Participants APIs should check if quorum is started (#95)

Author: fegin

torchft/manager.py

@@ -664,6 +664,9 @@ def participating_rank(self) -> Optional[int]:
         Returns:
             the rank of the current quorum
         """
+        if self._quorum_future is None:
+            return None
+
         self.wait_quorum()
 
         return self._participating_rank
@@ -679,6 +682,9 @@ def num_participants(self) -> int:
         Returns:
             the number of participants in the current quorum
         """
+        if self._quorum_future is None:
+            return 0
+
         self.wait_quorum()
 
         assert self._participating_world_size >= 0, "internal error"

torchft/manager_test.py

@@ -196,6 +196,9 @@ def test_quorum_heal_sync(self, client_mock: MagicMock) -> None:
         self.assertEqual(manager._quorum_id, -1)
         self.assertEqual(manager.current_step(), 0)
 
+        self.assertEqual(manager.num_participants(), 0)
+        self.assertEqual(manager.participating_rank(), None)
+
         manager.start_quorum()
         manager.allreduce(torch.tensor([1.0])).wait()
         self.assertFalse(manager._healing)