mmdetection/configs/faster_rcnn/faster-rcnn_r50_fpn_ciou_1x_coco.py

_base_ = './faster-rcnn_r50_fpn_1x_coco.py'
model = dict(
    roi_head=dict(
        bbox_head=dict(
            reg_decoded_bbox=True,
            loss_bbox=dict(type='CIoULoss', loss_weight=12.0))))