In series of yolo object detector, anchors play an important role. In some code, the target box is predicted by the best anchor which match it. It means that one target box is predicted by only one anchor. But,in other code, the anchors whose iou with the target box are greater than some threshold  will predict the target box. It means that one target box may be predicted by multiply  anchors. I want to know which is better in these two methods?