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自学教程：keras根据层名称来初始化网络
51自学网 2021-12-02 12:11:38
  Keras
这篇教程keras根据层名称来初始化网络写得很实用，希望能帮到您。

keras根据层名称来初始化网络

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def get_model(input_shape1=[75, 75, 3], input_shape2=[1], weights=None):
 bn_model = 0
 trainable = True
 # kernel_regularizer = regularizers.l2(1e-4)
 kernel_regularizer = None
 activation = 'relu'
 
 img_input = Input(shape=input_shape1)
 angle_input = Input(shape=input_shape2)
 
 # Block 1
 x = Conv2D(64, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block1_conv1')(img_input)
 x = Conv2D(64, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block1_conv2')(x)
 x = MaxPooling2D((2, 2), strides=(2, 2), name='block1_pool')(x)
 
 # Block 2
 x = Conv2D(128, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block2_conv1')(x)
 x = Conv2D(128, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block2_conv2')(x)
 x = MaxPooling2D((2, 2), strides=(2, 2), name='block2_pool')(x)
 
 # Block 3
 x = Conv2D(256, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block3_conv1')(x)
 x = Conv2D(256, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block3_conv2')(x)
 x = Conv2D(256, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block3_conv3')(x)
 x = MaxPooling2D((2, 2), strides=(2, 2), name='block3_pool')(x)
 
 # Block 4
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block4_conv1')(x)
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block4_conv2')(x)
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block4_conv3')(x)
 x = MaxPooling2D((2, 2), strides=(2, 2), name='block4_pool')(x)
 
 # Block 5
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block5_conv1')(x)
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block5_conv2')(x)
 x = Conv2D(512, (3, 3), activation=activation, padding='same',
    trainable=trainable, kernel_regularizer=kernel_regularizer,
    name='block5_conv3')(x)
 x = MaxPooling2D((2, 2), strides=(2, 2), name='block5_pool')(x)
 
 branch_1 = GlobalMaxPooling2D()(x)
 # branch_1 = BatchNormalization(momentum=bn_model)(branch_1)
 
 branch_2 = GlobalAveragePooling2D()(x)
 # branch_2 = BatchNormalization(momentum=bn_model)(branch_2)
 
 branch_3 = BatchNormalization(momentum=bn_model)(angle_input)
 
 x = (Concatenate()([branch_1, branch_2, branch_3]))
 x = Dense(1024, activation=activation, kernel_regularizer=kernel_regularizer)(x)
 # x = Dropout(0.5)(x)
 x = Dense(1024, activation=activation, kernel_regularizer=kernel_regularizer)(x)
 x = Dropout(0.6)(x)
 output = Dense(1, activation='sigmoid')(x)
 
 model = Model([img_input, angle_input], output)
 optimizer = Adam(lr=1e-5, beta_1=0.9, beta_2=0.999, epsilon=1e-8, decay=0.0)
 model.compile(loss='binary_crossentropy', optimizer=optimizer, metrics=['accuracy'])
 
 if weights is not None:
  # 将by_name设置成True
  model.load_weights(weights, by_name=True)
  # layer_weights = h5py.File(weights, 'r')
  # for idx in range(len(model.layers)):
  #  model.set_weights()
 print 'have prepared the model.'
 
 return model

补充知识：keras.layers.Dense()方法

keras.layers.Dense()是定义网络层的基本方法，执行的操作是：output = activation（dot（input，kernel）+ bias。

其中activation是激活函数，kernel是权重矩阵，bias是偏向量。如果层输入大于2，在进行初始点积之前会将其展平。

代码如下：

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class Dense(Layer):
 """Just your regular densely-connected NN layer.
 `Dense` implements the operation:
 `output = activation(dot(input, kernel) + bias)`
 where `activation` is the element-wise activation function
 passed as the `activation` argument, `kernel` is a weights matrix
 created by the layer, and `bias` is a bias vector created by the layer
 (only applicable if `use_bias` is `True`).
 Note: if the input to the layer has a rank greater than 2, then
 it is flattened prior to the initial dot product with `kernel`.
 # Example
 ```python
  # as first layer in a sequential model:
  model = Sequential()
  model.add(Dense(32, input_shape=(16,)))
  # now the model will take as input arrays of shape (*, 16)
  # and output arrays of shape (*, 32)
  # after the first layer, you don't need to specify
  # the size of the input anymore:
  model.add(Dense(32))
 ```
 # Arguments
  units: Positive integer, dimensionality of the output space.
  activation: Activation function to use
   (see [activations](../activations.md)).
   If you don't specify anything, no activation is applied
   (ie. "linear" activation: `a(x) = x`).
  use_bias: Boolean, whether the layer uses a bias vector.
  kernel_initializer: Initializer for the `kernel` weights matrix
   (see [initializers](../initializers.md)).
  bias_initializer: Initializer for the bias vector
   (see [initializers](../initializers.md)).
  kernel_regularizer: Regularizer function applied to
   the `kernel` weights matrix
   (see [regularizer](../regularizers.md)).
  bias_regularizer: Regularizer function applied to the bias vector
   (see [regularizer](../regularizers.md)).
  activity_regularizer: Regularizer function applied to
   the output of the layer (its "activation").
   (see [regularizer](../regularizers.md)).
  kernel_constraint: Constraint function applied to
   the `kernel` weights matrix
   (see [constraints](../constraints.md)).
  bias_constraint: Constraint function applied to the bias vector
   (see [constraints](../constraints.md)).
 # Input shape
  nD tensor with shape: `(batch_size, ..., input_dim)`.
  The most common situation would be
  a 2D input with shape `(batch_size, input_dim)`.
 # Output shape
  nD tensor with shape: `(batch_size, ..., units)`.
  For instance, for a 2D input with shape `(batch_size, input_dim)`,
  the output would have shape `(batch_size, units)`.
 """
  
 @interfaces.legacy_dense_support
 def __init__(self, units,
     activation=None,
     use_bias=True,
     kernel_initializer='glorot_uniform',
     bias_initializer='zeros',
     kernel_regularizer=None,
     bias_regularizer=None,
     activity_regularizer=None,
     kernel_constraint=None,
     bias_constraint=None,
     **kwargs):
  if 'input_shape' not in kwargs and 'input_dim' in kwargs:
   kwargs['input_shape'] = (kwargs.pop('input_dim'),)
  super(Dense, self).__init__(**kwargs)
  self.units = units
  self.activation = activations.get(activation)
  self.use_bias = use_bias
  self.kernel_initializer = initializers.get(kernel_initializer)
  self.bias_initializer = initializers.get(bias_initializer)
  self.kernel_regularizer = regularizers.get(kernel_regularizer)
  self.bias_regularizer = regularizers.get(bias_regularizer)
  self.activity_regularizer = regularizers.get(activity_regularizer)
  self.kernel_constraint = constraints.get(kernel_constraint)
  self.bias_constraint = constraints.get(bias_constraint)
  self.input_spec = InputSpec(min_ndim=2)
  self.supports_masking = True
  
 def build(self, input_shape):
  assert len(input_shape) >= 2
  input_dim = input_shape[-1]
  
  self.kernel = self.add_weight(shape=(input_dim, self.units),
          initializer=self.kernel_initializer,
          name='kernel',
          regularizer=self.kernel_regularizer,
          constraint=self.kernel_constraint)
  if self.use_bias:
   self.bias = self.add_weight(shape=(self.units,),
          initializer=self.bias_initializer,
          name='bias',
          regularizer=self.bias_regularizer,
          constraint=self.bias_constraint)
  else:
   self.bias = None
  self.input_spec = InputSpec(min_ndim=2, axes={-1: input_dim})
  self.built = True
  
 def call(self, inputs):
  output = K.dot(inputs, self.kernel)
  if self.use_bias:
   output = K.bias_add(output, self.bias)
  if self.activation is not None:
   output = self.activation(output)
  return output
  
 def compute_output_shape(self, input_shape):
  assert input_shape and len(input_shape) >= 2
  assert input_shape[-1]
  output_shape = list(input_shape)
  output_shape[-1] = self.units
  return tuple(output_shape)
  
 def get_config(self):
  config = {
   'units': self.units,
   'activation': activations.serialize(self.activation),
   'use_bias': self.use_bias,
   'kernel_initializer': initializers.serialize(self.kernel_initializer),
   'bias_initializer': initializers.serialize(self.bias_initializer),
   'kernel_regularizer': regularizers.serialize(self.kernel_regularizer),
   'bias_regularizer': regularizers.serialize(self.bias_regularizer),
   'activity_regularizer': regularizers.serialize(self.activity_regularizer),
   'kernel_constraint': constraints.serialize(self.kernel_constraint),
   'bias_constraint': constraints.serialize(self.bias_constraint)
  }
  base_config = super(Dense, self).get_config()
  return dict(list(base_config.items()) + list(config.items()))

参数说明如下：

units：正整数，输出空间的维数。

activation: 激活函数。如果未指定任何内容，则不会应用任何激活函数。即“线性”激活：a（x）= x）。

use_bias：Boolean，该层是否使用偏向量。

kernel_initializer：权重矩阵的初始化方法。

bias_initializer：偏向量的初始化方法。

kernel_regularizer：权重矩阵的正则化方法。

bias_regularizer：偏向量的正则化方法。

activity_regularizer：输出层正则化方法。

kernel_constraint：权重矩阵约束函数。

bias_constraint：偏向量约束函数。

以上这篇使用keras根据层名称来初始化网络就是小编分享给大家的全部内容


ImageDataGenerator参数详解及用法
Python layers.ActivityRegularization方法代码示例
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