论文地址：[1409.4842] Going Deeper with Convolutions (arxiv.org)
一、GoogLeNet概述
创新点
我认为，这篇文章最大的创新点是引入了一个名为Inception块的结构，能够增加神经网络模型大小的同时，减缓参数量的爆炸式增长，从而提升神经网络模型的表现。
准确率
一个简单的网络，是无法达到很好的表现，因为它的参数简单，表达的信息很少。所以我们想要一个表现很好的网络模型，我们就需要将这个网络变宽、变深。对应到网络模型中就是增加网络的层数（变深），增加通道数（变宽）。
问题
有过基础知识的我们都知道，增加网络的层数和通道数，这件事会让模型的参数增加，会需要占用很多的算力，我们有可能算不动；而且参数多了，容易过拟合。
所以我们需要一个能够代替堆叠卷积层，既可以让网络变宽变深的同时，又能够让参数爆炸式增长的东西。
解决方法
本文提出了一个名为Inception的模块，如图2，可以实现在不改变图片尺寸的前提下，只改变输入输出的通道数，关键这个模块比使用较大的kernel的卷积核所带来的参数量更少，使用Inception模块就可以让网络变宽变深，从而提高模型的准确率。
二、GoogLeNet网络结构
GoogLeNet开始模块
GoogLeNet架构
Inception Module基本组成结构有四个成分：1x1卷积，3x3卷积，5x5卷积，3x3最大池化，最后对四个成分运算结果进行通道上组合，这就是Naive Inception的核心思想：利用不同大小的卷积核实现不同尺度的感知，最后进行融合，可以得到图像更好的表征。
注意：每个分支得到的特征矩阵高和宽必须相同。
但是Naive Inception有两个非常严重的问题：首先，所有卷积层直接和前一层输入的数据对接，所以卷积层中的计算量会很大；其次，在这个单元中使用的最大池化层保留了输入数据的特征图的深度，所以在最后进行合并时，总的输出的特征图的深度只会增加，这样增加了该单元之后的网络结构的计算量。所以这里使用1x1 卷积核主要目的是进行压缩降维，减少参数量，也就是上图b，从而让网络更深、更宽，更好的提取特征，这种思想也称为Pointwise Conv，简称PW。
三、GoogLeNet使用PyTorch框架实现
因需要对GPU显存要求过高，本人在kaggle上的GPU T4X2上运行的
kaggle地址：GoogLeNet | Kaggle
import torch
from torch import nn
import sys
sys.path.append("../input/d2ld2l")
import d2l
from d2l.torch import load_data_fashion_mnist
from d2l.torch import train_ch6
from d2l.torch import try_gpuclass Inception(nn.Module):def __init__(self,in_channels,c1,c2,c3,c4,**kwarqs):super(Inception,self).__init__(**kwarqs)self.p1 = nn.Sequential(nn.Conv2d(in_channels,c1,kernel_size=1),nn.ReLU())self.p2 = nn.Sequential(nn.Conv2d(in_channels,c2[0],kernel_size=1),nn.ReLU(),nn.Conv2d(c2[0],c2[1],kernel_size=3,padding=1),nn.ReLU())self.p3 = nn.Sequential(nn.Conv2d(in_channels,c3[0],kernel_size=1),nn.ReLU(),nn.Conv2d(c3[0],c3[1],kernel_size=5,padding=2),nn.ReLU())self.p4 = nn.Sequential(nn.MaxPool2d(kernel_size=3,padding=1,stride=1),nn.Conv2d(in_channels,c4,kernel_size=1),nn.ReLU())def forward(self,x):return torch.cat((self.p1(x),self.p2(x),self.p3(x),self.p4(x)),dim=1)in_channels =1
b1 = nn.Sequential(nn.Conv2d(in_channels,64,kernel_size=7,stride=2,padding=3),nn.ReLU(),nn.MaxPool2d(kernel_size=3,stride=2,padding=1)
)
b2 = nn.Sequential(nn.Conv2d(64,64,kernel_size=1),nn.ReLU(),nn.Conv2d(64,192,kernel_size=3,padding=1),nn.ReLU(),nn.MaxPool2d(kernel_size=3,stride=2,padding=1)
)
b3 = nn.Sequential(Inception(192,64,(96,128),(16,32),32),Inception(256,128,(128,192),(32,96),64),nn.MaxPool2d(kernel_size=3,stride=2,padding=1)
)b4 = nn.Sequential(Inception(480,192,(96,208),(16,48),64),Inception(512,160,(112,224),(24,64),64),Inception(512,128,(128,256),(24,64),64),Inception(512,112,(144,288),(32,64),64),Inception(528,256,(160,320),(32,128),128),nn.MaxPool2d(kernel_size=3,stride=2,padding=1)
)b5 = nn.Sequential(Inception(832,256,(160,320),(32,128),128),Inception(832,384,(192,384),(48,128),128),nn.AdaptiveAvgPool2d((1,1)),nn.Dropout(p=0.4),nn.Flatten()
)
net = nn.Sequential(b1,b2,b3,b4,b5,nn.Linear(1024,10))test = torch.rand((1,1,224,224))
for layer in net:test = layer(test)print(layer.__class__.__name__,'output shape:\t',test.shape)
lr,num_epochs,batch_size = 0.1,10,128
train_iter,test_iter = load_data_fashion_mnist(batch_size,resize=128)
train_ch6(net,train_iter,test_iter,num_epochs,lr,try_gpu())
四、GoogLeNet使用keras框架实现
1、导入库
import cv2
import numpy as np
import keras
import math
import keras.backend as K
import tensorflow as tf
from keras.datasets import cifar10
from keras.models import Model
from keras.layers import Conv2D, MaxPool2D, \Dropout, Dense, Input, concatenate, \GlobalAveragePooling2D, AveragePooling2D,\Flatten
from keras.datasets import cifar10
from keras import backend as K
from keras.utils import to_categorical
from keras.optimizers import SGD
from keras.callbacks import LearningRateScheduler2、准备数据集
num_classes = 10def load_cifar10_data(img_rows, img_cols):# Load cifar10 training and validation sets(X_train, Y_train), (X_valid, Y_valid) = cifar10.load_data()# Resize training imagesX_train = np.array([cv2.resize(img, (img_rows,img_cols)) for img in X_train[:,:,:,:]])X_valid = np.array([cv2.resize(img, (img_rows,img_cols)) for img in X_valid[:,:,:,:]])# Transform targets to keras compatible formatY_train = to_categorical(Y_train, num_classes)Y_valid = to_categorical(Y_valid, num_classes)X_train = X_train.astype('float32')X_valid = X_valid.astype('float32')# preprocess dataX_train = X_train / 255.0X_valid = X_valid / 255.0return X_train, Y_train, X_valid, Y_validX_train, y_train, X_test, y_test = load_cifar10_data(224, 224)3、创建初始模块
def inception_module(x,filters_1x1,filters_3x3_reduce,filters_3x3,filters_5x5_reduce,filters_5x5,filters_pool_proj,name=None):conv_1x1 = Conv2D(filters_1x1, (1, 1), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(x)conv_3x3 = Conv2D(filters_3x3_reduce, (1, 1), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(x)conv_3x3 = Conv2D(filters_3x3, (3, 3), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(conv_3x3)conv_5x5 = Conv2D(filters_5x5_reduce, (1, 1), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(x)conv_5x5 = Conv2D(filters_5x5, (5, 5), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(conv_5x5)pool_proj = MaxPool2D((3, 3), strides=(1, 1), padding='same')(x)pool_proj = Conv2D(filters_pool_proj, (1, 1), padding='same', activation='relu', kernel_initializer=kernel_init, bias_initializer=bias_init)(pool_proj)output = concatenate([conv_1x1, conv_3x3, conv_5x5, pool_proj], axis=3, name=name)return output4.创建 GoogLeNet 架构
kernel_init = keras.initializers.glorot_uniform()
bias_init = keras.initializers.Constant(value=0.2)input_layer = Input(shape=(224, 224, 3))x = Conv2D(64, (7, 7), padding='same', strides=(2, 2), activation='relu', name='conv_1_7x7/2', kernel_initializer=kernel_init, bias_initializer=bias_init)(input_layer)
x = MaxPool2D((3, 3), padding='same', strides=(2, 2), name='max_pool_1_3x3/2')(x)
# x = Conv2D(64, (1, 1) padding='same', strides=(1, 1), activation='relu', name='conv_2a_3x3/1')(x)
x = Conv2D(192, (3, 3), padding='same', strides=(1, 1), activation='relu', name='conv_2b_3x3/1')(x)
x = MaxPool2D((3, 3), padding='same', strides=(2, 2), name='max_pool_2_3x3/2')(x)x = inception_module(x,filters_1x1=64,filters_3x3_reduce=96,filters_3x3=128,filters_5x5_reduce=16,filters_5x5=32,filters_pool_proj=32,name='inception_3a')x = inception_module(x,filters_1x1=128,filters_3x3_reduce=128,filters_3x3=192,filters_5x5_reduce=32,filters_5x5=96,filters_pool_proj=64,name='inception_3b')x = MaxPool2D((3, 3), padding='same', strides=(2, 2), name='max_pool_3_3x3/2')(x)x = inception_module(x,filters_1x1=192,filters_3x3_reduce=96,filters_3x3=208,filters_5x5_reduce=16,filters_5x5=48,filters_pool_proj=64,name='inception_4a')classifier_1 = AveragePooling2D((5, 5), strides=3)(x)
classifier_1 = Conv2D(128, (1, 1), padding='same', activation='relu')(classifier_1)
classifier_1 = Flatten()(classifier_1)
classifier_1 = Dense(1024, activation='relu')(classifier_1)
classifier_1 = Dropout(0.7)(classifier_1)
classifier_1 = Dense(10, activation='softmax', name='auxilliary_output_1')(classifier_1)x = inception_module(x,filters_1x1=160,filters_3x3_reduce=112,filters_3x3=224,filters_5x5_reduce=24,filters_5x5=64,filters_pool_proj=64,name='inception_4b')x = inception_module(x,filters_1x1=128,filters_3x3_reduce=128,filters_3x3=256,filters_5x5_reduce=24,filters_5x5=64,filters_pool_proj=64,name='inception_4c')x = inception_module(x,filters_1x1=112,filters_3x3_reduce=144,filters_3x3=288,filters_5x5_reduce=32,filters_5x5=64,filters_pool_proj=64,name='inception_4d')classifier_2 = AveragePooling2D((5, 5), strides=3)(x)
classifier_2 = Conv2D(128, (1, 1), padding='same', activation='relu')(classifier_2)
classifier_2 = Flatten()(classifier_2)
classifier_2 = Dense(1024, activation='relu')(classifier_2)
classifier_2 = Dropout(0.7)(classifier_2)
classifier_2 = Dense(10, activation='softmax', name='auxilliary_output_2')(classifier_2)x = inception_module(x,filters_1x1=256,filters_3x3_reduce=160,filters_3x3=320,filters_5x5_reduce=32,filters_5x5=128,filters_pool_proj=128,name='inception_4e')x = MaxPool2D((3, 3), padding='same', strides=(2, 2), name='max_pool_4_3x3/2')(x)x = inception_module(x,filters_1x1=256,filters_3x3_reduce=160,filters_3x3=320,filters_5x5_reduce=32,filters_5x5=128,filters_pool_proj=128,name='inception_5a')x = inception_module(x,filters_1x1=384,filters_3x3_reduce=192,filters_3x3=384,filters_5x5_reduce=48,filters_5x5=128,filters_pool_proj=128,name='inception_5b')x = AveragePooling2D(pool_size=(7,7), strides=1, padding='valid',name='avg_pool_5_3x3/1')(x)x = Dropout(0.4)(x)
x = Dense(1000, activation='relu', name='linear')(x)
x = Dense(1000, activation='softmax', name='output')(x)不带 1 类和 2 类过滤器的 GoogleNet 模型
model = Model(input_layer, [x], name='googlenet')model.summary()添加分类器 1 和 2 后的 GoogLeNet 模型
model_with_classifiers = Model(input_layer, [x, classifier_1, classifier_2], name='googlenet_complete_architecture')
model_with_classifiers.summary()用三个模型编制网络
epochs = 25
initial_lrate = 0.01def decay(epoch, steps=100):initial_lrate = 0.01drop = 0.96epochs_drop = 8lrate = initial_lrate * math.pow(drop, math.floor((1+epoch)/epochs_drop))return lratesgd = SGD(lr=initial_lrate, momentum=0.9, nesterov=False)lr_sc = LearningRateScheduler(decay, verbose=1)model_with_classifiers.compile(loss=['categorical_crossentropy', 'categorical_crossentropy', 'categorical_crossentropy'], loss_weights=[1, 0.3, 0.3], optimizer=sgd, metrics=['accuracy'])history = model_with_classifiers.fit(X_train, [y_train, y_train, y_train], validation_data=(X_test, [y_test, y_test, y_test]), epochs=epochs, batch_size=256, callbacks=[lr_sc])
