resnet.py 文件源码

def downsample_block(x, nb_channels, kernel_size=3, bottleneck=True,
                     l2_reg=1e-4):
    if bottleneck:
        out = bottleneck_layer(x, nb_channels, kernel_size=kernel_size,
                               stride=2, l2_reg=l2_reg)
        # The output channels is 4x bigger on this case
        nb_channels = nb_channels * 4
    else:
        out = two_conv_layer(x, nb_channels, kernel_size=kernel_size,
                             stride=2, l2_reg=l2_reg)
    # Projection on the shortcut
    proj = Convolution2D(nb_channels, 1, 1, subsample=(2, 2),
                         border_mode='valid', init='he_normal',
                         W_regularizer=l2(l2_reg), bias=False)(x)
    # proj = AveragePooling2D((1, 1), (2, 2))(x)
    out = merge([proj, out], mode='sum')
    return out