import tensorflow as tf

    pred1, pred2 = tf.split(pred, 2, axis=0)
    tgt1, tgt2 = tf.split(tgt, 2, axis=0)
    geq = tf.cast((tgt1 - tgt2) > 0, tf.bool)
    tgt_larg = tf.where(geq, tgt1, tgt2)
    tgt_small = tf.where(geq, tgt2, tgt1)
    pred_larg = tf.where(geq, pred1, pred2)
    pred_small = tf.where(geq, pred2, pred1)

    loss = tf.maximum(0.0, (tgt_larg - tgt_small) - (pred_larg - pred_small))
    loss = tf.reduce_mean(loss)
