This initializer can be used in transposed convolution operator to act as upsampling. Users can upsample a feature map with shape of (B, C, H, W) by any integer factor. The usage is:
import paddle.fluid as fluid factor = 2 C = 2 B = 8 H = W = 32 w_attr = fluid.param_attr.ParamAttr( learning_rate=0., regularizer=fluid.regularizer.L2Decay(0.), initializer=fluid.initializer.Bilinear()) x = fluid.data(name="data", shape=[B, 3, H, W], dtype="float32") conv_up = fluid.layers.conv2d_transpose( input=x, num_filters=C, output_size=None, filter_size=2 * factor - factor % 2, padding=int(math.ceil((factor - 1) / 2.)), stride=factor, groups=C, param_attr=w_attr, bias_attr=False)
Where, num_filters=C and groups=C means this is channel-wise transposed convolution. The filter shape will be (C, 1, K, K) where K is filer_size, This initializer will set a (K, K) interpolation kernel for every channel of the filter identically. The resulting shape of the output feature map will be (B, C, factor * H, factor * W). Note that the learning rate and the weight decay are set to 0 in order to keep coefficient values of bilinear interpolation unchanged during training.