Update doc for XLNet (#3833)

PaddleNLP/PaddleLARK/XLNet/README.md

@@ -8,7 +8,21 @@ For more details, please refer to the research paper
 
 [XLNet: Generalized Autoregressive Pretraining for Language Understanding](https://arxiv.org/abs/1906.08237)
 
+## Directory structure
 
+```
+├── model/                        # directory for model structure definition
+│   ├── classifier.py             # model for regression/classification
+│   ├── xlnet.py                  # model for XLNet
+├── reader/                       # directory for data reader
+│   ├── cls.py                    # data reader for regression/classification
+│   ├── squad.py                  # data reader for squad
+├── utils/                        # directory for utility files
+│── modeling.py                   # network modules
+│── optimization.py               # optimization method
+│── run_classifier.py             # script for running regression/classification task
+│── run_squad.py                  # script for running squad
+```
 
 ## Installation
 

PaddleNLP/PaddleLARK/XLNet/README_cn.md

@@ -8,11 +8,27 @@ XLNet 与 [BERT](https://github.com/PaddlePaddle/models/tree/develop/PaddleNLP/P
 
 [XLNet: Generalized Autoregressive Pretraining for Language Understanding](https://arxiv.org/abs/1906.08237)
 
+## 目录结构
+
+```
+├── model/                        # 模型结构定义目录
+│   ├── classifier.py             # 回归/分类模型结构
+│   ├── xlnet.py                  # XLNet 模型结构
+├── reader/                       # 数据读取 reader 定义目录
+│   ├── cls.py                    # 分类任务数据读取
+│   ├── squad.py                  # squad 数据读取
+├── utils/                        # 辅助文件目录
+│── modeling.py                   # 网络定义模块
+│── optimization.py               # 优化方法
+│── run_classifier.py             # 运行回归/分类任务的脚本
+│── run_squad.py                  # 运行 squad 任务的脚本
+```
+
 ## 安装
 
 该项目要求 Paddle Fluid 1.6.0 及以上版本，请参考 [安装指南](https://www.paddlepaddle.org.cn/start) 进行安装。
 
-## Pre-trained models
+## 预训练模型
 
 这里提供了从官方开源模型转换而来的两个预训练模型供下载
 

PaddleNLP/PaddleLARK/XLNet/modeling.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.
+
 import re
 import numpy as np
 import paddle.fluid as fluid
-import collections
 
 
 def log_softmax(logits, axis=-1):

README.md

@@ -170,6 +170,7 @@ PaddlePaddle 提供了丰富的计算单元，使得用户可以采用模块化
 | ------------------------------------------------------------ | ------------------------------------------------------------ |
 | [ERNIE](https://github.com/PaddlePaddle/ERNIE)(Enhanced Representation from kNowledge IntEgration) | 百度自研的语义表示模型，通过建模海量数据中的词、实体及实体关系，学习真实世界的语义知识。相较于 BERT 学习原始语言信号，ERNIE 直接对先验语义知识单元进行建模，增强了模型语义表示能力。 |
 | [BERT](https://github.com/PaddlePaddle/models/tree/develop/PaddleNLP/PaddleLARK/BERT)(Bidirectional Encoder Representation from Transformers) | 一个迁移能力很强的通用语义表示模型， 以 Transformer 为网络基本组件，以双向 Masked Language Model和 Next Sentence Prediction 为训练目标，通过预训练得到通用语义表示，再结合简单的输出层，应用到下游的 NLP 任务，在多个任务上取得了 SOTA 的结果。 |
+| [XLNet](https://github.com/PaddlePaddle/models/tree/develop/PaddleNLP/PaddleLARK/XLNet)(XLNet: Generalized Autoregressive Pretraining for Language Understanding) | 重要的语义表示模型之一，引入 Transformer-XL 为骨架，以 Permutation Language Modeling 为优化目标，在若干下游任务上优于 BERT 的性能。 |
 | [ELMo](https://github.com/PaddlePaddle/models/tree/develop/PaddleNLP/PaddleLARK/ELMo)(Embeddings from Language Models) | 重要的通用语义表示模型之一，以双向 LSTM 为网路基本组件，以 Language Model 为训练目标，通过预训练得到通用的语义表示，将通用的语义表示作为 Feature 迁移到下游 NLP 任务中，会显著提升下游任务的模型性能。 |
 
 #### 文本相似度计算