diff --git a/tracker/base_tracker.py b/tracker/base_tracker.py
index d008893..a544408 100644
--- a/tracker/base_tracker.py
+++ b/tracker/base_tracker.py
@@ -39,8 +39,10 @@ class BaseTracker:
             transforms.ToTensor(),
             im_normalization,
         ])
+        self.mapper = MaskMapper()
         self.device = device
 
+    @torch.no_grad()
     def resize_mask(self, mask):
         # mask transform is applied AFTER mapper, so we need to post-process it in eval.py
         h, w = mask.shape[-2:]
@@ -48,6 +50,7 @@ class BaseTracker:
         return F.interpolate(mask, (int(h/min_hw*self.size), int(w/min_hw*self.size)), 
                     mode='nearest')
 
+    @torch.no_grad()
     def track(self, frames, first_frame_annotation):
         """
         Input: 
@@ -57,34 +60,28 @@ class BaseTracker:
         Output:
         masks: numpy arrays: H, W
         """
-        shape = np.array(frames).shape[1:3] # H, W
-        frame_list = [self.im_transform(frame).to(self.device) for frame in frames]
-        frame_tensors = torch.stack(frame_list, dim=0)
-        
-        # data transformation
-        mapper = MaskMapper()
+        vid_length = len(frames)
+        masks = []
 
-        vid_length = len(frame_tensors)
-
-        for ti, frame_tensor in enumerate(frame_tensors):
+        for ti, frame in enumerate(frames):
+            # convert to tensor
+            frame_tensor = self.im_transform(frame).to(self.device)
             if ti == 0:
-                mask, labels = mapper.convert_mask(first_frame_annotation)
+                mask, labels = self.mapper.convert_mask(first_frame_annotation)
                 mask = torch.Tensor(mask).to(self.device)
-                self.tracker.set_all_labels(list(mapper.remappings.values()))
+                self.tracker.set_all_labels(list(self.mapper.remappings.values()))
             else:
                 mask = None
                 labels = None
             
             # track one frame
             prob = self.tracker.step(frame_tensor, mask, labels, end=(ti==vid_length-1))
-            
+            # convert to mask
             out_mask = torch.argmax(prob, dim=0)
             out_mask = (out_mask.detach().cpu().numpy()).astype(np.uint8)
+            masks.append(out_mask)
 
-            painted_image = mask_painter(frames[ti], out_mask)
-            # save
-            painted_image = Image.fromarray(painted_image)
-            painted_image.save(f'/ssd1/gaomingqi/results/TrackA/{ti}.png')
+        return np.stack(masks, 0)
 
 
 if __name__ == '__main__':
@@ -94,7 +91,7 @@ if __name__ == '__main__':
     # first frame
     first_frame_path = '/ssd1/gaomingqi/datasets/davis/Annotations/480p/dance-twirl/00000.png'
     # load frames
-    frames = ["test_confict"]
+    frames = []
     for video_path in video_path_list:
         frames.append(np.array(Image.open(video_path).convert('RGB')))
     frames = np.stack(frames, 0)    # N, H, W, C
@@ -104,9 +101,16 @@ if __name__ == '__main__':
     # ----------------------------------------------------------
     # initalise tracker
     # ----------------------------------------------------------
-    device = 'cuda:0'
+    device = 'cuda:1'
     XMEM_checkpoint = '/ssd1/gaomingqi/checkpoints/XMem-s012.pth'
-    tracker = BaseTracker('cuda:0', XMEM_checkpoint)
+    tracker = BaseTracker(device, XMEM_checkpoint)
     
     # track anything given in the first frame annotation
-    tracker.track(frames, first_frame_annotation)
+    masks = tracker.track(frames, first_frame_annotation)
+
+    # save
+    for ti, (frame, mask) in enumerate(zip(frames, masks)):
+        painted_image = mask_painter(frame, mask)
+        # save
+        painted_image = Image.fromarray(painted_image)
+        painted_image.save(f'/ssd1/gaomingqi/results/TrackA/{ti:05d}.png')