卷积神经网络
tf.nn.conv2d
tf.nn.conv2d(input, # [batch, in_height, in_width, in_channels]
filter, # [filter_height, filter_width, in_channels, out_channels]
strides, # [1,1,1,1]
padding, # SAME VALID
use_cudnn_on_gpu=True,
data_format='NHWC',
dilations=[1, 1, 1, 1],
name=None)
-
input: [batch, in_height, in_width, in_channels] 4-D的 Tensor (float32/float64)
batch_size,高度，宽度，通道数 -
filter：[filter_height, filter_width, in_channels, out_channels]
卷积核高度， 卷积核宽度 输入通道数 输出通道数(卷积核个数) -
strides：步长 [1,1,1,1] 1-D向量，长度为4
-
padding：填充 SAME VALID
-
use_cudnn_on_gpu：是否GPU加速
结果返回一个Tensor，这个输出，就是我们常说的 feature map，shape仍然是 [batch, height, width, channels] 这种形式。
图像卷积
3x3图像，1通道，1x1卷积核
1.考虑一种最简单的情况，现在有一张3×3单通道的图像（对应的shape：[1，3，3，1]），用一个1×1的卷积核（对应的shape：[1，1，1，1]）去做卷积，最后会得到一张3×3的feature map
In [4]:
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,3,3,1]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([1,1,1,1]))
op1 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op1),'\n')
print(sess.run(op1).shape)
运行结果
[[[[-0.06386475]
[ 0.30251193]
[-0.36254457]]
[[-0.1863834 ]
[-0.11046342]
[ 0.12128225]]
[[-0.16598591]
[-0.06247617]
[ 0.10344568]]]]
(1, 3, 3, 1)
3x3图像，5通道，1x1卷积核
2.增加图片的通道数，使用一张3×3五通道的图像（对应的shape：[1，3，3，5]），用一个1×1的卷积核（对应的shape：[1，1，1，1]）去做卷积，仍然是一张3×3的feature map，这就相当于每一个像素点，卷积核都与该像素点的每一个通道做卷积。
In [5]:
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,3,3,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([1,1,5,1]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[ 2.611188 ]
[ 1.1356436]
[ 0.1728566]]
[[ 1.7238054]
[-2.65044 ]
[-0.6026321]]
[[-0.9376406]
[-2.1341398]
[ 0.5801886]]]]
(1, 3, 3, 1)
3x3图像，5通道，3x3卷积核，文本卷积维度和图像一样大，所以卷积之后只有1列
3.把卷积核扩大，现在用3×3的卷积核做卷积，最后的输出是一个值，相当于情况2的feature map所有像素点的值求和
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,3,3,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,1]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[-3.8528938]]]]
(1, 1, 1, 1)
5x5图像，5通道，3x3卷积核
4.使用更大的图片将情况2的图片扩大到5×5，仍然是3×3的卷积核，令步长为1，输出3×3的feature map
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,5,5,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,1]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[-3.3537188]
[ 2.6631894]
[10.7735815]]
[[ 6.7866626]
[-5.753437 ]
[ 6.8379397]]
[[-7.2338777]
[-3.8412943]
[11.663807 ]]]]
(1, 3, 3, 1)
5x5图像，5通道，3x3卷积核
5.上面我们一直令参数padding的值为‘VALID’，当其为‘SAME’时，表示卷积核可以停留在图像边缘，如下，输出5×5的feature map
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,5,5,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,1]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='SAME')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[ -4.1736193 ]
[ 7.2922435 ]
[ 2.9188058 ]
[ 0.49713266]
[ -2.956664 ]]
[[ -3.305164 ]
[ -7.311406 ]
[ -5.045771 ]
[ -2.5354984 ]
[ -7.40237 ]]
[[ 9.273168 ]
[ 1.2130424 ]
[ -8.63011 ]
[ 8.675023 ]
[ 4.0911283 ]]
[[ -2.295607 ]
[ 5.2230077 ]
[-10.142306 ]
[ -6.135029 ]
[ 1.3315554 ]]
[[-11.159186 ]
[ -3.5029335 ]
[ -1.638276 ]
[ -4.381499 ]
[ -1.0199151 ]]]]
(1, 5, 5, 1)
5x5图像，5通道，3x3卷积核，3个卷积核
6.如果卷积核有多个
此时输出3张5×5的feature map
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,5,5,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,3]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='SAME')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[ 2.7570508 -3.232238 -2.6215773 ]
[ 2.532285 1.9889098 3.87929 ]
[ -3.187311 8.91769 3.224719 ]
[ 0.44387245 -9.403946 2.468867 ]
[ 0.21311586 -1.590601 5.749056 ]]
[[ -2.6277003 6.488189 9.992645 ]
[ 1.5766766 -11.48576 0.6145782 ]
[ -5.0482545 -0.96584886 4.0381684 ]
[ -0.797274 2.4302173 -3.8855307 ]
[ -2.6238062 2.05465 2.9259453 ]]
[[ 4.714437 -0.9536078 -2.9879472 ]
[ 1.5400691 1.5240853 -6.90153 ]
[ -3.6736727 3.85059 -0.5918405 ]
[ 7.023252 2.9593654 -13.595696 ]
[ -5.041815 -2.7133517 0.6385279 ]]
[[ 1.477376 0.47209492 5.653083 ]
[ -0.39575818 14.780628 -1.5949147 ]
[ 2.378466 -11.533363 -0.4041656 ]
[ -0.4129743 6.5807753 -2.7889323 ]
[ 6.1631317 -0.49479347 1.52246 ]]
[[ -6.97586 1.1432166 -5.064254 ]
[ -9.823753 -3.1042528 -1.6604922 ]
[ 9.015108 -10.42481 -4.7503257 ]
[ 2.3552632 0.43692362 2.7325256 ]
[ -2.1840062 2.729301 -4.588225 ]]]]
(1, 5, 5, 3)
5x5图像，5通道，3x3卷积核，3个卷积核，步长为2
7.步长不为1的情况，文档里说了对于图片，因为只有两维，通常strides取[1，stride，stride，1]
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([1,5,5,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,3]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 2, 2, 1], padding='SAME')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[ 2.783487 -2.09441 4.733526 ]
[-7.3059773 -3.108855 4.022243 ]
[-4.050215 3.0158758 -4.1893964]]
[[-6.3690815 -5.2265515 1.1703218]
[ 9.0784235 -3.5745146 14.855592 ]
[-0.4078823 4.0576644 4.617129 ]]
[[ 3.339266 -5.4302483 -3.154387 ]
[ 1.3765206 2.6518223 5.6584387]
[-3.9308991 1.4282804 -3.4455342]]]]
(1, 3, 3, 3)
5x5图像，5通道，3x3卷积核，3个卷积核，步长为2，10张图像
8.如果batch值不为1，同时输入10张图
每张图，都有3张3×3的feature map，输出的shape就是[10，3，3，3]
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([10,5,5,5]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,3,5,3]))
op2 = tf.nn.conv2d(input, filter, strides=[1, 2, 2, 1], padding='SAME')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op2),'\n')
print(sess.run(op2).shape)
运行结果
[[[[ 3.7294517 -3.107039 -3.3261778 ]
[ 5.441018 -4.0686336 5.619485 ]
[ 2.1390946 3.5674727 -1.5291997 ]]
[[ -5.6689725 16.974398 2.381929 ]
[ 2.4008992 -0.6694184 1.378117 ]
[ 1.2934582 7.2192235 0.48349503]]
[[ 2.9121394 -0.4573097 -9.765212 ]
[ 1.0088806 -0.7046843 6.591536 ]
[ -0.72504395 0.43721557 -4.999654 ]]]
[[[ 1.967625 -1.6568589 -6.145099 ]
[ -4.151078 -10.529405 -2.047928 ]
[ 3.4548922 2.7491624 2.9001775 ]]
[[ -1.6896939 3.1873543 6.188783 ]
[ 11.703161 1.6971766 -4.8438787 ]
[ 0.9549799 -1.1131762 4.593415 ]]
[[ -1.1170579 0.4810401 -1.3526723 ]
[ 2.529728 -1.1482326 3.7958796 ]
[ -0.24976896 3.3091352 -6.729189 ]]]
[[[ -3.33531 -1.9344107 2.8165019 ]
[ -1.6785766 -2.8081656 7.2197647 ]
[ 1.7976431 2.8334517 -0.08083367]]
[[ 2.5362453 -0.68693405 2.2952533 ]
[ 1.5236933 2.129165 0.194734 ]
[ 0.5964938 -8.6989565 5.084363 ]]
[[ 5.066878 -1.3026551 -5.7902007 ]
[ -2.9802423 4.8924155 5.9025197 ]
[ -3.933334 5.099715 -0.8536027 ]]]
[[[ -1.0145748 -10.15126 -7.0179715 ]
[ -8.451802 -0.17334843 -2.7171214 ]
[ 5.668031 -5.15528 -4.2402534 ]]
[[ -2.0954626 -1.0145442 3.2066696 ]
[ 2.289553 0.9271075 0.8146973 ]
[ -0.7423492 4.2153864 -4.70488 ]]
[[ 3.8675358 -0.35446188 -1.1588985 ]
[ -4.8492827 -5.2945166 3.944246 ]
[ -0.43092388 -0.8130417 2.3813803 ]]]
[[[ 0.66720986 3.8808417 2.1328838 ]
[ 7.446735 -4.522188 -5.990181 ]
[ -2.5916054 5.0853543 2.6371577 ]]
[[ -7.136207 0.6306949 -8.853178 ]
[ 3.7415988 -7.89348 -8.487032 ]
[ -0.69531 -3.222552 1.5073893 ]]
[[ -3.106504 -0.01809834 -9.029028 ]
[ -4.416857 0.13292897 7.7073345 ]
[ 0.9844466 4.2795186 -0.76342046]]]
[[[ -0.11672409 -7.369146 -4.8543487 ]
[ -4.230579 -1.1736143 0.74828875]
[ -0.6568188 6.765464 -4.9761944 ]]
[[ 3.8933635 -7.902747 -0.63001007]
[ 6.8245344 3.9199047 11.168122 ]
[ 3.7043867 0.31197003 0.04769279]]
[[ -4.1409 8.580945 8.486864 ]
[ -3.1867335 7.059393 6.296857 ]
[ -0.9835455 -3.6718185 0.97860974]]]
[[[ 5.193179 -1.2967495 8.170371 ]
[ -1.3087153 -5.5033283 -1.6919953 ]
[ 0.36510244 -6.296658 -3.7380807 ]]
[[ 3.5434737 13.3447695 1.7701437 ]
[-10.250333 -9.407058 -3.2337494 ]
[ 8.435421 4.078936 3.4657378 ]]
[[ 3.4681797 2.228949 0.45596147]
[ -0.57005715 4.670751 2.034872 ]
[ -1.915133 7.9970365 -3.8922138 ]]]
[[[ 3.950432 -4.4767623 -6.447672 ]
[ 2.595737 -8.553671 -0.45686972]
[ 3.391854 -2.003466 -2.2928245 ]]
[[ -3.6888146 3.5153918 1.2406276 ]
[ -0.25753272 2.6999128 -2.8501456 ]
[ -0.9058769 6.502099 -0.5419939 ]]
[[ -0.68687534 -6.5038085 2.8593688 ]
[ -3.683316 2.1430447 5.490655 ]
[ 5.7413816 3.3227494 -7.533464 ]]]
[[[ -3.484571 5.3650527 2.9336984 ]
[ 0.6027174 3.7776787 1.0154141 ]
[ -4.7919264 7.149525 1.9800262 ]]
[[ -2.1547816 -3.2360375 -5.2381744 ]
[ 7.6362724 8.085188 9.068025 ]
[ -4.549206 -3.8285804 5.8914824 ]]
[[ -1.9079026 2.9233663 0.9151974 ]
[ 6.70253 -10.376949 -2.2334673 ]
[ 2.7263498 3.202616 3.6564238 ]]]
[[[ 6.6487746 -0.2954742 3.0371974 ]
[ 3.576 -7.2807136 4.2893467 ]
[ -0.96813136 -5.533345 -6.83936 ]]
[[ -0.10136782 -1.4625425 -7.0081096 ]
[ 3.8160882 -2.4150543 -3.9401052 ]
[ 2.7480733 -1.4603323 10.289123 ]]
[[ 2.629776 -3.5297518 0.4979372 ]
[ 0.9985927 -8.139794 -0.5185237 ]
[ -4.5744176 -10.06965 5.6358476 ]]]]
(10, 3, 3, 3)
文本卷积
5x5文本，1通道，2-gram卷积核，3个卷积核，10句话
import tensorflow as tf
# [batch, in_height, in_width, in_channels]
input = tf.Variable(tf.random_normal([10,5,5,1]))
# [filter_height, filter_width, in_channels, out_channels]
filter = tf.Variable(tf.random_normal([3,5,1,3]))
op1 = tf.nn.conv2d(input, filter, strides=[1, 1, 1, 1], padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print(sess.run(op1),'\n')
print(sess.run(op1).shape)
运行结果
[[[[ -0.28560075 3.4164069 0.64287925]]
[[ 4.922906 6.569628 -4.377281 ]]
[[ 2.0096815 -0.9498653 -5.302 ]]]
[[[ -0.30866227 0.65657634 0.08617933]]
[[ 2.1648352 2.0540233 -6.2501183 ]]
[[ 1.8437229 -3.3579445 0.648278 ]]]
[[[ -6.248692 -8.374758 3.1102016 ]]
[[ -4.6158714 1.0821313 2.8032086 ]]
[[ 1.912092 0.933113 -3.0924444 ]]]
[[[ 7.5399313 9.936766 -1.6083889 ]]
[[ 2.4991071 -0.3938322 5.2363515 ]]
[[ -3.8184917 1.5327872 -0.9156568 ]]]
[[[ -1.0705962 1.3645588 -2.2302496 ]]
[[ 0.9711383 -2.6879628 -2.1285567 ]]
[[ -5.15031 -1.7857913 -0.64766765]]]
[[[ -4.300858 -0.74519587 4.707138 ]]
[[ 1.1525508 -1.9355469 1.1351813 ]]
[[ -1.930467 5.30831 -0.11006889]]]
[[[ -0.30049637 -3.3917482 -0.98812234]]
[[ -0.78466344 -3.508609 1.8363969 ]]
[[ 1.6145957 0.15216915 -0.27968606]]]
[[[ 1.201814 2.2275777 3.4975147 ]]
[[ 1.7633957 3.9830918 10.16128 ]]
[[ 1.9025049 4.217062 3.2219505 ]]]
[[[ 2.7462778 -0.87272054 -10.7139845 ]]
[[ 0.5596598 -7.9665465 -3.5733411 ]]
[[ 0.02203573 1.8229557 1.1090751 ]]]
[[[ -2.8659163 -6.198704 1.1388084 ]]
[[ -5.6100855 2.2285914 1.380748 ]]
[[ -0.3560774 7.3229613 1.1240004 ]]]]
(10, 3, 1, 3)
tf.nn.max_pool
tf.nn.max_pool(value, # [batch, in_height, in_width, in_channels]
ksize, # [1,in_height,in_width,1]
strides, # [1,height,width,1]
padding, # SAME VALID
data_format='NHWC',
name=None,)
-
value: 池化层的输入，一般池化层在卷积层后面，输入通常是feature_map
依然是 [batch, in_height, in_width, in_channels] -
ksize：池化窗口大小，4-D向量，一般是 [1,in_height,in_width,1]
因为我们不想在 batch，in_channels上做池化，所以维度为1 -
strides：步长 [1,height,width,1] 1-D向量，长度为4
-
padding：填充 SAME VALID
返回一个Tensor，类型不变，shape仍然是 [batch, in_height, in_width, in_channels] 这种形式
4x4图像，2通道，池化核2x2，步长1
卷积由 [batch, in_height, in_width, in_channels]
[1,4,4,2] -> [1,3,3,2]
# 2x4x4
a=tf.constant([
[[1.0,2.0,3.0,4.0],
[5.0,6.0,7.0,8.0],
[8.0,7.0,6.0,5.0],
[4.0,3.0,2.0,1.0]], # 通道1图像
[[4.0,3.0,2.0,1.0], # 通道2图像
[8.0,7.0,6.0,5.0],
[1.0,2.0,3.0,4.0],
[5.0,6.0,7.0,8.0]]
])
b=tf.reshape(a,[1,4,4,2])
max_pool_2x2 = tf.nn.max_pool(b,[1,2,2,1],[1,1,1,1],padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print('池化前原始，image：\n')
print(sess.run(a),'\n')
print(sess.run(a).shape,'\n')
print('池化前，reshape，image：\n')
print(sess.run(b),'\n')
print(sess.run(b).shape,'\n')
print('池化后image：\n')
print(sess.run(max_pool_2x2),'\n')
print(sess.run(max_pool_2x2).shape,'\n')
运行结果
池化前原始，image：
[[[1. 2. 3. 4.]
[5. 6. 7. 8.]
[8. 7. 6. 5.]
[4. 3. 2. 1.]]
[[4. 3. 2. 1.]
[8. 7. 6. 5.]
[1. 2. 3. 4.]
[5. 6. 7. 8.]]]
(2, 4, 4)
池化前，reshape，image：
[[[[1. 2.]
[3. 4.]
[5. 6.]
[7. 8.]]
[[8. 7.]
[6. 5.]
[4. 3.]
[2. 1.]]
[[4. 3.]
[2. 1.]
[8. 7.]
[6. 5.]]
[[1. 2.]
[3. 4.]
[5. 6.]
[7. 8.]]]]
(1, 4, 4, 2)
池化后image：
[[[[8. 7.]
[6. 6.]
[7. 8.]]
[[8. 7.]
[8. 7.]
[8. 7.]]
[[4. 4.]
[8. 7.]
[8. 8.]]]]
(1, 3, 3, 2)
4x4图像，2通道，池化核2x2，步长2
卷积由 [batch, in_height, in_width, in_channels]
[1,4,4,2] -> [1,2,2,2]
# 2x4x4
a=tf.constant([
[[1.0,2.0,3.0,4.0],
[5.0,6.0,7.0,8.0],
[8.0,7.0,6.0,5.0],
[4.0,3.0,2.0,1.0]], # 通道1图像
[[4.0,3.0,2.0,1.0], # 通道2图像
[8.0,7.0,6.0,5.0],
[1.0,2.0,3.0,4.0],
[5.0,6.0,7.0,8.0]]
])
b=tf.reshape(a,[1,4,4,2])
max_pool_2x2 = tf.nn.max_pool(b,[1,2,2,1],[1,2,2,1],padding='VALID')
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
print('池化前原始，image：\n')
print(sess.run(a),'\n')
print(sess.run(a).shape,'\n')
print('池化前，reshape，image：\n')
print(sess.run(b),'\n')
print(sess.run(b).shape,'\n')
print('池化后image：\n')
print(sess.run(max_pool_2x2),'\n')
print(sess.run(max_pool_2x2).shape,'\n')
运行结果
池化前原始，image：
[[[1. 2. 3. 4.]
[5. 6. 7. 8.]
[8. 7. 6. 5.]
[4. 3. 2. 1.]]
[[4. 3. 2. 1.]
[8. 7. 6. 5.]
[1. 2. 3. 4.]
[5. 6. 7. 8.]]]
(2, 4, 4)
池化前，reshape，image：
[[[[1. 2.]
[3. 4.]
[5. 6.]
[7. 8.]]
[[8. 7.]
[6. 5.]
[4. 3.]
[2. 1.]]
[[4. 3.]
[2. 1.]
[8. 7.]
[6. 5.]]
[[1. 2.]
[3. 4.]
[5. 6.]
[7. 8.]]]]
(1, 4, 4, 2)
池化后image：
[[[[8. 7.]
[7. 8.]]
[[4. 4.]
[8. 8.]]]]
(1, 2, 2, 2)
CNN手写数字识别
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 // batch_size
def weight_variable(shape):
return tf.Variable(tf.truncated_normal(shape,stddev=0.1))
def bias_vairable(shape):
return tf.Variable(tf.constant(0.1, shape=shape))
def conv2d(x,W):
return tf.nn.conv2d(x,W,strides=[1,1,1,1],padding='SAME')
def max_pool_2x2(x):
return tf.nn.max_pool(x,ksize=[1,2,2,1],strides=[1,2,2,1],padding='SAME')
x = tf.placeholder(tf.float32,[None,784])
y = tf.placeholder(tf.float32,[None,10])
keep_prob = tf.placeholder(tf.float32)
# x input [batch,in_height,in_width,in_channels]
# [?,784] reshape -> [-1,28,28,1]
x_image = tf.reshape(x,[-1,28,28,1])
#w [filter_height,filter_width,in_channels, out_channels]
W_conv1 = weight_variable([5,5,1,32]) # 5*5的采样窗口，32个卷积核从1个平面抽取特征
b_conv1 = bias_vairable([32]) #每个卷积核一个偏置值
# 28*28*1 的图片卷积之后变为 -1*28*28*32
h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1)
# 池化之后变为 -1*14*14*32
h_pool1 = max_pool_2x2(h_conv1)
# 第二次卷积之后变为 14*14*64
W_conv2 = weight_variable([5,5,32,64])
b_conv2 = bias_vairable([64])
h_conv2 = tf.nn.relu(conv2d(h_pool1,W_conv2) + b_conv2)
# 第二次池化之后变为 7*7*64
h_pool2 = max_pool_2x2(h_conv2)
# 第一个全连接层
W_fc1 = weight_variable([7*7*64,1024]) #上一层有7*7*64个神经元，全连接层有1024个神经元
b_fc1 = bias_vairable([1024])#1024个节点
# 把池化层2的输出扁平化为1维向量
h_pool2_flat = tf.reshape(h_pool2,[-1,7*7*64])
#求第一个全连接的输出
h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)
h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)
# 初始化第二个全连接层
W_fc2 = weight_variable([1024,10])
b_fc2 = bias_vairable([10])
logits = tf.matmul(h_fc1_drop,W_fc2) + b_fc2
#计算输出
prediction = tf.nn.sigmoid(logits)
#交叉熵代价函数
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(labels=y, logits=logits))
#AdamOptimizer
train_step = tf.train.AdamOptimizer(0.001).minimize(loss)
prediction_2 = tf.nn.softmax(prediction)
correct_prediction = (tf.equal(tf.argmax(prediction_2,1), tf.argmax(y,1)))
accuracy = tf.reduce_mean(tf.cast(correct_prediction,tf.float32))
with tf.Session() as sess:
sess.run(tf.global_variables_initializer())
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,keep_prob:0.7})
acc = sess.run(accuracy, feed_dict={x:mnist.test.images, y:mnist.test.labels, keep_prob:1.0})
print("Iter: " + str(epoch) + ", acc: " + str(acc))
运行结果
Iter: 0, acc: 0.9796
Iter: 1, acc: 0.9863
Iter: 2, acc: 0.9882
Iter: 3, acc: 0.9908
Iter: 4, acc: 0.99
Iter: 5, acc: 0.991
Iter: 6, acc: 0.9926
Iter: 7, acc: 0.989
Iter: 8, acc: 0.9913
Iter: 9, acc: 0.9896
Iter: 10, acc: 0.992
Iter: 11, acc: 0.9913
Iter: 12, acc: 0.9917
Iter: 13, acc: 0.9911
Iter: 14, acc: 0.9912
Iter: 15, acc: 0.9915
Iter: 16, acc: 0.9907
Iter: 17, acc: 0.9905
Iter: 18, acc: 0.9923
Iter: 19, acc: 0.9905
Iter: 20, acc: 0.9909
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