TensorFlow 学习笔记（四）优化器提升正确率

目录：

1.交叉熵

2.Dropout

3.优化

4.优化器

1.交叉熵

更改loss函数

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

对比两次结果：

二次代价函数：

loss = tf.reduce_mean(tf.square(y - prediction))

Iter0,Testing Accuracy0.9259
Iter1,Testing Accuracy0.9291
Iter2,Testing Accuracy0.9302
Iter3,Testing Accuracy0.9307
Iter4,Testing Accuracy0.9309
Iter5,Testing Accuracy0.9314
Iter6,Testing Accuracy0.9309
Iter7,Testing Accuracy0.9308
Iter8,Testing Accuracy0.9307
Iter9,Testing Accuracy0.9308
Iter10,Testing Accuracy0.9297
Iter11,Testing Accuracy0.9297
Iter12,Testing Accuracy0.9296
Iter13,Testing Accuracy0.9302
Iter14,Testing Accuracy0.9301
Iter15,Testing Accuracy0.9296
Iter16,Testing Accuracy0.9303
Iter17,Testing Accuracy0.9309
Iter18,Testing Accuracy0.9314
Iter19,Testing Accuracy0.9311
Iter20,Testing Accuracy0.9314
交叉熵：

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

Iter0,Testing Accuracy0.9283
Iter1,Testing Accuracy0.9297
Iter2,Testing Accuracy0.9301
Iter3,Testing Accuracy0.93
Iter4,Testing Accuracy0.9299
Iter5,Testing Accuracy0.93
Iter6,Testing Accuracy0.93
Iter7,Testing Accuracy0.9296
Iter8,Testing Accuracy0.93
Iter9,Testing Accuracy0.9301
Iter10,Testing Accuracy0.9294
Iter11,Testing Accuracy0.9297
Iter12,Testing Accuracy0.9294
Iter13,Testing Accuracy0.9295
Iter14,Testing Accuracy0.9295
Iter15,Testing Accuracy0.9294
Iter16,Testing Accuracy0.929
Iter17,Testing Accuracy0.9293
Iter18,Testing Accuracy0.9287
Iter19,Testing Accuracy0.9289
Iter20,Testing Accuracy0.9287

（理论上交叉熵应该比二次代价函数好，但我没看出来）

2.Dropout

# -*- coding:utf-8 -*-
# author: aihan time: 2019/1/21

import os
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'

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

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

#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

x = tf.placeholder(tf.float32,[None,784])
y = tf.placeholder(tf.float32,[None,10])
keep_prob = tf.placeholder(tf.float32)

#创建一个神经网络
W1 = tf.Variable(tf.truncated_normal([784,500],stddev=0.1))
b1 = tf.Variable(tf.zeros([500])+0.1)
L1 = tf.nn.tanh(tf.matmul(x,W1)+b1)  #激活函数为双曲正切
L1_drop = tf.nn.dropout(L1,keep_prob)
#隐含层
W2 = tf.Variable(tf.truncated_normal([500,500],stddev=0.1))
b2 = tf.Variable(tf.zeros([500])+0.1)
L2 = tf.nn.tanh(tf.matmul(L1_drop,W2)+b2)  #激活函数为双曲正切
L2_drop = tf.nn.dropout(L2,keep_prob)

W3 = tf.Variable(tf.truncated_normal([500,500],stddev=0.1))
b3 = tf.Variable(tf.zeros([500])+0.1)
L3 = tf.nn.tanh(tf.matmul(L2_drop,W3)+b3)  #激活函数为双曲正切
L3_drop = tf.nn.dropout(L3,keep_prob)

W4 = tf.Variable(tf.truncated_normal([500,10],stddev=0.1))
b4 = tf.Variable(tf.zeros([10])+0.1)
prediction = tf.nn.softmax(tf.matmul(L3_drop,W4)+b4)

# 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))
#交叉熵 作为代价函数 效果更好
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(labels=y,logits=prediction))
#使用梯度下降法
train_step = tf.train.GradientDescentOptimizer(0.2).minimize(loss)

#初始化变量
init = tf.global_variables_initializer()

#结果对比(true,false)存放在一个bool型列表中
correct_prediction = tf.equal(tf.argmax(y,1),tf.argmax(prediction,1))#argmax返回一维张量中最大的值所在的位置
#求准确率
accuracy = tf.reduce_mean(tf.cast(correct_prediction,tf.float32))

with tf.Session() as sess:
    sess.run(init)
    for epoch in range(10):
        for betch 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,keep_prob:1.0})
            #keep_prob:1.0  全部工作

        test_acc = sess.run(accuracy,feed_dict={x:mnist.test.images,y:mnist.test.labels,keep_prob:1.0})
        train_ass = sess.run(accuracy,feed_dict={x:mnist.train.images,y:mnist.train.labels,keep_prob:1.0})
        print("Iter"+str(epoch)+",Testing Accuracy"+str(test_acc)+",Training Accuracy"+str(train_ass))

结果：

3.优化

SGD

Momentum

NAG

Adagrad

RMSprop

Adadelta

4.优化器

# -*- coding:utf-8 -*-
# author: aihan time: 2019/1/22

import os
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'
import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data


mnist = input_data.read_data_sets("MNIST_data",one_hot=True)

batch_size = 100
n_batch = mnist.train.num_examples

x = tf.placeholder(tf.float32,[None,784])
y = tf.placeholder(tf.float32,[None,10])

W = tf.Variable(tf.zeros([784,10]))
b = tf.Variable(tf.zeros([10]))
prediction = tf.nn.softmax(tf.matmul(x,W)+b)

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

#train_step = tf.train.GradientDescentOptimizer(0.2).minimize(loss)
#优化器  1e-3为10的-3次方 (学习率)
train_step = tf.train.AdamOptimizer(1e-2).minimize(loss)

init = tf.global_variables_initializer()

correct_prediction = tf.equal(tf.argmax(y,1),tf.argmax(prediction,1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction,tf.float32))

with tf.Session() as sess:
    sess.run(init)
    for epoch in range(21):
        for betch 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) + ",Testing Accuracy" + str(acc))

结果：

TensorFlow 学习笔记（四） 优化器提升正确率

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