【YOLO改进】换遍IoU损失函数之Innerciou Loss（基于MMYOLO）

替换Inner CIoU损失函数(基于MMYOLO)

由于MMYOLO中没有实现Inner CIoU损失函数，所以需要在mmyolo/models/iou_loss.py中添加Inner CIoU的计算和对应的iou_mode，修改完以后在终端运行

python setup.py install

再在配置文件中进行修改即可。修改例子如下：

    elif iou_mode == "innerciou":
        ratio=1.0
        w1_, h1_, w2_, h2_ = w1 / 2, h1 / 2, w2 / 2, h2 / 2
        x1 = bbox1_x1 + w1_
        y1 = bbox1_y1 + h1_
        x2 = bbox2_x1 + w2_
        y2 = bbox2_y1 + h2_

        inner_b1_x1, inner_b1_x2, inner_b1_y1, inner_b1_y2 = x1 - w1_ * ratio, x1 + w1_ * ratio, \
                                                             y1 - h1_ * ratio, y1 + h1_ * ratio
        inner_b2_x1, inner_b2_x2, inner_b2_y1, inner_b2_y2 = x2 - w2_ * ratio, x2 + w2_ * ratio, \
                                                             y2 - h2_ * ratio, y2 + h2_ * ratio
        inner_inter = (torch.min(inner_b1_x2, inner_b2_x2) - torch.max(inner_b1_x1, inner_b2_x1)).clamp(0) * \
                      (torch.min(inner_b1_y2, inner_b2_y2) - torch.max(inner_b1_y1, inner_b2_y1)).clamp(0)
        inner_union = w1 * ratio * h1 * ratio + w2 * ratio * h2 * ratio - inner_inter + eps
        inner_iou = inner_inter / inner_union

        # CIoU = IoU - ( (ρ^2(b_pred,b_gt) / c^2) + (alpha x v) )

        # calculate enclose area (c^2)
        enclose_area = enclose_w**2 + enclose_h**2 + eps

        # calculate ρ^2(b_pred,b_gt):
        # euclidean distance between b_pred(bbox2) and b_gt(bbox1)
        # center point, because bbox format is xyxy -> left-top xy and
        # right-bottom xy, so need to / 4 to get center point.
        rho2_left_item = ((bbox2_x1 + bbox2_x2) - (bbox1_x1 + bbox1_x2))**2 / 4
        rho2_right_item = ((bbox2_y1 + bbox2_y2) -
                           (bbox1_y1 + bbox1_y2))**2 / 4
        rho2 = rho2_left_item + rho2_right_item  # rho^2 (ρ^2)

        # Width and height ratio (v)
        wh_ratio = (4 / (math.pi**2)) * torch.pow(
            torch.atan(w2 / h2) - torch.atan(w1 / h1), 2)

        with torch.no_grad():
            alpha = wh_ratio / (wh_ratio - ious + (1 + eps))

        # innerCIoU
        ious = inner_iou - ((rho2 / enclose_area) + (alpha * wh_ratio))

修改后的配置文件（以configs/yolov5/yolov5_s-v61_syncbn_8xb16-300e_coco.py为例）

_base_ = ['../_base_/default_runtime.py',