模型训练或推理所需环境，请参考requirements.txt文件。

数据预处理需要运行data_helper.py文件，会在data文件夹中生成训练集和测试集文件。

命令如下：

python3 data_helper.py

注意：如果需要修改数据生成路径或名称，请修改data_helper.py文件147-150行，自行定义。

模型训练需要运行train.py文件，会自动生成output_dir文件夹，存放每个epoch保存的模型文件。

命令如下：

python3 train.py --device 0 \
                 --data_dir "data/" \
                 --src_file "train.json" \
                 --model_name_or_path "pretrain_model/" \
                 --max_seq_length 256 \
                 --train_batch_size 16 \
                 --num_train_epochs 10  

注意：当服务器资源不同或读者更换数据等时，可以在模型训练时修改响应参数，详细参数说明见代码或阅读书3.5.4小节。

模型训练示例如下：

模型训练阶段损失值变化如下：

模型训练需要运行chatbot.py文件，可以采用项目中以提供的模型，也可以采用自己训练后的模型。

命令如下：

python3 chatbot.py --device 0 --topk 3 --topp 0.95 --max_len 32

注意：如果修改模型路径，请修改–model_path参数。

模型推理示例如下：

USER:工作不开心
CHAT-BOT:我也是，不过现在开始努力找工作啦！一起加油鸭～
USER:工作不开心
CHAT-BOT:那就祝福你，能找到喜欢的工作吧。
USER:工作不开心
CHAT-BOT:你也要加油鸭！
USER:工作不开心
CHAT-BOT:我也是，不过总有一天就会好起来的
样例2
USER:我分手了
CHAT-BOT:分手快乐，你会遇到更好的。
USER:我分手了
CHAT-BOT:旧的不去新的不来，你会遇见更好的
USER:我分手了
CHAT-BOT:分的好，下一个更乖
样例3
USER:好想去吃火锅，但是我在减肥
CHAT-BOT:你好棒！一定会瘦下来的！
USER:好像去吃火锅，但是我在减肥
CHAT-BOT:吃火锅是为了能更好的减肥，你真棒！


我自己没有gpu，训练了一天，运行的流程如下：
D:\book\ChatGPTBook``-``main\UniLMProj 的目录``2023``-``09``-``25` `17``:``54`  `<``DIR``>     .``2023``-``09``-``25` `17``:``22`  `<``DIR``>     ..``2023``-``09``-``25` `17``:``22`       `5``,``530` `chatbot.py``2023``-``09``-``25` `17``:``22`       `2``,``153` `configuration_unilm.py``2023``-``09``-``25` `21``:``04`  `<``DIR``>     data``2023``-``09``-``25` `17``:``22`       `4``,``375` `data_helper.py``2023``-``09``-``25` `17``:``22`       `9``,``173` `data_set.py``2023``-``09``-``25` `17``:``22`       `1``,``304` `dirty_recognize.py``2023``-``09``-``25` `17``:``22`  `<``DIR``>     images``2023``-``09``-``25` `17``:``22`  `<``DIR``>     kuakua_robot_model``2023``-``09``-``25` `17``:``22`      `13``,``452` `modeling_unilm.py``2023``-``09``-``25` `17``:``22`  `<``DIR``>     pretrain_model``2023``-``09``-``25` `17``:``22`       `4``,``199` `README.md``2023``-``09``-``25` `17``:``22`        `88` `requirements.txt``2023``-``09``-``25` `17``:``22`       `8``,``337` `train.py``2023``-``09``-``25` `17``:``22`       `1``,``861` `trie.py``2023``-``09``-``25` `17``:``54`  `<``DIR``>     __pycache__``       ``10` `个文件     ``50``,``472` `字节``        ``7` `个目录 ``175``,``152``,``689``,``152` `可用字节` `D:\book\ChatGPTBook``-``main\UniLMProj>python data_helper.py``total number of data: ``121687` `D:\book\ChatGPTBook``-``main\UniLMProj>``dir` `data`` ``驱动器 D 中的卷是 Data`` ``卷的序列号是 CA99``-``555E` ` ``D:\book\ChatGPTBook``-``main\UniLMProj\data 的目录` `2023``-``09``-``25` `21``:``06`  `<``DIR``>     .``2023``-``09``-``25` `17``:``54`  `<``DIR``>     ..``2023``-``09``-``25` `17``:``22`      `245``,``546` `dirty_words.txt``2023``-``09``-``25` `17``:``56`    `21``,``620``,``763` `douban_kuakua_qa.txt``2023``-``09``-``25` `17``:``22`        `446` `sample.json``2023``-``09``-``25` `21``:``06`    `14``,``272``,``447` `train.json``        ``4` `个文件   ``36``,``139``,``202` `字节``        ``2` `个目录 ``175``,``138``,``414``,``592` `可用字节` `D:\book\ChatGPTBook``-``main\UniLMProj>python train.py``Traceback (most recent call last):`` ``File` `"D:\book\ChatGPTBook-main\UniLMProj\train.py"``, line ``18``, ``in` `<module>``  ``import` `torch``ModuleNotFoundError: No module named ``'torch'` `D:\book\ChatGPTBook``-``main\UniLMProj>pip install torch`` ` `D:\book\ChatGPTBook``-``main\UniLMProj>pip install torch`` ` `D:\book\ChatGPTBook``-``main\UniLMProj>``D:\book\ChatGPTBook``-``main\UniLMProj>python train.py``Traceback (most recent call last):`` ``File` `"D:\book\ChatGPTBook-main\UniLMProj\train.py"``, line ``20``, ``in` `<module>``  ``from` `transformers ``import` `BertTokenizer``ModuleNotFoundError: No module named ``'transformers'` `D:\book\ChatGPTBook``-``main\UniLMProj>pip install transformers`` ` `D:\book\ChatGPTBook``-``main\UniLMProj>python train.py``Traceback (most recent call last):`` ``File` `"D:\book\ChatGPTBook-main\UniLMProj\train.py"``, line ``170``, ``in` `<module>``  ``main()`` ``File` `"D:\book\ChatGPTBook-main\UniLMProj\train.py"``, line ``86``, ``in` `main``  ``model ``=` `UnilmForSeq2Seq.from_pretrained(args.model_name_or_path, config``=``config)``      ``^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^`` ``File` `"C:\Python311\Lib\site-packages\transformers\modeling_utils.py"``, line ``2740``, ``in` `from_pretrained``  ``raise` `EnvironmentError(``OSError: Error no ``file` `named pytorch_model.``bin``, tf_model.h5, model.ckpt.index ``or` `flax_model.msgpack found ``in` `directory pretrain_model``/``.` `D:\book\ChatGPTBook``-``main\UniLMProj>python train.py``Loading Train Dataset data``/``convert seq2seq example: ``108730it` `[``00``:``29``, ``3741.34it``/``s]``Load ``108730` `data``C:\Python311\Lib\site``-``packages\transformers\optimization.py:``411``: FutureWarning: This implementation of AdamW ``is` `deprecated ``and` `will be removed ``in` `a future version. Use the PyTorch implementation torch.optim.AdamW instead, ``or` `set` ``no_deprecation_warning``=``True```to disable this warning`` ``warnings.warn(``09``/``25``/``2023` `21``:``45``:``57` `-` `INFO ``-` `__main__ ``-`  `*``*``*``*``*` `CUDA.empty_cache() ``*``*``*``*``*``09``/``25``/``2023` `21``:``45``:``57` `-` `INFO ``-` `__main__ ``-`  `*``*``*``*``*` `Running training ``*``*``*``*``*``09``/``25``/``2023` `21``:``45``:``57` `-` `INFO ``-` `__main__ ``-`   `Batch size ``=` `16``09``/``25``/``2023` `21``:``45``:``57` `-` `INFO ``-` `__main__ ``-`   `Num steps ``=` `67960``Epoch:  ``0``%``|                                          | ``0``/``10` `[``00``:``00``<?, ?it``/``s]C:\Python311\Lib\site``-``packages\torch\optim\lr_scheduler.py:``265``: UserWarning: To get the last learning rate computed by the scheduler, please use `get_last_lr()`.`` ``warnings.warn(``"To get the last learning rate computed by the scheduler, "``Iter` `(loss``=``3.279``): ``100``%``|████████████████████████████████████████████████████████| ``6796``/``6796` `[``25``:``32``:``28``<``00``:``00``, ``13.53s``/``it]``09``/``26``/``2023` `23``:``18``:``26` `-` `INFO ``-` `__main__ ``-`  `*``*` `*``*` `*` `Saving fine``-``tuned model ``and` `optimizer ``*``*` `*``*` `*` `32``:``28``<``00``:``00``, ``9.24s``/``it]``Epoch: ``10``%``|██████▌                              | ``1``/``10` `[``25``:``32``:``29``<``229``:``52``:``22``, ``91949.11s``/``it]``Iter` `(loss``=``3.525``): ``31``%``|████████████████▎                  | ``2096``/``6796` `[``10``:``55``:``33``<``16``:``16``:``17``, ``12.46s``/``it]

训练了一天，最后的聊天效果：

D:\book\ChatGPTBook``-``main\UniLMProj>python chatbot.py ``-``-``topk ``3` `-``-``topp ``0.95` `-``-``max_len ``32` `-``-``model_name_or_path output_dir\checkpoint``-``6796``\``cpu``Chitchat Robot Starting``user:你好啊``chat``-``bot:这么可爱的人真的很有缘分呢，你是最棒了！``user:终于训练好了一个大模型机器人了``chat``-``bot:好厉害！我也想学，但是还是没有做到``user:哈哈哈``chat``-``bot:你真的很可爱！我也是，但不想被表扬。``user:大模型是什么呢？``chat``-``bot:我们一起努力吧！``user:你是谁？``chat``-``bot:我是你！``user:你逗我呢``chat``-``bot:你也是个可爱的小可爱，我们一起夸

我们来分析下模型源码：

import` `copy``import` `math``import` `logging``import` `torch``from` `torch ``import` `nn``import` `torch.nn.functional as F``from` `torch.nn.modules.loss ``import` `_Loss``from` `transformers.modeling_utils ``import` `PreTrainedModel``from` `configuration_unilm ``import` `UnilmConfig``from` `transformers.models.bert.modeling_bert ``import` `load_tf_weights_in_bert, BertPooler, BertIntermediate, BertOutput, \``  ``BertSelfOutput, BertOnlyMLMHead, BertEmbeddings` `logger ``=` `logging.getLogger(__name__)` `BertLayerNorm ``=` `torch.nn.LayerNorm` `class` `BertSelfAttention(nn.Module):``  ``def` `__init__(``self``, config):``    ``super``(BertSelfAttention, ``self``).__init__()``    ``if` `config.hidden_size ``%` `config.num_attention_heads !``=` `0``:``      ``raise` `ValueError(``        ``"The hidden size (%d) is not a multiple of the number of attention "``        ``"heads (%d)"` `%` `(config.hidden_size, config.num_attention_heads))``    ``self``.num_attention_heads ``=` `config.num_attention_heads``    ``self``.attention_head_size ``=` `int``(``      ``config.hidden_size ``/` `config.num_attention_heads)``    ``self``.all_head_size ``=` `self``.num_attention_heads ``*` `self``.attention_head_size` `    ``self``.query ``=` `nn.Linear(config.hidden_size, ``self``.all_head_size)``    ``self``.key ``=` `nn.Linear(config.hidden_size, ``self``.all_head_size)``    ``self``.value ``=` `nn.Linear(config.hidden_size, ``self``.all_head_size)` `    ``self``.dropout ``=` `nn.Dropout(config.attention_probs_dropout_prob)` `  ``def` `transpose_for_scores(``self``, x):``    ``sz ``=` `x.size()[:``-``1``] ``+` `(``self``.num_attention_heads,``               ``self``.attention_head_size)``    ``x ``=` `x.view(``*``sz)``    ``return` `x.permute(``0``, ``2``, ``1``, ``3``)` `  ``def` `forward(``self``, hidden_states, attention_mask, history_states``=``None``):``    ``if` `history_states ``is` `None``:``      ``mixed_query_layer ``=` `self``.query(hidden_states)``      ``mixed_key_layer ``=` `self``.key(hidden_states)``      ``mixed_value_layer ``=` `self``.value(hidden_states)``    ``else``:``      ``x_states ``=` `torch.cat((history_states, hidden_states), dim``=``1``)``      ``mixed_query_layer ``=` `self``.query(hidden_states)``      ``mixed_key_layer ``=` `self``.key(x_states)``      ``mixed_value_layer ``=` `self``.value(x_states)` `    ``query_layer ``=` `self``.transpose_for_scores(mixed_query_layer)``    ``key_layer ``=` `self``.transpose_for_scores(mixed_key_layer)``    ``value_layer ``=` `self``.transpose_for_scores(mixed_value_layer)` `    ``attention_scores ``=` `torch.matmul(``      ``query_layer ``/` `math.sqrt(``self``.attention_head_size), key_layer.transpose(``-``1``, ``-``2``))``    ``attention_scores ``=` `attention_scores ``+` `attention_mask` `    ``attention_probs ``=` `nn.Softmax(dim``=``-``1``)(attention_scores)` `    ``attention_probs ``=` `self``.dropout(attention_probs)` `    ``context_layer ``=` `torch.matmul(attention_probs, value_layer)``    ``context_layer ``=` `context_layer.permute(``0``, ``2``, ``1``, ``3``).contiguous()``    ``new_context_layer_shape ``=` `context_layer.size()[``                 ``:``-``2``] ``+` `(``self``.all_head_size,)``    ``context_layer ``=` `context_layer.view(``*``new_context_layer_shape)``    ``return` `context_layer` `class` `BertAttention(nn.Module):``  ``def` `__init__(``self``, config):``    ``super``(BertAttention, ``self``).__init__()``    ``self``.``self` `=` `BertSelfAttention(config)``    ``self``.output ``=` `BertSelfOutput(config)` `  ``def` `forward(``self``, input_tensor, attention_mask, history_states``=``None``):``    ``self_output ``=` `self``.``self``(``      ``input_tensor, attention_mask, history_states``=``history_states)``    ``attention_output ``=` `self``.output(self_output, input_tensor)``    ``return` `attention_output` `class` `BertLayer(nn.Module):``  ``def` `__init__(``self``, config):``    ``super``(BertLayer, ``self``).__init__()``    ``self``.attention ``=` `BertAttention(config)``    ``self``.intermediate ``=` `BertIntermediate(config)``    ``self``.output ``=` `BertOutput(config)` `  ``def` `forward(``self``, hidden_states, attention_mask, history_states``=``None``):``    ``attention_output ``=` `self``.attention(``      ``hidden_states, attention_mask, history_states``=``history_states)``    ``intermediate_output ``=` `self``.intermediate(attention_output)``    ``layer_output ``=` `self``.output(intermediate_output, attention_output)``    ``return` `layer_output` `class` `BertEncoder(nn.Module):``  ``def` `__init__(``self``, config):``    ``super``(BertEncoder, ``self``).__init__()``    ``layer ``=` `BertLayer(config)``    ``self``.layer ``=` `nn.ModuleList([copy.deepcopy(layer)``                  ``for` `_ ``in` `range``(config.num_hidden_layers)])` `  ``def` `forward(``self``, hidden_states, attention_mask, output_all_encoded_layers``=``True``, prev_embedding``=``None``,``        ``prev_encoded_layers``=``None``):``    ``assert` `(prev_embedding ``is` `None``) ``=``=` `(prev_encoded_layers ``is` `None``)` `    ``all_encoder_layers ``=` `[]``    ``if` `(prev_embedding ``is` `not` `None``) ``and` `(prev_encoded_layers ``is` `not` `None``):``      ``history_states ``=` `prev_embedding``      ``for` `i, layer_module ``in` `enumerate``(``self``.layer):``        ``hidden_states ``=` `layer_module(``          ``hidden_states, attention_mask, history_states``=``history_states)``        ``if` `output_all_encoded_layers:``          ``all_encoder_layers.append(hidden_states)``        ``if` `prev_encoded_layers ``is` `not` `None``:``          ``history_states ``=` `prev_encoded_layers[i]``    ``else``:``      ``for` `layer_module ``in` `self``.layer:``        ``hidden_states ``=` `layer_module(``          ``hidden_states, attention_mask)``        ``if` `output_all_encoded_layers:``          ``all_encoder_layers.append(hidden_states)``    ``if` `not` `output_all_encoded_layers:``      ``all_encoder_layers.append(hidden_states)``    ``return` `all_encoder_layers` `class` `UnilmPreTrainedModel(PreTrainedModel):``  ``config_class ``=` `UnilmConfig``  ``load_tf_weights ``=` `load_tf_weights_in_bert``  ``base_model_prefix ``=` `"unilm"` `  ``def` `_init_weights(``self``, module):``    ``if` `isinstance``(module, (nn.Linear, nn.Embedding)):``      ``module.weight.data.normal_(mean``=``0.0``, std``=``self``.config.initializer_range)``    ``elif` `isinstance``(module, BertLayerNorm):``      ``module.bias.data.zero_()``      ``module.weight.data.fill_(``1.0``)``    ``if` `isinstance``(module, nn.Linear) ``and` `module.bias ``is` `not` `None``:``      ``module.bias.data.zero_()` `class` `UnilmModel(UnilmPreTrainedModel):``  ``def` `__init__(``self``, config):``    ``super``(UnilmModel, ``self``).__init__(config)``    ``self``.embeddings ``=` `BertEmbeddings(config)``    ``self``.encoder ``=` `BertEncoder(config)``    ``self``.pooler ``=` `BertPooler(config)``    ``self``.init_weights()` `  ``def` `get_extended_attention_mask(``self``, input_ids, token_type_ids, attention_mask):``    ``if` `attention_mask ``is` `None``:``      ``attention_mask ``=` `torch.ones_like(input_ids)``    ``if` `token_type_ids ``is` `None``:``      ``token_type_ids ``=` `torch.zeros_like(input_ids)` `    ``if` `attention_mask.dim() ``=``=` `2``:``      ``extended_attention_mask ``=` `attention_mask.unsqueeze(``1``).unsqueeze(``2``)``    ``elif` `attention_mask.dim() ``=``=` `3``:``      ``extended_attention_mask ``=` `attention_mask.unsqueeze(``1``)``    ``else``:``      ``raise` `NotImplementedError``    ``extended_attention_mask ``=` `extended_attention_mask.to(``      ``dtype``=``next``(``self``.parameters()).dtype) ``# fp16 compatibility``    ``extended_attention_mask ``=` `(``1.0` `-` `extended_attention_mask) ``*` `-``10000.0``    ``return` `extended_attention_mask` `  ``def` `forward(``self``, input_ids, token_type_ids``=``None``, attention_mask``=``None``, output_all_encoded_layers``=``True``):``    ``extended_attention_mask ``=` `self``.get_extended_attention_mask(``      ``input_ids, token_type_ids, attention_mask)` `    ``embedding_output ``=` `self``.embeddings(``      ``input_ids, token_type_ids)``    ``encoded_layers ``=` `self``.encoder(embedding_output, extended_attention_mask,``                   ``output_all_encoded_layers``=``output_all_encoded_layers)``    ``sequence_output ``=` `encoded_layers[``-``1``]``    ``pooled_output ``=` `self``.pooler(sequence_output)``    ``if` `not` `output_all_encoded_layers:``      ``encoded_layers ``=` `encoded_layers[``-``1``]``    ``return` `encoded_layers, pooled_output` `class` `LabelSmoothingLoss(_Loss):``  ``def` `__init__(``self``, label_smoothing``=``0``, tgt_vocab_size``=``0``, ignore_index``=``0``, size_average``=``None``, ``reduce``=``None``,``         ``reduction``=``'mean'``):``    ``assert` `0.0` `< label_smoothing <``=` `1.0``    ``self``.ignore_index ``=` `ignore_index``    ``super``(LabelSmoothingLoss, ``self``).__init__(``      ``size_average``=``size_average, ``reduce``=``reduce``, reduction``=``reduction)` `    ``assert` `label_smoothing > ``0``    ``assert` `tgt_vocab_size > ``0` `    ``smoothing_value ``=` `label_smoothing ``/` `(tgt_vocab_size ``-` `2``)``    ``one_hot ``=` `torch.full((tgt_vocab_size,), smoothing_value)``    ``one_hot[``self``.ignore_index] ``=` `0``    ``self``.register_buffer(``'one_hot'``, one_hot.unsqueeze(``0``))``    ``self``.confidence ``=` `1.0` `-` `label_smoothing``    ``self``.tgt_vocab_size ``=` `tgt_vocab_size` `  ``def` `forward(``self``, output, target):``    ``assert` `self``.tgt_vocab_size ``=``=` `output.size(``2``)``    ``batch_size, num_pos ``=` `target.size(``0``), target.size(``1``)``    ``output ``=` `output.view(``-``1``, ``self``.tgt_vocab_size)``    ``target ``=` `target.view(``-``1``)``    ``model_prob ``=` `self``.one_hot.repeat(target.size(``0``), ``1``)``    ``model_prob.scatter_(``1``, target.unsqueeze(``1``), ``self``.confidence)``    ``model_prob.masked_fill_((target ``=``=` `self``.ignore_index).unsqueeze(``1``), ``0``)` `    ``return` `F.kl_div(output, model_prob.type_as(output), reduction``=``'none'``).view(batch_size, num_pos, ``-``1``).``sum``(``2``)` `class` `UnilmForSeq2Seq(UnilmPreTrainedModel):``  ``"""UniLM模型进行Seq2Seq的训练模型类"""` `  ``def` `__init__(``self``, config):``    ``"""模型初始化函数，定义模型训练所需的各个模块"""``    ``super``(UnilmForSeq2Seq, ``self``).__init__(config)``    ``self``.bert ``=` `UnilmModel(config)``    ``self``.``cls` `=` `BertOnlyMLMHead(config)``    ``self``.mask_lm ``=` `nn.CrossEntropyLoss(reduction``=``'none'``)``    ``if` `hasattr``(config, ``'label_smoothing'``) ``and` `config.label_smoothing:``      ``self``.mask_lm_smoothed ``=` `LabelSmoothingLoss(config.label_smoothing, config.vocab_size, ignore_index``=``0``,``                            ``reduction``=``'none'``)``    ``else``:``      ``self``.mask_lm_smoothed ``=` `None``    ``self``.init_weights()``    ``self``.tie_weights()` `  ``def` `tie_weights(``self``):``    ``"""权重加载，加载预训练模型的embeddings部分权重"""``    ``self``._tie_or_clone_weights(``self``.``cls``.predictions.decoder,``                  ``self``.bert.embeddings.word_embeddings)` `  ``def` `forward(``self``, input_ids, token_type_ids``=``None``, attention_mask``=``None``, masked_lm_labels``=``None``, masked_pos``=``None``,``        ``masked_weights``=``None``):``    ``"""模型forward，向前传递函数"""``    ``# 获取Encoder部分的序列输出，维度[bs,seq_len,hidden_size]``    ``sequence_output, __ ``=` `self``.bert(input_ids, token_type_ids, attention_mask, output_all_encoded_layers``=``False``)` `    ``def` `gather_seq_out_by_pos(seq, pos):``      ``return` `torch.gather(seq, ``1``, pos.unsqueeze(``2``).expand(``-``1``, ``-``1``, seq.size(``-``1``)))` `    ``def` `loss_mask_and_normalize(loss, mask):``      ``mask ``=` `mask.type_as(loss)``      ``loss ``=` `loss ``*` `mask``      ``denominator ``=` `torch.``sum``(mask) ``+` `1e``-``5``      ``return` `(loss ``/` `denominator).``sum``()` `    ``if` `masked_lm_labels ``is` `None``:``      ``if` `masked_pos ``is` `None``:``        ``prediction_scores ``=` `self``.``cls``(sequence_output)``      ``else``:``        ``sequence_output_masked ``=` `gather_seq_out_by_pos(sequence_output, masked_pos)``        ``prediction_scores ``=` `self``.``cls``(sequence_output_masked)``      ``return` `prediction_scores``    ``# 获取被掩码位置的向量``    ``sequence_output_masked ``=` `gather_seq_out_by_pos(sequence_output, masked_pos)``    ``prediction_scores_masked ``=` `self``.``cls``(sequence_output_masked)``    ``if` `self``.mask_lm_smoothed:``      ``masked_lm_loss ``=` `self``.mask_lm_smoothed(F.log_softmax(prediction_scores_masked.``float``(), dim``=``-``1``),``                          ``masked_lm_labels)``    ``else``:``      ``masked_lm_loss ``=` `self``.mask_lm(prediction_scores_masked.transpose(``1``, ``2``).``float``(), masked_lm_labels)``    ``# 计算[Mask]标记的损失值``    ``masked_lm_loss ``=` `loss_mask_and_normalize(masked_lm_loss.``float``(), masked_weights)` `    ``return` `masked_lm_loss` `class` `UnilmForSeq2SeqDecodeSample(UnilmPreTrainedModel):``  ``"""UniLM模型进行Seq2Seq的模型解码类"""``  ``def` `__init__(``self``, config):``    ``"""模型初始化函数，定义模型训练所需的各个模块"""``    ``super``(UnilmForSeq2SeqDecodeSample, ``self``).__init__(config)``    ``self``.bert ``=` `UnilmModel(config)``    ``self``.``cls` `=` `BertOnlyMLMHead(config)``    ``self``.init_weights()``    ``self``.tie_weights()` `  ``def` `tie_weights(``self``):``    ``"""权重加载，加载预训练模型的embeddings部分权重"""``    ``self``._tie_or_clone_weights(``self``.``cls``.predictions.decoder, ``self``.bert.embeddings.word_embeddings)` `  ``def` `forward(``self``, input_ids, token_type_ids, attention_mask):``    ``# 获取Encoder部分的序列输出，维度[bs,seq_len,hidden_size]``    ``sequence_output, __ ``=` `self``.bert(input_ids, token_type_ids, attention_mask, output_all_encoded_layers``=``False``)``    ``# 获取最优一个节点的输出``    ``last_hidden ``=` `sequence_output[:, ``-``1``:, :]``    ``# 将其映射到词表中，为后面解码提供内容``    ``prediction_scores ``=` `self``.``cls``(last_hidden)``    ``return` `prediction_scores

文件定义了一个基于UniLM（Unified Language Model）的Seq2Seq模型，主要用于序列生成任务。UniLM是一种预训练的语言模型，它在单一的语言模型架构下整合了双向和单向的语言模型。

文件中定义了以下几个主要的类：

\1. BertSelfAttention：这是一个自注意力机制的实现，用于计算输入序列中每个元素的注意力分数。

\2. BertAttention、BertLayer、BertEncoder：这些类是BERT模型的主要组成部分，用于处理输入序列并生成隐藏状态。

\3. UnilmPreTrainedModel：这是一个预训练模型的基类，定义了权重初始化和加载预训练权重的方法。

\4. UnilmModel：这是UniLM模型的主要实现，它包含了BERT的嵌入层、编码器和池化层。

\5. LabelSmoothingLoss：这是一个实现了标签平滑的损失函数，用于训练过程中减少模型对于标签的过拟合。

\6. UnilmForSeq2Seq：这是一个用于序列到序列任务的UniLM模型，它在UnilmModel的基础上添加了一个预测头，用于预测下一个词。

\7. UnilmForSeq2SeqDecodeSample：这是一个用于序列到序列任务的解码器，它使用UnilmModel生成的隐藏状态，通过预测头生成下一个词的预测。

总的来说，这个文件定义的模型结构主要用于处理序列到序列的任务，如机器翻译、文本摘要等。模型的最终目标是根据输入的序列生成一个新的序列。

【模型训练】

这个训练代码使用的模型是UnilmForSeq2Seq，这是一个基于UniLM（Unified Language Model）的序列到序列模型。这个模型主要用于处理序列生成任务，如机器翻译、文本摘要等。在代码中，模型的加载过程如下：

config = UnilmConfig.from_pretrained(args.model_name_or_path)

tokenizer = BertTokenizer.from_pretrained(args.model_name_or_path, do_lower_case=args.do_lower_case)

model = UnilmForSeq2Seq.from_pretrained(args.model_name_or_path, config=config)

model.to(device)

这段代码首先从预训练模型的路径加载UniLM的配置和BERT的分词器，然后使用这些配置和分词器从预训练模型的路径加载UnilmForSeq2Seq模型，并将模型移动到指定的设备上（如果有GPU则使用GPU，否则使用CPU）。

class` `UnilmForSeq2Seq(UnilmPreTrainedModel):``  ``"""UniLM模型进行Seq2Seq的训练模型类"""` `  ``def` `__init__(``self``, config):``    ``"""模型初始化函数，定义模型训练所需的各个模块"""``    ``super``(UnilmForSeq2Seq, ``self``).__init__(config)``    ``self``.bert ``=` `UnilmModel(config)``    ``self``.``cls` `=` `BertOnlyMLMHead(config)``    ``self``.mask_lm ``=` `nn.CrossEntropyLoss(reduction``=``'none'``)``    ``if` `hasattr``(config, ``'label_smoothing'``) ``and` `config.label_smoothing:``      ``self``.mask_lm_smoothed ``=` `LabelSmoothingLoss(config.label_smoothing, config.vocab_size, ignore_index``=``0``,``                            ``reduction``=``'none'``)``    ``else``:``      ``self``.mask_lm_smoothed ``=` `None``    ``self``.init_weights()``    ``self``.tie_weights()` `  ``def` `tie_weights(``self``):``    ``"""权重加载，加载预训练模型的embeddings部分权重"""``    ``self``._tie_or_clone_weights(``self``.``cls``.predictions.decoder,``                  ``self``.bert.embeddings.word_embeddings)` `  ``def` `forward(``self``, input_ids, token_type_ids``=``None``, attention_mask``=``None``, masked_lm_labels``=``None``, masked_pos``=``None``,``        ``masked_weights``=``None``):``    ``"""模型forward，向前传递函数"""``    ``# 获取Encoder部分的序列输出，维度[bs,seq_len,hidden_size]``    ``sequence_output, __ ``=` `self``.bert(input_ids, token_type_ids, attention_mask, output_all_encoded_layers``=``False``)` `    ``def` `gather_seq_out_by_pos(seq, pos):``      ``return` `torch.gather(seq, ``1``, pos.unsqueeze(``2``).expand(``-``1``, ``-``1``, seq.size(``-``1``)))` `    ``def` `loss_mask_and_normalize(loss, mask):``      ``mask ``=` `mask.type_as(loss)``      ``loss ``=` `loss ``*` `mask``      ``denominator ``=` `torch.``sum``(mask) ``+` `1e``-``5``      ``return` `(loss ``/` `denominator).``sum``()` `    ``if` `masked_lm_labels ``is` `None``:``      ``if` `masked_pos ``is` `None``:``        ``prediction_scores ``=` `self``.``cls``(sequence_output)``      ``else``:``        ``sequence_output_masked ``=` `gather_seq_out_by_pos(sequence_output, masked_pos)``        ``prediction_scores ``=` `self``.``cls``(sequence_output_masked)``      ``return` `prediction_scores``    ``# 获取被掩码位置的向量``    ``sequence_output_masked ``=` `gather_seq_out_by_pos(sequence_output, masked_pos)``    ``prediction_scores_masked ``=` `self``.``cls``(sequence_output_masked)``    ``if` `self``.mask_lm_smoothed:``      ``masked_lm_loss ``=` `self``.mask_lm_smoothed(F.log_softmax(prediction_scores_masked.``float``(), dim``=``-``1``),``                          ``masked_lm_labels)``    ``else``:``      ``masked_lm_loss ``=` `self``.mask_lm(prediction_scores_masked.transpose(``1``, ``2``).``float``(), masked_lm_labels)``    ``# 计算[Mask]标记的损失值``    ``masked_lm_loss ``=` `loss_mask_and_normalize(masked_lm_loss.``float``(), masked_weights)` `    ``return` `masked_lm_loss

我们重点看看这个模型类：

UnilmForSeq2Seq是一个基于UniLM模型的序列到序列模型，主要用于处理序列生成任务，如机器翻译、文本摘要等。下面是UnilmForSeq2Seq模型的主要组成部分及其功能：

1. self.bert = UnilmModel(config)：这是UniLM模型的主体部分，包括BERT的嵌入层、编码器和池化层。这部分用于处理输入序列并生成隐藏状态。

2. self.cls = BertOnlyMLMHead(config)：这是一个预测头，用于预测下一个词。它接收UnilmModel生成的隐藏状态，并输出每个词的预测分数。

3. self.mask_lm = nn.CrossEntropyLoss(reduction=‘none’)：这是一个交叉熵损失函数，用于计算预测和真实标签之间的损失。

4. self.mask_lm_smoothed = LabelSmoothingLoss(config.label_smoothing, config.vocab_size, ignore_index=0, reduction=‘none’)：这是一个实现了标签平滑的损失函数，用于训练过程中减少模型对于标签的过拟合。

5. forward函数：这是模型的前向传播函数，它接收输入序列、注意力掩码和标签，然后通过UnilmModel和预测头计算预测分数，最后使用损失函数计算损失。

总的来说，UnilmForSeq2Seq模型的主要功能是根据输入的序列生成一个新的序列，并通过计算预测和真实标签之间的损失进行训练。