bn值的計算方法？

BN的過程，具體是怎樣計算均值和方差的？

下來找到部分相關代碼如下：（\tensorflow\python\layers\normalization.py)

def call(self, inputs, training=False):

# First, compute the axes along which to reduce the mean / variance,

# as well as the broadcast shape to be used for all parameters.

input_shape = inputs.get_shape()

ndim = len(input_shape)

reduction_axes = list(range(len(input_shape)))

del reduction_axes[self.axis]

broadcast_shape = [1] * len(input_shape)

broadcast_shape[self.axis] = input_shape[self.axis].value

# Determines whether broadcasting is needed.

needs_broadcasting = (sorted(reduction_axes) != list(range(ndim))[:-1])

scale, offset = self.gamma, self.beta