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  • 003-2-TensorFlow识别手写数字数据集MNIST(简单版本)

    构建神经网络:

    import tensorflow as tf
    from tensorflow.examples.tutorials.mnist import input_data
    #载入数据
    mnist = input_data.read_data_sets("MNIST_data",one_hot = True)
    
    #定义每个批次的大小
    batch_size = 100
    #计算一共有多少个批次
    n_batch = mnist.train.num_examples//batch_size
    
    #定义2个placeholder
    x = tf.placeholder(tf.float32,[None,784])
    y = tf.placeholder(tf.float32,[None,10])
    
    #创建一个简单的神经网络:
    W = tf.Variable(tf.zeros([784,10]))
    b = tf.Variable(tf.zeros([10]))
    prediction = tf.nn.softmax(tf.matmul(x,W)+b)
    
    
    
    #二次代价函数:
    loss = tf.reduce_mean(tf.square(y-prediction))
    #梯度下降
    train_step = tf.train.GradientDescentOptimizer(0.2).minimize(loss)
    
    #初始化变量
    init = tf.global_variables_initializer()
    
    #求准确率
    #比较预测值最大标签位置与真实值最大标签位置是否相等
    correct_prediction = tf.equal(tf.argmax(y,1),tf.argmax(prediction,1))
    #求准去率
    accuracy = tf.reduce_mean(tf.cast(correct_prediction,tf.float32))
    
    with tf.Session() as sess:
        sess.run(init)
        for epoch in range(21):
            for batch in range(n_batch):
                batch_xs,batch_ys = mnist.train.next_batch(batch_size)
                sess.run(train_step,feed_dict = {x:batch_xs,y:batch_ys})
            acc = sess.run(accuracy,feed_dict ={x:mnist.test.images,
                                                y:mnist.test.labels})
            print("Iter"+str(epoch+1)+",Testing accuracy"+str(acc))
            
    

      

    Extracting MNIST_data	rain-images-idx3-ubyte.gz
    Extracting MNIST_data	rain-labels-idx1-ubyte.gz
    Extracting MNIST_data	10k-images-idx3-ubyte.gz
    Extracting MNIST_data	10k-labels-idx1-ubyte.gz
    Iter1,Testing accuracy0.8296
    Iter2,Testing accuracy0.8714
    Iter3,Testing accuracy0.8817
    Iter4,Testing accuracy0.8878
    Iter5,Testing accuracy0.894
    Iter6,Testing accuracy0.8967
    Iter7,Testing accuracy0.9
    Iter8,Testing accuracy0.9016
    Iter9,Testing accuracy0.9038
    Iter10,Testing accuracy0.9051
    Iter11,Testing accuracy0.9063
    Iter12,Testing accuracy0.9071
    Iter13,Testing accuracy0.9091
    Iter14,Testing accuracy0.9092
    Iter15,Testing accuracy0.9098
    Iter16,Testing accuracy0.9107
    Iter17,Testing accuracy0.9117
    Iter18,Testing accuracy0.9122
    Iter19,Testing accuracy0.9126
    Iter20,Testing accuracy0.9136
    Iter21,Testing accuracy0.9139
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  • 原文地址:https://www.cnblogs.com/Mjerry/p/9827821.html
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