loss_functions.py 文件源码

def smoothL1(x, sigma):
    '''
    Tensorflow implementation of smooth L1 loss defined in Fast RCNN:
        (https://arxiv.org/pdf/1504.08083v2.pdf)

                    0.5 * (sigma * x)^2         if |x| < 1/sigma^2
    smoothL1(x) = {
                    |x| - 0.5/sigma^2           otherwise
    '''
    with tf.variable_scope('smoothL1'):
        conditional = tf.less(tf.abs(x), 1/sigma**2)

        close = 0.5 * (sigma * x)**2
        far = tf.abs(x) - 0.5/sigma**2

    return tf.where(conditional, close, far)