fix torch 1.10 amp error (#330)

mmengine/runner/amp.py

@@ -77,7 +77,20 @@ def autocast(enabled: bool = True, **kwargs):
                     'If pytorch versions is between 1.5.0 and 1.10, '
                     '`autocast` is only available in gpu mode')
 
-    elif digit_version(TORCH_VERSION) >= digit_version('1.10.0'):
+    elif (digit_version('1.11.0') > digit_version(TORCH_VERSION) >=
+          digit_version('1.10.0')):
+        if torch.cuda.is_available():
+            kwargs.setdefault('device_type', 'cuda')
+        else:
+            kwargs.setdefault('device_type', 'cpu')
+            # torch.autocast only support `dtype=torch.bfloat16` in
+            # pytorch 1.10
+            kwargs.setdefault('dtype', torch.bfloat16)
+
+        with torch.autocast(enabled=enabled, **kwargs):
+            yield
+
+    elif digit_version(TORCH_VERSION) >= digit_version('1.11.0'):
         if torch.cuda.is_available():
             kwargs.setdefault('device_type', 'cuda')
         else: