How you solve the issue of batch size?

[Yujia-Tang]

When calculate IOU between bbox and other groudtruth. We always use iou(bbox[1],groundtruth)(here bbox and groundtruth are all [n,4]). For batch-size=1, no probelm here. However, for batch-size>1, we cannot use this commend, cuz groundtruth this tensor contains groundtruth from other images(maybe[n*32,4]). How can I distinguish this groundtruth is from another image or not?