Merge branch 'master' into idist

tests/ignite/handlers/test_checkpoint.py

@@ -907,10 +907,28 @@ def _test(ext):
     _test(".pt")
 
 
+def _test_checkpoint_with_ddp(device):
+    model = DummyModel().to(device)
+    ddp_model = nn.parallel.DistributedDataParallel(model)
+    to_save = {"model": ddp_model}
+
+    save_handler = MagicMock(spec=BaseSaveHandler)
+    checkpointer = Checkpoint(to_save, save_handler=save_handler)
+
+    trainer = Engine(lambda e, b: None)
+    trainer.state = State(epoch=0, iteration=0)
+
+    checkpointer(trainer)
+    assert save_handler.call_count == 1
+    metadata = {"basename": "model", "score_name": None, "priority": 0}
+    save_handler.assert_called_with(model.state_dict(), "model_0.pt", metadata)
+
+
 @pytest.mark.distributed
 def test_distrib_cpu(distributed_context_single_node_gloo, get_rank_zero_dirname):
     dirname = get_rank_zero_dirname("cpu")
     _test_save_model_optimizer_lr_scheduler_with_state_dict("cpu", os.path.join(dirname, "1"))
+    _test_checkpoint_with_ddp("cpu")
 
 
 @pytest.mark.distributed
@@ -919,6 +937,7 @@ def test_distrib_gpu(distributed_context_single_node_nccl, get_rank_zero_dirname
     device = idist.device()
     dirname = get_rank_zero_dirname(device)
     _test_save_model_optimizer_lr_scheduler_with_state_dict(device, os.path.join(dirname, "1"))
+    _test_checkpoint_with_ddp(device=device)
 
 
 def _test_tpu_saves_to_cpu(device, dirname):