【python实现卷积神经网络】Dropout层实现

class Dropout(Layer):
    """A layer that randomly sets a fraction p of the output units of the previous layer
    to zero.
    Parameters:
    -----------
    p: float
        The probability that unit x is set to zero.
    """
    def __init__(self, p=0.2):
        self.p = p
        self._mask = None
        self.input_shape = None
        self.n_units = None
        self.pass_through = True
        self.trainable = True

    def forward_pass(self, X, training=True):
        c = (1 - self.p)
        if training:
            self._mask = np.random.uniform(size=X.shape) > self.p
            c = self._mask
        return X * c

    def backward_pass(self, accum_grad):
        return accum_grad * self._mask

    def output_shape(self):
        return self.input_shape