add some comments

train.py

@@ -671,11 +671,13 @@ def main():
                 loader_train.sampler.set_epoch(epoch)
 
             if not args.cuda_graph:
+                # The default eager mode without cuda graph.
                 train_metrics = train_one_epoch(
                     epoch, model, loader_train, optimizer, train_loss_fn, args,
                     lr_scheduler=lr_scheduler, saver=saver, output_dir=output_dir,
                     amp_autocast=amp_autocast, loss_scaler=loss_scaler, model_ema=model_ema, mixup_fn=mixup_fn)
             else:
+                # Replay an already captured cuda graph from previous epochs.
                 if cuda_graph_ is not None:
                     train_metrics = train_one_epoch(        # cuda graph replay
                         epoch, model, loader_train, optimizer, train_loss_fn, args,
@@ -683,12 +685,13 @@ def main():
                         amp_autocast=amp_autocast, loss_scaler=loss_scaler, model_ema=model_ema, mixup_fn=mixup_fn,
                         cuda_graph=cuda_graph_, cg_stage='replay',
                         cg_static_input=cg_static_input, cg_static_target=cg_static_target, cg_static_loss=cg_static_loss)
+                # Capture a cuda graph.
                 else:
-                    input_, target_, loss_ = train_one_epoch(   # cuda graph get_static_data
+                    input_, target_, loss_ = train_one_epoch(   # cuda graph get_static_shapes
                         epoch, model, loader_train, optimizer, train_loss_fn, args,
                         lr_scheduler=lr_scheduler, saver=saver, output_dir=output_dir,
                         amp_autocast=amp_autocast, loss_scaler=loss_scaler, model_ema=model_ema, mixup_fn=mixup_fn,
-                        cg_stage='get_static_data')
+                        cg_stage='get_static_shapes')
                     cg_static_input = torch.empty_like(input_)
                     cg_static_target = torch.empty_like(target_)
                     cg_static_loss = torch.empty_like(loss_)
@@ -808,7 +811,7 @@ def train_one_epoch(
 
         if cg_stage is None:    # The default non-CUDAGraph mode
             loss = _step(input, target)
-        elif cg_stage == 'get_static_data':
+        elif cg_stage == 'get_static_shapes':
             s = torch.cuda.Stream()
             s.wait_stream(torch.cuda.current_stream())
             with torch.cuda.stream(s):
@@ -828,7 +831,7 @@ def train_one_epoch(
             g = torch.cuda.CUDAGraph()
             optimizer.zero_grad(set_to_none=True)
             with torch.cuda.graph(g):
-                _step(cg_static_input, cg_static_target, cg_static_loss, False)
+                _step(cg_static_input, cg_static_target, cg_static_loss, scaler_step_and_update=False)
             return g
         elif cg_stage == 'replay':
             cg_static_input.copy_(input)