keras搬砖系列-GoogLeNet

GoogLeNet小结

emmm，应该不算小结吧，充其量就是蜻蜓点水，所有的东西都等考试再弄吧。Andrew课对inception讲的很好。

主要的创新在于他的Inception，这是一种网中网（Network In Network）的结构，即原来的结点也是一个网络。Inception一直在不断发展，目前已经V2、V3、V4了，感兴趣的同学可以查阅相关资料。Inception的结构如图9所示，其中1*1卷积主要用来降维，用了Inception之后整个网络结构的宽度和深度都可扩大，能够带来2-3倍的性能提升。

现如今，GPU设备已经很好了，所以大家通常做法是牺牲运行速度来得到最大性能。

keras代码：

#coding=utf-8
from keras.models import Model
from keras.layers import Input,Dense,Dropout,BatchNormalization,Conv2D,MaxPooling2D,AveragePooling2D,concatenate
from keras.layers.convolutional import Conv2D,MaxPooling2D,AveragePooling2D
import numpy as np
seed = 7
np.random.seed(seed)

def Conv2d_BN(x, nb_filter,kernel_size, padding='same',strides=(1,1),name=None):
    if name is not None:
        bn_name = name + '_bn'
        conv_name = name + '_conv'
    else:
        bn_name = None
        conv_name = None

    x = Conv2D(nb_filter,kernel_size,padding=padding,strides=strides,activation='relu',name=conv_name)(x)
    x = BatchNormalization(axis=3,name=bn_name)(x)
    return x

def Inception(x,nb_filter):
    branch1x1 = Conv2d_BN(x,nb_filter,(1,1), padding='same',strides=(1,1),name=None)

    branch3x3 = Conv2d_BN(x,nb_filter,(1,1), padding='same',strides=(1,1),name=None)
    branch3x3 = Conv2d_BN(branch3x3,nb_filter,(3,3), padding='same',strides=(1,1),name=None)

    branch5x5 = Conv2d_BN(x,nb_filter,(1,1), padding='same',strides=(1,1),name=None)
    branch5x5 = Conv2d_BN(branch5x5,nb_filter,(1,1), padding='same',strides=(1,1),name=None)

    branchpool = MaxPooling2D(pool_size=(3,3),strides=(1,1),padding='same')(x)
    branchpool = Conv2d_BN(branchpool,nb_filter,(1,1),padding='same',strides=(1,1),name=None)

    x = concatenate([branch1x1,branch3x3,branch5x5,branchpool],axis=3)

    return x

inpt = Input(shape=(224,224,3))
#padding = 'same'，填充为(步长-1）/2,还可以用ZeroPadding2D((3,3))
x = Conv2d_BN(inpt,64,(7,7),strides=(2,2),padding='same')
x = MaxPooling2D(pool_size=(3,3),strides=(2,2),padding='same')(x)
x = Conv2d_BN(x,192,(3,3),strides=(1,1),padding='same')
x = MaxPooling2D(pool_size=(3,3),strides=(2,2),padding='same')(x)
x = Inception(x,64)#256
x = Inception(x,120)#480
x = MaxPooling2D(pool_size=(3,3),strides=(2,2),padding='same')(x)
x = Inception(x,128)#512
x = Inception(x,128)
x = Inception(x,128)
x = Inception(x,132)#528
x = Inception(x,208)#832
x = MaxPooling2D(pool_size=(3,3),strides=(2,2),padding='same')(x)
x = Inception(x,208)
x = Inception(x,256)#1024
x = AveragePooling2D(pool_size=(7,7),strides=(7,7),padding='same')(x)
x = Dropout(0.4)(x)
x = Dense(1000,activation='relu')(x)
x = Dense(1000,activation='softmax')(x)
model = Model(inpt,x,name='inception')
model.compile(loss='categorical_crossentropy',optimizer='sgd',metrics=['accuracy'])
model.summary()