Add load_optim option to load checkpoint but not optimizer state (#229)

fairseq/trainer.py

@@ -80,15 +80,17 @@ class Trainer(object):
                 self.lr_scheduler, self._num_updates, self._optim_history, extra_state,
             )
 
-    def load_checkpoint(self, filename):
+    def load_checkpoint(self, filename, load_optim=True):
         """Load all training state from a checkpoint file."""
-        extra_state, self._optim_history, last_optim_state = \
+        extra_state, optim_history, last_optim_state = \
             utils.load_model_state(filename, self.model)
 
         if last_optim_state is not None:
             # rebuild optimizer after loading model, since params may have changed
             self._build_optimizer()
 
+            if load_optim:
+                self._optim_history = optim_history
                 # only reload optimizer and lr_scheduler if they match
                 last_optim = self._optim_history[-1]
                 if last_optim['criterion_name'] == self.criterion.__class__.__name__: