managed the import of torch.amp to be compatible with all pytorch ver…

…sions

train.py

@@ -36,6 +36,12 @@
 import torch.nn as nn
 import yaml
 from torch.optim import lr_scheduler
+
+try:
+    import torch.amp as amp
+except ImportError:
+    import torch.cuda.amp as amp
+
 from tqdm import tqdm
 
 FILE = Path(__file__).resolve()
@@ -94,6 +100,7 @@
     torch_distributed_zero_first,
 )
 
+
 LOCAL_RANK = int(os.getenv("LOCAL_RANK", -1))  # https://pytorch.org/docs/stable/elastic/run.html
 RANK = int(os.getenv("RANK", -1))
 WORLD_SIZE = int(os.getenv("WORLD_SIZE", 1))
@@ -221,7 +228,7 @@ def train(hyp, opt, device, callbacks):
         LOGGER.info(f"Transferred {len(csd)}/{len(model.state_dict())} items from {weights}")  # report
     else:
         model = Model(cfg, ch=3, nc=nc, anchors=hyp.get("anchors")).to(device)  # create
-    amp = check_amp(model)  # check AMP
+    use_amp = check_amp(model)  # check AMP
 
     # Freeze
     freeze = [f"model.{x}." for x in (freeze if len(freeze) > 1 else range(freeze[0]))]  # layers to freeze
@@ -238,7 +245,7 @@ def train(hyp, opt, device, callbacks):
 
     # Batch size
     if RANK == -1 and batch_size == -1:  # single-GPU only, estimate best batch size
-        batch_size = check_train_batch_size(model, imgsz, amp)
+        batch_size = check_train_batch_size(model, imgsz, use_amp)
         loggers.on_params_update({"batch_size": batch_size})
 
     # Optimizer
@@ -352,7 +359,8 @@ def lf(x):
     maps = np.zeros(nc)  # mAP per class
     results = (0, 0, 0, 0, 0, 0, 0)  # P, R, mAP@.5, mAP@.5-.95, val_loss(box, obj, cls)
     scheduler.last_epoch = start_epoch - 1  # do not move
-    scaler = torch.cuda.amp.GradScaler(enabled=amp)
+    # scaler = torch.cuda.amp.GradScaler(enabled=amp)
+    scaler = amp.GradScaler(enabled=use_amp)
     stopper, stop = EarlyStopping(patience=opt.patience), False
     compute_loss = ComputeLoss(model)  # init loss class
     callbacks.run("on_train_start")
@@ -409,7 +417,8 @@ def lf(x):
                     imgs = nn.functional.interpolate(imgs, size=ns, mode="bilinear", align_corners=False)
 
             # Forward
-            with torch.cuda.amp.autocast(amp):
+            # with torch.cuda.amp.autocast(amp):
+            with amp.autocast(enabled=use_amp, device_type=device.type):
                 pred = model(imgs)  # forward
                 loss, loss_items = compute_loss(pred, targets.to(device))  # loss scaled by batch_size
                 if RANK != -1:
@@ -458,7 +467,7 @@ def lf(x):
                     data_dict,
                     batch_size=batch_size // WORLD_SIZE * 2,
                     imgsz=imgsz,
-                    half=amp,
+                    half=use_amp,
                     model=ema.ema,
                     single_cls=single_cls,
                     dataloader=val_loader,