seqToseq_net.py

# edit-mode: -*- python -*-

# Copyright (c) 2016 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.

import os
from paddle.trainer_config_helpers import *

### Data Definiation
data_dir = "./data/pre-wmt14"
src_lang_dict = os.path.join(data_dir, 'src.dict')
trg_lang_dict = os.path.join(data_dir, 'trg.dict')
is_generating = get_config_arg("is_generating", bool, False)

if not is_generating:
    train_list = os.path.join(data_dir, 'train.list')
    test_list = os.path.join(data_dir, 'test.list')
else:
    train_list = None
    test_list = os.path.join(data_dir, 'gen.list')

define_py_data_sources2(
    train_list,
    test_list,
    module="dataprovider",
    obj="process",
    args={
        "src_dict_path": src_lang_dict,
        "trg_dict_path": trg_lang_dict,
        "is_generating": is_generating
    })

### Algorithm Configuration
settings(learning_method=AdamOptimizer(), batch_size=50, learning_rate=5e-4)

### Network Architecture
source_dict_dim = len(open(src_lang_dict, "r").readlines())
target_dict_dim = len(open(trg_lang_dict, "r").readlines())
word_vector_dim = 512  # dimension of word vector
decoder_size = 512  # dimension of hidden unit in GRU Decoder network
encoder_size = 512  # dimension of hidden unit in GRU Encoder network

if is_generating:
    beam_size = 3  # expand width in beam search
    max_length = 250  # a stop condition of sequence generation
    gen_trans_file = get_config_arg("gen_trans_file", str, None)

#### Encoder
src_word_id = data_layer(name='source_language_word', size=source_dict_dim)
src_embedding = embedding_layer(
    input=src_word_id,
    size=word_vector_dim,
    param_attr=ParamAttr(name='_source_language_embedding'))
src_forward = simple_gru(input=src_embedding, size=encoder_size)
src_backward = simple_gru(input=src_embedding, size=encoder_size, reverse=True)
encoded_vector = concat_layer(input=[src_forward, src_backward])

#### Decoder
with mixed_layer(size=decoder_size) as encoded_proj:
    encoded_proj += full_matrix_projection(input=encoded_vector)

backward_first = first_seq(input=src_backward)
with mixed_layer(
        size=decoder_size,
        act=TanhActivation(), ) as decoder_boot:
    decoder_boot += full_matrix_projection(input=backward_first)


def gru_decoder_with_attention(enc_vec, enc_proj, current_word):
    decoder_mem = memory(
        name='gru_decoder', size=decoder_size, boot_layer=decoder_boot)

    context = simple_attention(
        encoded_sequence=enc_vec,
        encoded_proj=enc_proj,
        decoder_state=decoder_mem, )

    with mixed_layer(size=decoder_size * 3) as decoder_inputs:
        decoder_inputs += full_matrix_projection(input=context)
        decoder_inputs += full_matrix_projection(input=current_word)

    gru_step = gru_step_layer(
        name='gru_decoder',
        input=decoder_inputs,
        output_mem=decoder_mem,
        size=decoder_size)

    with mixed_layer(
            size=target_dict_dim, bias_attr=True,
            act=SoftmaxActivation()) as out:
        out += full_matrix_projection(input=gru_step)
    return out


decoder_group_name = "decoder_group"
group_input1 = StaticInput(input=encoded_vector, is_seq=True)
group_input2 = StaticInput(input=encoded_proj, is_seq=True)
group_inputs = [group_input1, group_input2]

if not is_generating:
    trg_embedding = embedding_layer(
        input=data_layer(
            name='target_language_word', size=target_dict_dim),
        size=word_vector_dim,
        param_attr=ParamAttr(name='_target_language_embedding'))
    group_inputs.append(trg_embedding)

    # For decoder equipped with attention mechanism, in training,
    # target embeding (the groudtruth) is the data input,
    # while encoded source sequence is accessed to as an unbounded memory.
    # Here, the StaticInput defines a read-only memory
    # for the recurrent_group.
    decoder = recurrent_group(
        name=decoder_group_name,
        step=gru_decoder_with_attention,
        input=group_inputs)

    lbl = data_layer(name='target_language_next_word', size=target_dict_dim)
    cost = classification_cost(input=decoder, label=lbl)
    outputs(cost)
else:
    # In generation, the decoder predicts a next target word based on
    # the encoded source sequence and the last generated target word.

    # The encoded source sequence (encoder's output) must be specified by
    # StaticInput, which is a read-only memory.
    # Embedding of the last generated word is automatically gotten by
    # GeneratedInputs, which is initialized by a start mark, such as <s>,
    # and must be included in generation.

    trg_embedding = GeneratedInput(
        size=target_dict_dim,
        embedding_name='_target_language_embedding',
        embedding_size=word_vector_dim)
    group_inputs.append(trg_embedding)

    beam_gen = beam_search(
        name=decoder_group_name,
        step=gru_decoder_with_attention,
        input=group_inputs,
        bos_id=0,
        eos_id=1,
        beam_size=beam_size,
        max_length=max_length)

    seqtext_printer_evaluator(
        input=beam_gen,
        id_input=data_layer(
            name="sent_id", size=1),
        dict_file=trg_lang_dict,
        result_file=gen_trans_file)
    outputs(beam_gen)