卷积神经网络文本分类算法

随着这几年深度学习的出现,人工智能也得到了更好的发展, 不知不觉已进入我们的生活,并且一点一点地影响着我们.之前待过一家公司里面主要是做ai算法项目.虽然负责的工程这块,几十种算法模型都有nlp和cv算法工程师开发.我们只是包装这些算法模型成一个个对外的服务,随着耳濡目染,慢慢地会去研究下平时这些算法是怎么训练的

1. 网络结构
卷积神经网络一般包括卷积层，池化层和全连接层,这些层通常我们叫做隐藏层

1.1卷积层
如图一个5x5的矩阵 通过一个3x3的卷积核的得到一个3x3的矩阵(为什么做卷积呢,我们把这个矩阵想象成一个rgb的图, 那么图片上每个色素值附近的值都是相近或相等的,那么我们完全可以只取某一部分特征,没必要使用全部提取,那样参数会很多成百上千亿的参数,而且参数过多也容易过拟合)

1.2池化层

池化层（pooling）的作用主要是降低维度，通过对卷积后的结果进行降采样来降低维度，分为最大池化和平均池化两类。

1.2.1 最大池化

最大池化顾名思义，降采样的时候采用最大值的方式采样，如图所示，其中池化核的大小为22，步长也为22
1.2.2 平均池化

平均池化就是用局部的平均值作为采样的值，还是上面的数据，平均池化后的结果为：

1.3全连接层

全连接层就是把卷积层和池化层的输出展开成一维形式，在后面接上与普通网络结构相同的回归网络或者分类网络，一般接在池化层后面，如图所示;

2.文本分类实战
在深度学习领域已经有多种框架本次才有谷歌的tensorflow来实现,在tensorflow有三个比较重要的概念

• tensor 张量输入的数据和那些参数都是tensor,就像我们做化学实验的化学物品
• graph 计算图就是整个网络结构的定义,包括输入层 隐藏层 输出层, 就像我们化学实验拼接的导管
• session 会话,我们要想run起来都要都过session.run()方法 就像加热化学物质

下图就是本次模型的计算图

首先通过embedding

然后做卷积操作 和池化

再是全连接层 和做dropout 和选择激活函数relu
后面通过 softmax 和 argmax 得到分类结果

…
再来一个详细图

3. 代码实战

# coding: utf-8

import tensorflow as tf


class TCNNConfig(object):
    """CNN配置参数"""

    embedding_dim = 64  # 词向量维度
    seq_length = 600  # 序列长度
    num_classes = 10  # 类别数
    num_filters = 256  # 卷积核数目
    kernel_size = 5  # 卷积核尺寸
    vocab_size = 5000  # 词汇表达小

    hidden_dim = 128  # 全连接层神经元

    dropout_keep_prob = 0.5  # dropout保留比例
    learning_rate = 1e-3  # 学习率

    batch_size = 64  # 每批训练大小
    num_epochs = 1  # 总迭代轮次

    print_per_batch = 100  # 每多少轮输出一次结果
    save_per_batch = 10  # 每多少轮存入tensorboard


class TextCNN(object):
    """文本分类，CNN模型"""

    def __init__(self, config):
        self.config = config

        # 三个待输入的数据
        self.input_x = tf.placeholder(tf.int32, [None, self.config.seq_length], name='input_x')
        self.input_y = tf.placeholder(tf.float32, [None, self.config.num_classes], name='input_y')
        self.keep_prob = tf.placeholder(tf.float32, name='keep_prob')

        self.cnn()

    def cnn(self):
        """CNN模型"""
        # 词向量映射
        with tf.device('/cpu:0'):
            embedding = tf.get_variable('embedding', [self.config.vocab_size, self.config.embedding_dim])
            embedding_inputs = tf.nn.embedding_lookup(embedding, self.input_x)

        with tf.name_scope("cnn"):
            # CNN layer
            conv = tf.layers.conv1d(embedding_inputs, self.config.num_filters, self.config.kernel_size, name='conv')
            # global max pooling layer
            gmp = tf.reduce_max(conv, reduction_indices=[1], name='gmp')

        with tf.name_scope("score"):
            # 全连接层，后面接dropout以及relu激活
            fc = tf.layers.dense(gmp, self.config.hidden_dim, name='fc1')
            fc = tf.contrib.layers.dropout(fc, self.keep_prob)
            fc = tf.nn.relu(fc)

            # 分类器 logits shape shape=(?, 10)
            self.logits = tf.layers.dense(fc, self.config.num_classes, name='fc2')

            # tf.nn.softmax 把logits 的数字变成总和等于1  tf.argmax取最大值的下标 准确率最高的
            self.y_pred_cls_min = tf.nn.softmax(self.logits)  # 预测类别
            self.y_pred_cls = tf.argmax(self.y_pred_cls_min, 1)  # 预测类别

        with tf.name_scope("optimize"):
            # 损失函数，交叉熵
            cross_entropy = tf.nn.softmax_cross_entropy_with_logits(logits=self.logits, labels=self.input_y)
            self.loss = tf.reduce_mean(cross_entropy)
            # 优化器
            self.optim = tf.train.AdamOptimizer(learning_rate=self.config.learning_rate).minimize(self.loss)

        with tf.name_scope("accuracy"):
            # 准确率
            correct_pred = tf.equal(tf.argmax(self.input_y, 1), self.y_pred_cls)

            self.acc = tf.reduce_mean(tf.cast(correct_pred, tf.float32))

#!/usr/bin/python
# -*- coding: utf-8 -*-

from __future__ import print_function

import os
import sys
import time
from datetime import timedelta

import numpy as np
import tensorflow as tf
from sklearn import metrics

from cnn_model import TCNNConfig, TextCNN
from data.cnews_loader import read_vocab, read_category, batch_iter, process_file, build_vocab

base_dir = 'data/cnews'
train_dir = os.path.join(base_dir, 'cnews.train.txt')
test_dir = os.path.join(base_dir, 'cnews.test.txt')
val_dir = os.path.join(base_dir, 'cnews.val.txt')
vocab_dir = os.path.join(base_dir, 'cnews.vocab.txt')

save_dir = 'checkpoints/textcnn'
save_path = os.path.join(save_dir, 'best_validation')  # 最佳验证结果保存路径


def get_time_dif(start_time):
    """获取已使用时间"""
    end_time = time.time()
    time_dif = end_time - start_time
    return timedelta(seconds=int(round(time_dif)))


def feed_data(x_batch, y_batch, keep_prob):
    feed_dict = {
        model.input_x: x_batch,
        model.input_y: y_batch,
        model.keep_prob: keep_prob
    }
    return feed_dict


def evaluate(sess, x_, y_):
    """评估在某一数据上的准确率和损失"""
    data_len = len(x_)
    batch_eval = batch_iter(x_, y_, 128)
    total_loss = 0.0
    total_acc = 0.0
    for x_batch, y_batch in batch_eval:
        batch_len = len(x_batch)
        feed_dict = feed_data(x_batch, y_batch, 1.0)
        loss, acc = sess.run([model.loss, model.acc], feed_dict=feed_dict)
        total_loss += loss * batch_len
        total_acc += acc * batch_len

    return total_loss / data_len, total_acc / data_len


def train():
    print("Configuring TensorBoard and Saver...")
    # 配置 Tensorboard，重新训练时，请将tensorboard文件夹删除，不然图会覆盖
    tensorboard_dir = 'tensorboard/textcnn'
    if not os.path.exists(tensorboard_dir):
        os.makedirs(tensorboard_dir)

    tf.summary.scalar("loss", model.loss)
    tf.summary.scalar("accuracy", model.acc)
    merged_summary = tf.summary.merge_all()
    writer = tf.summary.FileWriter(tensorboard_dir)

    # 配置 Saver
    saver = tf.train.Saver()
    if not os.path.exists(save_dir):
        os.makedirs(save_dir)

    print("Loading training and validation data...")
    # 载入训练集与验证集
    start_time = time.time()
    x_train, y_train = process_file(train_dir, word_to_id, cat_to_id, config.seq_length)
    x_val, y_val = process_file(val_dir, word_to_id, cat_to_id, config.seq_length)
    time_dif = get_time_dif(start_time)
    print("Time usage:", time_dif)

    # 创建session
    session = tf.Session()
    session.run(tf.global_variables_initializer())
    writer.add_graph(session.graph)

    print('Training and evaluating...')
    start_time = time.time()
    total_batch = 0  # 总批次
    best_acc_val = 0.0  # 最佳验证集准确率
    last_improved = 0  # 记录上一次提升批次
    require_improvement = 1000  # 如果超过1000轮未提升，提前结束训练

    flag = False
    for epoch in range(config.num_epochs):
        print('Epoch:', epoch + 1)
        batch_train = batch_iter(x_train, y_train, config.batch_size)
        for x_batch, y_batch in batch_train:
            feed_dict = feed_data(x_batch, y_batch, config.dropout_keep_prob)

            if total_batch % config.save_per_batch == 0:
                # 每多少轮次将训练结果写入tensorboard scalar
                s = session.run(merged_summary, feed_dict=feed_dict)
                writer.add_summary(s, total_batch)

            if total_batch % config.print_per_batch == 0:
                # 每多少轮次输出在训练集和验证集上的性能
                feed_dict[model.keep_prob] = 1.0
                loss_train, acc_train = session.run([model.loss, model.acc], feed_dict=feed_dict)
                loss_val, acc_val = evaluate(session, x_val, y_val)  # todo

                if acc_val > best_acc_val:
                    # 保存最好结果
                    best_acc_val = acc_val
                    last_improved = total_batch
                    saver.save(sess=session, save_path=save_path)
                    improved_str = '*'
                else:
                    improved_str = ''

                time_dif = get_time_dif(start_time)
                msg = 'Iter: {0:>6}, Train Loss: {1:>6.2}, Train Acc: {2:>7.2%},' \
                      + ' Val Loss: {3:>6.2}, Val Acc: {4:>7.2%}, Time: {5} {6}'
                print(msg.format(total_batch, loss_train, acc_train, loss_val, acc_val, time_dif, improved_str))

            feed_dict[model.keep_prob] = config.dropout_keep_prob
            session.run(model.optim, feed_dict=feed_dict)  # 运行优化
            total_batch += 1

            if total_batch - last_improved > require_improvement:
                # 验证集正确率长期不提升，提前结束训练
                print("No optimization for a long time, auto-stopping...")
                flag = True
                break  # 跳出循环
        if flag:  # 同上
            break


def test():
    print("Loading test data...")
    start_time = time.time()
    x_test, y_test = process_file(test_dir, word_to_id, cat_to_id, config.seq_length)

    session = tf.Session()
    session.run(tf.global_variables_initializer())
    saver = tf.train.Saver()
    saver.restore(sess=session, save_path=save_path)  # 读取保存的模型

    print('Testing...')
    loss_test, acc_test = evaluate(session, x_test, y_test)
    msg = 'Test Loss: {0:>6.2}, Test Acc: {1:>7.2%}'
    print(msg.format(loss_test, acc_test))

    batch_size = 128
    data_len = len(x_test)
    num_batch = int((data_len - 1) / batch_size) + 1

    y_test_cls = np.argmax(y_test, 1)
    y_pred_cls = np.zeros(shape=len(x_test), dtype=np.int32)  # 保存预测结果
    for i in range(num_batch):  # 逐批次处理
        start_id = i * batch_size
        end_id = min((i + 1) * batch_size, data_len)
        feed_dict = {
            model.input_x: x_test[start_id:end_id],
            model.keep_prob: 1.0
        }
        y_pred_cls[start_id:end_id] = session.run(model.y_pred_cls, feed_dict=feed_dict)

    # 评估
    print("Precision, Recall and F1-Score...")
    print(metrics.classification_report(y_test_cls, y_pred_cls, target_names=categories))

    # 混淆矩阵
    print("Confusion Matrix...")
    cm = metrics.confusion_matrix(y_test_cls, y_pred_cls)
    print(cm)

    time_dif = get_time_dif(start_time)
    print("Time usage:", time_dif)


if __name__ == '__main__':
    # if len(sys.argv) != 2 or sys.argv[1] not in ['train', 'test']:
    #     raise ValueError("""usage: python run_cnn.py [train / test]""")

    print('Configuring CNN model...')
    config = TCNNConfig()
    if not os.path.exists(vocab_dir):  # 如果不存在词汇表，重建
        build_vocab(train_dir, vocab_dir, config.vocab_size)
    categories, cat_to_id = read_category()
    words, word_to_id = read_vocab(vocab_dir)
    config.vocab_size = len(words)
    model = TextCNN(config)
    train()
    # if sys.argv[1] == 'train':
    #     train()
    # else:
    #     test()

# coding: utf-8

import sys
from collections import Counter

import numpy as np
#import tensorflow.keras as kr
import keras as kr

if sys.version_info[0] > 2:
    is_py3 = True
else:
    reload(sys)
    sys.setdefaultencoding("utf-8")
    is_py3 = False


def native_word(word, encoding='utf-8'):
    """如果在python2下面使用python3训练的模型，可考虑调用此函数转化一下字符编码"""
    if not is_py3:
        return word.encode(encoding)
    else:
        return word


def native_content(content):
    if not is_py3:
        return content.decode('utf-8')
    else:
        return content


def open_file(filename, mode='r'):
    """
    常用文件操作，可在python2和python3间切换.
    mode: 'r' or 'w' for read or write
    """
    if is_py3:
        return open(filename, mode, encoding='utf-8', errors='ignore')
    else:
        return open(filename, mode)


def read_file(filename):
    """读取文件数据"""
    contents, labels = [], []
    with open_file(filename) as f:
        for line in f:
            try:
                label, content = line.strip().split('\t')
                if content:
                    contents.append(list(native_content(content)))
                    labels.append(native_content(label))
            except:
                pass
    return contents, labels


def build_vocab(train_dir, vocab_dir, vocab_size=5000):
    """根据训练集构建词汇表，存储"""
    data_train, _ = read_file(train_dir)

    all_data = []
    for content in data_train:
        all_data.extend(content)

    counter = Counter(all_data)
    count_pairs = counter.most_common(vocab_size - 1)
    words, _ = list(zip(*count_pairs))
    # 添加一个  来将所有文本pad为同一长度
    words = [''] + list(words)
    open_file(vocab_dir, mode='w').write('\n'.join(words) + '\n')


def read_vocab(vocab_dir):
    """读取词汇表"""
    # words = open_file(vocab_dir).read().strip().split('\n')
    with open_file(vocab_dir) as fp:
        # 如果是py2 则每个值都转化为unicode
        words = [native_content(_.strip()) for _ in fp.readlines()]
    word_to_id = dict(zip(words, range(len(words))))
    return words, word_to_id


def read_category():
    """读取分类目录，固定"""
    categories = ['体育', '财经', '房产', '家居', '教育', '科技', '时尚', '时政', '游戏', '娱乐']

    categories = [native_content(x) for x in categories]

    cat_to_id = dict(zip(categories, range(len(categories))))

    return categories, cat_to_id


def to_words(content, words):
    """将id表示的内容转换为文字"""
    return ''.join(words[x] for x in content)


def process_file(filename, word_to_id, cat_to_id, max_length=600):
    """将文件转换为id表示"""
    contents, labels = read_file(filename)

    data_id, label_id = [], []
    for i in range(len(contents)):
        data_id.append([word_to_id[x] for x in contents[i] if x in word_to_id])
        label_id.append(cat_to_id[labels[i]])

    # 使用keras提供的pad_sequences来将文本pad为固定长度
    x_pad = kr.preprocessing.sequence.pad_sequences(data_id, max_length)
    y_pad = kr.utils.to_categorical(label_id, num_classes=len(cat_to_id))  # 将标签转换为one-hot表示

    return x_pad, y_pad


def batch_iter(x, y, batch_size=64):
    """生成批次数据"""
    data_len = len(x)
    num_batch = int((data_len - 1) / batch_size) + 1

    indices = np.random.permutation(np.arange(data_len))
    x_shuffle = x[indices]
    y_shuffle = y[indices]

    for i in range(num_batch):
        start_id = i * batch_size
        end_id = min((i + 1) * batch_size, data_len)
        yield x_shuffle[start_id:end_id], y_shuffle[start_id:end_id]

# coding: utf-8

from __future__ import print_function

import os
import tensorflow as tf
#import tensorflow.contrib.keras as kr
import keras as kr



from cnn_model import TCNNConfig, TextCNN
from data.cnews_loader import read_category, read_vocab

try:
    bool(type(unicode))
except NameError:
    unicode = str

base_dir = 'data/cnews'
vocab_dir = os.path.join(base_dir, 'cnews.vocab.txt')

save_dir = 'checkpoints/textcnn'
save_path = os.path.join(save_dir, 'best_validation')  # 最佳验证结果保存路径

class CnnModel:
    def __init__(self):
        self.config = TCNNConfig()
        self.categories, self.cat_to_id = read_category()
        self.words, self.word_to_id = read_vocab(vocab_dir)
        self.config.vocab_size = len(self.words)
        self.model = TextCNN(self.config)

        self.session = tf.Session()
        self.session.run(tf.global_variables_initializer())
        saver = tf.train.Saver()
        saver.restore(sess=self.session, save_path=save_path)  # 读取保存的模型

    def predict(self, message):
        # 支持不论在python2还是python3下训练的模型都可以在2或者3的环境下运行
        content = unicode(message)
        data = [self.word_to_id[x] for x in content if x in self.word_to_id]

        feed_dict = {
            self.model.input_x: kr.preprocessing.sequence.pad_sequences([data], self.config.seq_length),
            self.model.keep_prob: 1.0
        }

        # y_pred_cls = self.session.run(self.model.y_pred_cls, feed_dict=feed_dict)

        y_pred_cls, y_pred_cls_min = self.session.run([self.model.y_pred_cls, self.model.y_pred_cls_min],
                                                      feed_dict=feed_dict)
        print(y_pred_cls_min)
        print(y_pred_cls)
        return self.categories[y_pred_cls[0]]


if __name__ == '__main__':
    cnn_model = CnnModel()
    test_demo = ['vivo手机超感光微云台双主摄，蔡司联合影像系统，高通骁龙888芯片，120Hz高刷新率，55W闪充',
                 '詹姆斯：100%健康比排位重要，提出附加赛想法的人该被解雇']
    for i in test_demo:
        print(cnn_model.predict(i))

附做其分类效果(只做了三分类 广告 色情 谩骂)

• 注意深度学习如果要提供线上服务远比这复杂,有得需要给出文本中具体的哪个词语命中分类,也要考虑算法模型的预测时间调整网络结构参数,还要考虑部署方案,是提供http调用呢,还是java直接引入tensorflow的jar包去调用