Amp2 (#1580)

* fixed new amp bugs

* fixed new amp bugs

pytorch_lightning/core/lightning.py

@@ -1159,19 +1159,19 @@ class LightningModule(ABC, GradInformation, ModelIO, ModelHooks):
         elif isinstance(optimizer, torch.optim.LBFGS):
 
             # native amp + lbfgs is a no go right now
-            if self.use_amp and self.use_native_amp:
+            if self.trainer.use_amp and self.trainer.use_native_amp:
                 m = 'native PyTorch amp and lbfgs are not compatible. To request, please file' \
                     'a Github issue in PyTorch and tag @mcarilli'
                 raise MisconfigurationException(m)
             optimizer.step(second_order_closure)
         else:
-            if self.use_amp and self.use_native_amp:
+            if self.trainer.use_amp and self.trainer.use_native_amp:
                 self.trainer.scaler.step(optimizer)
             else:
                 optimizer.step()
 
         # in native 16-bit we need to update scaler after optimizer step
-        if self.use_amp and self.use_native_amp:
+        if self.trainer.use_amp and self.trainer.use_native_amp:
             self.trainer.scaler.update()
 
         # model hook

pytorch_lightning/trainer/trainer.py

@@ -492,13 +492,12 @@ class Trainer(
         # we wrap the user's forward with autocast and give it back at the end of fit
         self.autocast_original_forward = None
         self.use_native_amp = hasattr(torch.cuda, "amp") and hasattr(torch.cuda.amp, "autocast")
+        self.precision = precision
         if self.use_native_amp and self.precision == 16:
             self.scaler = torch.cuda.amp.GradScaler()
-            self.precision = precision
 
         # TODO: remove for v0.8.0
         self.amp_level = amp_level
-        self.precision = precision
         self.init_amp(use_amp)
 
         # Callback system