def _filter_boxes(self, boxes, min_size):
        """Remove all boxes with any side smaller than min_size."""
        ws = boxes[:, :, 2] - boxes[:, :, 0] + 1
        hs = boxes[:, :, 3] - boxes[:, :, 1] + 1
        keep = ((ws >= min_size.view(-1,1).expand_as(ws)) & (hs >= min_size.view(-1,1).expand_as(hs)))
        return keep
Remove all boxes with any side smaller than min_size.
lib/model/rpn/proposal_layer.py