Do not use offload_optimizer with local_updates by deafult (#462)

* Do not use offload optimizer with local_updates by deafult

* fix black

hivemind/optim/optimizer.py

@@ -201,7 +201,8 @@ class Optimizer(torch.optim.Optimizer):
 
         client_mode = client_mode if client_mode is None else dht.client_mode
         delay_optimizer_step = delay_optimizer_step if delay_optimizer_step is not None else delay_grad_averaging
-        offload_optimizer = offload_optimizer if offload_optimizer is not None else (params is not None)
+        if offload_optimizer is None:
+            offload_optimizer = params is not None and not use_local_updates
         allreduce_timeout = allreduce_timeout if allreduce_timeout is not None else averaging_timeout
         next_chunk_timeout = next_chunk_timeout if next_chunk_timeout is not None else matchmaking_time
         assert not delay_grad_averaging or delay_optimizer_step, "delay_grad_averaging requires delay_optimizer_step"