[fbsync] Add missing device info. (#3651)

Reviewed By: NicolasHug

Differential Revision: D27706953

fbshipit-source-id: c3810183d8acb7feec6868e28705ee25806acc27

Author: fmassa

torchvision/models/detection/retinanet.py

@@ -386,7 +386,8 @@ def compute_loss(self, targets, head_outputs, anchors):
         matched_idxs = []
         for anchors_per_image, targets_per_image in zip(anchors, targets):
             if targets_per_image['boxes'].numel() == 0:
-                matched_idxs.append(torch.full((anchors_per_image.size(0),), -1, dtype=torch.int64))
+                matched_idxs.append(torch.full((anchors_per_image.size(0),), -1, dtype=torch.int64,
+                                               device=anchors_per_image.device))
                 continue
 
             match_quality_matrix = box_ops.box_iou(targets_per_image['boxes'], anchors_per_image)