在Tensorflow中实现梯度下降法更新参数值

 tf.train.GradientDescentOptimizer(0.01).minimize(cross_entropy)

 train_step = tf.train.GradientDescentOptimizer(0.01).minimize(cross_entropy,var_list=[w,b])

 #导入Minst数据集 import input_data mnist = input_data.read_data_sets("data",one_hot=True) #导入tensorflow库 import tensorflow as tf #输入变量，把28*28的图片变成一维数组（丢失结构信息） x = tf.placeholder("float",[None,784]) #权重矩阵，把28*28=784的一维输入，变成0-9这10个数字的输出 w = tf.Variable(tf.zeros([784,10])) #偏置 b = tf.Variable(tf.zeros([10])) #核心运算，其实就是softmax（x*w+b） y = tf.nn.softmax(tf.matmul(x,w) + b) #这个是训练集的正确结果 y_ = tf.placeholder("float",[None,10]) #交叉熵，作为损失函数 cross_entropy = -tf.reduce_sum(y_ * tf.log(y)) #梯度下降算法，最小化交叉熵 train_step = tf.train.GradientDescentOptimizer(0.01).minimize(cross_entropy) #初始化，在run之前必须进行的 init = tf.initialize_all_variables() #创建session以便运算 sess = tf.Session() sess.run(init) #迭代1000次 for i in range(1000): #获取训练数据集的图片输入和正确表示数字 batch_xs, batch_ys = mnist.train.next_batch(100) #运行刚才建立的梯度下降算法，x赋值为图片输入，y_赋值为正确的表示数字 sess.run(train_step,feed_dict = {x:batch_xs, y_: batch_ys}) #tf.argmax获取最大值的索引。比较运算后的结果和本身结果是否相同。 #这步的结果应该是[1,1,1,1,1,1,1,1,0,1...........1,1,0,1]这种形式。 #1代表正确，0代表错误 correct_prediction = tf.equal(tf.argmax(y,1), tf.argmax(y_,1)) #tf.cast先将数据转换成float，防止求平均不准确。 #tf.reduce_mean由于只有一个参数，就是上面那个数组的平均值。 accuracy = tf.reduce_mean(tf.cast(correct_prediction,"float")) #输出 print(sess.run(accuracy,feed_dict={x:mnist.test.images,y_: mnist.test.labels}))

 "C:\Program Files\Anaconda3\python.exe" D:/pycharmprogram/tensorflow_learn/softmax_learn/softmax_learn.py Extracting data\train-images-idx3-ubyte.gz Extracting data\train-labels-idx1-ubyte.gz Extracting data\t10k-images-idx3-ubyte.gz Extracting data\t10k-labels-idx1-ubyte.gz WARNING:tensorflow:From C:\Program Files\Anaconda3\lib\site-packages\tensorflow\python\util\tf_should_use.py:175: initialize_all_variables (from tensorflow.python.ops.variables) is deprecated and will be removed after 2017-03-02. Instructions for updating: Use `tf.global_variables_initializer` instead. 2018-05-14 15:49:45.866600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX instructions, but these are available on your machine and could speed up CPU computations. 2018-05-14 15:49:45.866600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX2 instructions, but these are available on your machine and could speed up CPU computations. 0.9163 Process finished with exit code 0

 "C:\Program Files\Anaconda3\python.exe" D:/pycharmprogram/tensorflow_learn/softmax_learn/softmax_learn.py Extracting data\train-images-idx3-ubyte.gz Extracting data\train-labels-idx1-ubyte.gz Extracting data\t10k-images-idx3-ubyte.gz Extracting data\t10k-labels-idx1-ubyte.gz WARNING:tensorflow:From C:\Program Files\Anaconda3\lib\site-packages\tensorflow\python\util\tf_should_use.py:175: initialize_all_variables (from tensorflow.python.ops.variables) is deprecated and will be removed after 2017-03-02. Instructions for updating: Use `tf.global_variables_initializer` instead. 2018-05-14 15:51:08.543600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX instructions, but these are available on your machine and could speed up CPU computations. 2018-05-14 15:51:08.544600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX2 instructions, but these are available on your machine and could speed up CPU computations. 0.9<i style="color:transparent">来源gaodai$ma#com搞$$代**码)网</i>187 Process finished with exit code 0

 #导入Minst数据集 import input_data mnist = input_data.read_data_sets("data",one_hot=True) #导入tensorflow库 import tensorflow as tf #输入变量，把28*28的图片变成一维数组（丢失结构信息） x = tf.placeholder("float",[None,784]) #权重矩阵，把28*28=784的一维输入，变成0-9这10个数字的输出 w = tf.Variable(tf.zeros([784,10])) #偏置 b = tf.Variable(tf.zeros([10])) #核心运算，其实就是softmax（x*w+b） y = tf.nn.softmax(tf.matmul(x,w) + b) #这个是训练集的正确结果 y_ = tf.placeholder("float",[None,10]) #交叉熵，作为损失函数 cross_entropy = -tf.reduce_sum(y_ * tf.log(y)) #梯度下降算法，最小化交叉熵 train_step = tf.train.GradientDescentOptimizer(0.01).minimize(cross_entropy,var_list=[b]) #初始化，在run之前必须进行的 init = tf.initialize_all_variables() #创建session以便运算 sess = tf.Session() sess.run(init) #迭代1000次 for i in range(1000): #获取训练数据集的图片输入和正确表示数字 batch_xs, batch_ys = mnist.train.next_batch(100) #运行刚才建立的梯度下降算法，x赋值为图片输入，y_赋值为正确的表示数字 sess.run(train_step,feed_dict = {x:batch_xs, y_: batch_ys}) #tf.argmax获取最大值的索引。比较运算后的结果和本身结果是否相同。 #这步的结果应该是[1,1,1,1,1,1,1,1,0,1...........1,1,0,1]这种形式。 #1代表正确，0代表错误 correct_prediction = tf.equal(tf.argmax(y,1), tf.argmax(y_,1)) #tf.cast先将数据转换成float，防止求平均不准确。 #tf.reduce_mean由于只有一个参数，就是上面那个数组的平均值。 accuracy = tf.reduce_mean(tf.cast(correct_prediction,"float")) #输出 print(sess.run(accuracy,feed_dict={x:mnist.test.images,y_: mnist.test.labels})) 

 "C:\Program Files\Anaconda3\python.exe" D:/pycharmprogram/tensorflow_learn/softmax_learn/softmax_learn.py Extracting data\train-images-idx3-ubyte.gz Extracting data\train-labels-idx1-ubyte.gz Extracting data\t10k-images-idx3-ubyte.gz Extracting data\t10k-labels-idx1-ubyte.gz WARNING:tensorflow:From C:\Program Files\Anaconda3\lib\site-packages\tensorflow\python\util\tf_should_use.py:175: initialize_all_variables (from tensorflow.python.ops.variables) is deprecated and will be removed after 2017-03-02. Instructions for updating: Use `tf.global_variables_initializer` instead. 2018-05-14 15:52:04.483600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX instructions, but these are available on your machine and could speed up CPU computations. 2018-05-14 15:52:04.483600: W C:\tf_jenkins\home\workspace\rel-win\M\windows\PY\35\tensorflow\core\platform\cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX2 instructions, but these are available on your machine and could speed up CPU computations. 0.1135 Process finished with exit code 0