Remove `AcceleratorConnector.num_gpus` and deprecate `Trainer.num_gpus` (#12384)

CHANGELOG.md

@@ -527,7 +527,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated `Trainer.devices` in favor of `Trainer.num_devices` and `Trainer.device_ids` ([#12151](https://github.com/PyTorchLightning/pytorch-lightning/pull/12151))
 
 
-- Deprecated `Trainer.root_gpu` in favor of `Trainer.strategy.root_device.index` when GPU is used. ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
+- Deprecated `Trainer.root_gpu` in favor of `Trainer.strategy.root_device.index` when GPU is used ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
+
+
+- Deprecated `Trainer.num_gpus` in favor of `Trainer.num_devices` when GPU is used ([#12384](https://github.com/PyTorchLightning/pytorch-lightning/pull/12384))
 
 
 ### Removed
@@ -720,6 +723,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Removed `AcceleratorConnector.root_gpu` property ([#12262](https://github.com/PyTorchLightning/pytorch-lightning/pull/12262))
 
 
+- Removed `AcceleratorConnector.num_gpus` property ([#12384](https://github.com/PyTorchLightning/pytorch-lightning/pull/12384))
+
+
 ### Fixed
 
 - Fixed an issue where `ModelCheckpoint` could delete older checkpoints when `dirpath` has changed during resumed training ([#12045](https://github.com/PyTorchLightning/pytorch-lightning/pull/12045))

pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -815,12 +815,6 @@ class AcceleratorConnector:
             return self.devices
         return 0
 
-    @property
-    def num_gpus(self) -> int:
-        if isinstance(self.accelerator, GPUAccelerator):
-            return self.devices
-        return 0
-
     @property
     def gpus(self) -> Optional[Union[List[int], str, int]]:
         return self._gpus

pytorch_lightning/trainer/trainer.py

@@ -2071,7 +2071,11 @@ class Trainer(
 
     @property
     def num_gpus(self) -> int:
-        return self._accelerator_connector.num_gpus
+        rank_zero_deprecation(
+            "`Trainer.num_gpus` was deprecated in v1.6 and will be removed in v1.8."
+            " Please use `Trainer.num_devices` instead."
+        )
+        return self.num_devices if isinstance(self.accelerator, GPUAccelerator) else 0
 
     @property
     def devices(self) -> int:

tests/deprecated_api/test_remove_1-8.py

@@ -925,3 +925,40 @@ def test_root_gpu_property_0_passing(monkeypatch, gpus, expected_root_gpu, strat
         "Please use `Trainer.strategy.root_device.index` instead."
     ):
         assert Trainer(gpus=gpus, strategy=strategy).root_gpu == expected_root_gpu
+
+
+@pytest.mark.parametrize(
+    ["gpus", "expected_num_gpus", "strategy"],
+    [
+        pytest.param(None, 0, None, id="None - expect 0 gpu to use."),
+        pytest.param(0, 0, None, id="Oth gpu, expect 1 gpu to use."),
+        pytest.param(1, 1, None, id="1st gpu, expect 1 gpu to use."),
+        pytest.param(-1, 16, "ddp", id="-1 - use all gpus"),
+        pytest.param("-1", 16, "ddp", id="'-1' - use all gpus"),
+        pytest.param(3, 3, "ddp", id="3rd gpu - 1 gpu to use (backend:ddp)"),
+    ],
+)
+def test_trainer_gpu_parse(monkeypatch, gpus, expected_num_gpus, strategy):
+    monkeypatch.setattr(torch.cuda, "is_available", lambda: True)
+    monkeypatch.setattr(torch.cuda, "device_count", lambda: 16)
+    with pytest.deprecated_call(
+        match="`Trainer.num_gpus` was deprecated in v1.6 and will be removed in v1.8."
+        " Please use `Trainer.num_devices` instead."
+    ):
+        assert Trainer(gpus=gpus, strategy=strategy).num_gpus == expected_num_gpus
+
+
+@pytest.mark.parametrize(
+    ["gpus", "expected_num_gpus", "strategy"],
+    [
+        pytest.param(None, 0, None, id="None - expect 0 gpu to use."),
+        pytest.param(None, 0, "ddp", id="None - expect 0 gpu to use."),
+    ],
+)
+def test_trainer_num_gpu_0(monkeypatch, gpus, expected_num_gpus, strategy):
+    monkeypatch.setattr(torch.cuda, "device_count", lambda: 0)
+    with pytest.deprecated_call(
+        match="`Trainer.num_gpus` was deprecated in v1.6 and will be removed in v1.8."
+        " Please use `Trainer.num_devices` instead."
+    ):
+        assert Trainer(gpus=gpus, strategy=strategy).num_gpus == expected_num_gpus

tests/models/test_gpu.py

@@ -92,32 +92,6 @@ def mocked_device_count_0(monkeypatch):
     monkeypatch.setattr(torch.cuda, "device_count", device_count)
 
 
-@pytest.mark.parametrize(
-    ["gpus", "expected_num_gpus", "strategy"],
-    [
-        pytest.param(None, 0, None, id="None - expect 0 gpu to use."),
-        pytest.param(0, 0, None, id="Oth gpu, expect 1 gpu to use."),
-        pytest.param(1, 1, None, id="1st gpu, expect 1 gpu to use."),
-        pytest.param(-1, PRETEND_N_OF_GPUS, "ddp", id="-1 - use all gpus"),
-        pytest.param("-1", PRETEND_N_OF_GPUS, "ddp", id="'-1' - use all gpus"),
-        pytest.param(3, 3, "ddp", id="3rd gpu - 1 gpu to use (backend:ddp)"),
-    ],
-)
-def test_trainer_gpu_parse(mocked_device_count, gpus, expected_num_gpus, strategy):
-    assert Trainer(gpus=gpus, strategy=strategy).num_gpus == expected_num_gpus
-
-
-@pytest.mark.parametrize(
-    ["gpus", "expected_num_gpus", "strategy"],
-    [
-        pytest.param(None, 0, None, id="None - expect 0 gpu to use."),
-        pytest.param(None, 0, "ddp", id="None - expect 0 gpu to use."),
-    ],
-)
-def test_trainer_num_gpu_0(mocked_device_count_0, gpus, expected_num_gpus, strategy):
-    assert Trainer(gpus=gpus, strategy=strategy).num_gpus == expected_num_gpus
-
-
 # Asking for a gpu when non are available will result in a MisconfigurationException
 @pytest.mark.parametrize(
     ["gpus", "expected_root_gpu", "strategy"],

tests/trainer/test_trainer.py

@@ -1222,7 +1222,8 @@ def test_trainer_config_accelerator(
     assert isinstance(trainer.strategy, strategy_cls)
     assert strategy_cls.strategy_name == strategy_name
     assert isinstance(trainer.accelerator, accelerator_cls)
-    assert trainer.num_gpus == num_gpus
+    trainer_num_gpus = trainer.num_devices if isinstance(trainer.accelerator, GPUAccelerator) else 0
+    assert trainer_num_gpus == num_gpus
 
 
 def test_trainer_subclassing():
@@ -2097,7 +2098,8 @@ def test_trainer_config_strategy(monkeypatch, trainer_kwargs, strategy_cls, stra
     assert isinstance(trainer.strategy, strategy_cls)
     assert strategy_cls.strategy_name == strategy_name
     assert isinstance(trainer.accelerator, accelerator_cls)
-    assert trainer.num_gpus == num_gpus
+    trainer_num_gpus = trainer.num_devices if isinstance(trainer.accelerator, GPUAccelerator) else 0
+    assert trainer_num_gpus == num_gpus
     assert trainer.num_nodes == trainer_kwargs.get("num_nodes", 1)