diff --git a/utils/utils.py b/utils/utils.py
index e53cea33..e6b39794 100755
--- a/utils/utils.py
+++ b/utils/utils.py
@@ -267,20 +267,16 @@ def bbox_iou(box1, box2, x1y1x2y2=True, GIoU=False, DIoU=False, CIoU=False):
         if GIoU:  # Generalized IoU https://arxiv.org/pdf/1902.09630.pdf
             c_area = cw * ch + 1e-16  # convex area
             return iou - (c_area - union_area) / c_area  # GIoU
-        if DIoU or CIoU:  # Distance IoU https://arxiv.org/abs/1911.08287v1
-            c2 = cw ** 2 + ch ** 2 + 1e-16  # convex diagonal squared
-            # b1_xc, b1_yc = (b1_x1 + b1_x2) / 2, (b1_y1 + b1_y2) / 2
-            # b2_xc, b2_yc = (b2_x1 + b2_x2) / 2, (b2_y1 + b2_y2) / 2
-            # rho2 = (b2_xc - b1_xc) ** 2 + (b2_yc - b1_yc) ** 2  # centerpoint distance squared
+        if DIoU or CIoU:  # Distance or Complete IoU https://arxiv.org/abs/1911.08287v1
+            # convex diagonal squared
+            c2 = cw ** 2 + ch ** 2 + 1e-16
+            # centerpoint distance squared
             rho2 = ((b2_x1 + b2_x2) - (b1_x1 + b1_x2)) ** 2 / 4 + ((b2_y1 + b2_y2) - (b1_y1 + b1_y2)) ** 2 / 4
             if DIoU:
                 return iou - rho2 / c2  # DIoU
             elif CIoU:
-                atan = torch.atan(w2 / h2) - torch.atan(w1 / h1)
-                v = (4 / math.pi ** 2) * torch.pow(atan, 2)
-                alpha = v / (1 - iou + v)
-                # ar = - (8 / (math.pi ** 2)) * atan * (w1 * h1)
-                return iou - (rho2 / c2 + alpha * v)  # CIoU
+                v = (4 / math.pi ** 2) * torch.pow(torch.atan(w2 / h2) - torch.atan(w1 / h1), 2)
+                return iou - (rho2 / c2 + v ** 2 / (1 - iou + v))  # CIoU
 
     return iou