Add beam search for dygraph Transformer. (#3555)

* Add beam search for dygraph Transformer.
Re-organize dygraph Transformer.

* Add custumed data support for dygraph Transformer.

* Add validation in dygraph Transformer.

* Update notes for multi-gpu for dygraph Transformer.

dygraph/transformer/README.md

@@ -8,19 +8,19 @@
 
 ### 数据集说明
 
-我们使用公开的 [WMT'16 EN-DE 数据集](http://www.statmt.org/wmt16/translation-task.html)训练
+我们使用[WMT-16](http://www.statmt.org/wmt16/)新增的[multimodal task](http://www.statmt.org/wmt16/multimodal-task.html)中的[translation task](http://www.statmt.org/wmt16/multimodal-task.html#task1)的数据集作为示例。该数据集为英德翻译数据，包含29001条训练数据，1000条测试数据。
 
-
-可以将下载好的wmt16数据集放在`~/.cache/paddle/dataset/wmt16/`目录下
+该数据集内置在了Paddle中，可以通过 `paddle.dataset.wmt16` 使用，执行本项目中的训练代码数据集将自动下载到 `~/.cache/paddle/dataset/wmt16/` 目录下。
 
 ### 安装说明
 
 1. paddle安装
 
-   本项目依赖于 Paddlepaddle Fluid 1.4.1，请参考安装指南进行安装。
+   本项目依赖于 PaddlePaddle Fluid 1.6.0 及以上版本（1.6.0 待近期正式发版，可先使用 develop），请参考 [安装指南](http://www.paddlepaddle.org/#quick-start) 进行安装
+
+2. 环境依赖
 
-2. 安装代码
-3. 环境依赖
+   多卡运行需要 NCCL 2.4.7 版本。
 
 ### 执行训练：
 如果是使用GPU单卡训练，启动训练的方式:
@@ -28,11 +28,19 @@
 env CUDA_VISIBLE_DEVICES=0 python train.py
 ```
 
-这里`CUDA_VISIBLE_DEVICES=0`表示是执行在0号设备卡上，请根据自身情况修改这个参数。
+这里`CUDA_VISIBLE_DEVICES=0`表示是执行在0号设备卡上，请根据自身情况修改这个参数。如需调整其他模型及训练参数，可在 `config.py` 中修改或使用如下方式传入：
+
+```sh
+python train.py \
+  n_head 16 \
+  d_model 1024 \
+  d_inner_hid 4096 \
+  prepostprocess_dropout 0.3
+```
 
 Paddle动态图支持多进程多卡进行模型训练，启动训练的方式：
 ```
-python -m paddle.distributed.launch --selected_gpus=0,1,2,3 --log_dir ./mylog train.py   --use_data_parallel 1
+python -m paddle.distributed.launch --started_port 9999 --selected_gpus=0,1,2,3 --log_dir ./mylog train.py --use_data_parallel 1
 ```
 此时，程序会将每个进程的输出log导入到`./mylog`路径下：
 ```
@@ -64,8 +72,105 @@ python -m paddle.distributed.launch --selected_gpus=0,1,2,3 --log_dir ./mylog tr
     pass num : 0, batch_id: 110, dy_graph avg loss: [7.4179897]
     pass num : 0, batch_id: 120, dy_graph avg loss: [7.318419]
 
+
+### 执行预测
+
+训练完成后，使用如下命令进行预测：
+
+```
+env CUDA_VISIBLE_DEVICES=0 python predict.py
+```
+
+预测结果将输出到 `predict.txt` 文件中（可在运行时通过 `--output_file` 更改），其他模型与预测参数也可在 `config.py` 中修改或使用如下方式传入：
+
+```sh
+python predict.py \
+  n_head 16 \
+  d_model 1024 \
+  d_inner_hid 4096 \
+  prepostprocess_dropout 0.3
+```
+
+完成预测后，可以借助第三方工具进行 BLEU 指标的评估，可按照如下方式进行：
+
+```sh
+# 提取 reference 数据
+tar -zxvf ~/.cache/paddle/dataset/wmt16/wmt16.tar.gz
+awk 'BEGIN {FS="\t"}; {print $2}' wmt16/test > ref.de
+
+# clone mosesdecoder代码
+git clone https://github.com/moses-smt/mosesdecoder.git
+
+# 进行评估
+perl mosesdecoder/scripts/generic/multi-bleu.perl ref.de < predict.txt
+```
+
+使用默认配置单卡训练20个 epoch 训练的模型约有如下评估结果：
+```
+BLEU = 32.38, 64.3/39.1/25.9/16.9 (BP=1.000, ratio=1.001, hyp_len=12122, ref_len=12104)
+```
+
+
 ## 进阶使用
 
+### 自定义数据
+
+- 训练：
+  
+  修改 `train.py` 中的如下代码段
+
+  ```python
+        reader = paddle.batch(wmt16.train(ModelHyperParams.src_vocab_size,
+                                          ModelHyperParams.trg_vocab_size),
+                              batch_size=TrainTaskConfig.batch_size)
+  ```
+  
+  
+  将其中的 `wmt16.train` 替换为类似如下的 python generator ：
+
+  ```python
+  def reader(file_name, src_dict, trg_dict):
+    start_id = src_dict[START_MARK]  # BOS
+    end_id = src_dict[END_MARK]  # EOS
+    unk_id = src_dict[UNK_MARK]  # UNK
+
+    src_col, trg_col = 0, 1
+
+    for line in open(file_name, "r"):
+        line = line.strip()
+        line_split = line.strip().split("\t")
+        if len(line_split) != 2:
+            continue
+        src_words = line_split[src_col].split()
+        src_ids = [start_id] + [
+            src_dict.get(w, unk_id) for w in src_words
+        ] + [end_id]
+
+        trg_words = line_split[trg_col].split()
+        trg_ids = [trg_dict.get(w, unk_id) for w in trg_words]
+
+        trg_ids_next = trg_ids + [end_id]
+        trg_ids = [start_id] + trg_ids
+
+        yield src_ids, trg_ids, trg_ids_next
+  ```
+
+该 generator 产生的数据为单个样本，是包含源句（src_ids），目标句（trg_ids）和标签（trg_ids_next）三个 integer list 的 tuple；其中 src_ids 包含 BOS 和 EOS 的 id，trg_ids 包含 BOS 的 id，trg_ids_next 包含 EOS 的 id。
+
+- 预测：
+  修改 `predict.py` 中的如下代码段
+
+  ```python
+        reader = paddle.batch(wmt16.test(ModelHyperParams.src_vocab_size,
+                                         ModelHyperParams.trg_vocab_size),
+                              batch_size=InferTaskConfig.batch_size)
+        id2word = wmt16.get_dict("de",
+                                 ModelHyperParams.trg_vocab_size,
+                                 reverse=True)
+  ```
+
+  将其中的 `wmt16.test` 替换为和训练部分类似的 python generator ；另外还需要提供将 id 映射到 word 的 python dict 作为 `id2word` .
+
 ### 模型原理介绍
 
 Transformer 是论文 [Attention Is All You Need](https://arxiv.org/abs/1706.03762) 中提出的用以完成机器翻译（machine translation, MT）等序列到序列（sequence to sequence, Seq2Seq）学习任务的一种全新网络结构。其同样使用了 Seq2Seq 任务中典型的编码器-解码器（Encoder-Decoder）的框架结构，但相较于此前广泛使用的循环神经网络（Recurrent Neural Network, RNN），其完全使用注意力（Attention）机制来实现序列到序列的建模，整体网络结构如图1所示。

dygraph/transformer/config.py

+# Copyright (c) 2019 PaddlePaddle Authors. 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.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+class TrainTaskConfig(object):
+    """
+    TrainTaskConfig
+    """
+    # the epoch number to train.
+    pass_num = 20
+    # the number of sequences contained in a mini-batch.
+    # deprecated, set batch_size in args.
+    batch_size = 32
+    # the hyper parameters for Adam optimizer.
+    # This static learning_rate will be multiplied to the LearningRateScheduler
+    # derived learning rate the to get the final learning rate.
+    learning_rate = 2.0
+    beta1 = 0.9
+    beta2 = 0.997
+    eps = 1e-9
+    # the parameters for learning rate scheduling.
+    warmup_steps = 8000
+    # the weight used to mix up the ground-truth distribution and the fixed
+    # uniform distribution in label smoothing when training.
+    # Set this as zero if label smoothing is not wanted.
+    label_smooth_eps = 0.1
+
+
+class InferTaskConfig(object):
+    # the number of examples in one run for sequence generation.
+    batch_size = 4
+    # the parameters for beam search.
+    beam_size = 4
+    alpha=0.6
+    # max decoded length, should be less than ModelHyperParams.max_length
+    max_out_len = 30
+
+
+
+class ModelHyperParams(object):
+    """
+    ModelHyperParams
+    """
+    # These following five vocabularies related configurations will be set
+    # automatically according to the passed vocabulary path and special tokens.
+    # size of source word dictionary.
+    src_vocab_size = 10000
+    # size of target word dictionay
+    trg_vocab_size = 10000
+    # index for <bos> token
+    bos_idx = 0
+    # index for <eos> token
+    eos_idx = 1
+    # index for <unk> token
+    unk_idx = 2
+
+    # max length of sequences deciding the size of position encoding table.
+    max_length = 50
+    # the dimension for word embeddings, which is also the last dimension of
+    # the input and output of multi-head attention, position-wise feed-forward
+    # networks, encoder and decoder.
+    d_model = 512
+    # size of the hidden layer in position-wise feed-forward networks.
+    d_inner_hid = 2048
+    # the dimension that keys are projected to for dot-product attention.
+    d_key = 64
+    # the dimension that values are projected to for dot-product attention.
+    d_value = 64
+    # number of head used in multi-head attention.
+    n_head = 8
+    # number of sub-layers to be stacked in the encoder and decoder.
+    n_layer = 6
+    # dropout rates of different modules.
+    prepostprocess_dropout = 0.1
+    attention_dropout = 0.1
+    relu_dropout = 0.1
+    # to process before each sub-layer
+    preprocess_cmd = "n"  # layer normalization
+    # to process after each sub-layer
+    postprocess_cmd = "da"  # dropout + residual connection
+    # the flag indicating whether to share embedding and softmax weights.
+    # vocabularies in source and target should be same for weight sharing.
+    weight_sharing = False
+
+
+# The placeholder for batch_size in compile time. Must be -1 currently to be
+# consistent with some ops' infer-shape output in compile time, such as the
+# sequence_expand op used in beamsearch decoder.
+batch_size = -1
+# The placeholder for squence length in compile time.
+seq_len = ModelHyperParams.max_length
+# Here list the data shapes and data types of all inputs.
+# The shapes here act as placeholder and are set to pass the infer-shape in
+# compile time.
+input_descs = {
+    # The actual data shape of src_word is:
+    # [batch_size, max_src_len_in_batch, 1]
+    "src_word": [(batch_size, seq_len, 1), "int64", 2],
+    # The actual data shape of src_pos is:
+    # [batch_size, max_src_len_in_batch, 1]
+    "src_pos": [(batch_size, seq_len, 1), "int64"],
+    # This input is used to remove attention weights on paddings in the
+    # encoder.
+    # The actual data shape of src_slf_attn_bias is:
+    # [batch_size, n_head, max_src_len_in_batch, max_src_len_in_batch]
+    "src_slf_attn_bias":
+    [(batch_size, ModelHyperParams.n_head, seq_len, seq_len), "float32"],
+    # The actual data shape of trg_word is:
+    # [batch_size, max_trg_len_in_batch, 1]
+    "trg_word": [(batch_size, seq_len, 1), "int64",
+                 2],  # lod_level is only used in fast decoder.
+    # The actual data shape of trg_pos is:
+    # [batch_size, max_trg_len_in_batch, 1]
+    "trg_pos": [(batch_size, seq_len, 1), "int64"],
+    # This input is used to remove attention weights on paddings and
+    # subsequent words in the decoder.
+    # The actual data shape of trg_slf_attn_bias is:
+    # [batch_size, n_head, max_trg_len_in_batch, max_trg_len_in_batch]
+    "trg_slf_attn_bias":
+    [(batch_size, ModelHyperParams.n_head, seq_len, seq_len), "float32"],
+    # This input is used to remove attention weights on paddings of the source
+    # input in the encoder-decoder attention.
+    # The actual data shape of trg_src_attn_bias is:
+    # [batch_size, n_head, max_trg_len_in_batch, max_src_len_in_batch]
+    "trg_src_attn_bias":
+    [(batch_size, ModelHyperParams.n_head, seq_len, seq_len), "float32"],
+    # This input is used in independent decoder program for inference.
+    # The actual data shape of enc_output is:
+    # [batch_size, max_src_len_in_batch, d_model]
+    "enc_output": [(batch_size, seq_len, ModelHyperParams.d_model), "float32"],
+    # The actual data shape of label_word is:
+    # [batch_size * max_trg_len_in_batch, 1]
+    "lbl_word": [(batch_size * seq_len, 1), "int64"],
+    # This input is used to mask out the loss of paddding tokens.
+    # The actual data shape of label_weight is:
+    # [batch_size * max_trg_len_in_batch, 1]
+    "lbl_weight": [(batch_size * seq_len, 1), "float32"],
+    # This input is used in beam-search decoder.
+    "init_score": [(batch_size, 1), "float32", 2],
+    # This input is used in beam-search decoder for the first gather
+    # (cell states updation)
+    "init_idx": [(batch_size, ), "int32"],
+}
+
+# Names of word embedding table which might be reused for weight sharing.
+word_emb_param_names = (
+    "src_word_emb_table",
+    "trg_word_emb_table",
+)
+# Names of position encoding table which will be initialized externally.
+pos_enc_param_names = (
+    "src_pos_enc_table",
+    "trg_pos_enc_table",
+)
+# separated inputs for different usages.
+encoder_data_input_fields = (
+    "src_word",
+    "src_pos",
+    "src_slf_attn_bias",
+)
+decoder_data_input_fields = (
+    "trg_word",
+    "trg_pos",
+    "trg_slf_attn_bias",
+    "trg_src_attn_bias",
+    "enc_output",
+)
+label_data_input_fields = (
+    "lbl_word",
+    "lbl_weight",
+)
+# In fast decoder, trg_pos (only containing the current time step) is generated
+# by ops and trg_slf_attn_bias is not needed.
+fast_decoder_data_input_fields = (
+    "trg_word",
+    # "init_score",
+    # "init_idx",
+    "trg_src_attn_bias",
+)
+
+
+def merge_cfg_from_list(cfg_list, g_cfgs):
+    """
+    Set the above global configurations using the cfg_list.
+    """
+    assert len(cfg_list) % 2 == 0
+    for key, value in zip(cfg_list[0::2], cfg_list[1::2]):
+        for g_cfg in g_cfgs:
+            if hasattr(g_cfg, key):
+                try:
+                    value = eval(value)
+                except Exception:  # for file path
+                    pass
+                setattr(g_cfg, key, value)
+                break

dygraph/transformer/data_util.py

+# Copyright (c) 2019 PaddlePaddle Authors. 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.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import numpy as np
+from paddle.fluid.dygraph import to_variable
+
+
+def pad_batch_data(insts,
+                   pad_idx,
+                   n_head,
+                   is_target=False,
+                   is_label=False,
+                   return_attn_bias=True,
+                   return_max_len=True,
+                   return_num_token=False):
+    """
+    Pad the instances to the max sequence length in batch, and generate the
+    corresponding position data and attention bias.
+    """
+    return_list = []
+    max_len = max(len(inst) for inst in insts)
+    # Any token included in dict can be used to pad, since the paddings' loss
+    # will be masked out by weights and make no effect on parameter gradients.
+    inst_data = np.array(
+        [inst + [pad_idx] * (max_len - len(inst)) for inst in insts])
+    return_list += [inst_data.astype("int64").reshape([-1, 1])]
+    if is_label:  # label weight
+        inst_weight = np.array([[1.] * len(inst) + [0.] * (max_len - len(inst))
+                                for inst in insts])
+        return_list += [inst_weight.astype("float32").reshape([-1, 1])]
+    else:  # position data
+        inst_pos = np.array([
+            list(range(0, len(inst))) + [0] * (max_len - len(inst))
+            for inst in insts
+        ])
+        return_list += [inst_pos.astype("int64").reshape([-1, 1])]
+    if return_attn_bias:
+        if is_target:
+            # This is used to avoid attention on paddings and subsequent
+            # words.
+            slf_attn_bias_data = np.ones((inst_data.shape[0], max_len, max_len))
+            slf_attn_bias_data = np.triu(slf_attn_bias_data,
+                                         1).reshape([-1, 1, max_len, max_len])
+            slf_attn_bias_data = np.tile(slf_attn_bias_data,
+                                         [1, n_head, 1, 1]) * [-1e9]
+        else:
+            # This is used to avoid attention on paddings.
+            slf_attn_bias_data = np.array([[0] * len(inst) + [-1e9] *
+                                           (max_len - len(inst))
+                                           for inst in insts])
+            slf_attn_bias_data = np.tile(
+                slf_attn_bias_data.reshape([-1, 1, 1, max_len]),
+                [1, n_head, max_len, 1])
+        return_list += [slf_attn_bias_data.astype("float32")]
+    if return_max_len:
+        return_list += [max_len]
+    if return_num_token:
+        num_token = 0
+        for inst in insts:
+            num_token += len(inst)
+        return_list += [num_token]
+    return return_list if len(return_list) > 1 else return_list[0]

dygraph/transformer/model.py

+# Copyright (c) 2019 PaddlePaddle Authors. 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.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import numpy as np
+
+import paddle.fluid as fluid
+import paddle.fluid.layers as layers
+from paddle.fluid.dygraph import Embedding, LayerNorm, FC, to_variable, Layer, guard
+from paddle.fluid.dygraph.learning_rate_scheduler import LearningRateDecay
+
+from config import word_emb_param_names, pos_enc_param_names
+
+
+def position_encoding_init(n_position, d_pos_vec):
+    """
+    Generate the initial values for the sinusoid position encoding table.
+    """
+    channels = d_pos_vec
+    position = np.arange(n_position)
+    num_timescales = channels // 2
+    log_timescale_increment = (np.log(float(1e4) / float(1)) /
+                               (num_timescales - 1))
+    inv_timescales = np.exp(
+        np.arange(num_timescales)) * -log_timescale_increment
+    scaled_time = np.expand_dims(position, 1) * np.expand_dims(
+        inv_timescales, 0)
+    signal = np.concatenate([np.sin(scaled_time), np.cos(scaled_time)], axis=1)
+    signal = np.pad(signal, [[0, 0], [0, np.mod(channels, 2)]], 'constant')
+    position_enc = signal
+    return position_enc.astype("float32")
+
+
+class NoamDecay(LearningRateDecay):
+    """
+    learning rate scheduler
+    """
+    def __init__(self,
+                 d_model,
+                 warmup_steps,
+                 static_lr=2.0,
+                 begin=1,
+                 step=1,
+                 dtype='float32'):
+        super(NoamDecay, self).__init__(begin, step, dtype)
+        self.d_model = d_model
+        self.warmup_steps = warmup_steps
+        self.static_lr = static_lr
+
+    def step(self):
+        a = self.create_lr_var(self.step_num**-0.5)
+        b = self.create_lr_var((self.warmup_steps**-1.5) * self.step_num)
+        lr_value = (self.d_model**-0.5) * layers.elementwise_min(
+            a, b) * self.static_lr
+        return lr_value
+
+
+class PrePostProcessLayer(Layer):
+    """
+    PrePostProcessLayer
+    """
+    def __init__(self, name_scope, process_cmd, shape_len=None):
+        super(PrePostProcessLayer, self).__init__(name_scope)
+        for cmd in process_cmd:
+            if cmd == "n":
+                self._layer_norm = LayerNorm(
+                    name_scope=self.full_name(),
+                    begin_norm_axis=shape_len - 1,
+                    param_attr=fluid.ParamAttr(
+                        initializer=fluid.initializer.Constant(1.)),
+                    bias_attr=fluid.ParamAttr(
+                        initializer=fluid.initializer.Constant(0.)))
+
+    def forward(self, prev_out, out, process_cmd, dropout_rate=0.):
+        """
+        forward
+        :param prev_out:
+        :param out:
+        :param process_cmd:
+        :param dropout_rate:
+        :return:
+        """
+        for cmd in process_cmd:
+            if cmd == "a":  # add residual connection
+                out = out + prev_out if prev_out else out
+            elif cmd == "n":  # add layer normalization
+                out = self._layer_norm(out)
+            elif cmd == "d":  # add dropout
+                if dropout_rate:
+                    out = layers.dropout(out,
+                                         dropout_prob=dropout_rate,
+                                         is_test=False)
+        return out
+
+
+class PositionwiseFeedForwardLayer(Layer):
+    """
+    PositionwiseFeedForwardLayer
+    """
+    def __init__(self, name_scope, d_inner_hid, d_hid, dropout_rate):
+        super(PositionwiseFeedForwardLayer, self).__init__(name_scope)
+        self._i2h = FC(name_scope=self.full_name(),
+                       size=d_inner_hid,
+                       num_flatten_dims=2,
+                       act="relu")
+        self._h2o = FC(name_scope=self.full_name(),
+                       size=d_hid,
+                       num_flatten_dims=2)
+        self._dropout_rate = dropout_rate
+
+    def forward(self, x):
+        """
+        forward
+        :param x:
+        :return:
+        """
+        hidden = self._i2h(x)
+        if self._dropout_rate:
+            hidden = layers.dropout(hidden,
+                                    dropout_prob=self._dropout_rate,
+                                    is_test=False)
+        out = self._h2o(hidden)
+        return out
+
+
+class MultiHeadAttentionLayer(Layer):
+    """
+    MultiHeadAttentionLayer
+    """
+    def __init__(self,
+                 name_scope,
+                 d_key,
+                 d_value,
+                 d_model,
+                 n_head=1,
+                 dropout_rate=0.,
+                 cache=None,
+                 gather_idx=None,
+                 static_kv=False):
+        super(MultiHeadAttentionLayer, self).__init__(name_scope)
+        self._n_head = n_head
+        self._d_key = d_key
+        self._d_value = d_value
+        self._d_model = d_model
+        self._dropout_rate = dropout_rate
+        self._q_fc = FC(name_scope=self.full_name(),
+                        size=d_key * n_head,
+                        bias_attr=False,
+                        num_flatten_dims=2)
+        self._k_fc = FC(name_scope=self.full_name(),
+                        size=d_key * n_head,
+                        bias_attr=False,
+                        num_flatten_dims=2)
+        self._v_fc = FC(name_scope=self.full_name(),
+                        size=d_value * n_head,
+                        bias_attr=False,
+                        num_flatten_dims=2)
+        self._proj_fc = FC(name_scope=self.full_name(),
+                           size=self._d_model,
+                           bias_attr=False,
+                           num_flatten_dims=2)
+
+    def forward(self,
+                queries,
+                keys,
+                values,
+                attn_bias,
+                cache=None,
+                gather_idx=None):
+        """
+        forward
+        :param queries:
+        :param keys:
+        :param values:
+        :param attn_bias:
+        :return:
+        """
+        # compute q ,k ,v
+        keys = queries if keys is None else keys
+        values = keys if values is None else values
+
+        q = self._q_fc(queries)
+        k = self._k_fc(keys)
+        v = self._v_fc(values)
+
+        # split head
+        reshaped_q = layers.reshape(x=q,
+                                    shape=[0, 0, self._n_head, self._d_key],
+                                    inplace=False)
+        transpose_q = layers.transpose(x=reshaped_q, perm=[0, 2, 1, 3])
+        reshaped_k = layers.reshape(x=k,
+                                    shape=[0, 0, self._n_head, self._d_key],
+                                    inplace=False)
+        transpose_k = layers.transpose(x=reshaped_k, perm=[0, 2, 1, 3])
+        reshaped_v = layers.reshape(x=v,
+                                    shape=[0, 0, self._n_head, self._d_value],
+                                    inplace=False)
+        transpose_v = layers.transpose(x=reshaped_v, perm=[0, 2, 1, 3])
+
+        if cache is not None:
+            cache_k, cache_v = cache["k"], cache["v"]
+            transpose_k = layers.concat([cache_k, transpose_k], axis=2)
+            transpose_v = layers.concat([cache_v, transpose_v], axis=2)
+            cache["k"], cache["v"] = transpose_k, transpose_v
+
+        # scale dot product attention
+        product = layers.matmul(x=transpose_q,
+                                y=transpose_k,
+                                transpose_y=True,
+                                alpha=self._d_model**-0.5)
+        if attn_bias:
+            product += attn_bias
+        weights = layers.softmax(product)
+        if self._dropout_rate:
+            weights_droped = layers.dropout(weights,
+                                            dropout_prob=self._dropout_rate,
+                                            is_test=False)
+            out = layers.matmul(weights_droped, transpose_v)
+        else:
+            out = layers.matmul(weights, transpose_v)
+
+        # combine heads
+        if len(out.shape) != 4:
+            raise ValueError("Input(x) should be a 4-D Tensor.")
+        trans_x = layers.transpose(out, perm=[0, 2, 1, 3])
+        final_out = layers.reshape(
+            x=trans_x,
+            shape=[0, 0, trans_x.shape[2] * trans_x.shape[3]],
+            inplace=False)
+
+        # fc to output
+        proj_out = self._proj_fc(final_out)
+        return proj_out
+
+
+class EncoderSubLayer(Layer):
+    """
+    EncoderSubLayer
+    """
+    def __init__(self,
+                 name_scope,
+                 n_head,
+                 d_key,
+                 d_value,
+                 d_model,
+                 d_inner_hid,
+                 prepostprocess_dropout,
+                 attention_dropout,
+                 relu_dropout,
+                 preprocess_cmd="n",
+                 postprocess_cmd="da"):
+
+        super(EncoderSubLayer, self).__init__(name_scope)
+        self._preprocess_cmd = preprocess_cmd
+        self._postprocess_cmd = postprocess_cmd
+        self._prepostprocess_dropout = prepostprocess_dropout
+
+        self._preprocess_layer = PrePostProcessLayer(self.full_name(),
+                                                     self._preprocess_cmd, 3)
+        self._multihead_attention_layer = MultiHeadAttentionLayer(
+            self.full_name(), d_key, d_value, d_model, n_head,
+            attention_dropout)
+        self._postprocess_layer = PrePostProcessLayer(self.full_name(),
+                                                      self._postprocess_cmd,
+                                                      None)
+        self._preprocess_layer2 = PrePostProcessLayer(self.full_name(),
+                                                      self._preprocess_cmd, 3)
+        self._positionwise_feed_forward = PositionwiseFeedForwardLayer(
+            self.full_name(), d_inner_hid, d_model, relu_dropout)
+        self._postprocess_layer2 = PrePostProcessLayer(self.full_name(),
+                                                       self._postprocess_cmd,
+                                                       None)
+
+    def forward(self, enc_input, attn_bias):
+        """
+        forward
+        :param enc_input:
+        :param attn_bias:
+        :return:
+        """
+        pre_process_multihead = self._preprocess_layer(
+            None, enc_input, self._preprocess_cmd, self._prepostprocess_dropout)
+        attn_output = self._multihead_attention_layer(pre_process_multihead,
+                                                      None, None, attn_bias)
+        attn_output = self._postprocess_layer(enc_input, attn_output,
+                                              self._postprocess_cmd,
+                                              self._prepostprocess_dropout)
+        pre_process2_output = self._preprocess_layer2(
+            None, attn_output, self._preprocess_cmd,
+            self._prepostprocess_dropout)
+        ffd_output = self._positionwise_feed_forward(pre_process2_output)
+        return self._postprocess_layer2(attn_output, ffd_output,
+                                        self._postprocess_cmd,
+                                        self._prepostprocess_dropout)
+
+
+class EncoderLayer(Layer):
+    """
+    encoder
+    """
+    def __init__(self,
+                 name_scope,
+                 n_layer,
+                 n_head,
+                 d_key,
+                 d_value,
+                 d_model,
+                 d_inner_hid,
+                 prepostprocess_dropout,
+                 attention_dropout,
+                 relu_dropout,
+                 preprocess_cmd="n",
+                 postprocess_cmd="da"):
+
+        super(EncoderLayer, self).__init__(name_scope)
+        self._preprocess_cmd = preprocess_cmd
+        self._encoder_sublayers = list()
+        self._prepostprocess_dropout = prepostprocess_dropout
+        self._n_layer = n_layer
+        self._preprocess_layer = PrePostProcessLayer(self.full_name(),
+                                                     self._preprocess_cmd, 3)
+        for i in range(n_layer):
+            self._encoder_sublayers.append(
+                self.add_sublayer(
+                    'esl_%d' % i,
+                    EncoderSubLayer(self.full_name(), n_head, d_key, d_value,
+                                    d_model, d_inner_hid,
+                                    prepostprocess_dropout, attention_dropout,
+                                    relu_dropout, preprocess_cmd,
+                                    postprocess_cmd)))
+
+    def forward(self, enc_input, attn_bias):
+        """
+        forward
+        :param enc_input:
+        :param attn_bias:
+        :return:
+        """
+        for i in range(self._n_layer):
+            enc_output = self._encoder_sublayers[i](enc_input, attn_bias)
+            enc_input = enc_output
+
+        return self._preprocess_layer(None, enc_output, self._preprocess_cmd,
+                                      self._prepostprocess_dropout)
+
+
+class PrepareEncoderDecoderLayer(Layer):
+    """
+    PrepareEncoderDecoderLayer
+    """
+    def __init__(self,
+                 name_scope,
+                 src_vocab_size,
+                 src_emb_dim,
+                 src_max_len,
+                 dropout_rate,
+                 word_emb_param_name=None,
+                 pos_enc_param_name=None):
+        super(PrepareEncoderDecoderLayer, self).__init__(name_scope)
+        self._src_max_len = src_max_len
+        self._src_emb_dim = src_emb_dim
+        self._src_vocab_size = src_vocab_size
+        self._dropout_rate = dropout_rate
+        self._input_emb = Embedding(name_scope=self.full_name(),
+                                    size=[src_vocab_size, src_emb_dim],
+                                    padding_idx=0,
+                                    param_attr=fluid.ParamAttr(
+                                        name=word_emb_param_name,
+                                        initializer=fluid.initializer.Normal(
+                                            0., src_emb_dim**-0.5)))
+
+        pos_inp = position_encoding_init(src_max_len, src_emb_dim)
+        self._pos_emb = Embedding(
+            name_scope=self.full_name(),
+            size=[self._src_max_len, src_emb_dim],
+            param_attr=fluid.ParamAttr(
+                name=pos_enc_param_name,
+                initializer=fluid.initializer.NumpyArrayInitializer(pos_inp),
+                trainable=False))
+
+        # use in dygraph_mode to fit different length batch
+        # self._pos_emb._w = to_variable(
+        #     position_encoding_init(self._src_max_len, self._src_emb_dim))
+
+    def forward(self, src_word, src_pos):
+        """
+        forward
+        :param src_word:
+        :param src_pos:
+        :return:
+        """
+        # print("here")
+        # print(self._input_emb._w._numpy().shape)
+        src_word_emb = self._input_emb(src_word)
+
+        src_word_emb = layers.scale(x=src_word_emb,
+                                    scale=self._src_emb_dim**0.5)
+        # # TODO change this to fit dynamic length input
+        src_pos_emb = self._pos_emb(src_pos)
+        src_pos_emb.stop_gradient = True
+        enc_input = src_word_emb + src_pos_emb
+        return layers.dropout(
+            enc_input, dropout_prob=self._dropout_rate,
+            is_test=False) if self._dropout_rate else enc_input
+
+
+class WrapEncoderLayer(Layer):
+    """
+    encoderlayer
+    """
+    def __init__(self, name_cope, src_vocab_size, max_length, n_layer, n_head,
+                 d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
+                 attention_dropout, relu_dropout, preprocess_cmd,
+                 postprocess_cmd, weight_sharing):
+        """
+        The wrapper assembles together all needed layers for the encoder.
+        """
+        super(WrapEncoderLayer, self).__init__(name_cope)
+
+        self._prepare_encoder_layer = PrepareEncoderDecoderLayer(
+            self.full_name(),
+            src_vocab_size,
+            d_model,
+            max_length,
+            prepostprocess_dropout,
+            word_emb_param_name=word_emb_param_names[0],
+            pos_enc_param_name=pos_enc_param_names[0])
+        self._encoder = EncoderLayer(self.full_name(), n_layer, n_head, d_key,
+                                     d_value, d_model, d_inner_hid,
+                                     prepostprocess_dropout, attention_dropout,
+                                     relu_dropout, preprocess_cmd,
+                                     postprocess_cmd)
+
+    def forward(self, enc_inputs):
+        """forward"""
+        src_word, src_pos, src_slf_attn_bias = enc_inputs
+        enc_input = self._prepare_encoder_layer(src_word, src_pos)
+        enc_output = self._encoder(enc_input, src_slf_attn_bias)
+        return enc_output
+
+
+class DecoderSubLayer(Layer):
+    """
+    decoder
+    """
+    def __init__(self, name_scope, n_head, d_key, d_value, d_model, d_inner_hid,
+                 prepostprocess_dropout, attention_dropout, relu_dropout,
+                 preprocess_cmd, postprocess_cmd):
+        super(DecoderSubLayer, self).__init__(name_scope)
+        self._postprocess_cmd = postprocess_cmd
+        self._preprocess_cmd = preprocess_cmd
+        self._prepostprcess_dropout = prepostprocess_dropout
+        self._pre_process_layer = PrePostProcessLayer(self.full_name(),
+                                                      preprocess_cmd, 3)
+        self._multihead_attention_layer = MultiHeadAttentionLayer(
+            self.full_name(), d_key, d_value, d_model, n_head,
+            attention_dropout)
+        self._post_process_layer = PrePostProcessLayer(self.full_name(),
+                                                       postprocess_cmd, None)
+        self._pre_process_layer2 = PrePostProcessLayer(self.full_name(),
+                                                       preprocess_cmd, 3)
+        self._multihead_attention_layer2 = MultiHeadAttentionLayer(
+            self.full_name(), d_key, d_value, d_model, n_head,
+            attention_dropout)
+        self._post_process_layer2 = PrePostProcessLayer(self.full_name(),
+                                                        postprocess_cmd, None)
+        self._pre_process_layer3 = PrePostProcessLayer(self.full_name(),
+                                                       preprocess_cmd, 3)
+        self._positionwise_feed_forward_layer = PositionwiseFeedForwardLayer(
+            self.full_name(), d_inner_hid, d_model, relu_dropout)
+        self._post_process_layer3 = PrePostProcessLayer(self.full_name(),
+                                                        postprocess_cmd, None)
+
+    def forward(self,
+                dec_input,
+                enc_output,
+                slf_attn_bias,
+                dec_enc_attn_bias,
+                cache=None,
+                gather_idx=None):
+        """
+        forward
+        :param dec_input:
+        :param enc_output:
+        :param slf_attn_bias:
+        :param dec_enc_attn_bias:
+        :return:
+        """
+        pre_process_rlt = self._pre_process_layer(None, dec_input,
+                                                  self._preprocess_cmd,
+                                                  self._prepostprcess_dropout)
+        slf_attn_output = self._multihead_attention_layer(
+            pre_process_rlt, None, None, slf_attn_bias, cache, gather_idx)
+        slf_attn_output_pp = self._post_process_layer(
+            dec_input, slf_attn_output, self._postprocess_cmd,
+            self._prepostprcess_dropout)
+        pre_process_rlt2 = self._pre_process_layer2(None, slf_attn_output_pp,
+                                                    self._preprocess_cmd,
+                                                    self._prepostprcess_dropout)
+        enc_attn_output_pp = self._multihead_attention_layer2(
+            pre_process_rlt2, enc_output, enc_output, dec_enc_attn_bias)
+        enc_attn_output = self._post_process_layer2(slf_attn_output_pp,
+                                                    enc_attn_output_pp,
+                                                    self._postprocess_cmd,
+                                                    self._prepostprcess_dropout)
+        pre_process_rlt3 = self._pre_process_layer3(None, enc_attn_output,
+                                                    self._preprocess_cmd,
+                                                    self._prepostprcess_dropout)
+        ffd_output = self._positionwise_feed_forward_layer(pre_process_rlt3)
+        dec_output = self._post_process_layer3(enc_attn_output, ffd_output,
+                                               self._postprocess_cmd,
+                                               self._prepostprcess_dropout)
+        return dec_output
+
+
+class DecoderLayer(Layer):
+    """
+    decoder
+    """
+    def __init__(self, name_scope, n_layer, n_head, d_key, d_value, d_model,
+                 d_inner_hid, prepostprocess_dropout, attention_dropout,
+                 relu_dropout, preprocess_cmd, postprocess_cmd):
+        super(DecoderLayer, self).__init__(name_scope)
+        self._pre_process_layer = PrePostProcessLayer(self.full_name(),
+                                                      preprocess_cmd, 3)
+        self._decoder_sub_layers = list()
+        self._n_layer = n_layer
+        self._preprocess_cmd = preprocess_cmd
+        self._prepostprocess_dropout = prepostprocess_dropout
+        for i in range(n_layer):
+            self._decoder_sub_layers.append(
+                self.add_sublayer(
+                    'dsl_%d' % i,
+                    DecoderSubLayer(self.full_name(), n_head, d_key, d_value,
+                                    d_model, d_inner_hid,
+                                    prepostprocess_dropout, attention_dropout,
+                                    relu_dropout, preprocess_cmd,
+                                    postprocess_cmd)))
+
+    def forward(self,
+                dec_input,
+                enc_output,
+                dec_slf_attn_bias,
+                dec_enc_attn_bias,
+                caches=None,
+                gather_idx=None):
+        """
+        forward
+        :param dec_input:
+        :param enc_output:
+        :param dec_slf_attn_bias:
+        :param dec_enc_attn_bias:
+        :return:
+        """
+        for i in range(self._n_layer):
+            tmp_dec_output = self._decoder_sub_layers[i](
+                dec_input, enc_output, dec_slf_attn_bias, dec_enc_attn_bias,
+                None if caches is None else caches[i], gather_idx)
+            dec_input = tmp_dec_output
+
+        dec_output = self._pre_process_layer(None, tmp_dec_output,
+                                             self._preprocess_cmd,
+                                             self._prepostprocess_dropout)
+        return dec_output
+
+
+class WrapDecoderLayer(Layer):
+    """
+    decoder
+    """
+    def __init__(self,
+                 name_scope,
+                 trg_vocab_size,
+                 max_length,
+                 n_layer,
+                 n_head,
+                 d_key,
+                 d_value,
+                 d_model,
+                 d_inner_hid,
+                 prepostprocess_dropout,
+                 attention_dropout,
+                 relu_dropout,
+                 preprocess_cmd,
+                 postprocess_cmd,
+                 weight_sharing,
+                 gather_idx=None):
+        """
+        The wrapper assembles together all needed layers for the encoder.
+        """
+        super(WrapDecoderLayer, self).__init__(name_scope)
+
+        self._prepare_decoder_layer = PrepareEncoderDecoderLayer(
+            self.full_name(),
+            trg_vocab_size,
+            d_model,
+            max_length,
+            prepostprocess_dropout,
+            word_emb_param_name=word_emb_param_names[1],
+            pos_enc_param_name=pos_enc_param_names[1])
+        self._decoder_layer = DecoderLayer(self.full_name(), n_layer, n_head,
+                                           d_key, d_value, d_model, d_inner_hid,
+                                           prepostprocess_dropout,
+                                           attention_dropout, relu_dropout,
+                                           preprocess_cmd, postprocess_cmd)
+        self._weight_sharing = weight_sharing
+        if not weight_sharing:
+            self._fc = FC(self.full_name(),
+                          size=trg_vocab_size,
+                          bias_attr=False)
+
+    def forward(self, dec_inputs, enc_output, caches=None, gather_idx=None):
+        """
+        forward
+        :param dec_inputs:
+        :param enc_output:
+        :return:
+        """
+        trg_word, trg_pos, trg_slf_attn_bias, trg_src_attn_bias = dec_inputs
+        dec_input = self._prepare_decoder_layer(trg_word, trg_pos)
+        dec_output = self._decoder_layer(dec_input, enc_output,
+                                         trg_slf_attn_bias, trg_src_attn_bias,
+                                         caches, gather_idx)
+
+        dec_output_reshape = layers.reshape(dec_output,
+                                            shape=[-1, dec_output.shape[-1]],
+                                            inplace=False)
+
+        if self._weight_sharing:
+            predict = layers.matmul(x=dec_output_reshape,
+                                    y=self._prepare_decoder_layer._input_emb._w,
+                                    transpose_y=True)
+        else:
+            predict = self._fc(dec_output_reshape)
+
+        if dec_inputs is None:
+            # Return probs for independent decoder program.
+            predict_out = layers.softmax(predict)
+            return predict_out
+        return predict
+
+
+class TransFormer(Layer):
+    """
+    model
+    """
+    def __init__(self,
+                 name_scope,
+                 src_vocab_size,
+                 trg_vocab_size,
+                 max_length,
+                 n_layer,
+                 n_head,
+                 d_key,
+                 d_value,
+                 d_model,
+                 d_inner_hid,
+                 prepostprocess_dropout,
+                 attention_dropout,
+                 relu_dropout,
+                 preprocess_cmd,
+                 postprocess_cmd,
+                 weight_sharing,
+                 label_smooth_eps=0.0):
+        super(TransFormer, self).__init__(name_scope)
+        self._label_smooth_eps = label_smooth_eps
+        self._trg_vocab_size = trg_vocab_size
+        if weight_sharing:
+            assert src_vocab_size == trg_vocab_size, (
+                "Vocabularies in source and target should be same for weight sharing."
+            )
+        self._wrap_encoder_layer = WrapEncoderLayer(
+            self.full_name(), src_vocab_size, max_length, n_layer, n_head,
+            d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
+            attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd,
+            weight_sharing)
+        self._wrap_decoder_layer = WrapDecoderLayer(
+            self.full_name(), trg_vocab_size, max_length, n_layer, n_head,
+            d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
+            attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd,
+            weight_sharing)
+
+        if weight_sharing:
+            self._wrap_decoder_layer._prepare_decoder_layer._input_emb._w = self._wrap_encoder_layer._prepare_encoder_layer._input_emb._w
+
+        self.n_layer = n_layer
+        self.n_head = n_head
+        self.d_key = d_key
+        self.d_value = d_value
+
+    def forward(self, enc_inputs, dec_inputs, label, weights):
+        """
+        forward
+        :param enc_inputs:
+        :param dec_inputs:
+        :param label:
+        :param weights:
+        :return:
+        """
+        enc_output = self._wrap_encoder_layer(enc_inputs)
+        predict = self._wrap_decoder_layer(dec_inputs, enc_output)
+        if self._label_smooth_eps:
+            label_out = layers.label_smooth(label=layers.one_hot(
+                input=label, depth=self._trg_vocab_size),
+                                            epsilon=self._label_smooth_eps)
+
+        cost = layers.softmax_with_cross_entropy(
+            logits=predict,
+            label=label_out,
+            soft_label=True if self._label_smooth_eps else False)
+        weighted_cost = cost * weights
+        sum_cost = layers.reduce_sum(weighted_cost)
+        token_num = layers.reduce_sum(weights)
+        token_num.stop_gradient = True
+        avg_cost = sum_cost / token_num
+        return sum_cost, avg_cost, predict, token_num
+
+    def beam_search(self,
+                    enc_inputs,
+                    dec_inputs,
+                    bos_id=0,
+                    eos_id=1,
+                    beam_size=4,
+                    max_len=30,
+                    alpha=0.6):
+        """
+        Beam search with the alive and finished two queues, both have a beam size
+        capicity separately. It includes `grow_topk` `grow_alive` `grow_finish` as
+        steps. 
+        
+        1. `grow_topk` selects the top `2*beam_size` candidates to avoid all getting
+        EOS.
+
+        2. `grow_alive` selects the top `beam_size` non-EOS candidates as the inputs
+        of next decoding step.
+
+        3. `grow_finish` compares the already finished candidates in the finished queue
+        and newly added finished candidates from `grow_topk`, and selects the top
+        `beam_size` finished candidates.
+        """
+        def expand_to_beam_size(tensor, beam_size):
+            tensor = layers.reshape(tensor,
+                                    [tensor.shape[0], 1] + tensor.shape[1:])
+            tile_dims = [1] * len(tensor.shape)
+            tile_dims[1] = beam_size
+            return layers.expand(tensor, tile_dims)
+
+        def merge_beam_dim(tensor):
+            return layers.reshape(tensor, [-1] + tensor.shape[2:])
+
+        # run encoder
+        enc_output = self._wrap_encoder_layer(enc_inputs)
+
+        # constant number
+        inf = float(1. * 1e7)
+        batch_size = enc_output.shape[0]
+
+        ### initialize states of beam search ###
+        ## init for the alive ##
+        initial_ids, trg_src_attn_bias = dec_inputs  # (batch_size, 1)
+        initial_log_probs = to_variable(
+            np.array([[0.] + [-inf] * (beam_size - 1)], dtype="float32"))
+        alive_log_probs = layers.expand(initial_log_probs, [batch_size, 1])
+        alive_seq = to_variable(
+            np.tile(np.array([[[bos_id]]], dtype="int64"),
+                    (batch_size, beam_size, 1)))
+
+        ## init for the finished ##
+        finished_scores = to_variable(
+            np.array([[-inf] * beam_size], dtype="float32"))
+        finished_scores = layers.expand(finished_scores, [batch_size, 1])
+        finished_seq = to_variable(
+            np.tile(np.array([[[bos_id]]], dtype="int64"),
+                    (batch_size, beam_size, 1)))
+        finished_flags = layers.zeros_like(finished_scores)
+
+        ### initialize inputs and states of transformer decoder ###
+        ## init inputs for decoder, shaped `[batch_size*beam_size, ...]`
+        trg_word = layers.reshape(alive_seq[:, :, -1],
+                                  [batch_size * beam_size, 1, 1])
+        trg_pos = layers.zeros_like(trg_word)
+        trg_src_attn_bias = merge_beam_dim(
+            expand_to_beam_size(trg_src_attn_bias, beam_size))
+        enc_output = merge_beam_dim(expand_to_beam_size(enc_output, beam_size))
+        ## init states (caches) for transformer, need to be updated according to selected beam
+        caches = [{
+            "k":
+            layers.fill_constant(
+                shape=[batch_size * beam_size, self.n_head, 0, self.d_key],
+                dtype=enc_output.dtype,
+                value=0),
+            "v":
+            layers.fill_constant(
+                shape=[batch_size * beam_size, self.n_head, 0, self.d_value],
+                dtype=enc_output.dtype,
+                value=0),
+        } for i in range(self.n_layer)]
+
+        def update_states(caches, beam_idx, beam_size):
+            for cache in caches:
+                cache["k"] = gather_2d_by_gather(cache["k"], beam_idx,
+                                                 beam_size, batch_size, False)
+                cache["v"] = gather_2d_by_gather(cache["v"], beam_idx,
+                                                 beam_size, batch_size, False)
+            return caches
+
+        def gather_2d_by_gather(tensor_nd,
+                                beam_idx,
+                                beam_size,
+                                batch_size,
+                                need_flat=True):
+            batch_idx = layers.range(0, batch_size, 1,
+                                     dtype="int64") * beam_size
+            flat_tensor = merge_beam_dim(tensor_nd) if need_flat else tensor_nd
+            idx = layers.reshape(layers.elementwise_add(beam_idx, batch_idx, 0),
+                                 [-1])
+            new_flat_tensor = layers.gather(flat_tensor, idx)
+            new_tensor_nd = layers.reshape(
+                new_flat_tensor,
+                shape=[batch_size, beam_idx.shape[1]] +
+                tensor_nd.shape[2:]) if need_flat else new_flat_tensor
+            return new_tensor_nd
+
+        def early_finish(alive_log_probs, finished_scores,
+                         finished_in_finished):
+            max_length_penalty = np.power(((5. + max_len) / 6.), alpha)
+            # The best possible score of the most likely alive sequence
+            lower_bound_alive_scores = alive_log_probs[:, 0] / max_length_penalty
+
+            # Now to compute the lowest score of a finished sequence in finished
+            # If the sequence isn't finished, we multiply it's score by 0. since
+            # scores are all -ve, taking the min will give us the score of the lowest
+            # finished item.
+            lowest_score_of_fininshed_in_finished = layers.reduce_min(
+                finished_scores * finished_in_finished, 1)
+            # If none of the sequences have finished, then the min will be 0 and
+            # we have to replace it by -ve INF if it is. The score of any seq in alive
+            # will be much higher than -ve INF and the termination condition will not
+            # be met.
+            lowest_score_of_fininshed_in_finished += (
+                1. - layers.reduce_max(finished_in_finished, 1)) * -inf
+            bound_is_met = layers.reduce_all(
+                layers.greater_than(lowest_score_of_fininshed_in_finished,
+                                    lower_bound_alive_scores))
+
+            return bound_is_met
+
+        def grow_topk(i, logits, alive_seq, alive_log_probs, states):
+            logits = layers.reshape(logits, [batch_size, beam_size, -1])
+            candidate_log_probs = layers.log(layers.softmax(logits, axis=2))
+            log_probs = layers.elementwise_add(candidate_log_probs,
+                                               alive_log_probs, 0)
+
+            length_penalty = np.power(5.0 + (i + 1.0) / 6.0, alpha)
+            curr_scores = log_probs / length_penalty
+            flat_curr_scores = layers.reshape(curr_scores, [batch_size, -1])
+
+            topk_scores, topk_ids = layers.topk(flat_curr_scores,
+                                                k=beam_size * 2)
+
+            topk_log_probs = topk_scores * length_penalty
+
+            topk_beam_index = topk_ids // self._trg_vocab_size
+            topk_ids = topk_ids % self._trg_vocab_size
+
+            # use gather as gather_nd, TODO: use gather_nd
+            topk_seq = gather_2d_by_gather(alive_seq, topk_beam_index,
+                                           beam_size, batch_size)
+            topk_seq = layers.concat(
+                [topk_seq,
+                 layers.reshape(topk_ids, topk_ids.shape + [1])],
+                axis=2)
+            states = update_states(states, topk_beam_index, beam_size)
+            eos = layers.fill_constant(shape=topk_ids.shape,
+                                       dtype="int64",
+                                       value=eos_id)
+            topk_finished = layers.cast(layers.equal(topk_ids, eos), "float32")
+
+            #topk_seq: [batch_size, 2*beam_size, i+1]
+            #topk_log_probs, topk_scores, topk_finished: [batch_size, 2*beam_size]
+            return topk_seq, topk_log_probs, topk_scores, topk_finished, states
+
+        def grow_alive(curr_seq, curr_scores, curr_log_probs, curr_finished,
+                       states):
+            curr_scores += curr_finished * -inf
+            _, topk_indexes = layers.topk(curr_scores, k=beam_size)
+            alive_seq = gather_2d_by_gather(curr_seq, topk_indexes,
+                                            beam_size * 2, batch_size)
+            alive_log_probs = gather_2d_by_gather(curr_log_probs, topk_indexes,
+                                                  beam_size * 2, batch_size)
+            states = update_states(states, topk_indexes, beam_size * 2)
+
+            return alive_seq, alive_log_probs, states
+
+        def grow_finished(finished_seq, finished_scores, finished_flags,
+                          curr_seq, curr_scores, curr_finished):
+            # finished scores
+            finished_seq = layers.concat([
+                finished_seq,
+                layers.fill_constant(shape=[batch_size, beam_size, 1],
+                                     dtype="int64",
+                                     value=eos_id)
+            ],
+                                         axis=2)
+            # Set the scores of the unfinished seq in curr_seq to large negative
+            # values
+            curr_scores += (1. - curr_finished) * -inf
+            # concatenating the sequences and scores along beam axis
+            curr_finished_seq = layers.concat([finished_seq, curr_seq], axis=1)
+            curr_finished_scores = layers.concat([finished_scores, curr_scores],
+                                                 axis=1)
+            curr_finished_flags = layers.concat([finished_flags, curr_finished],
+                                                axis=1)
+            _, topk_indexes = layers.topk(curr_finished_scores, k=beam_size)
+            finished_seq = gather_2d_by_gather(curr_finished_seq, topk_indexes,
+                                               beam_size * 3, batch_size)
+            finished_scores = gather_2d_by_gather(curr_finished_scores,
+                                                  topk_indexes, beam_size * 3,
+                                                  batch_size)
+            finished_flags = gather_2d_by_gather(curr_finished_flags,
+                                                 topk_indexes, beam_size * 3,
+                                                 batch_size)
+            return finished_seq, finished_scores, finished_flags
+
+        for i in range(max_len):
+            logits = self._wrap_decoder_layer(
+                (trg_word, trg_pos, None, trg_src_attn_bias), enc_output,
+                caches)
+            topk_seq, topk_log_probs, topk_scores, topk_finished, states = grow_topk(
+                i, logits, alive_seq, alive_log_probs, caches)
+            alive_seq, alive_log_probs, states = grow_alive(
+                topk_seq, topk_scores, topk_log_probs, topk_finished, states)
+            finished_seq, finished_scores, finished_flags = grow_finished(
+                finished_seq, finished_scores, finished_flags, topk_seq,
+                topk_scores, topk_finished)
+            trg_word = layers.reshape(alive_seq[:, :, -1],
+                                      [batch_size * beam_size, 1, 1])
+            trg_pos = layers.fill_constant(shape=trg_word.shape,
+                                           dtype="int64",
+                                           value=i)
+            if early_finish(alive_log_probs, finished_scores,
+                            finished_flags).numpy():
+                break
+
+        return finished_seq, finished_scores

dygraph/transformer/predict.py

+# Copyright (c) 2019 PaddlePaddle Authors. 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.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+import argparse
+import ast
+
+import numpy as np
+import paddle
+import paddle.fluid as fluid
+import paddle.dataset.wmt16 as wmt16
+
+from model import TransFormer
+from config import *
+from data_util import *
+
+
+def parse_args():
+    parser = argparse.ArgumentParser("Arguments for Inference")
+    parser.add_argument(
+        "--use_data_parallel",
+        type=ast.literal_eval,
+        default=False,
+        help="The flag indicating whether to shuffle instances in each pass.")
+    parser.add_argument(
+        "--model_file",
+        type=str,
+        default="transformer_params",
+        help="Load model from the file named `model_file.pdparams`.")
+    parser.add_argument(
+        "--output_file",
+        type=str,
+        default="predict.txt",
+        help="The file to output the translation results of predict_file to.")
+    parser.add_argument('opts',
+                        help='See config.py for all options',
+                        default=None,
+                        nargs=argparse.REMAINDER)
+    args = parser.parse_args()
+    merge_cfg_from_list(args.opts, [InferTaskConfig, ModelHyperParams])
+    return args
+
+
+def prepare_infer_input(insts, src_pad_idx, bos_idx, n_head):
+    """
+    inputs for inferencs
+    """
+    src_word, src_pos, src_slf_attn_bias, src_max_len = pad_batch_data(
+        [inst[0] for inst in insts], src_pad_idx, n_head, is_target=False)
+    # start tokens
+    trg_word = np.asarray([[bos_idx]] * len(insts), dtype="int64")
+    trg_src_attn_bias = np.tile(src_slf_attn_bias[:, :, ::src_max_len, :],
+                                [1, 1, 1, 1]).astype("float32")
+    trg_word = trg_word.reshape(-1, 1, 1)
+    src_word = src_word.reshape(-1, src_max_len, 1)
+    src_pos = src_pos.reshape(-1, src_max_len, 1)
+
+    data_inputs = [
+        src_word, src_pos, src_slf_attn_bias, trg_word, trg_src_attn_bias
+    ]
+
+    var_inputs = []
+    for i, field in enumerate(encoder_data_input_fields +
+                              fast_decoder_data_input_fields):
+        var_inputs.append(to_variable(data_inputs[i], name=field))
+
+    enc_inputs = var_inputs[0:len(encoder_data_input_fields)]
+    dec_inputs = var_inputs[len(encoder_data_input_fields):]
+    return enc_inputs, dec_inputs
+
+
+def post_process_seq(seq, bos_idx, eos_idx, output_bos=False, output_eos=False):
+    """
+    Post-process the decoded sequence.
+    """
+    eos_pos = len(seq) - 1
+    for i, idx in enumerate(seq):
+        if idx == eos_idx:
+            eos_pos = i
+            break
+    seq = [
+        idx for idx in seq[:eos_pos + 1]
+        if (output_bos or idx != bos_idx) and (output_eos or idx != eos_idx)
+    ]
+    return seq
+
+
+def infer(args):
+    place = fluid.CUDAPlace(fluid.dygraph.parallel.Env().dev_id) \
+        if args.use_data_parallel else fluid.CUDAPlace(0)
+    with fluid.dygraph.guard(place):
+        transformer = TransFormer(
+            'transformer', ModelHyperParams.src_vocab_size,
+            ModelHyperParams.trg_vocab_size, ModelHyperParams.max_length + 1,
+            ModelHyperParams.n_layer, ModelHyperParams.n_head,
+            ModelHyperParams.d_key, ModelHyperParams.d_value,
+            ModelHyperParams.d_model, ModelHyperParams.d_inner_hid,
+            ModelHyperParams.prepostprocess_dropout,
+            ModelHyperParams.attention_dropout, ModelHyperParams.relu_dropout,
+            ModelHyperParams.preprocess_cmd, ModelHyperParams.postprocess_cmd,
+            ModelHyperParams.weight_sharing)
+        # load checkpoint
+        model_dict, _ = fluid.load_dygraph(args.model_file)
+        transformer.load_dict(model_dict)
+        print("checkpoint loaded")
+        # start evaluate mode
+        transformer.eval()
+
+        reader = paddle.batch(wmt16.test(ModelHyperParams.src_vocab_size,
+                                         ModelHyperParams.trg_vocab_size),
+                              batch_size=InferTaskConfig.batch_size)
+        id2word = wmt16.get_dict("de",
+                                 ModelHyperParams.trg_vocab_size,
+                                 reverse=True)
+
+        f = open(args.output_file, "wb")
+        for batch in reader():
+            enc_inputs, dec_inputs = prepare_infer_input(
+                batch, ModelHyperParams.eos_idx, ModelHyperParams.bos_idx,
+                ModelHyperParams.n_head)
+
+            finished_seq, finished_scores = transformer.beam_search(
+                enc_inputs,
+                dec_inputs,
+                bos_id=ModelHyperParams.bos_idx,
+                eos_id=ModelHyperParams.eos_idx,
+                max_len=InferTaskConfig.max_out_len,
+                alpha=InferTaskConfig.alpha)
+            finished_seq = finished_seq.numpy()
+            finished_scores = finished_scores.numpy()
+            for ins in finished_seq:
+                for beam in ins:
+                    id_list = post_process_seq(beam, ModelHyperParams.bos_idx,
+                                                ModelHyperParams.eos_idx)
+                    word_list = [id2word[id] for id in id_list]
+                    sequence = " ".join(word_list) + "\n"
+                    f.write(sequence.encode("utf8"))
+                    break  # only print the best
+
+
+if __name__ == '__main__':
+    args = parse_args()
+    infer(args)

dygraph/transformer/train.py

-# Copyright (c) 2018 PaddlePaddle Authors. All Rights Reserved.
+# Copyright (c) 2019 PaddlePaddle Authors. 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.
@@ -15,377 +15,48 @@
 from __future__ import print_function
 import argparse
 import ast
-import paddle.fluid as fluid
-from paddle.fluid.dygraph import Embedding, LayerNorm, FC, to_variable, Layer, guard
+
 import numpy as np
 import paddle
+import paddle.fluid as fluid
 import paddle.dataset.wmt16 as wmt16
 
+from model import TransFormer, NoamDecay
+from config import *
+from data_util import *
+
 
 def parse_args():
-    parser = argparse.ArgumentParser("Training for Mnist.")
+    parser = argparse.ArgumentParser("Arguments for Training")
     parser.add_argument(
         "--use_data_parallel",
         type=ast.literal_eval,
         default=False,
-        help="The flag indicating whether to use data parallel mode to train the model."
-    )
+        help="The flag indicating whether to use multi-GPU.")
+    parser.add_argument(
+        "--model_file",
+        type=str,
+        default="transformer_params",
+        help="Save the model as a file named `model_file.pdparams`.")
+    parser.add_argument(
+        'opts',
+        help='See config.py for all options',
+        default=None,
+        nargs=argparse.REMAINDER)
     args = parser.parse_args()
+    merge_cfg_from_list(args.opts, [TrainTaskConfig, ModelHyperParams])
     return args
 
 
-args = parse_args()
-
-
-# Copy from models
-class TrainTaskConfig(object):
-    """
-    TrainTaskConfig
-    """
-    # support both CPU and GPU now.
-    use_gpu = True
-    # the epoch number to train.
-    pass_num = 30
-    # the number of sequences contained in a mini-batch.
-    # deprecated, set batch_size in args.
-    batch_size = 32
-    # the hyper parameters for Adam optimizer.
-    # This static learning_rate will be multiplied to the LearningRateScheduler
-    # derived learning rate the to get the final learning rate.
-    learning_rate = 2.0
-    beta1 = 0.9
-    beta2 = 0.997
-    eps = 1e-9
-    # the parameters for learning rate scheduling.
-    warmup_steps = 8000
-    # the weight used to mix up the ground-truth distribution and the fixed
-    # uniform distribution in label smoothing when training.
-    # Set this as zero if label smoothing is not wanted.
-    label_smooth_eps = 0.1
-
-
-class ModelHyperParams(object):
-    """
-    ModelHyperParams
-    """
-    # These following five vocabularies related configurations will be set
-    # automatically according to the passed vocabulary path and special tokens.
-    # size of source word dictionary.
-    src_vocab_size = 10000
-    # size of target word dictionay
-    trg_vocab_size = 10000
-    # # index for <bos> token
-    # bos_idx = 0
-    # # index for <eos> token
-    # eos_idx = 1
-    # # index for <unk> token
-    # unk_idx = 2
-
-    src_pad_idx = 0
-
-    # index for <pad> token in target language.
-    trg_pad_idx = 1
-
-    # max length of sequences deciding the size of position encoding table.
-    max_length = 50
-    # the dimension for word embeddings, which is also the last dimension of
-    # the input and output of multi-head attention, position-wise feed-forward
-    # networks, encoder and decoder.
-    d_model = 512
-    # size of the hidden layer in position-wise feed-forward networks.
-    d_inner_hid = 2048
-    # the dimension that keys are projected to for dot-product attention.
-    d_key = 64
-    # the dimension that values are projected to for dot-product attention.
-    d_value = 64
-    # number of head used in multi-head attention.
-    n_head = 8
-    # number of sub-layers to be stacked in the encoder and decoder.
-    n_layer = 6
-    # dropout rates of different modules.
-    prepostprocess_dropout = 0.1
-    attention_dropout = 0.1
-    relu_dropout = 0.1
-    # to process before each sub-layer
-    preprocess_cmd = "n"  # layer normalization
-    # to process after each sub-layer
-    postprocess_cmd = "da"  # dropout + residual connection
-    # random seed used in dropout for CE.
-    dropout_seed = 0
-    # the flag indicating whether to share embedding and softmax weights.
-    # vocabularies in source and target should be same for weight sharing.
-    weight_sharing = False
-
-
-# The placeholder for batch_size in compile time. Must be -1 currently to be
-# consistent with some ops' infer-shape output in compile time, such as the
-# sequence_expand op used in beamsearch decoder.
-batch_size = -1
-# The placeholder for squence length in compile time.
-seq_len = ModelHyperParams.max_length
-# Here list the data shapes and data types of all inputs.
-# The shapes here act as placeholder and are set to pass the infer-shape in
-# compile time.
-input_descs = {
-    # The actual data shape of src_word is:
-    # [batch_size, max_src_len_in_batch, 1]
-    "src_word": [(batch_size, seq_len, 1), "int64", 2],
-    # The actual data shape of src_pos is:
-    # [batch_size, max_src_len_in_batch, 1]
-    "src_pos": [(batch_size, seq_len, 1), "int64"],
-    # This input is used to remove attention weights on paddings in the
-    # encoder.
-    # The actual data shape of src_slf_attn_bias is:
-    # [batch_size, n_head, max_src_len_in_batch, max_src_len_in_batch]
-    "src_slf_attn_bias": [(batch_size, ModelHyperParams.n_head, seq_len,
-                           seq_len), "float32"],
-    # The actual data shape of trg_word is:
-    # [batch_size, max_trg_len_in_batch, 1]
-    "trg_word": [(batch_size, seq_len, 1), "int64",
-                 2],  # lod_level is only used in fast decoder.
-    # The actual data shape of trg_pos is:
-    # [batch_size, max_trg_len_in_batch, 1]
-    "trg_pos": [(batch_size, seq_len, 1), "int64"],
-    # This input is used to remove attention weights on paddings and
-    # subsequent words in the decoder.
-    # The actual data shape of trg_slf_attn_bias is:
-    # [batch_size, n_head, max_trg_len_in_batch, max_trg_len_in_batch]
-    "trg_slf_attn_bias": [(batch_size, ModelHyperParams.n_head, seq_len,
-                           seq_len), "float32"],
-    # This input is used to remove attention weights on paddings of the source
-    # input in the encoder-decoder attention.
-    # The actual data shape of trg_src_attn_bias is:
-    # [batch_size, n_head, max_trg_len_in_batch, max_src_len_in_batch]
-    "trg_src_attn_bias": [(batch_size, ModelHyperParams.n_head, seq_len,
-                           seq_len), "float32"],
-    # This input is used in independent decoder program for inference.
-    # The actual data shape of enc_output is:
-    # [batch_size, max_src_len_in_batch, d_model]
-    "enc_output": [(batch_size, seq_len, ModelHyperParams.d_model), "float32"],
-    # The actual data shape of label_word is:
-    # [batch_size * max_trg_len_in_batch, 1]
-    "lbl_word": [(batch_size * seq_len, 1), "int64"],
-    # This input is used to mask out the loss of paddding tokens.
-    # The actual data shape of label_weight is:
-    # [batch_size * max_trg_len_in_batch, 1]
-    "lbl_weight": [(batch_size * seq_len, 1), "float32"],
-    # This input is used in beam-search decoder.
-    "init_score": [(batch_size, 1), "float32", 2],
-    # This input is used in beam-search decoder for the first gather
-    # (cell states updation)
-    "init_idx": [(batch_size, ), "int32"],
-}
-
-# Names of word embedding table which might be reused for weight sharing.
-word_emb_param_names = (
-    "src_word_emb_table",
-    "trg_word_emb_table", )
-# Names of position encoding table which will be initialized externally.
-pos_enc_param_names = (
-    "src_pos_enc_table",
-    "trg_pos_enc_table", )
-# separated inputs for different usages.
-encoder_data_input_fields = (
-    "src_word",
-    "src_pos",
-    "src_slf_attn_bias", )
-decoder_data_input_fields = (
-    "trg_word",
-    "trg_pos",
-    "trg_slf_attn_bias",
-    "trg_src_attn_bias",
-    "enc_output", )
-label_data_input_fields = (
-    "lbl_word",
-    "lbl_weight", )
-# In fast decoder, trg_pos (only containing the current time step) is generated
-# by ops and trg_slf_attn_bias is not needed.
-fast_decoder_data_input_fields = (
-    "trg_word",
-    "init_score",
-    "init_idx",
-    "trg_src_attn_bias", )
-
-
-def merge_cfg_from_list(cfg_list, g_cfgs):
-    """
-    Set the above global configurations using the cfg_list.
-    """
-    assert len(cfg_list) % 2 == 0
-    for key, value in zip(cfg_list[0::2], cfg_list[1::2]):
-        for g_cfg in g_cfgs:
-            if hasattr(g_cfg, key):
-                try:
-                    value = eval(value)
-                except Exception:  # for file path
-                    pass
-                setattr(g_cfg, key, value)
-                break
-
-
-def position_encoding_init(n_position, d_pos_vec):
-    """
-    Generate the initial values for the sinusoid position encoding table.
-    """
-    channels = d_pos_vec
-    position = np.arange(n_position)
-    num_timescales = channels // 2
-    log_timescale_increment = (np.log(float(1e4) / float(1)) /
-                               (num_timescales - 1))
-    inv_timescales = np.exp(np.arange(
-        num_timescales)) * -log_timescale_increment
-    scaled_time = np.expand_dims(position, 1) * np.expand_dims(inv_timescales,
-                                                               0)
-    signal = np.concatenate([np.sin(scaled_time), np.cos(scaled_time)], axis=1)
-    signal = np.pad(signal, [[0, 0], [0, np.mod(channels, 2)]], 'constant')
-    position_enc = signal
-    return position_enc.astype("float32")
-
-
-def create_data(np_values, is_static=False):
-    """
-    create_data
-    :param np_values:
-    :param is_static:
-    :return:
-    """
-    # pdb.set_trace()
-    [
-        src_word_np, src_pos_np, trg_word_np, trg_pos_np, src_slf_attn_bias_np,
-        trg_slf_attn_bias_np, trg_src_attn_bias_np, lbl_word_np, lbl_weight_np
-    ] = np_values
-
-    if is_static:
-        return [
-            src_word_np, src_pos_np, src_slf_attn_bias_np, trg_word_np,
-            trg_pos_np, trg_slf_attn_bias_np, trg_src_attn_bias_np, lbl_word_np,
-            lbl_weight_np
-        ]
-    else:
-        enc_inputs = [
-            to_variable(
-                src_word_np, name='src_word'), to_variable(
-                    src_pos_np, name='src_pos'), to_variable(
-                        src_slf_attn_bias_np, name='src_slf_attn_bias')
-        ]
-        dec_inputs = [
-            to_variable(
-                trg_word_np, name='trg_word'), to_variable(
-                    trg_pos_np, name='trg_pos'), to_variable(
-                        trg_slf_attn_bias_np, name='trg_slf_attn_bias'),
-            to_variable(
-                trg_src_attn_bias_np, name='trg_src_attn_bias')
-        ]
-        label = to_variable(lbl_word_np, name='lbl_word')
-        weight = to_variable(lbl_weight_np, name='lbl_weight')
-        return enc_inputs, dec_inputs, label, weight
-
-
-def create_feed_dict_list(data, init=False):
-    """
-    create_feed_dict_list
-    :param data:
-    :param init:
-    :return:
-    """
-    if init:
-        data_input_names = encoder_data_input_fields + \
-                           decoder_data_input_fields[:-1] + label_data_input_fields + pos_enc_param_names
-    else:
-        data_input_names = encoder_data_input_fields + \
-                           decoder_data_input_fields[:-1] + label_data_input_fields
-    feed_dict_list = dict()
-    for i in range(len(data_input_names)):
-        feed_dict_list[data_input_names[i]] = data[i]
-    return feed_dict_list
-
-
-def make_all_inputs(input_fields):
-    """
-    Define the input data layers for the transformer model.
-    """
-    inputs = []
-    for input_field in input_fields:
-        input_var = fluid.layers.data(
-            name=input_field,
-            shape=input_descs[input_field][0],
-            dtype=input_descs[input_field][1],
-            lod_level=input_descs[input_field][2]
-            if len(input_descs[input_field]) == 3 else 0,
-            append_batch_size=False)
-        inputs.append(input_var)
-    return inputs
-
-
-def prepare_batch_input(insts, src_pad_idx, trg_pad_idx, n_head):
+def prepare_train_input(insts, src_pad_idx, trg_pad_idx, n_head):
     """
-    Pad the instances to the max sequence length in batch, and generate the
-    corresponding position data and attention bias. Then, convert the numpy
-    data to tensors and return a dict mapping names to tensors.
+    inputs for training
     """
-
-    def __pad_batch_data(insts,
-                         pad_idx,
-                         n_head,
-                         is_target=False,
-                         is_label=False,
-                         return_attn_bias=True,
-                         return_max_len=True,
-                         return_num_token=False):
-        """
-        Pad the instances to the max sequence length in batch, and generate the
-        corresponding position data and attention bias.
-        """
-        return_list = []
-        max_len = max(len(inst) for inst in insts)
-        # Any token included in dict can be used to pad, since the paddings' loss
-        # will be masked out by weights and make no effect on parameter gradients.
-        inst_data = np.array(
-            [inst + [pad_idx] * (max_len - len(inst)) for inst in insts])
-        return_list += [inst_data.astype("int64").reshape([-1, 1])]
-        if is_label:  # label weight
-            inst_weight = np.array([[1.] * len(inst) + [0.] *
-                                    (max_len - len(inst)) for inst in insts])
-            return_list += [inst_weight.astype("float32").reshape([-1, 1])]
-        else:  # position data
-            inst_pos = np.array([
-                list(range(0, len(inst))) + [0] * (max_len - len(inst))
-                for inst in insts
-            ])
-            return_list += [inst_pos.astype("int64").reshape([-1, 1])]
-        if return_attn_bias:
-            if is_target:
-                # This is used to avoid attention on paddings and subsequent
-                # words.
-                slf_attn_bias_data = np.ones(
-                    (inst_data.shape[0], max_len, max_len))
-                slf_attn_bias_data = np.triu(
-                    slf_attn_bias_data, 1).reshape([-1, 1, max_len, max_len])
-                slf_attn_bias_data = np.tile(slf_attn_bias_data,
-                                             [1, n_head, 1, 1]) * [-1e9]
-            else:
-                # This is used to avoid attention on paddings.
-                slf_attn_bias_data = np.array([[0] * len(inst) + [-1e9] *
-                                               (max_len - len(inst))
-                                               for inst in insts])
-                slf_attn_bias_data = np.tile(
-                    slf_attn_bias_data.reshape([-1, 1, 1, max_len]),
-                    [1, n_head, max_len, 1])
-            return_list += [slf_attn_bias_data.astype("float32")]
-        if return_max_len:
-            return_list += [max_len]
-        if return_num_token:
-            num_token = 0
-            for inst in insts:
-                num_token += len(inst)
-            return_list += [num_token]
-        return return_list if len(return_list) > 1 else return_list[0]
-
-    src_word, src_pos, src_slf_attn_bias, src_max_len = __pad_batch_data(
+    src_word, src_pos, src_slf_attn_bias, src_max_len = pad_batch_data(
         [inst[0] for inst in insts], src_pad_idx, n_head, is_target=False)
     src_word = src_word.reshape(-1, src_max_len, 1)
     src_pos = src_pos.reshape(-1, src_max_len, 1)
-    trg_word, trg_pos, trg_slf_attn_bias, trg_max_len = __pad_batch_data(
+    trg_word, trg_pos, trg_slf_attn_bias, trg_max_len = pad_batch_data(
         [inst[1] for inst in insts], trg_pad_idx, n_head, is_target=True)
     trg_word = trg_word.reshape(-1, trg_max_len, 1)
     trg_pos = trg_pos.reshape(-1, trg_max_len, 1)
@@ -393,7 +64,7 @@ def prepare_batch_input(insts, src_pad_idx, trg_pad_idx, n_head):
     trg_src_attn_bias = np.tile(src_slf_attn_bias[:, :, ::src_max_len, :],
                                 [1, 1, trg_max_len, 1]).astype("float32")
 
-    lbl_word, lbl_weight, num_token = __pad_batch_data(
+    lbl_word, lbl_weight, num_token = pad_batch_data(
         [inst[2] for inst in insts],
         trg_pad_idx,
         n_head,
@@ -403,708 +74,28 @@ def prepare_batch_input(insts, src_pad_idx, trg_pad_idx, n_head):
         return_max_len=False,
         return_num_token=True)
 
-    return [
-        src_word, src_pos, trg_word, trg_pos, src_slf_attn_bias,
+    data_inputs = [
+        src_word, src_pos, src_slf_attn_bias, trg_word, trg_pos,
         trg_slf_attn_bias, trg_src_attn_bias, lbl_word, lbl_weight
     ]
 
+    var_inputs = []
+    for i, field in enumerate(encoder_data_input_fields +
+                              decoder_data_input_fields[:-1] +
+                              label_data_input_fields):
+        var_inputs.append(to_variable(data_inputs[i], name=field))
 
-pos_inp1 = position_encoding_init(ModelHyperParams.max_length + 1,
-                                  ModelHyperParams.d_model)
-pos_inp2 = position_encoding_init(ModelHyperParams.max_length + 1,
-                                  ModelHyperParams.d_model)
-
-
-class PrePostProcessLayer(Layer):
-    """
-    PrePostProcessLayer
-    """
-
-    def __init__(self, name_scope, process_cmd, shape_len=None):
-        super(PrePostProcessLayer, self).__init__(name_scope)
-        for cmd in process_cmd:
-            if cmd == "n":
-                self._layer_norm = LayerNorm(
-                    name_scope=self.full_name(),
-                    begin_norm_axis=shape_len - 1,
-                    param_attr=fluid.ParamAttr(
-                        initializer=fluid.initializer.Constant(1.)),
-                    bias_attr=fluid.ParamAttr(
-                        initializer=fluid.initializer.Constant(0.)))
-
-    def forward(self, prev_out, out, process_cmd, dropout_rate=0.):
-        """
-        forward
-        :param prev_out:
-        :param out:
-        :param process_cmd:
-        :param dropout_rate:
-        :return:
-        """
-        for cmd in process_cmd:
-            if cmd == "a":  # add residual connection
-                out = out + prev_out if prev_out else out
-            elif cmd == "n":  # add layer normalization
-                out = self._layer_norm(out)
-            elif cmd == "d":  # add dropout
-                if dropout_rate:
-                    out = fluid.layers.dropout(
-                        out,
-                        dropout_prob=dropout_rate,
-                        seed=ModelHyperParams.dropout_seed,
-                        is_test=False)
-        return out
-
-
-class PositionwiseFeedForwardLayer(Layer):
-    """
-    PositionwiseFeedForwardLayer
-    """
-
-    def __init__(self, name_scope, d_inner_hid, d_hid, dropout_rate):
-        super(PositionwiseFeedForwardLayer, self).__init__(name_scope)
-        self._i2h = FC(name_scope=self.full_name(),
-                       size=d_inner_hid,
-                       num_flatten_dims=2,
-                       act="relu")
-        self._h2o = FC(name_scope=self.full_name(),
-                       size=d_hid,
-                       num_flatten_dims=2)
-        self._dropout_rate = dropout_rate
-
-    def forward(self, x):
-        """
-        forward
-        :param x:
-        :return:
-        """
-        hidden = self._i2h(x)
-        if self._dropout_rate:
-            hidden = fluid.layers.dropout(
-                hidden,
-                dropout_prob=self._dropout_rate,
-                seed=ModelHyperParams.dropout_seed,
-                is_test=False)
-        out = self._h2o(hidden)
-        return out
-
-
-class MultiHeadAttentionLayer(Layer):
-    """
-    MultiHeadAttentionLayer
-    """
-
-    def __init__(self,
-                 name_scope,
-                 d_key,
-                 d_value,
-                 d_model,
-                 n_head=1,
-                 dropout_rate=0.,
-                 cache=None,
-                 gather_idx=None,
-                 static_kv=False):
-        super(MultiHeadAttentionLayer, self).__init__(name_scope)
-        self._n_head = n_head
-        self._d_key = d_key
-        self._d_value = d_value
-        self._d_model = d_model
-        self._dropout_rate = dropout_rate
-        self._q_fc = FC(name_scope=self.full_name(),
-                        size=d_key * n_head,
-                        bias_attr=False,
-                        num_flatten_dims=2)
-        self._k_fc = FC(name_scope=self.full_name(),
-                        size=d_key * n_head,
-                        bias_attr=False,
-                        num_flatten_dims=2)
-        self._v_fc = FC(name_scope=self.full_name(),
-                        size=d_value * n_head,
-                        bias_attr=False,
-                        num_flatten_dims=2)
-        self._proj_fc = FC(name_scope=self.full_name(),
-                           size=self._d_model,
-                           bias_attr=False,
-                           num_flatten_dims=2)
-
-    def forward(self, queries, keys, values, attn_bias):
-        """
-        forward
-        :param queries:
-        :param keys:
-        :param values:
-        :param attn_bias:
-        :return:
-        """
-        # compute q ,k ,v
-        keys = queries if keys is None else keys
-        values = keys if values is None else values
-
-        q = self._q_fc(queries)
-        k = self._k_fc(keys)
-        v = self._v_fc(values)
-
-        # split head
-        reshaped_q = fluid.layers.reshape(
-            x=q, shape=[0, 0, self._n_head, self._d_key], inplace=False)
-        transpose_q = fluid.layers.transpose(x=reshaped_q, perm=[0, 2, 1, 3])
-        reshaped_k = fluid.layers.reshape(
-            x=k, shape=[0, 0, self._n_head, self._d_key], inplace=False)
-        transpose_k = fluid.layers.transpose(x=reshaped_k, perm=[0, 2, 1, 3])
-        reshaped_v = fluid.layers.reshape(
-            x=v, shape=[0, 0, self._n_head, self._d_value], inplace=False)
-        transpose_v = fluid.layers.transpose(x=reshaped_v, perm=[0, 2, 1, 3])
-
-        # scale dot product attention
-        product = fluid.layers.matmul(
-            x=transpose_q,
-            y=transpose_k,
-            transpose_y=True,
-            alpha=self._d_model**-0.5)
-        if attn_bias:
-            product += attn_bias
-        weights = fluid.layers.softmax(product)
-        if self._dropout_rate:
-            weights_droped = fluid.layers.dropout(
-                weights,
-                dropout_prob=self._dropout_rate,
-                seed=ModelHyperParams.dropout_seed,
-                is_test=False)
-            out = fluid.layers.matmul(weights_droped, transpose_v)
-        else:
-            out = fluid.layers.matmul(weights, transpose_v)
+    enc_inputs = var_inputs[0:len(encoder_data_input_fields)]
+    dec_inputs = var_inputs[len(encoder_data_input_fields
+                                ):len(encoder_data_input_fields) +
+                            len(decoder_data_input_fields[:-1])]
+    label = var_inputs[-2]
+    weights = var_inputs[-1]
 
-        # combine heads
-        if len(out.shape) != 4:
-            raise ValueError("Input(x) should be a 4-D Tensor.")
-        trans_x = fluid.layers.transpose(out, perm=[0, 2, 1, 3])
-        final_out = fluid.layers.reshape(
-            x=trans_x,
-            shape=[0, 0, trans_x.shape[2] * trans_x.shape[3]],
-            inplace=False)
+    return enc_inputs, dec_inputs, label, weights
 
-        # fc to output
-        proj_out = self._proj_fc(final_out)
-        return proj_out
 
-
-class EncoderSubLayer(Layer):
-    """
-    EncoderSubLayer
-    """
-
-    def __init__(self,
-                 name_scope,
-                 n_head,
-                 d_key,
-                 d_value,
-                 d_model,
-                 d_inner_hid,
-                 prepostprocess_dropout,
-                 attention_dropout,
-                 relu_dropout,
-                 preprocess_cmd="n",
-                 postprocess_cmd="da"):
-
-        super(EncoderSubLayer, self).__init__(name_scope)
-        self._preprocess_cmd = preprocess_cmd
-        self._postprocess_cmd = postprocess_cmd
-        self._prepostprocess_dropout = prepostprocess_dropout
-
-        self._preprocess_layer = PrePostProcessLayer(self.full_name(),
-                                                     self._preprocess_cmd, 3)
-        self._multihead_attention_layer = MultiHeadAttentionLayer(
-            self.full_name(), d_key, d_value, d_model, n_head,
-            attention_dropout)
-        self._postprocess_layer = PrePostProcessLayer(
-            self.full_name(), self._postprocess_cmd, None)
-        self._preprocess_layer2 = PrePostProcessLayer(self.full_name(),
-                                                      self._preprocess_cmd, 3)
-        self._positionwise_feed_forward = PositionwiseFeedForwardLayer(
-            self.full_name(), d_inner_hid, d_model, relu_dropout)
-        self._postprocess_layer2 = PrePostProcessLayer(
-            self.full_name(), self._postprocess_cmd, None)
-
-    def forward(self, enc_input, attn_bias):
-        """
-        forward
-        :param enc_input:
-        :param attn_bias:
-        :return:
-        """
-        pre_process_multihead = self._preprocess_layer(
-            None, enc_input, self._preprocess_cmd, self._prepostprocess_dropout)
-        attn_output = self._multihead_attention_layer(pre_process_multihead,
-                                                      None, None, attn_bias)
-        attn_output = self._postprocess_layer(enc_input, attn_output,
-                                              self._postprocess_cmd,
-                                              self._prepostprocess_dropout)
-        pre_process2_output = self._preprocess_layer2(
-            None, attn_output, self._preprocess_cmd,
-            self._prepostprocess_dropout)
-        ffd_output = self._positionwise_feed_forward(pre_process2_output)
-        return self._postprocess_layer2(attn_output, ffd_output,
-                                        self._postprocess_cmd,
-                                        self._prepostprocess_dropout)
-
-
-class EncoderLayer(Layer):
-    """
-    encoder
-    """
-
-    def __init__(self,
-                 name_scope,
-                 n_layer,
-                 n_head,
-                 d_key,
-                 d_value,
-                 d_model,
-                 d_inner_hid,
-                 prepostprocess_dropout,
-                 attention_dropout,
-                 relu_dropout,
-                 preprocess_cmd="n",
-                 postprocess_cmd="da"):
-
-        super(EncoderLayer, self).__init__(name_scope)
-        self._preprocess_cmd = preprocess_cmd
-        self._encoder_sublayers = list()
-        self._prepostprocess_dropout = prepostprocess_dropout
-        self._n_layer = n_layer
-        self._preprocess_layer = PrePostProcessLayer(self.full_name(),
-                                                     self._preprocess_cmd, 3)
-        for i in range(n_layer):
-            self._encoder_sublayers.append(
-                self.add_sublayer(
-                    'esl_%d' % i,
-                    EncoderSubLayer(
-                        self.full_name(), n_head, d_key, d_value, d_model,
-                        d_inner_hid, prepostprocess_dropout, attention_dropout,
-                        relu_dropout, preprocess_cmd, postprocess_cmd)))
-
-    def forward(self, enc_input, attn_bias):
-        """
-        forward
-        :param enc_input:
-        :param attn_bias:
-        :return:
-        """
-        for i in range(self._n_layer):
-            enc_output = self._encoder_sublayers[i](enc_input, attn_bias)
-            enc_input = enc_output
-
-        return self._preprocess_layer(None, enc_output, self._preprocess_cmd,
-                                      self._prepostprocess_dropout)
-
-
-class PrepareEncoderDecoderLayer(Layer):
-    """
-    PrepareEncoderDecoderLayer
-    """
-
-    def __init__(self,
-                 name_scope,
-                 src_vocab_size,
-                 src_emb_dim,
-                 src_max_len,
-                 dropout_rate,
-                 word_emb_param_name=None,
-                 pos_enc_param_name=None):
-        super(PrepareEncoderDecoderLayer, self).__init__(name_scope)
-        self._src_max_len = src_max_len
-        self._src_emb_dim = src_emb_dim
-        self._src_vocab_size = src_vocab_size
-        self._dropout_rate = dropout_rate
-        self._input_emb = Embedding(
-            name_scope=self.full_name(),
-            size=[src_vocab_size, src_emb_dim],
-            padding_idx=0,
-            param_attr=fluid.ParamAttr(
-                name=word_emb_param_name,
-                initializer=fluid.initializer.Normal(0., src_emb_dim**-0.5)))
-
-        if pos_enc_param_name is pos_enc_param_names[0]:
-            pos_inp = pos_inp1
-        else:
-            pos_inp = pos_inp2
-        self._pos_emb = Embedding(
-            name_scope=self.full_name(),
-            size=[self._src_max_len, src_emb_dim],
-            param_attr=fluid.ParamAttr(
-                name=pos_enc_param_name,
-                initializer=fluid.initializer.NumpyArrayInitializer(pos_inp),
-                trainable=False))
-
-        # use in dygraph_mode to fit different length batch
-        # self._pos_emb._w = to_variable(
-        #     position_encoding_init(self._src_max_len, self._src_emb_dim))
-
-    def forward(self, src_word, src_pos):
-        """
-        forward
-        :param src_word:
-        :param src_pos:
-        :return:
-        """
-        # print("here")
-        # print(self._input_emb._w._numpy().shape)
-        src_word_emb = self._input_emb(src_word)
-
-        src_word_emb = fluid.layers.scale(
-            x=src_word_emb, scale=self._src_emb_dim**0.5)
-        # # TODO change this to fit dynamic length input
-        src_pos_emb = self._pos_emb(src_pos)
-        src_pos_emb.stop_gradient = True
-        enc_input = src_word_emb + src_pos_emb
-        return fluid.layers.dropout(
-            enc_input,
-            dropout_prob=self._dropout_rate,
-            seed=ModelHyperParams.dropout_seed,
-            is_test=False) if self._dropout_rate else enc_input
-
-
-class WrapEncoderLayer(Layer):
-    """
-    encoderlayer
-    """
-
-    def __init__(self, name_cope, src_vocab_size, max_length, n_layer, n_head,
-                 d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
-                 attention_dropout, relu_dropout, preprocess_cmd,
-                 postprocess_cmd, weight_sharing):
-        """
-        The wrapper assembles together all needed layers for the encoder.
-        """
-        super(WrapEncoderLayer, self).__init__(name_cope)
-
-        self._prepare_encoder_layer = PrepareEncoderDecoderLayer(
-            self.full_name(),
-            src_vocab_size,
-            d_model,
-            max_length,
-            prepostprocess_dropout,
-            word_emb_param_name=word_emb_param_names[0],
-            pos_enc_param_name=pos_enc_param_names[0])
-        self._encoder = EncoderLayer(
-            self.full_name(), n_layer, n_head, d_key, d_value, d_model,
-            d_inner_hid, prepostprocess_dropout, attention_dropout,
-            relu_dropout, preprocess_cmd, postprocess_cmd)
-
-    def forward(self, enc_inputs):
-        """forward"""
-        src_word, src_pos, src_slf_attn_bias = enc_inputs
-        enc_input = self._prepare_encoder_layer(src_word, src_pos)
-        enc_output = self._encoder(enc_input, src_slf_attn_bias)
-        return enc_output
-
-
-class DecoderSubLayer(Layer):
-    """
-    decoder
-    """
-
-    def __init__(self,
-                 name_scope,
-                 n_head,
-                 d_key,
-                 d_value,
-                 d_model,
-                 d_inner_hid,
-                 prepostprocess_dropout,
-                 attention_dropout,
-                 relu_dropout,
-                 preprocess_cmd,
-                 postprocess_cmd,
-                 cache=None,
-                 gather_idx=None):
-        super(DecoderSubLayer, self).__init__(name_scope)
-        self._postprocess_cmd = postprocess_cmd
-        self._preprocess_cmd = preprocess_cmd
-        self._prepostprcess_dropout = prepostprocess_dropout
-        self._pre_process_layer = PrePostProcessLayer(self.full_name(),
-                                                      preprocess_cmd, 3)
-        self._multihead_attention_layer = MultiHeadAttentionLayer(
-            self.full_name(),
-            d_key,
-            d_value,
-            d_model,
-            n_head,
-            attention_dropout,
-            cache=cache,
-            gather_idx=gather_idx)
-        self._post_process_layer = PrePostProcessLayer(self.full_name(),
-                                                       postprocess_cmd, None)
-        self._pre_process_layer2 = PrePostProcessLayer(self.full_name(),
-                                                       preprocess_cmd, 3)
-        self._multihead_attention_layer2 = MultiHeadAttentionLayer(
-            self.full_name(),
-            d_key,
-            d_value,
-            d_model,
-            n_head,
-            attention_dropout,
-            cache=cache,
-            gather_idx=gather_idx,
-            static_kv=True)
-        self._post_process_layer2 = PrePostProcessLayer(self.full_name(),
-                                                        postprocess_cmd, None)
-        self._pre_process_layer3 = PrePostProcessLayer(self.full_name(),
-                                                       preprocess_cmd, 3)
-        self._positionwise_feed_forward_layer = PositionwiseFeedForwardLayer(
-            self.full_name(), d_inner_hid, d_model, relu_dropout)
-        self._post_process_layer3 = PrePostProcessLayer(self.full_name(),
-                                                        postprocess_cmd, None)
-
-    def forward(self, dec_input, enc_output, slf_attn_bias, dec_enc_attn_bias):
-        """
-        forward
-        :param dec_input:
-        :param enc_output:
-        :param slf_attn_bias:
-        :param dec_enc_attn_bias:
-        :return:
-        """
-        pre_process_rlt = self._pre_process_layer(
-            None, dec_input, self._preprocess_cmd, self._prepostprcess_dropout)
-        slf_attn_output = self._multihead_attention_layer(pre_process_rlt, None,
-                                                          None, slf_attn_bias)
-        slf_attn_output_pp = self._post_process_layer(
-            dec_input, slf_attn_output, self._postprocess_cmd,
-            self._prepostprcess_dropout)
-        pre_process_rlt2 = self._pre_process_layer2(None, slf_attn_output_pp,
-                                                    self._preprocess_cmd,
-                                                    self._prepostprcess_dropout)
-        enc_attn_output_pp = self._multihead_attention_layer2(
-            pre_process_rlt2, enc_output, enc_output, dec_enc_attn_bias)
-        enc_attn_output = self._post_process_layer2(
-            slf_attn_output_pp, enc_attn_output_pp, self._postprocess_cmd,
-            self._prepostprcess_dropout)
-        pre_process_rlt3 = self._pre_process_layer3(None, enc_attn_output,
-                                                    self._preprocess_cmd,
-                                                    self._prepostprcess_dropout)
-        ffd_output = self._positionwise_feed_forward_layer(pre_process_rlt3)
-        dec_output = self._post_process_layer3(enc_attn_output, ffd_output,
-                                               self._postprocess_cmd,
-                                               self._prepostprcess_dropout)
-        return dec_output
-
-
-class DecoderLayer(Layer):
-    """
-    decoder
-    """
-
-    def __init__(self,
-                 name_scope,
-                 n_layer,
-                 n_head,
-                 d_key,
-                 d_value,
-                 d_model,
-                 d_inner_hid,
-                 prepostprocess_dropout,
-                 attention_dropout,
-                 relu_dropout,
-                 preprocess_cmd,
-                 postprocess_cmd,
-                 caches=None,
-                 gather_idx=None):
-        super(DecoderLayer, self).__init__(name_scope)
-        self._pre_process_layer = PrePostProcessLayer(self.full_name(),
-                                                      preprocess_cmd, 3)
-        self._decoder_sub_layers = list()
-        self._n_layer = n_layer
-        self._preprocess_cmd = preprocess_cmd
-        self._prepostprocess_dropout = prepostprocess_dropout
-        for i in range(n_layer):
-            self._decoder_sub_layers.append(
-                self.add_sublayer(
-                    'dsl_%d' % i,
-                    DecoderSubLayer(
-                        self.full_name(),
-                        n_head,
-                        d_key,
-                        d_value,
-                        d_model,
-                        d_inner_hid,
-                        prepostprocess_dropout,
-                        attention_dropout,
-                        relu_dropout,
-                        preprocess_cmd,
-                        postprocess_cmd,
-                        cache=None if caches is None else caches[i],
-                        gather_idx=gather_idx)))
-
-    def forward(self, dec_input, enc_output, dec_slf_attn_bias,
-                dec_enc_attn_bias):
-        """
-        forward
-        :param dec_input:
-        :param enc_output:
-        :param dec_slf_attn_bias:
-        :param dec_enc_attn_bias:
-        :return:
-        """
-        for i in range(self._n_layer):
-            tmp_dec_output = self._decoder_sub_layers[i](
-                dec_input, enc_output, dec_slf_attn_bias, dec_enc_attn_bias)
-            dec_input = tmp_dec_output
-
-        dec_output = self._pre_process_layer(None, tmp_dec_output,
-                                             self._preprocess_cmd,
-                                             self._prepostprocess_dropout)
-        return dec_output
-
-
-class WrapDecoderLayer(Layer):
-    """
-    decoder
-    """
-
-    def __init__(self,
-                 name_scope,
-                 trg_vocab_size,
-                 max_length,
-                 n_layer,
-                 n_head,
-                 d_key,
-                 d_value,
-                 d_model,
-                 d_inner_hid,
-                 prepostprocess_dropout,
-                 attention_dropout,
-                 relu_dropout,
-                 preprocess_cmd,
-                 postprocess_cmd,
-                 weight_sharing,
-                 caches=None,
-                 gather_idx=None):
-        """
-        The wrapper assembles together all needed layers for the encoder.
-        """
-        super(WrapDecoderLayer, self).__init__(name_scope)
-
-        self._prepare_decoder_layer = PrepareEncoderDecoderLayer(
-            self.full_name(),
-            trg_vocab_size,
-            d_model,
-            max_length,
-            prepostprocess_dropout,
-            word_emb_param_name=word_emb_param_names[1],
-            pos_enc_param_name=pos_enc_param_names[1])
-        self._decoder_layer = DecoderLayer(
-            self.full_name(),
-            n_layer,
-            n_head,
-            d_key,
-            d_value,
-            d_model,
-            d_inner_hid,
-            prepostprocess_dropout,
-            attention_dropout,
-            relu_dropout,
-            preprocess_cmd,
-            postprocess_cmd,
-            caches=caches,
-            gather_idx=gather_idx)
-        self._weight_sharing = weight_sharing
-        if not weight_sharing:
-            self._fc = FC(self.full_name(),
-                          size=trg_vocab_size,
-                          bias_attr=False)
-
-    def forward(self, dec_inputs=None, enc_output=None):
-        """
-        forward
-        :param dec_inputs:
-        :param enc_output:
-        :return:
-        """
-        trg_word, trg_pos, trg_slf_attn_bias, trg_src_attn_bias = dec_inputs
-        dec_input = self._prepare_decoder_layer(trg_word, trg_pos)
-        dec_output = self._decoder_layer(dec_input, enc_output,
-                                         trg_slf_attn_bias, trg_src_attn_bias)
-
-        dec_output_reshape = fluid.layers.reshape(
-            dec_output, shape=[-1, dec_output.shape[-1]], inplace=False)
-
-        if self._weight_sharing:
-            predict = fluid.layers.matmul(
-                x=dec_output_reshape,
-                y=self._prepare_decoder_layer._input_emb._w,
-                transpose_y=True)
-        else:
-            predict = self._fc(dec_output_reshape)
-
-        if dec_inputs is None:
-            # Return probs for independent decoder program.
-            predict_out = fluid.layers.softmax(predict)
-            return predict_out
-        return predict
-
-
-class TransFormer(Layer):
-    """
-    model
-    """
-
-    def __init__(self, name_scope, src_vocab_size, trg_vocab_size, max_length,
-                 n_layer, n_head, d_key, d_value, d_model, d_inner_hid,
-                 prepostprocess_dropout, attention_dropout, relu_dropout,
-                 preprocess_cmd, postprocess_cmd, weight_sharing,
-                 label_smooth_eps):
-        super(TransFormer, self).__init__(name_scope)
-        self._label_smooth_eps = label_smooth_eps
-        self._trg_vocab_size = trg_vocab_size
-        if weight_sharing:
-            assert src_vocab_size == trg_vocab_size, (
-                "Vocabularies in source and target should be same for weight sharing."
-            )
-        self._wrap_encoder_layer = WrapEncoderLayer(
-            self.full_name(), src_vocab_size, max_length, n_layer, n_head,
-            d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
-            attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd,
-            weight_sharing)
-        self._wrap_decoder_layer = WrapDecoderLayer(
-            self.full_name(), trg_vocab_size, max_length, n_layer, n_head,
-            d_key, d_value, d_model, d_inner_hid, prepostprocess_dropout,
-            attention_dropout, relu_dropout, preprocess_cmd, postprocess_cmd,
-            weight_sharing)
-
-        if weight_sharing:
-            self._wrap_decoder_layer._prepare_decoder_layer._input_emb._w = self._wrap_encoder_layer._prepare_encoder_layer._input_emb._w
-
-    def forward(self, enc_inputs, dec_inputs, label, weights):
-        """
-        forward
-        :param enc_inputs:
-        :param dec_inputs:
-        :param label:
-        :param weights:
-        :return:
-        """
-        enc_output = self._wrap_encoder_layer(enc_inputs)
-        predict = self._wrap_decoder_layer(dec_inputs, enc_output)
-        if self._label_smooth_eps:
-            label_out = fluid.layers.label_smooth(
-                label=fluid.layers.one_hot(
-                    input=label, depth=self._trg_vocab_size),
-                epsilon=self._label_smooth_eps)
-
-        cost = fluid.layers.softmax_with_cross_entropy(
-            logits=predict,
-            label=label_out,
-            soft_label=True if self._label_smooth_eps else False)
-        weighted_cost = cost * weights
-        sum_cost = fluid.layers.reduce_sum(weighted_cost)
-        token_num = fluid.layers.reduce_sum(weights)
-        token_num.stop_gradient = True
-        avg_cost = sum_cost / token_num
-        return sum_cost, avg_cost, predict, token_num
-
-
-def train():
+def train(args):
     """
     train models
     :return:
@@ -1117,6 +108,7 @@ def train():
         if args.use_data_parallel:
             strategy = fluid.dygraph.parallel.prepare_context()
 
+        # define model
         transformer = TransFormer(
             'transformer', ModelHyperParams.src_vocab_size,
             ModelHyperParams.trg_vocab_size, ModelHyperParams.max_length + 1,
@@ -1127,28 +119,39 @@ def train():
             ModelHyperParams.attention_dropout, ModelHyperParams.relu_dropout,
             ModelHyperParams.preprocess_cmd, ModelHyperParams.postprocess_cmd,
             ModelHyperParams.weight_sharing, TrainTaskConfig.label_smooth_eps)
-
-        optimizer = fluid.optimizer.SGD(learning_rate=0.003)
-
+        # define optimizer
+        optimizer = fluid.optimizer.Adam(learning_rate=NoamDecay(
+            ModelHyperParams.d_model, TrainTaskConfig.warmup_steps,
+            TrainTaskConfig.learning_rate),
+                                         beta1=TrainTaskConfig.beta1,
+                                         beta2=TrainTaskConfig.beta2,
+                                         epsilon=TrainTaskConfig.eps)
+        #
         if args.use_data_parallel:
-            transformer = fluid.dygraph.parallel.DataParallel(transformer,
-                                                              strategy)
+            transformer = fluid.dygraph.parallel.DataParallel(
+                transformer, strategy)
 
-        reader = paddle.batch(
-            wmt16.train(ModelHyperParams.src_vocab_size,
-                        ModelHyperParams.trg_vocab_size),
+        # define data generator for training and validation
+        train_reader = paddle.batch(wmt16.train(
+            ModelHyperParams.src_vocab_size, ModelHyperParams.trg_vocab_size),
                                     batch_size=TrainTaskConfig.batch_size)
         if args.use_data_parallel:
-            reader = fluid.contrib.reader.distributed_batch_reader(reader)
+            train_reader = fluid.contrib.reader.distributed_batch_reader(
+                train_reader)
+        val_reader = paddle.batch(wmt16.test(ModelHyperParams.src_vocab_size,
+                                             ModelHyperParams.trg_vocab_size),
+                                  batch_size=TrainTaskConfig.batch_size)
 
-        for i in range(200):
+        # loop for training iterations
+        for i in range(TrainTaskConfig.pass_num):
             dy_step = 0
-            for batch in reader():
-                np_values = prepare_batch_input(
-                    batch, ModelHyperParams.src_pad_idx,
-                    ModelHyperParams.trg_pad_idx, ModelHyperParams.n_head)
+            sum_cost = 0
+            transformer.train()
+            for batch in train_reader():
+                enc_inputs, dec_inputs, label, weights = prepare_train_input(
+                    batch, ModelHyperParams.eos_idx, ModelHyperParams.eos_idx,
+                    ModelHyperParams.n_head)
 
-                enc_inputs, dec_inputs, label, weights = create_data(np_values)
                 dy_sum_cost, dy_avg_cost, dy_predict, dy_token_num = transformer(
                     enc_inputs, dec_inputs, label, weights)
 
@@ -1158,15 +161,35 @@ def train():
                     transformer.apply_collective_grads()
                 else:
                     dy_avg_cost.backward()
-
                 optimizer.minimize(dy_avg_cost)
                 transformer.clear_gradients()
+
                 dy_step = dy_step + 1
                 if dy_step % 10 == 0:
                     print("pass num : {}, batch_id: {}, dy_graph avg loss: {}".
-                          format(i, dy_step, dy_avg_cost.numpy()))
-            print("pass : {} finished".format(i))
+                          format(i, dy_step,
+                                 dy_avg_cost.numpy() * trainer_count))
+
+            # switch to evaluation mode
+            transformer.eval()
+            sum_cost = 0
+            token_num = 0
+            for batch in val_reader():
+                enc_inputs, dec_inputs, label, weights = prepare_train_input(
+                    batch, ModelHyperParams.eos_idx, ModelHyperParams.eos_idx,
+                    ModelHyperParams.n_head)
+
+                dy_sum_cost, dy_avg_cost, dy_predict, dy_token_num = transformer(
+                    enc_inputs, dec_inputs, label, weights)
+                sum_cost += dy_sum_cost.numpy()
+                token_num += dy_token_num.numpy()
+            print("pass : {} finished, validation avg loss: {}".format(
+                i, sum_cost / token_num))
+
+        if fluid.dygraph.parallel.Env().dev_id == 0:
+            fluid.save_dygraph(transformer.state_dict(), args.model_file)
 
 
 if __name__ == '__main__':
-    train()
+    args = parse_args()
+    train(args)