address comments

Author: DuYicong515

pytorch_lightning/trainer/trainer.py

@@ -58,7 +58,7 @@
     SimpleProfiler,
     XLAProfiler,
 )
-from pytorch_lightning.strategies import ParallelStrategy, Strategy
+from pytorch_lightning.strategies import ParallelStrategy, SingleDeviceStrategy, Strategy
 from pytorch_lightning.strategies.ddp_spawn import DDPSpawnStrategy
 from pytorch_lightning.trainer.callback_hook import TrainerCallbackHookMixin
 from pytorch_lightning.trainer.configuration_validator import verify_loop_configurations
@@ -2028,6 +2028,7 @@ def num_nodes(self) -> int:
 
     @property
     def device_ids(self) -> List[int]:
+        """List of device indexes per node."""
         devices = getattr(self.strategy, "parallel_devices", [self.strategy.root_device])
         device_ids = []
         for idx, device in enumerate(devices):
@@ -2039,7 +2040,12 @@ def device_ids(self) -> List[int]:
 
     @property
     def num_devices(self) -> int:
-        return len(self.device_ids)
+        """Number of devices per node."""
+        if isinstance(self.strategy, SingleDeviceStrategy):
+            return 1
+        elif isinstance(self.strategy, ParallelStrategy):
+            return len(self.strategy.parallel_devices)
+        return 0
 
     @property
     def num_processes(self) -> int:

tests/deprecated_api/test_remove_1-8.py

@@ -688,3 +688,29 @@ def on_load_checkpoint(self, checkpoint):
         " v1.6 and will be removed in v1.8. Use `load_state_dict` instead."
     ):
         trainer.fit(model)
+
+
+@pytest.mark.parametrize(
+    ["trainer_kwargs", "expected_devices"],
+    [
+        ({}, 1),
+        ({"devices": 1}, 1),
+        ({"accelerator": "gpu", "devices": 1}, 1),
+        ({"strategy": "ddp", "devices": 1}, 1),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": 1}, 1),
+        ({"strategy": "ddp", "devices": 2}, 2),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": 2}, 2),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": [2]}, 1),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": [0, 2]}, 2),
+    ],
+)
+def test_v1_8_0_trainer_devices(monkeypatch, trainer_kwargs, expected_devices):
+    if trainer_kwargs.get("accelerator") == "gpu":
+        monkeypatch.setattr(torch.cuda, "is_available", lambda: True)
+        monkeypatch.setattr(torch.cuda, "device_count", lambda: 4)
+    trainer = Trainer(**trainer_kwargs)
+    with pytest.deprecated_call(
+        match="`Trainer.devices` was deprecated in v1.6 and will be removed in v1.8."
+        " Please use `Trainer.num_devices` or `Trainer.device_ids` to get device information instead."
+    ):
+        trainer.devices == expected_devices

tests/trainer/test_trainer.py

@@ -2151,13 +2151,14 @@ def test_dataloaders_are_not_loaded_if_disabled_through_limit_batches(running_st
 @pytest.mark.parametrize(
     ["trainer_kwargs", "expected_device_ids"],
     [
-        ({"strategy": None}, [0]),
-        ({"num_processes": 1}, [0]),
+        ({}, [0]),
         ({"devices": 1}, [0]),
         ({"accelerator": "gpu", "devices": 1}, [0]),
         ({"strategy": "ddp", "devices": 1}, [0]),
-        ({"strategy": "ddp", "accelerator": "gpu", "devices": 2}, [0, 1]),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": 1}, [0]),
         ({"strategy": "ddp", "devices": 2}, [0, 1]),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": 2}, [0, 1]),
+        ({"strategy": "ddp", "accelerator": "gpu", "devices": [2]}, [2]),
         ({"strategy": "ddp", "accelerator": "gpu", "devices": [0, 2]}, [0, 2]),
     ],
 )
@@ -2167,3 +2168,4 @@ def test_trainer_config_device_ids(monkeypatch, trainer_kwargs, expected_device_
         monkeypatch.setattr(torch.cuda, "device_count", lambda: 4)
     trainer = Trainer(**trainer_kwargs)
     assert trainer.device_ids == expected_device_ids
+    assert len(trainer.device_ids) == trainer.num_devices