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使用keras實(shí)現(xiàn)孿生網(wǎng)絡(luò)中的權(quán)值共享教程

更新時(shí)間：2020年06月11日 10:17:38 作者：Master He

這篇文章主要介紹了使用keras實(shí)現(xiàn)孿生網(wǎng)絡(luò)中的權(quán)值共享教程，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。一起跟隨小編過來看看吧

首先聲明，這里的權(quán)值共享指的不是CNN原理中的共享權(quán)值，而是如何在構(gòu)建類似于Siamese Network這樣的多分支網(wǎng)絡(luò)，且分支結(jié)構(gòu)相同時(shí)，如何使用keras使分支的權(quán)重共享。

Functional API

為達(dá)到上述的目的，建議使用keras中的Functional API，當(dāng)然Sequential 類型的模型也可以使用，本篇博客將主要以Functional API為例講述。

keras的多分支權(quán)值共享功能實(shí)現(xiàn)，官方文檔介紹

上面是官方的鏈接，本篇博客也是基于上述官方文檔，實(shí)現(xiàn)的此功能。(插一句，keras雖然有中文文檔，但中文文檔已停更，且中文文檔某些函數(shù)介紹不全，建議直接看英文官方文檔)

不共享參數(shù)的模型

以MatchNet網(wǎng)絡(luò)結(jié)構(gòu)為例子，為方便顯示，將卷積模塊個(gè)數(shù)減為2個(gè)。首先是展示不共享參數(shù)的模型，以便觀看完整的網(wǎng)絡(luò)結(jié)構(gòu)。

整體的網(wǎng)絡(luò)結(jié)構(gòu)如下所示：

代碼包含兩部分，第一部分定義了兩個(gè)函數(shù)，F(xiàn)eatureNetwork()生成特征提取網(wǎng)絡(luò)，ClassiFilerNet()生成決策網(wǎng)絡(luò)或稱度量網(wǎng)絡(luò)。網(wǎng)絡(luò)結(jié)構(gòu)的可視化在博客末尾。在ClassiFilerNet()函數(shù)中，可以看到調(diào)用了兩次FeatureNetwork()函數(shù)，keras.models.Model也被使用的兩次，因此生成的input1和input2是兩個(gè)完全獨(dú)立的模型分支，參數(shù)是不共享的。

from keras.models import Sequential
from keras.layers import merge, Conv2D, MaxPool2D, Activation, Dense, concatenate, Flatten
from keras.layers import Input
from keras.models import Model
from keras.utils import np_utils
import tensorflow as tf
import keras
from keras.datasets import mnist
import numpy as np
from keras.utils import np_utils
from keras.callbacks import EarlyStopping, ModelCheckpoint, TensorBoard, ReduceLROnPlateau
from keras.utils.vis_utils import plot_model

# ---------------------函數(shù)功能區(qū)-------------------------
def FeatureNetwork():
  """生成特征提取網(wǎng)絡(luò)"""
  """這是根據(jù)，MNIST數(shù)據(jù)調(diào)整的網(wǎng)絡(luò)結(jié)構(gòu)，下面注釋掉的部分是，原始的Matchnet網(wǎng)絡(luò)中feature network結(jié)構(gòu)"""
  inp = Input(shape = (28, 28, 1), name='FeatureNet_ImageInput')
  models = Conv2D(filters=24, kernel_size=(3, 3), strides=1, padding='same')(inp)
  models = Activation('relu')(models)
  models = MaxPool2D(pool_size=(3, 3))(models)

  models = Conv2D(filters=64, kernel_size=(3, 3), strides=1, padding='same')(models)
  # models = MaxPool2D(pool_size=(3, 3), strides=(2, 2))(models)
  models = Activation('relu')(models)

  models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
  models = Activation('relu')(models)

  models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
  models = Activation('relu')(models)
  models = Flatten()(models)
  models = Dense(512)(models)
  models = Activation('relu')(models)
  model = Model(inputs=inp, outputs=models)
  return model

def ClassiFilerNet(): # add classifier Net
  """生成度量網(wǎng)絡(luò)和決策網(wǎng)絡(luò)，其實(shí)maychnet是兩個(gè)網(wǎng)絡(luò)結(jié)構(gòu)，一個(gè)是特征提取層(孿生)，一個(gè)度量層+匹配層(統(tǒng)稱為決策層)"""
  input1 = FeatureNetwork()           # 孿生網(wǎng)絡(luò)中的一個(gè)特征提取
  input2 = FeatureNetwork()           # 孿生網(wǎng)絡(luò)中的另一個(gè)特征提取
  for layer in input2.layers:          # 這個(gè)for循環(huán)一定要加，否則網(wǎng)絡(luò)重名會(huì)出錯(cuò)。
    layer.name = layer.name + str("_2")
  inp1 = input1.input
  inp2 = input2.input
  merge_layers = concatenate([input1.output, input2.output])    # 進(jìn)行融合，使用的是默認(rèn)的sum，即簡單的相加
  fc1 = Dense(1024, activation='relu')(merge_layers)
  fc2 = Dense(1024, activation='relu')(fc1)
  fc3 = Dense(2, activation='softmax')(fc2)

  class_models = Model(inputs=[inp1, inp2], outputs=[fc3])
  return class_models

# ---------------------主調(diào)區(qū)-------------------------
matchnet = ClassiFilerNet()
matchnet.summary() # 打印網(wǎng)絡(luò)結(jié)構(gòu)
plot_model(matchnet, to_file='G:/csdn攻略/picture/model.png') # 網(wǎng)絡(luò)結(jié)構(gòu)輸出成png圖片

共享參數(shù)的模型

FeatureNetwork()的功能和上面的功能相同，為方便選擇，在ClassiFilerNet()函數(shù)中加入了判斷是否使用共享參數(shù)模型功能，令reuse=True，便使用的是共享參數(shù)的模型。

關(guān)鍵地方就在，只使用的一次Model，也就是說只創(chuàng)建了一次模型，雖然輸入了兩個(gè)輸入，但其實(shí)使用的是同一個(gè)模型，因此權(quán)重共享的。

from keras.models import Sequential
from keras.layers import merge, Conv2D, MaxPool2D, Activation, Dense, concatenate, Flatten
from keras.layers import Input
from keras.models import Model
from keras.utils import np_utils
import tensorflow as tf
import keras
from keras.datasets import mnist
import numpy as np
from keras.utils import np_utils
from keras.callbacks import EarlyStopping, ModelCheckpoint, TensorBoard, ReduceLROnPlateau
from keras.utils.vis_utils import plot_model

# ----------------函數(shù)功能區(qū)-----------------------
def FeatureNetwork():
  """生成特征提取網(wǎng)絡(luò)"""
  """這是根據(jù)，MNIST數(shù)據(jù)調(diào)整的網(wǎng)絡(luò)結(jié)構(gòu)，下面注釋掉的部分是，原始的Matchnet網(wǎng)絡(luò)中feature network結(jié)構(gòu)"""
  inp = Input(shape = (28, 28, 1), name='FeatureNet_ImageInput')
  models = Conv2D(filters=24, kernel_size=(3, 3), strides=1, padding='same')(inp)
  models = Activation('relu')(models)
  models = MaxPool2D(pool_size=(3, 3))(models)

  models = Conv2D(filters=64, kernel_size=(3, 3), strides=1, padding='same')(models)
  # models = MaxPool2D(pool_size=(3, 3), strides=(2, 2))(models)
  models = Activation('relu')(models)

  models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
  models = Activation('relu')(models)

  models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
  models = Activation('relu')(models)

  # models = Conv2D(64, kernel_size=(3, 3), strides=2, padding='valid')(models)
  # models = Activation('relu')(models)
  # models = MaxPool2D(pool_size=(3, 3), strides=(2, 2))(models)
  models = Flatten()(models)
  models = Dense(512)(models)
  models = Activation('relu')(models)
  model = Model(inputs=inp, outputs=models)
  return model

def ClassiFilerNet(reuse=False): # add classifier Net
  """生成度量網(wǎng)絡(luò)和決策網(wǎng)絡(luò)，其實(shí)maychnet是兩個(gè)網(wǎng)絡(luò)結(jié)構(gòu)，一個(gè)是特征提取層(孿生)，一個(gè)度量層+匹配層(統(tǒng)稱為決策層)"""

  if reuse:
    inp = Input(shape=(28, 28, 1), name='FeatureNet_ImageInput')
    models = Conv2D(filters=24, kernel_size=(3, 3), strides=1, padding='same')(inp)
    models = Activation('relu')(models)
    models = MaxPool2D(pool_size=(3, 3))(models)

    models = Conv2D(filters=64, kernel_size=(3, 3), strides=1, padding='same')(models)
    # models = MaxPool2D(pool_size=(3, 3), strides=(2, 2))(models)
    models = Activation('relu')(models)

    models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
    models = Activation('relu')(models)

    models = Conv2D(filters=96, kernel_size=(3, 3), strides=1, padding='valid')(models)
    models = Activation('relu')(models)

    # models = Conv2D(64, kernel_size=(3, 3), strides=2, padding='valid')(models)
    # models = Activation('relu')(models)
    # models = MaxPool2D(pool_size=(3, 3), strides=(2, 2))(models)
    models = Flatten()(models)
    models = Dense(512)(models)
    models = Activation('relu')(models)
    model = Model(inputs=inp, outputs=models)

    inp1 = Input(shape=(28, 28, 1)) # 創(chuàng)建輸入
    inp2 = Input(shape=(28, 28, 1)) # 創(chuàng)建輸入2
    model_1 = model(inp1) # 孿生網(wǎng)絡(luò)中的一個(gè)特征提取分支
    model_2 = model(inp2) # 孿生網(wǎng)絡(luò)中的另一個(gè)特征提取分支
    merge_layers = concatenate([model_1, model_2]) # 進(jìn)行融合，使用的是默認(rèn)的sum，即簡單的相加

  else:
    input1 = FeatureNetwork()           # 孿生網(wǎng)絡(luò)中的一個(gè)特征提取
    input2 = FeatureNetwork()           # 孿生網(wǎng)絡(luò)中的另一個(gè)特征提取
    for layer in input2.layers:          # 這個(gè)for循環(huán)一定要加，否則網(wǎng)絡(luò)重名會(huì)出錯(cuò)。
      layer.name = layer.name + str("_2")
    inp1 = input1.input
    inp2 = input2.input
    merge_layers = concatenate([input1.output, input2.output])    # 進(jìn)行融合，使用的是默認(rèn)的sum，即簡單的相加
  fc1 = Dense(1024, activation='relu')(merge_layers)
  fc2 = Dense(1024, activation='relu')(fc1)
  fc3 = Dense(2, activation='softmax')(fc2)

  class_models = Model(inputs=[inp1, inp2], outputs=[fc3])
  return class_models

如何看是否真的是權(quán)值共享呢？直接對(duì)比特征提取部分的網(wǎng)絡(luò)參數(shù)個(gè)數(shù)！

不共享參數(shù)模型的參數(shù)數(shù)量：

共享參數(shù)模型的參數(shù)總量

共享參數(shù)模型中的特征提取部分的參數(shù)量為：

由于截圖限制，不共享參數(shù)模型的特征提取網(wǎng)絡(luò)參數(shù)數(shù)量不再展示。其實(shí)經(jīng)過計(jì)算，特征提取網(wǎng)絡(luò)部分的參數(shù)數(shù)量，不共享參數(shù)模型是共享參數(shù)的兩倍。兩個(gè)網(wǎng)絡(luò)總參數(shù)量的差值就是，共享模型中，特征提取部分的參數(shù)的量

網(wǎng)絡(luò)結(jié)構(gòu)可視化

不共享權(quán)重的網(wǎng)絡(luò)結(jié)構(gòu)