Rename class method of ZeroDDP (#2692)

colossalai/nn/parallel/data_parallel.py

@@ -294,7 +294,7 @@ class ZeroDDP(ColoDDP):
                 continue
             p.grad = None
 
-    def _pre_bacward(self):
+    def _pre_backward(self):
         # set a visit label for all parameters
         # the label is used to check whether the parameter is correctly reduced
         for param in self.param2name:
@@ -318,7 +318,7 @@ class ZeroDDP(ColoDDP):
         self.gemini_manager.post_iter()
 
     def backward(self, loss: torch.Tensor):
-        self._pre_bacward()
+        self._pre_backward()
         with self.param_op_hook.switch_to_backward(), ColoParamOpHookManager.use_hooks(self.param_op_hook):
             loss.backward()
         self._post_backward()