
      luong | scaled_luong | bahdanau | normed_bahdanau or set to "" for no
      attention\
      """)
  parser.add_argument(
      "--attention_architecture",
      type=str,
      default="gnmt_v2",
      help="""\
      standard | gnmt | gnmt_v2.
      standard: use top layer to compute attention.
      gnmt: GNMT style of computing attention, use previous bottom layer to
          compute attention.
      gnmt_v2: similar to gnmt, but use current bottom layer to compute
          attention.\
      """)
  parser.add_argument(
      "--output_attention", type="bool", nargs="?", const=True,
      default=True,
      help="""\
      Only used in standard attention_architecture. Whether use attention as
      the cell output at each timestep.
      .\
      """)
  parser.add_argument(
      "--pass_hidden_state", type="bool", nargs="?", const=True,
      default=True,
      help="""\
      Whether to pass encoder's hidden state to decoder when using an attention
      based model.\
      """)

  # optimizer
  parser.add_argument(
      "--optimizer", type=str, default="adam", help="sgd | adam")
  parser.add_argument(
      "--learning_rate",
      type=float,
      default=5e-4,
      help="Learning rate. Adam: 0.001 | 0.0001")
  parser.add_argument("--warmup_steps", type=int, default=200,
                      help="How many steps we inverse-decay learning.")
  parser.add_argument("--warmup_scheme", type=str, default="t2t", help="""\
      How to warmup learning rates. Options include:
        t2t: Tensor2Tensor's way, start with lr 100 times smaller, then
             exponentiate until the specified lr.\
      """)
  parser.add_argument(
      "--decay_scheme", type=str, default="luong234", help="""\
      How we decay learning rate. Options include:
        luong234: after 2/3 num train steps, we start halving the learning rate
          for 4 times before finishing.
        luong5: after 1/2 num train steps, we start halving the learning rate
          for 5 times before finishing.\
        luong10: after 1/2 num train steps, we start halving the learning rate
          for 10 times before finishing.\
      """)

  parser.add_argument(
      "--max_train_epochs", type=int, default=6, help="Max number of epochs.")
  parser.add_argument(
      "--target_bleu", type=float, default=None, help="Target bleu.")
  parser.add_argument("--colocate_gradients_with_ops", type="bool", nargs="?",
                      const=True,
                      default=True,
                      help=("Whether try colocating gradients with "
                            "corresponding op"))
  parser.add_argument("--label_smoothing", type=float, default=0.1,
                      help=("If nonzero, smooth the labels towards "
                            "1/num_classes."))

  # initializer
  parser.add_argument("--init_op", type=str, default="uniform",
                      help="uniform | glorot_normal | glorot_uniform")
  parser.add_argument("--init_weight", type=float, default=0.1,
                      help=("for uniform init_op, initialize weights "
                            "between [-this, this]."))

  # data
  parser.add_argument(
      "--src", type=str, default="en", help="Source suffix, e.g., en.")
  parser.add_argument(
      "--tgt", type=str, default="de", help="Target suffix, e.g., de.")
  parser.add_argument(
      "--data_dir", type=str, default="data/wmt16_de_en",
      help="Training/eval data directory.")

  parser.add_argument(
      "--train_prefix",
      type=str,
      default="train.tok.clean.bpe.32000",
      help="Train prefix, expect files with src/tgt suffixes.")
  parser.add_argument(
      "--test_prefix",
      type=str,
      default="newstest2014.tok.bpe.32000",
      help="Test prefix, expect files with src/tgt suffixes.")

  parser.add_argument(
      "--translate_file",
      type=str,
      help="File to translate, works only with translate mode")

  parser.add_argument(
      "--output_dir", type=str, default="results",
      help="Store log/model files.")

  # Vocab
  parser.add_argument(
      "--vocab_prefix",
      type=str,
      default="vocab.bpe.32000",
      help="""\
      Vocab prefix, expect files with src/tgt suffixes.\
      """)

  parser.add_argument(
      "--embed_prefix",
      type=str,
      default=None,
      help="""\
      Pretrained embedding prefix, expect files with src/tgt suffixes.
      The embedding files should be Glove formatted txt files.\
      """)
  parser.add_argument("--sos", type=str, default="<s>",
                      help="Start-of-sentence symbol.")
  parser.add_argument("--eos", type=str, default="</s>",
                      help="End-of-sentence symbol.")
  parser.add_argument(
      "--share_vocab",
      type="bool",
      nargs="?",
      const=True,
      default=True,
      help="""\
      Whether to use the source vocab and embeddings for both source and
      target.\
      """)
  parser.add_argument("--check_special_token", type="bool", default=True,
                      help="""\
                      Whether check special sos, eos, unk tokens exist in the
                      vocab files.\
                      """)

  # Sequence lengths
  parser.add_argument(
      "--src_max_len",
      type=int,
      default=50,
      help="Max length of src sequences during training (including EOS).")
  parser.add_argument(
      "--tgt_max_len",
      type=int,
      default=50,
      help="Max length of tgt sequences during training (including BOS).")
  parser.add_argument("--src_max_len_infer", type=int, default=None,
                      help="Max length of src sequences during inference (including EOS).")
  parser.add_argument("--tgt_max_len_infer", type=int, default=80,
                      help="""\
      Max length of tgt sequences during inference (including BOS).  Also use to restrict the
      maximum decoding length.\
      """)

  # Default settings works well (rarely need to change)
  parser.add_argument("--unit_type", type=str, default="lstm",
                      help="lstm | gru | layer_norm_lstm | nas")
  parser.add_argument("--forget_bias", type=float, default=0.0,
                      help="Forget bias for BasicLSTMCell.")
  parser.add_argument("--dropout", type=float, default=0.2,
                      help="Dropout rate (not keep_prob)")
  parser.add_argument("--max_gradient_norm", type=float, default=5.0,
                      help="Clip gradients to this norm.")
  parser.add_argument("--batch_size", type=int, default=128, help="Total batch size.")

  parser.add_argument(
      "--num_buckets",
      type=int,
      default=5,
      help="Put data into similar-length buckets (only for training).")

  # SPM
  parser.add_argument("--subword_option", type=str, default="bpe",
                      choices=["", "bpe", "spm"],
                      help="""\
                      Set to bpe or spm to activate subword desegmentation.\
                      """)

  # Experimental encoding feature.
  parser.add_argument("--use_char_encode", type="bool", default=False,
                      help="""\
                      Whether to split each word or bpe into character, and then
                      generate the word-level representation from the character
                      reprentation.
                      """)

  # Misc
  parser.add_argument(
      "--save_checkpoints_steps", type=int, default=2000,
      help="save_checkpoints_steps")
  parser.add_argument(
      "--log_step_count_steps", type=int, default=10,
      help=("The frequency, in number of global steps, that the global step "
            "and the loss will be logged during training"))
  parser.add_argument(
      "--num_gpus", type=int, default=1, help="Number of gpus in each worker.")
  parser.add_argument("--hparams_path", type=str, default=None,
      help=("Path to standard hparams json file that overrides"
            "hparams values from FLAGS."))
  parser.add_argument(
      "--random_seed",
      type=int,
      default=1,
      help="Random seed (>0, set a specific seed).")
  parser.add_argument("--language_model", type="bool", nargs="?",
                      const=True, default=False,
                      help="True to train a language model, ignoring encoder")

  # Inference
  parser.add_argument("--ckpt", type=str, default=None,
                      help="Checkpoint file to load a model for inference. (defaults to newest checkpoint)")
  parser.add_argument(
      "--infer_batch_size",
      type=int,
      default=128,
      help="Batch size for inference mode.")
  parser.add_argument("--detokenizer_file", type=str,
                      default=None,
                      help=("""Detokenizer script file. Default: DATA_DIR/mosesdecoder/scripts/tokenizer/detokenizer.perl"""))
  parser.add_argument("--tokenizer_file", type=str,
                      default=None,
                      help=("""Tokenizer script file. Default: DATA_DIR/mosesdecoder/scripts/tokenizer/tokenizer.perl"""))

  # Advanced inference arguments
  parser.add_argument("--infer_mode", type=str, default="beam_search",
                      choices=["greedy", "beam_search"],
                      help="Which type of decoder to use during inference.")
  parser.add_argument("--beam_width", type=int, default=5,
                      help=("""\
      beam width when using beam search decoder. If 0, use standard
      decoder with greedy helper.\
      """))
  parser.add_argument(
      "--length_penalty_weight",
      type=float,
      default=0.6,
      help="Length penalty for beam search.")
  parser.add_argument(
      "--coverage_penalty_weight",
      type=float,
      default=0.1,
      help="Coverage penalty for beam search.")

  # Job info
  parser.add_argument("--num_workers", type=int, default=1,
                      help="Number of workers (inference only).")

  parser.add_argument("--use_amp", type="bool", default=True,
                      help="use_amp for training and inference")
  parser.add_argument("--use_fastmath", type="bool", default=False,
                      help="use_fastmath for training and inference")
  parser.add_argument("--use_fp16", type="bool", default=False,
                      help="use_fp16 for training and inference")
  parser.add_argument(
      "--fp16_loss_scale",
      type=float,
      default=128,
      help="If fp16 is enabled, the loss is multiplied by this amount "
      "right before gradients are computed, then each gradient "
      "is divided by this amount. Mathematically, this has no "
      "effect, but it helps avoid fp16 underflow. Set to 1 to "
      "effectively disable.")
  parser.add_argument(
      "--enable_auto_loss_scale",
      type="bool",
      default=True,
      help="If True and use_fp16 is True, automatically adjust the "
      "loss scale during training.")
  parser.add_argument(
      "--fp16_inc_loss_scale_every_n",
      type=int,
      default=128,
      help="If fp16 is enabled and enable_auto_loss_scale is "
      "True, increase the loss scale every n steps.")
  parser.add_argument(
      "--check_tower_loss_numerics",
      type="bool",
      default=False,  # Set to false for xla.compile()
      help="whether to check tower loss numerics")
  parser.add_argument(
      "--use_fp32_batch_matmul",
      type="bool",
      default=False,
      help="Whether to use fp32 batch matmul")

  # Performance
  # XLA
  parser.add_argument(
      "--force_inputs_padding",
      type="bool",
      default=False,
      help="Force padding input batch to src_max_len and tgt_max_len")
  parser.add_argument(
      "--use_xla",
      type="bool",
      default=False,
      help="Use xla to compile a few selected locations, mostly Defuns.")
  parser.add_argument(
      "--xla_compile",
      type="bool",
      default=False,
      help="Use xla.compile() for each tower's fwd and bak pass.")
  parser.add_argument(
      "--use_autojit_xla",
      type="bool",
      default=False,
      help="Use auto jit xla.")
  # GPU knobs
  parser.add_argument(
      "--use_pintohost_optimizer",
      type="bool",
      default=False,
      help="whether to use PinToHost optimizer")
  parser.add_argument(
      "--use_cudnn_lstm",
      type="bool",
      default=False,
      help="whether to use cudnn_lstm for encoder, non residual layers")
  parser.add_argument(
      "--use_loose_bidi_cudnn_lstm",
      type="bool",
      default=False,
      help="whether to use loose bidi cudnn_lstm")
  parser.add_argument(
      "--use_fused_lstm",
      type="bool",
      default=True,
      help="whether to use fused lstm and variant. If enabled, training will "
      "use LSTMBlockFusedCell, infer will use LSTMBlockCell when appropriate.")
  parser.add_argument(
      "--use_fused_lstm_dec",
      type="bool",
      default=False,
      help="whether to use fused lstm for decoder (training only).")
  parser.add_argument(
      "--gpu_indices",
      type=str,
      default="",
      help="Indices of worker GPUs in ring order")
  # Graph knobs
  parser.add_argument("--parallel_iterations", type=int, default=10,
                      help="number of parallel iterations in dynamic_rnn")
  parser.add_argument("--use_dist_strategy", type="bool", default=False,
                      help="whether to use distribution strategy")
  parser.add_argument(
      "--hierarchical_copy",
      type="bool",
      default=False,
      help="Use hierarchical copies. Currently only optimized for "
      "use on a DGX-1 with 8 GPUs and may perform poorly on "
      "other hardware. Requires --num_gpus > 1, and only "
      "recommended when --num_gpus=8")
  parser.add_argument(
      "--network_topology",
      type=constants.NetworkTopology,
      default=constants.NetworkTopology.DGX1,
      choices=list(constants.NetworkTopology))
  parser.add_argument(
      "--use_block_lstm",
      type="bool",
      default=False,
      help="whether to use block lstm")
  parser.add_argument(
      "--use_defun",
      type="bool",
      default=False,
      help="whether to use Defun")

  # Gradient tricks
  parser.add_argument(
      "--gradient_repacking",
      type=int,
      default=0,
      help="Use gradient repacking. It"
      "currently only works with replicated mode. At the end of"
      "of each step, it repacks the gradients for more efficient"
      "cross-device transportation. A non-zero value specifies"
      "the number of split packs that will be formed.")
  parser.add_argument(
      "--compact_gradient_transfer",
      type="bool",
      default=True,
      help="Compact gradient as much as possible for cross-device transfer and "
      "aggregation.")
  parser.add_argument(
      "--all_reduce_spec",
      type=str,
      default="nccl",
      help="A specification of the all_reduce algorithm to be used "
      "for reducing gradients.  For more details, see "
      "parse_all_reduce_spec in variable_mgr.py.  An "
      "all_reduce_spec has BNF form:\n"
      "int ::= positive whole number\n"
      "g_int ::= int[KkMGT]?\n"
      "alg_spec ::= alg | alg#int\n"
      "range_spec ::= alg_spec | alg_spec/alg_spec\n"
      "spec ::= range_spec | range_spec:g_int:range_spec\n"
      "NOTE: not all syntactically correct constructs are "
      "supported.\n\n"
      "Examples:\n "
      "\"xring\" == use one global ring reduction for all "
      "tensors\n"
      "\"pscpu\" == use CPU at worker 0 to reduce all tensors\n"
      "\"nccl\" == use NCCL to locally reduce all tensors.  "
      "Limited to 1 worker.\n"
      "\"nccl/xring\" == locally (to one worker) reduce values "
      "using NCCL then ring reduce across workers.\n"
      "\"pscpu:32k:xring\" == use pscpu algorithm for tensors of "
      "size up to 32kB, then xring for larger tensors.")
  parser.add_argument(
      "--agg_small_grads_max_bytes",
      type=int,
      default=0,
      help="If > 0, try to aggregate tensors of less than this "
      "number of bytes prior to all-reduce.")
  parser.add_argument(
      "--agg_small_grads_max_group",
      type=int,
      default=10,
      help="When aggregating small tensors for all-reduce do not "
      "aggregate more than this many into one new tensor.")
  parser.add_argument(
      "--allreduce_merge_scope",
      type=int,
      default=1,
      help="Establish a name scope around this many "
      "gradients prior to creating the all-reduce operations. "
      "It may affect the ability of the backend to merge "
      "parallel ops.")
  # Other knobs
  parser.add_argument(
      "--local_parameter_device",
      type=str,
      default="gpu",
      help="Device to use as parameter server: cpu or gpu. For "
      "distributed training, it can affect where caching of "
      "variables happens.")
  parser.add_argument(
      "--use_resource_vars",
      type="bool",
      default=False,
      help="Use resource variables instead of normal variables. "
      "Resource variables are slower, but this option is useful "
      "for debugging their performance.")


  parser.add_argument("--debug", type="bool", default=False,
                      help="Debug train and eval")
  parser.add_argument(
      "--debug_num_train_steps", type=int, default=None, help="Num steps to train.")
  parser.add_argument("--show_metrics", type="bool", default=True,
                      help="whether to show detailed metrics")
  parser.add_argument("--clip_grads", type="bool", default=True,
                      help="whether to clip gradients")
  parser.add_argument("--profile", type="bool", default=False,
                      help="If generate profile")
  parser.add_argument("--profile_save_steps", type=int, default=10,
                      help="Save timeline every N steps.")

  parser.add_argument("--use_dynamic_rnn", type="bool", default=True)
  parser.add_argument("--use_synthetic_data", type="bool", default=False)
  parser.add_argument(
      "--mode", type=str, default="train_and_eval",
      choices=("train_and_eval", "infer", "translate"))


def create_hparams(flags):
  """Create training hparams."""
  return tf.contrib.training.HParams(
      # Data
      src=flags.src,
      tgt=flags.tgt,
      train_prefix=os.path.join(flags.data_dir, flags.train_prefix),
      test_prefix=os.path.join(flags.data_dir, flags.test_prefix),
      translate_file=flags.translate_file,
      vocab_prefix=os.path.join(flags.data_dir, flags.vocab_prefix),
      embed_prefix=flags.embed_prefix,
      output_dir=flags.output_dir,

      # Networks
      num_units=flags.num_units,
      num_encoder_layers=(flags.num_encoder_layers or flags.num_layers),
      num_decoder_layers=(flags.num_decoder_layers or flags.num_layers),
      dropout=flags.dropout,
      unit_type=flags.unit_type,
      encoder_type=flags.encoder_type,
      residual=flags.residual,
      time_major=flags.time_major,
      num_embeddings_partitions=flags.num_embeddings_partitions,

      # Attention mechanisms
      attention=flags.attention,
      attention_architecture=flags.attention_architecture,
      output_attention=flags.output_attention,
      pass_hidden_state=flags.pass_hidden_state,

      # Train
      optimizer=flags.optimizer,
      max_train_epochs=flags.max_train_epochs,
      target_bleu=flags.target_bleu,
      label_smoothing=flags.label_smoothing,
      batch_size=flags.batch_size,
      init_op=flags.init_op,
      init_weight=flags.init_weight,
      max_gradient_norm=flags.max_gradient_norm,
      learning_rate=flags.learning_rate,
      warmup_steps=flags.warmup_steps,
      warmup_scheme=flags.warmup_scheme,
      decay_scheme=flags.decay_scheme,
      colocate_gradients_with_ops=flags.colocate_gradients_with_ops,

      # Data constraints
      num_buckets=flags.num_buckets,
      src_max_len=flags.src_max_len,
      tgt_max_len=flags.tgt_max_len,

      # Inference
      src_max_len_infer=flags.src_max_len_infer,
      tgt_max_len_infer=flags.tgt_max_len_infer,
      ckpt=flags.ckpt,
      infer_batch_size=flags.infer_batch_size,
      detokenizer_file=flags.detokenizer_file if flags.detokenizer_file is not None \
                       else os.path.join(flags.data_dir, 'mosesdecoder/scripts/tokenizer/detokenizer.perl'),
      tokenizer_file=flags.tokenizer_file if flags.tokenizer_file is not None \
                       else os.path.join(flags.data_dir, 'mosesdecoder/scripts/tokenizer/tokenizer.perl'),

      # Advanced inference arguments
      infer_mode=flags.infer_mode,
      beam_width=flags.beam_width,
      length_penalty_weight=flags.length_penalty_weight,
      coverage_penalty_weight=flags.coverage_penalty_weight,

      # Vocab
      sos=flags.sos if flags.sos else vocab_utils.SOS,
      eos=flags.eos if flags.eos else vocab_utils.EOS,
      subword_option=flags.subword_option,
      check_special_token=flags.check_special_token,
      use_char_encode=flags.use_char_encode,

      # Misc
      forget_bias=flags.forget_bias,
      num_gpus=flags.num_gpus,
      save_checkpoints_steps=flags.save_checkpoints_steps,
      log_step_count_steps=flags.log_step_count_steps,
      epoch_step=0,  # record where we were within an epoch.
      share_vocab=flags.share_vocab,
      random_seed=flags.random_seed,
      language_model=flags.language_model,

      use_amp=flags.use_amp,
      use_fastmath=flags.use_fastmath,
      use_fp16=flags.use_fp16,
      fp16_loss_scale=flags.fp16_loss_scale,
      enable_auto_loss_scale=flags.enable_auto_loss_scale,
      fp16_inc_loss_scale_every_n=flags.fp16_inc_loss_scale_every_n,
      check_tower_loss_numerics=flags.check_tower_loss_numerics,
      use_fp32_batch_matmul=flags.use_fp32_batch_matmul,

      # Performance
      # GPU knbs
      force_inputs_padding=flags.force_inputs_padding,
      use_xla=flags.use_xla,
      xla_compile=flags.xla_compile,
      use_autojit_xla=flags.use_autojit_xla,
      use_pintohost_optimizer=flags.use_pintohost_optimizer,
      use_cudnn_lstm=flags.use_cudnn_lstm,
      use_loose_bidi_cudnn_lstm=flags.use_loose_bidi_cudnn_lstm,
      use_fused_lstm=flags.use_fused_lstm,
      use_fused_lstm_dec=flags.use_fused_lstm_dec,
      gpu_indices=flags.gpu_indices,
      # Graph knobs
      parallel_iterations=flags.parallel_iterations,
      use_dynamic_rnn=flags.use_dynamic_rnn,
      use_dist_strategy=flags.use_dist_strategy,
      hierarchical_copy=flags.hierarchical_copy,
      network_topology=flags.network_topology,
      use_block_lstm=flags.use_block_lstm,
      # Grad tricks
      gradient_repacking=flags.gradient_repacking,
      compact_gradient_transfer=flags.compact_gradient_transfer,
      all_reduce_spec=flags.all_reduce_spec,
      agg_small_grads_max_bytes=flags.agg_small_grads_max_bytes,
      agg_small_grads_max_group=flags.agg_small_grads_max_group,
      allreduce_merge_scope=flags.allreduce_merge_scope,
      # Other knobs
      local_parameter_device=("cpu" if flags.num_gpus ==0
                              else flags.local_parameter_device),
      use_resource_vars=flags.use_resource_vars,

      debug=flags.debug,
      debug_num_train_steps=flags.debug_num_train_steps,
      clip_grads=flags.clip_grads,
      profile=flags.profile,
      profile_save_steps=flags.profile_save_steps,
      show_metrics=flags.show_metrics,

      use_synthetic_data=flags.use_synthetic_data,
      mode=flags.mode,
  )


def _add_argument(hparams, key, value, update=True):
  """Add an argument to hparams; if exists, change the value if update==True."""
  if hasattr(hparams, key):
    if update:
      setattr(hparams, key, value)
  else:
    hparams.add_hparam(key, value)


def extend_hparams(hparams):
  """Add new arguments to hparams."""
  # Sanity checks
  if hparams.encoder_type == "bi" and hparams.num_encoder_layers % 2 != 0:
    raise ValueError("For bi, num_encoder_layers %d should be even" %
                     hparams.num_encoder_layers)
  if (hparams.attention_architecture in ["gnmt"] and
      hparams.num_encoder_layers < 2):
    raise ValueError("For gnmt attention architecture, "
                     "num_encoder_layers %d should be >= 2" %
                     hparams.num_encoder_layers)
  if hparams.subword_option and hparams.subword_option not in ["spm", "bpe"]:
    raise ValueError("subword option must be either spm, or bpe")
  if hparams.infer_mode == "beam_search" and hparams.beam_width <= 0:
    raise ValueError("beam_width must greater than 0 when using beam_search"
                     "decoder.")
  if hparams.mode == "translate" and not hparams.translate_file:
    raise ValueError("--translate_file flag must be specified in translate mode")

  # Different number of encoder / decoder layers
  assert hparams.num_encoder_layers and hparams.num_decoder_layers
  if hparams.num_encoder_layers != hparams.num_decoder_layers:
    hparams.pass_hidden_state = False
    utils.print_out("Num encoder layer %d is different from num decoder layer"
                    " %d, so set pass_hidden_state to False" % (
                        hparams.num_encoder_layers,
                        hparams.num_decoder_layers))

  # Set residual layers
  num_encoder_residual_layers = 0
  num_decoder_residual_layers = 0
  if hparams.residual:
    if hparams.num_encoder_layers > 1:
      num_encoder_residual_layers = hparams.num_encoder_layers - 1
    if hparams.num_decoder_layers > 1:
      num_decoder_residual_layers = hparams.num_decoder_layers - 1

    if hparams.encoder_type == "gnmt":
      # The first unidirectional layer (after the bi-directional layer) in
      # the GNMT encoder can't have residual connection due to the input is
      # the concatenation of fw_cell and bw_cell's outputs.
      num_encoder_residual_layers = hparams.num_encoder_layers - 2

      # Compatible for GNMT models
      if hparams.num_encoder_layers == hparams.num_decoder_layers:
        num_decoder_residual_layers = num_encoder_residual_layers
  _add_argument(hparams, "num_encoder_residual_layers",
                num_encoder_residual_layers)
  _add_argument(hparams, "num_decoder_residual_layers",
                num_decoder_residual_layers)

  # Language modeling
  if hparams.language_model:
    hparams.attention = ""
    hparams.attention_architecture = ""
    hparams.pass_hidden_state = False
    hparams.share_vocab = True
    hparams.src = hparams.tgt
    utils.print_out("For language modeling, we turn off attention and "
                    "pass_hidden_state; turn on share_vocab; set src to tgt.")

  ## Vocab
  # Get vocab file names first
  if hparams.vocab_prefix:
    src_vocab_file = hparams.vocab_prefix + "." + hparams.src
    tgt_vocab_file = hparams.vocab_prefix + "." + hparams.tgt
  else:
    raise ValueError("hparams.vocab_prefix must be provided.")

  # Source vocab
  src_vocab_size, src_vocab_file = vocab_utils.check_vocab(
      src_vocab_file,
      hparams.output_dir,
      check_special_token=hparams.check_special_token,
      sos=hparams.sos,
      eos=hparams.eos,
      unk=vocab_utils.UNK,
      pad_vocab=True)

  # Target vocab
  if hparams.share_vocab:
    utils.print_out("  using source vocab for target")
    tgt_vocab_file = src_vocab_file
    tgt_vocab_size = src_vocab_size
  else:
    tgt_vocab_size, tgt_vocab_file = vocab_utils.check_vocab(
        tgt_vocab_file,
        hparams.output_dir,
        check_special_token=hparams.check_special_token,
        sos=hparams.sos,
        eos=hparams.eos,
        unk=vocab_utils.UNK)
  _add_argument(hparams, "src_vocab_size", src_vocab_size)
  _add_argument(hparams, "tgt_vocab_size", tgt_vocab_size)
  _add_argument(hparams, "src_vocab_file", src_vocab_file)
  _add_argument(hparams, "tgt_vocab_file", tgt_vocab_file)

  # Num embedding partitions
  _add_argument(
      hparams, "num_enc_emb_partitions", hparams.num_embeddings_partitions)
  _add_argument(
      hparams, "num_dec_emb_partitions", hparams.num_embeddings_partitions)

  # Pretrained Embeddings
  _add_argument(hparams, "src_embed_file", "")
  _add_argument(hparams, "tgt_embed_file", "")
  if hparams.embed_prefix:
    src_embed_file = hparams.embed_prefix + "." + hparams.src
    tgt_embed_file = hparams.embed_prefix + "." + hparams.tgt

    if tf.gfile.Exists(src_embed_file):
      utils.print_out("  src_embed_file %s exist" % src_embed_file)
      hparams.src_embed_file = src_embed_file

      utils.print_out(
          "For pretrained embeddings, set num_enc_emb_partitions to 1")
      hparams.num_enc_emb_partitions = 1
    else:
      utils.print_out("  src_embed_file %s doesn't exist" % src_embed_file)

    if tf.gfile.Exists(tgt_embed_file):
      utils.print_out("  tgt_embed_file %s exist" % tgt_embed_file)
      hparams.tgt_embed_file = tgt_embed_file

      utils.print_out(
          "For pretrained embeddings, set num_dec_emb_partitions to 1")
      hparams.num_dec_emb_partitions = 1
    else:
      utils.print_out("  tgt_embed_file %s doesn't exist" % tgt_embed_file)

  # Evaluation
  metric = "bleu"
  best_metric_dir = os.path.join(hparams.output_dir, "best_" + metric)
  tf.gfile.MakeDirs(best_metric_dir)
  _add_argument(hparams, "best_" + metric, 0, update=False)
  _add_argument(hparams, "best_" + metric + "_dir", best_metric_dir)

  return hparams


def create_or_load_hparams(default_hparams, hparams_path):
  """Create hparams or load hparams from output_dir."""
  hparams = utils.maybe_parse_standard_hparams(default_hparams, hparams_path)
  hparams = extend_hparams(hparams)
  # Print HParams
  utils.print_hparams(hparams)
  return hparams


def run_main(flags, default_hparams, estimator_fn):
  """Run main."""
  # Random
  random_seed = flags.random_seed
  if random_seed is not None and random_seed > 0:
    utils.print_out("# Set random seed to %d" % random_seed)
    random.seed(random_seed)
    np.random.seed(random_seed)
    tf.set_random_seed(random_seed)

  # Model output directory
  output_dir = flags.output_dir
  if output_dir and not tf.gfile.Exists(output_dir):
    utils.print_out("# Creating output directory %s ..." % output_dir)
    tf.gfile.MakeDirs(output_dir)

  # Load hparams.
  hparams = create_or_load_hparams(default_hparams, flags.hparams_path)

  # Train or Evaluation
  estimator_fn(hparams)
  return hparams

def tokenize(hparams, file, tokenized_file):
  utils.print_out("tokenizing {} -> {}".format(file, tokenized_file))
  with open(file, 'rb') as input_file:
    with open(tokenized_file, 'wb') as output_file:
      subprocess.run([hparams.tokenizer_file, '-l', hparams.src], stdin=input_file, stdout=output_file)

def detokenize(hparams, file, detokenized_file):
  utils.print_out("detokenizing {} -> {}".format(file, detokenized_file))
  with open(file, 'rb') as input_file:
    with open(detokenized_file, 'wb') as output_file:
      subprocess.run([hparams.detokenizer_file, '-l', hparams.tgt], stdin=input_file, stdout=output_file)

def main(unused_argv):
  experiment_start = time.time()

  tf.logging.set_verbosity(tf.logging.INFO)

  if FLAGS.use_fp16 and FLAGS.use_dist_strategy:
    raise ValueError("use_fp16 and use_dist_strategy aren't compatible")

  if FLAGS.use_fp16 + FLAGS.use_amp + FLAGS.use_fastmath > 1:
    raise ValueError("Only one of use_fp16, use_amp, use_fastmath can be set")

  if FLAGS.use_amp:
    utils.print_out('Enabling TF-AMP')

    os.environ['TF_ENABLE_AUTO_MIXED_PRECISION'] = '1'

  if FLAGS.use_fastmath:
    utils.print_out('Enabling FastMath')

    os.environ["TF_ENABLE_CUBLAS_TENSOR_OP_MATH_FP32"] = '1'
    os.environ["TF_ENABLE_CUDNN_TENSOR_OP_MATH_FP32"] = '1'
    os.environ["TF_ENABLE_CUDNN_RNN_TENSOR_OP_MATH_FP32"] = '1'

  # Set up hacky envvars.
  # Hack that affects Defun in attention_wrapper.py
  active_xla_option_nums = np.sum([FLAGS.use_xla, FLAGS.use_autojit_xla,
                                   FLAGS.xla_compile])
  if active_xla_option_nums > 1:
    raise ValueError(
        "Only one of use_xla, xla_compile, use_autojit_xla can be set")

  os.environ["use_xla"] = str(FLAGS.use_xla).lower()
  if FLAGS.use_xla:
    os.environ["use_defun"] = str(True).lower()
  else:
    os.environ["use_defun"] = str(FLAGS.use_defun).lower()
  utils.print_out("use_defun is %s for attention" % os.environ["use_defun"])

  # TODO(jamesqin): retire this config after Cuda9.1
  os.environ["use_fp32_batch_matmul"] = ("true" if FLAGS.use_fp32_batch_matmul
                                         else "false")
  os.environ["xla_compile"] = "true" if FLAGS.xla_compile else "false"
  os.environ["force_inputs_padding"] = (
      "true" if FLAGS.force_inputs_padding else "false")

  if FLAGS.mode == "train":
    utils.print_out("Running training mode.")
    default_hparams = create_hparams(FLAGS)
    run_main(FLAGS, default_hparams, estimator.train_fn)
  elif FLAGS.mode == "infer" or FLAGS.mode == "translate":
    if FLAGS.mode == "infer":
        utils.print_out("Running inference mode.")
        translate_mode = False
    else:
        utils.print_out("Running translate mode on file {}.".format(FLAGS.translate_file))
        translate_mode = True

    # Random
    random_seed = FLAGS.random_seed
    if random_seed is not None and random_seed > 0:
      utils.print_out("# Set random seed to %d" % random_seed)
      random.seed(random_seed)
      np.random.seed(random_seed)
      tf.set_random_seed(random_seed)

    # Model output directory
    output_dir = FLAGS.output_dir
    if output_dir and not tf.gfile.Exists(output_dir):
      utils.print_out("# Creating output directory %s ..." % output_dir)
      tf.gfile.MakeDirs(output_dir)

    # Load hparams.
    default_hparams = create_hparams(FLAGS)
    default_hparams.num_buckets = 1
    # The estimator model_fn is written in a way allowing train hparams to be
    # passed in infer mode.
    hparams = create_or_load_hparams(default_hparams, FLAGS.hparams_path)
    utils.print_out("infer_hparams:")
    utils.print_hparams(hparams)

    if translate_mode:
      tokenize(hparams, hparams.translate_file, hparams.translate_file + ".tok")

    eval_sentences, eval_src_tokens, _ = iterator_utils.get_effective_epoch_size(hparams, train=False)

    # Run evaluation when there's a new checkpoint
    tf.logging.info("Starting to evaluate...")
    eval_start = time.time()
    _, (eval_speed, eval_latencies), eval_output_tokens = estimator.eval_fn(hparams, hparams.ckpt, only_translate=translate_mode)
    eval_end = time.time()
    eval_delta = eval_end - eval_start
    utils.print_out("eval time for ckpt: %.2f mins (%.2f sent/sec, %.2f tokens/sec)" %
                    (eval_delta / 60., eval_speed, eval_speed * (eval_src_tokens + eval_output_tokens) / eval_sentences), f=sys.stderr)
    for lat in sorted(eval_latencies):
      utils.print_out("eval latency_%s for ckpt: %.2f ms" % (lat, eval_latencies[lat] * 1000))

    if translate_mode:
      detokenize(hparams, hparams.translate_file + ".trans.tok", hparams.translate_file + ".trans")

  else:
    assert FLAGS.mode == "train_and_eval"
    utils.print_out("Running train and eval mode.")

    # Random
    random_seed = FLAGS.random_seed
    if random_seed is not None and random_seed > 0:
      utils.print_out("# Set random seed to %d" % random_seed)
      random.seed(random_seed)
      np.random.seed(random_seed)
      tf.set_random_seed(random_seed)

    # Model output directory
    output_dir = FLAGS.output_dir
    if output_dir and not tf.gfile.Exists(output_dir):
      utils.print_out("# Creating output directory %s ..." % output_dir)
      tf.gfile.MakeDirs(output_dir)

    # Load hparams.
    default_hparams = create_hparams(FLAGS)

    hparams = create_or_load_hparams(default_hparams, FLAGS.hparams_path)
    utils.print_out("training hparams:")
    utils.print_hparams(hparams)
    with tf.gfile.GFile(os.path.join(output_dir, "train_hparams.txt"), "w") as f:
      f.write(utils.serialize_hparams(hparams) + "\n")

    # The estimator model_fn is written in a way allowing train hparams to be
    # passed in infer mode.
    infer_hparams = tf.contrib.training.HParams(**hparams.values())
    infer_hparams.num_buckets = 1
    utils.print_out("infer_hparams:")
    utils.print_hparams(infer_hparams)
    with tf.gfile.GFile(os.path.join(output_dir, "infer_hparams.txt"), "w") as f:
      f.write(utils.serialize_hparams(infer_hparams) + "\n")

    epochs = 0
    should_stop = epochs >= FLAGS.max_train_epochs

    train_sentences, train_src_tokens, train_tgt_tokens = iterator_utils.get_effective_epoch_size(hparams)
    eval_sentences, eval_src_tokens, _ = iterator_utils.get_effective_epoch_size(hparams, train=False)

    while not should_stop:
      utils.print_out("Starting epoch %d" % epochs)
      try:
        train_start = time.time()
        train_speed, _ = estimator.train_fn(hparams)
      except tf.errors.OutOfRangeError:
        utils.print_out("training hits OutOfRangeError", f=sys.stderr)

      train_end = time.time()
      train_delta = train_end - train_start
      utils.print_out("training time for epoch %d: %.2f mins (%.2f sent/sec, %.2f tokens/sec)" %
                      (epochs + 1, train_delta / 60., train_speed, train_speed * (train_src_tokens + train_tgt_tokens) / train_sentences), f=sys.stderr)

      # This is probably sub-optimal, doing eval per-epoch
      eval_start = time.time()
      bleu_score, (eval_speed, eval_latencies), eval_output_tokens = estimator.eval_fn(infer_hparams)
      eval_end = time.time()
      eval_delta = eval_end - eval_start
      utils.print_out("eval time for epoch %d: %.2f mins (%.2f sent/sec, %.2f tokens/sec)" %
                      (epochs + 1, eval_delta / 60., eval_speed, eval_speed * (eval_src_tokens + eval_output_tokens) / eval_sentences), f=sys.stderr)
      for lat in sorted(eval_latencies):
        utils.print_out("eval latency_%s for epoch %d: %.2f ms" % (lat, epochs + 1, eval_latencies[lat] * 1000))


      if FLAGS.debug or (FLAGS.target_bleu is not None and bleu_score > FLAGS.target_bleu):
        should_stop = True
        utils.print_out(
            "Stop job since target bleu is reached at epoch %d ." % epochs,
            f=sys.stderr)

      epochs += 1
      if epochs >= FLAGS.max_train_epochs:
        should_stop = True
        utils.print_out("Stop job since max_train_epochs is reached.",
                        f=sys.stderr)

  experiment_end = time.time()
  utils.print_out('Experiment took {} min'.format((experiment_end - experiment_start) / 60))


if __name__ == "__main__":
  nmt_parser = argparse.ArgumentParser()
  add_arguments(nmt_parser)
  FLAGS, unparsed = nmt_parser.parse_known_args()
  tf.app.run(main=main, argv=[sys.argv[0]] + unparsed)