一个简单的线性回归模型

  import os
  os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'
  
  import tensorflow as tf
  import numpy as np
  import matplotlib.pyplot as plt
  
  # 随机生成1000个点，分布在 y=0.1x+0.3 附近
  num_point = 1000
  vectors_set = []
  for i in range(num_point):
      x1 = np.random.normal(0.0, 0.55)        # x 取值范围
      y1 = x1 * 0.1 + 0.3 + np.random.normal(0.0, 0.03)
      vectors_set.append([x1, y1])
  
  # 生成样本
  x_data = [v[0] for v in vectors_set]
  y_data = [v[1] for v in vectors_set]
  
  plt.scatter(x_data, y_data, c='r')          # 生成散点图
  
  # 生成一维矩阵 W，取值为[-1,1]之间的随机值
  W = tf.Variable(tf.random_uniform([1], -1.0, 1.0), name='W')

  # 生成一维矩阵 b，初始值为0
  b = tf.Variable(tf.zeros([1]), name='b')

  # 经过计算得出预估值 y
  y = W * x_data + b
  
  # 以预估值 y 和实际值 y_data 之间的均方误差作为损失
  loss = tf.reduce_mean(tf.square(y - y_data), name='loss')

  # 采样梯度下降法来优化参数
  optimizer = tf.train.GradientDescentOptimizer(0.5)

  # 训练的过程就是最小化这个误差值
  train = optimizer.minimize(loss, name='train')
  
  sess = tf.Session()
  init = tf.global_variables_initializer()
  sess.run(init)
  
  # 初始化的 W 和 b 是多少
  print('W = ', sess.run(W), 'b = ', sess.run(b), 'loss = ', sess.run(loss))
  
  # 执行20次训练
  for step in range(20):
      sess.run(train)

      # 输出训练好的 W 和 b
      print('W = ', sess.run(W), 'b = ', sess.run(b), 'loss = ', sess.run(loss))
  
  # 将函数构造成一条直线
  plt.scatter(x_data, y_data, c='r')
  plt.plot(x_data, sess.run(W) * x_data + sess.run(b))
  plt.show()

一个简单的逻辑回归模型迭代

  import tensorflow as tf
  import numpy as np
  from tensorflow.examples.tutorials.mnist import input_data
  
  tf.logging.set_verbosity(tf.logging.ERROR)

  # 数据读取以及样本导入
  mnist = input_data.read_data_sets('MNIST_data/',one_hot=True)
  trainimg = mnist.train.images
  trainlabel = mnist.train.labels
  testimg = mnist.test.images
  testlabel = mnist.test.labels
  print('mnist loaded...')
  
  print(trainimg.shape)
  print(trainlabel.shape)
  print(testimg.shape)
  print(testlabel.shape)
  print(trainimg)
  print(trainlabel[0])
  
  # 变量初始化，None 表示无穷
  x = tf.placeholder('float', [None, 784])
  y = tf.placeholder('float', [None, 10])
  W = tf.Variable(tf.zeros([784, 10]))
  b = tf.Variable(tf.zeros([10]))
  
  # 逻辑参数模型
  actv = tf.nn.softmax(tf.matmul(x, W) + b)
  
  # 损失函数（cost function）
  cost = tf.reduce_mean(-tf.reduce_sum(y*tf.log(actv), reduction_indices=1))
  
  # 优化，使用梯度下降
  learning_rate = 0.01
  optm = tf.train.GradientDescentOptimizer(learning_rate).minimize(cost)
  
  # 预测，取出每行里面的最大值
  pred = tf.equal(tf.argmax(actv, 1), tf.argmax(y, 1))
  
  # 准确率，精度
  accr = tf.reduce_mean(tf.cast(pred, 'float'))
  
  # 初始化
  init = tf.global_variables_initializer()
  
  training_epochs = 50            # 迭代50次
  batch_size = 100                # 每次迭代选阵100个样本
  display_step = 5
  
  sess = tf.Session()
  sess.run(init)
  
  # 最小批次训练
  for epoch in range(training_epochs):
      avg_cost = 0.
      num_batch = int(mnist.train.num_examples/batch_size)
      for i in range(num_batch):
          batch_xs, batch_ys = mnist.train.next_batch(batch_size)
          sess.run(optm, feed_dict={x: batch_xs, y: batch_ys})            # 求解
          feeds = {x: batch_xs, y: batch_ys}
          avg_cost += sess.run(cost, feed_dict=feeds)/num_batch           # 损失值
  
      if epoch % display_step == 0:
          feeds_train = {x: batch_xs, y: batch_ys}
          feeds_test = {x: mnist.test.images, y: mnist.test.labels}
          train_acc = sess.run(accr, feed_dict=feeds_train)
          test_acc = sess.run(accr, feed_dict=feeds_test)
          print('Epoch: %03d/%03d cost: %.9f train_acc: %03f test_acc: %.3f'
                % (epoch, training_epochs, avg_cost, train_acc, test_acc))
  
  print('DONE')

一个简单的卷积神经网络

  import tensorflow as tf      
  from tensorflow.examples.tutorials.mnist import input_data
  
  tf.logging.set_verbosity(tf.logging.ERROR)
  # 只显示错误
  
  mnist = input_data.read_data_sets('MNIST_data/',one_hot=True)

  trainimg   = mnist.train.images
  trainlabel = mnist.train.labels
  testimg    = mnist.test.images
  testlabel  = mnist.test.labels
  
  print('MNIST Ready...')
  
  n_input = 784       # 输入像素点个数（28*28）
  n_output = 10       # 输出的分类数
  
  # 权重参数
  weights = {
      # 卷积层第一层参数，filter = 3*3，深度为1，得出的特征图为64个
      'wc1': tf.Variable(tf.random_normal([3, 3, 1, 64], stddev=0.1)),
  
      # 卷积层第一层参数，filter = 3*3，上一步得到64个特征图，深度为64，输出深度为128
      'wc2': tf.Variable(tf.random_normal([3, 3, 64, 128], stddev=0.1)),
  
      # 全连接层1，28*28*1——14*14*64——7*7*128，将其转换为1024维向量
      'wd1': tf.Variable(tf.random_normal([7*7*128, 1024], stddev=0.1)),
  
      # 全连接层2，将1024维向量输出为 n_output = 10 个分类
      'wd2': tf.Variable(tf.random_normal([1024, n_output], stddev=0.1))
  }
  
  # 偏置参数
  biases = {
      'bc1': tf.Variable(tf.random_normal([64], stddev=0.1)),
      'bc2': tf.Variable(tf.random_normal([128], stddev=0.1)),
      'bd1': tf.Variable(tf.random_normal([1024], stddev=0.1)),
      'bd2': tf.Variable(tf.random_normal([n_output], stddev=0.1)),
  }
  
  # 卷积与池化
  def conv_basic(_input, _w, _b, _keepratio):
      # 输入，对输入进行预处理，将数据转换为 tensorflow 格式
      _input_r = tf.reshape(_input, shape=[-1, 28, 28, 1])
  
      # 第一层卷积层，一般 strides 只修改中间的 width 和 deep
      _conv1 = tf.nn.conv2d(_input_r, _w['wc1'], strides=[1, 1, 1, 1], padding='SAME')
      # _mean, _var = tf.nn.moments(_conv1, [0, 1, 2])
      # _conv1 = tf.nn.batch_normalization(_conv1, _mean, _var, 0, 1, 0.0001)
  
      _conv1 = tf.nn.relu(tf.nn.bias_add(_conv1, _b['bc1']))
      _pool1 = tf.nn.max_pool(_conv1, ksize=[1, 2, 2, 1], strides=[1, 2, 2, 1], padding='SAME')
      # 随机杀死一些节点，保留一部分节点
      _pool_dr1 = tf.nn.dropout(_pool1, _keepratio)
  
      # 第二层卷积层
      _conv2 = tf.nn.conv2d(_pool_dr1, _w['wc2'], strides=[1, 1, 1, 1], padding='SAME')
      # _mean, _var = tf.nn.moments(_conv2, [0, 1, 2])
      # _conv2 = tf.nn.batch_normalization(_conv2, _mean, _var, 0, 1, 0.0001)
  
      _conv2 = tf.nn.relu(tf.nn.bias_add(_conv2, _b['bc2']))
      _pool2 = tf.nn.max_pool(_conv2, ksize=[1, 2, 2, 1], strides=[1, 2, 2, 1], padding='SAME')
      _pool_dr2 = tf.nn.dropout(_pool2, _keepratio)
  
      # 矢量化，将 tensor 转换为 list
      _dense1 = tf.reshape(_pool_dr2, [-1, _w['wd1'].get_shape().as_list()[0]])
  
      # 全连接层第一层
      _fc1 = tf.nn.relu(tf.add(tf.matmul(_dense1, _w['wd1']), _b['bd1']))
      _fc_dr1 = tf.nn.dropout(_fc1, _keepratio)
  
      # 全连接层第二层
      _out = tf.add(tf.matmul(_fc_dr1, _w['wd2']), _b['bd2'])
      out = {
          'input_r': _input_r,
          'conv1': _conv1,
          'pool1': _pool1,
          'pool_dr1': _pool_dr1,
          'conv2': _conv2,
          'pool2': _pool2,
          'pool_dr2': _pool_dr2,
          'densel': _dense1,
          'fc1': _fc1,
          'fc_dr1':_fc_dr1,
          'out': _out
      }
      return out
  print('CNN Ready...')
  
  a = tf.Variable(tf.random_normal([3, 3, 1, 64], stddev=0.1))
  a = tf.Print(a, [a], 'a: ')
  
  # 初始化变量
  init = tf.global_variables_initializer()
  sess = tf.Session()
  sess.run(init)
  
  # 占位 x,y
  x = tf.placeholder(tf.float32, [None, n_input])
  y = tf.placeholder(tf.float32, [None, n_output])
  keepratio = tf.placeholder(tf.float32)
  
  _pred = conv_basic(x, weights, biases, keepratio)['out']
  cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits=_pred,labels=y))
  optm = tf.train.AdadeltaOptimizer(learning_rate=0.001).minimize(cost)
  _corr = tf.equal(tf.argmax(_pred, 1), tf.argmax(y, 1))
  accr = tf.reduce_mean(tf.cast(_corr, tf.float32))
  
  # 初始化变量
  init = tf.global_variables_initializer()
  sess = tf.Session()
  sess.run(init)
  
  print('Graph Ready...')
  
  training_epochs = 15           # 迭代15次
  batch_size      = 16           # 每次迭代选择16个样品
  display_step    = 1
  
  # 参数优化
  for epoch in range(training_epochs):
      avg_cost = 0.
      # total_batch = int(mnist.train.num_examples / batch_size)
      total_batch = 10
  
      # 循环遍历所有批次
      for i in range(total_batch):
          batch_xs, batch_ys = mnist.train.next_batch(batch_size)
  
          # 使用批量数据进行训练
          sess.run(optm, feed_dict={x: batch_xs, y: batch_ys, keepratio: 0.7})
          # 电脑平均损失
          avg_cost += sess.run(cost, feed_dict={x: batch_xs, y: batch_ys, keepratio: 1.}) / total_batch
  
      # 显示每个时期的日志
      if epoch % display_step == 0:
          print('Epoch: %03d/%03d cost : %.9f' % (epoch, training_epochs, avg_cost))
  
          train_acc = sess.run(accr, feed_dict={x: batch_xs, y: batch_ys, keepratio: 1.})
          print('Training Accuracy: %.3f' % (train_acc))
  
  
          # test_acc = sess.run(accr, feed_dict={x: mnist.test.images, y: mnist.test.labels, keepratio:1.})
          # print('Test Accuracy: %.3f' % (test_acc))
  
  print('Optimization Finished...')

一个简单的神经网络模型

  import tensorflow as tf
  import numpy as np
  from tensorflow.examples.tutorials.mnist import input_data

  tf.logging.set_verbosity(tf.logging.ERROR)
  # 只显示错误

  mnist = input_data.read_data_sets('MNIST_data/',one_hot=True)

  # 网络拓扑
  n_hidden_1 = 256        # 第一层神经元个数
  n_hidden_2 = 128        # 第二层神经元个数
  n_input = 784           # 输入像素点个数
  n_classes = 10          # 输出的分类的类别
  
  # 输入和输出
  x = tf.placeholder('float', [None, n_input])
  y = tf.placeholder('float', [None, n_classes])
  
  # 神经网络参数初始化
  stddev = 0.1
  
  # 权重参数，初始化
  weights = {
      'w1': tf.Variable(tf.random_normal([n_input, n_hidden_1], stddev=stddev)),
      'w2': tf.Variable(tf.random_normal([n_hidden_1, n_hidden_2], stddev=stddev)),
      'out': tf.Variable(tf.random_normal([n_hidden_2, n_classes], stddev=stddev))
  }
  
  # 偏置参数，初始化
  biases = {
      'b1': tf.Variable(tf.random_normal([n_hidden_1])),
      'b2': tf.Variable(tf.random_normal([n_hidden_2])),
      'out': tf.Variable(tf.random_normal([n_classes]))
  }
  print('Network Ready...')
  
  def multilayer_preceptron(_X, _weights, _biases):
      layer_1 = tf.nn.sigmoid(tf.add(tf.matmul(_X, _weights['w1']), _biases['b1']))
      layer_2 = tf.nn.sigmoid(tf.add(tf.matmul(layer_1, _weights['w2']), _biases['b2']))
      return (tf.matmul(layer_2, _weights['out']) + _biases['out'])
  
  # 预测
  pred = multilayer_preceptron(x, weights, biases)
  
  # 损失和优化参数
  # 损失函数，两种方式
  # cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits_v2(pred, y))
  cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits=pred, labels=y))
  
  # 梯度下降
  optm = tf.train.GradientDescentOptimizer(learning_rate=0.001).minimize(cost)
  corr = tf.equal(tf.argmax(pred, 1), tf.argmax(y, 1))              # 准确率
  accr = tf.reduce_mean(tf.cast(corr, 'float'))                     # 精度
  
  # 初始化
  init = tf.global_variables_initializer()
  print('Function Ready...')
  
  training_epochs = 20            # 迭代20次
  batch_size = 100                # 每次迭代选择100个样本
  display_step = 4
  
  sess = tf.Session()
  sess.run(init)
  
  # 优化
  for epoch in range(training_epochs):
      avg_cost = 0
      total_batch = int(mnist.train.num_examples/batch_size)
  
      for i in range(total_batch):
          batch_xs, batch_ys = mnist.train.next_batch(batch_size)
          feeds = {x: batch_xs, y: batch_ys}
          sess.run(optm, feed_dict=feeds)
          avg_cost += sess.run(cost, feed_dict=feeds)
      avg_cost = avg_cost/total_batch
  
      if (epoch+1) % display_step == 0:
          print('Epoch: %03d/%03d cost : %.9f'%(epoch, training_epochs, avg_cost))
  
          feeds = {x: batch_xs, y: batch_ys}
          train_acc = sess.run(accr, feed_dict=feeds)
          print('Train Accuracy: %.3f'%(train_acc))
  
          feeds = {x:mnist.test.images, y: mnist.test.labels}
          test_acc = sess.run(accr, feed_dict=feeds)
          print('Test Accuracy: %.3f'%(test_acc))

  print('Optimization Finished...')