搭建模块化的神经网络八股:
前向传播就是搭建网络,设计网络结构(forward.py)
一般新建一个forward.py文件来描述前向传播过程,一般包括下面几个函数:
def forward(x, regularizer): """ 定义了前向传播过程 :param x: 输入x :param regularizer: 正则化权重 :return: 返回y """ w = b = y = return y def get_weight(shape, regularizer): w = tf.Variable( ) tf.add_to_collection('losses', tf.contrib.layers.l2_regularizer(regularizer)(w)) return w def get_bias(shape): b = tf.Variable( ) return b
反向传播就是训练网络,优化网络参数(backward.py)
同样,一般新建一个backward.py文件来描述反向传播过程,一般包含以下内容:
def backward(): x = tf.placehoder( ) y_ = tf.placehoder( ) y = forward.forward(x, REGULARIZER) global_step = tf.Variable(0, trainable=False) loss =
正则化过程
loss可以是y与y_的差距(loss_mse)=tf.reduce_mean(tf.square(y-y_))
也可以是:
ce=tf.nn.sparse_softmax_cross_entropy_with_logits(logite=y, labels=tf.argmax(y_, 1))
y与y_的差距(cem) = tf.reduce_mean(ce)
加入正则化后:
loss = y与y_的差距 + tf.add_n(tf.get_colection('losses))
指数衰减学习率:(如果要使用,加下面的代码)
learning_rate = tf.train.exponential_decay( LEARNING_RATE_BASE, global_step, 数据集总样本数/BATCH_SIZE, LEARNING_RATE_DECAY, staircase=True )
train_step = tf.train.GradientDescentOptimizer(learning_rate).minimize(loss, global_step=global_step)
滑动平均:(如果要使用,加下面代码)
ema = tf.train.ExponentialMovingAverage(MOVING_AVERAGE_DECAY, global_step) ema_op = ema.apply(tf.trainable_variables()) # tf.trainable_variables()是所有待训练参数 with tf.control_dependencies([train_step,ema_op]): train_op = tf.no_op(name='train')
with tf.Session() as sess: # 初始化 init_op = tf.global_variables_initializer() sess.run(init_op) for i in range(STEPS): sess.run(train_step, feed_dict={x: ,y_: }) if i % 轮数 == 0: print () if __name__=='__main__': backward()