tencent_2.3_shallow_neural_networks

课程地址：https://cloud.tencent.com/developer/labs/lab/10298/console

数据准备

wget https://devlab-1251520893.cos.ap-guangzhou.myqcloud.com/t10k-images-idx3-ubyte.gz
wget https://devlab-1251520893.cos.ap-guangzhou.myqcloud.com/t10k-labels-idx1-ubyte.gz
wget https://devlab-1251520893.cos.ap-guangzhou.myqcloud.com/train-images-idx3-ubyte.gz
wget https://devlab-1251520893.cos.ap-guangzhou.myqcloud.com/train-labels-idx1-ubyte.gz

 

shallow_neural_networks.py

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

def add_layer(inputs, in_size, out_size, activation_function=None):
    W = tf.Variable(tf.random_normal([in_size, out_size]))
    b = tf.Variable(tf.zeros([1, out_size]) + 0.01)

    Z = tf.matmul(inputs, W) + b
    if activation_function is None:
        outputs = Z
    else:
        outputs = activation_function(Z)

    return outputs


if __name__ == "__main__":

    MNIST = input_data.read_data_sets("./", one_hot=True)

    learning_rate = 0.05
    batch_size = 128
    n_epochs = 10

    X = tf.placeholder(tf.float32, [batch_size, 784])
    Y = tf.placeholder(tf.float32, [batch_size, 10])

    l1 = add_layer(X, 784, 1000, activation_function=tf.nn.relu)
    prediction = add_layer(l1, 1000, 10, activation_function=None)

    entropy = tf.nn.softmax_cross_entropy_with_logits(labels=Y, logits=prediction)
    loss = tf.reduce_mean(entropy)

    optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(loss)

    init = tf.initialize_all_variables()

    with tf.Session() as sess:
        sess.run(init)

        n_batches = int(MNIST.train.num_examples/batch_size)
        for i in range(n_epochs):
            for j in range(n_batches):
                X_batch, Y_batch = MNIST.train.next_batch(batch_size)
                _, loss_ = sess.run([optimizer, loss], feed_dict={X: X_batch, Y: Y_batch})
                if j == 0:
                    print "Loss of epochs[{0}] batch[{1}]: {2}".format(i, j, loss_)

        # test the model
        n_batches = int(MNIST.test.num_examples/batch_size)
        total_correct_preds = 0
        for i in range(n_batches):
            X_batch, Y_batch = MNIST.test.next_batch(batch_size)
            preds = sess.run(prediction, feed_dict={X: X_batch, Y: Y_batch})
            correct_preds = tf.equal(tf.argmax(preds, 1), tf.argmax(Y_batch, 1))
            accuracy = tf.reduce_sum(tf.cast(correct_preds, tf.float32)) 

            total_correct_preds += sess.run(accuracy)

        print "Accuracy {0}".format(total_correct_preds/MNIST.test.num_examples)

我尝试修改learning_rate和weights的标准差：

w = tf.Variable(tf.random_normal(shape=[in_size, out_size], stddev=0.1))
...
learning_rate=0.2

收敛明显加快：