fix(mge/optimizer): fix optimizer's state_dict bug

GitOrigin-RevId: 67fb112fb8

imperative/python/megengine/optimizer/optimizer.py

@@ -6,6 +6,7 @@
 # Unless required by applicable law or agreed to in writing,
 # software distributed under the License is distributed on an
 # "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+import copy
 from abc import ABCMeta, abstractmethod
 from collections.abc import Iterable
 from typing import Dict
@@ -197,10 +198,11 @@ class Optimizer(metaclass=ABCMeta):
                     cur_id += 1
 
         for param, st in self._state.items():
+            _st = copy.copy(st)
             if not keep_var:
                 for k, v in st.items():
-                    st[k] = v.numpy()
-            state[param2id[param]] = st
+                    _st[k] = v.numpy()
+            state[param2id[param]] = _st
 
         for group in self.param_groups:
             param_group = {k: v for k, v in group.items() if k != "params"}

imperative/python/test/integration/test_optimizer.py

@@ -104,6 +104,10 @@ def _test_optimizer(opt_str, test_case, check_class, update_lr=False):
             )
             step += 1
             check_func(ori_params, net.parameters(), step)
+            try_state_dict = {
+                "net": net.state_dict(),
+                "opt": opt.state_dict(),
+            }
 
 
 def test_sgd():