Hub device mismatch bug fix (#1619)

utils/general.py

@@ -265,7 +265,7 @@ def non_max_suppression(prediction, conf_thres=0.1, iou_thres=0.6, classes=None,
          detections with shape: nx6 (x1, y1, x2, y2, conf, cls)
     """
 
-    nc = prediction[0].shape[1] - 5  # number of classes
+    nc = prediction.shape[2] - 5  # number of classes
     xc = prediction[..., 4] > conf_thres  # candidates
 
     # Settings
@@ -277,7 +277,7 @@ def non_max_suppression(prediction, conf_thres=0.1, iou_thres=0.6, classes=None,
     merge = False  # use merge-NMS
 
     t = time.time()
-    output = [torch.zeros(0, 6)] * prediction.shape[0]
+    output = [torch.zeros((0, 6), device=prediction.device)] * prediction.shape[0]
     for xi, x in enumerate(prediction):  # image index, image inference
         # Apply constraints
         # x[((x[..., 2:4] < min_wh) | (x[..., 2:4] > max_wh)).any(1), 4] = 0  # width-height