Add strategy argument to Trainer

CHANGELOG.md

@@ -178,6 +178,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added support for `torch.autograd.set_detect_anomaly` through `Trainer` constructor argument `detect_anomaly` ([#9848](https://github.com/PyTorchLightning/pytorch-lightning/pull/9848))
 
 
+- Added `strategy` argument to Trainer ([#8597](https://github.com/PyTorchLightning/pytorch-lightning/pull/8597))
+
+
 ### Changed
 
 - Module imports are now catching `ModuleNotFoundError` instead of `ImportError` ([#9867](https://github.com/PyTorchLightning/pytorch-lightning/pull/9867))

pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -94,6 +94,7 @@ def __init__(
         ipus,
         distributed_backend,
         accelerator,
+        strategy,
         gpus,
         gpu_ids,
         num_nodes,
@@ -111,12 +112,9 @@ def __init__(
         self._distrib_type = None
         self._accelerator_type = None
 
-        if distributed_backend is not None:
-            rank_zero_deprecation(
-                f"`Trainer(distributed_backend={distributed_backend})` has been deprecated and will be removed in v1.5."
-                f" Use `Trainer(accelerator={distributed_backend})` instead."
-            )
-        distributed_backend = distributed_backend or accelerator
+        self.strategy = strategy
+        self.distributed_backend = distributed_backend or accelerator
+
         self._init_deterministic(deterministic)
 
         self.num_processes = num_processes
@@ -126,7 +124,6 @@ def __init__(
         self.parallel_device_ids = gpu_ids
         self.tpu_cores = tpu_cores
         self.ipus = ipus
-        self.distributed_backend = distributed_backend
         self.num_nodes = num_nodes
         self.sync_batchnorm = sync_batchnorm
         self.benchmark = benchmark
@@ -151,16 +148,23 @@ def __init__(
 
         self.plugins = plugins
 
+        self._handle_accelerator_and_distributed_backend(distributed_backend, accelerator)
+
         self._validate_accelerator_and_devices()
 
         self._warn_if_devices_flag_ignored()
 
         self.select_accelerator_type()
-        self.set_distributed_mode()
+
+        if self.strategy is not None:
+            self._set_training_type_plugin()
+        else:
+            self.set_distributed_mode()
         self.configure_slurm_ddp()
 
         self.handle_given_plugins()
         self.update_device_type_if_ipu_plugin()
+        self.update_device_type_if_training_type_plugin_passed()
 
         self._validate_accelerator_type()
         self._set_devices_if_none()
@@ -228,11 +232,11 @@ def select_accelerator_type(self) -> None:
             self._set_devices_to_cpu_num_processes()
             self._accelerator_type = DeviceType.CPU
 
-        if self.distributed_backend in ["auto"] + list(DeviceType):
+        if self.distributed_backend in self.accelerator_types:
             self.distributed_backend = None
 
     def _validate_accelerator_and_devices(self) -> None:
-        if self.distributed_backend not in ["auto"] + list(DeviceType) and self.devices is not None:
+        if self.distributed_backend not in self.accelerator_types and self.devices is not None:
             raise MisconfigurationException(
                 f"You passed `devices={self.devices}` but haven't specified"
                 " `accelerator=('auto'|'tpu'|'gpu'|'ipu'|'cpu')` for the devices mapping,"
@@ -285,9 +289,56 @@ def _set_devices_if_none(self) -> None:
         elif self._accelerator_type == DeviceType.CPU:
             self.devices = self.num_processes
 
+    def _handle_accelerator_and_distributed_backend(
+        self, distributed_backend: Optional[str], accelerator: Optional[Union[str, Accelerator]]
+    ) -> None:
+        if distributed_backend is not None:
+            rank_zero_deprecation(
+                f"`Trainer(distributed_backend={distributed_backend})` has been deprecated and will be removed in v1.5."
+                f" Use `Trainer(strategy={distributed_backend})` instead."
+            )
+            if self.strategy is not None:
+                raise MisconfigurationException(
+                    f"You have passed `Trainer(strategy={self.strategy})` but have"
+                    f" also passed `Trainer(distributed_backend={distributed_backend})`."
+                    f"HINT: Use just `Trainer(strategy={self.strategy})` instead."
+                )
+
+        if accelerator is not None and accelerator in list(DistributedType):
+            rank_zero_deprecation(
+                f"Passing {accelerator} `strategy` to the `accelerator` flag in Trainer has been deprecated"
+                f" in v1.5 and will be removed in v1.6. Use `Trainer(strategy={accelerator})` instead."
+            )
+            if self.strategy is not None:
+                raise MisconfigurationException(
+                    f"You have passed `Trainer(strategy={self.strategy})` but have"
+                    f" also passed `Trainer(accelerator={accelerator})`."
+                    f"HINT: Use just `Trainer(strategy={self.strategy})` instead."
+                )
+
+    def _set_training_type_plugin(self) -> None:
+        if isinstance(self.strategy, str) and self.strategy in TrainingTypePluginsRegistry:
+            self._training_type_plugin = TrainingTypePluginsRegistry.get(self.strategy)
+        if isinstance(self.strategy, str):
+            self.set_distributed_mode(self.strategy)
+        elif isinstance(self.strategy, TrainingTypePlugin):
+            self._training_type_plugin = self.strategy
+
     def handle_given_plugins(self) -> None:
 
-        training_type = None
+        for plug in self.plugins:
+            if self.strategy is not None and self._is_plugin_training_type(plug):
+                raise MisconfigurationException(
+                    f"You have passed `Trainer(strategy={self.strategy})`"
+                    f" and you can only specify one training type plugin, but you have passed {plug} as a plugin."
+                )
+            if self._is_plugin_training_type(plug):
+                rank_zero_deprecation(
+                    f"Passing {plug} `strategy` to the `plugins` flag in Trainer has been deprecated"
+                    f" in v1.5 and will be removed in v1.6. Use `Trainer(strategy={plug})` instead."
+                )
+
+        training_type = self._training_type_plugin or None
         checkpoint = None
         precision = None
         cluster_environment = None
@@ -350,6 +401,10 @@ def handle_given_plugins(self) -> None:
         self._checkpoint_io = checkpoint
         self._cluster_environment = cluster_environment or self.select_cluster_environment()
 
+    @property
+    def accelerator_types(self) -> List[str]:
+        return ["auto"] + list(DeviceType)
+
     @property
     def precision_plugin(self) -> PrecisionPlugin:
         if self._precision_plugin is None:
@@ -540,9 +595,18 @@ def root_gpu(self) -> Optional[int]:
             else None
         )
 
+    @staticmethod
+    def _is_plugin_training_type(plugin: Union[str, TrainingTypePlugin]) -> bool:
+        if isinstance(plugin, str) and (plugin in TrainingTypePluginsRegistry or plugin in list(DistributedType)):
+            return True
+        return isinstance(plugin, TrainingTypePlugin)
+
     @property
     def is_training_type_in_plugins(self) -> bool:
-        return any(isinstance(plug, str) and plug in TrainingTypePluginsRegistry for plug in self.plugins)
+        return any(
+            (isinstance(plug, str) and plug in TrainingTypePluginsRegistry) or isinstance(plug, TrainingTypePlugin)
+            for plug in self.plugins
+        )
 
     def select_precision_plugin(self) -> PrecisionPlugin:
         # set precision type
@@ -873,6 +937,25 @@ def update_device_type_if_ipu_plugin(self) -> None:
         if isinstance(self._training_type_plugin, IPUPlugin) and self._device_type != DeviceType.IPU:
             self._device_type = DeviceType.IPU
 
+    def update_device_type_if_training_type_plugin_passed(self) -> None:
+        if isinstance(self.strategy, TrainingTypePlugin) or any(
+            isinstance(plug, TrainingTypePlugin) for plug in self.plugins
+        ):
+            if self._accelerator_type is not None:
+                if self.use_ipu:
+                    self._device_type = DeviceType.IPU
+                elif self.use_tpu:
+                    self._device_type = DeviceType.TPU
+                elif self.use_gpu:
+                    self._device_type = DeviceType.GPU
+            else:
+                if self.has_ipu:
+                    self._device_type = DeviceType.IPU
+                elif self.has_tpu:
+                    self._device_type = DeviceType.TPU
+                elif self.has_gpu:
+                    self._device_type = DeviceType.GPU
+
     def configure_slurm_ddp(self):
         # extract SLURM flag vars
         # whenever we have the correct number of tasks, we let slurm manage processes

pytorch_lightning/trainer/trainer.py

@@ -154,6 +154,7 @@ def __init__(
         flush_logs_every_n_steps: Optional[int] = None,
         log_every_n_steps: int = 50,
         accelerator: Optional[Union[str, Accelerator]] = None,
+        strategy: Optional[Union[str, TrainingTypePlugin]] = None,
         sync_batchnorm: bool = False,
         precision: Union[int, str] = 32,
         weights_summary: Optional[str] = "top",
@@ -346,6 +347,9 @@ def __init__(
                 no checkpoint file at the path, start from scratch. If resuming from mid-epoch checkpoint,
                 training will start from the beginning of the next epoch.
 
+            strategy: Supports different training strategies with aliases
+                as well custom training type plugins.
+
             sync_batchnorm: Synchronize batch norm layers between process groups/whole world.
 
             terminate_on_nan: If set to True, will terminate training (by raising a `ValueError`) at the
@@ -408,6 +412,7 @@ def __init__(
             ipus,
             distributed_backend,
             accelerator,
+            strategy,
             gpus,
             gpu_ids,
             num_nodes,

tests/accelerators/test_accelerator_connector.py

@@ -26,6 +26,7 @@
 from pytorch_lightning.accelerators.gpu import GPUAccelerator
 from pytorch_lightning.callbacks import Callback
 from pytorch_lightning.plugins import (
+    DataParallelPlugin,
     DDP2Plugin,
     DDPPlugin,
     DDPShardedPlugin,
@@ -42,7 +43,7 @@
     SLURMEnvironment,
     TorchElasticEnvironment,
 )
-from pytorch_lightning.utilities import DistributedType
+from pytorch_lightning.utilities import DeviceType, DistributedType
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from tests.helpers.boring_model import BoringModel
 from tests.helpers.runif import RunIf
@@ -631,6 +632,78 @@ def test_accelerator_ddp_for_cpu(tmpdir):
     assert isinstance(trainer.training_type_plugin, DDPPlugin)
 
 
+def test_exception_when_strategy_used_with_distributed_backend():
+    with pytest.raises(MisconfigurationException, match="but have also passed"):
+        Trainer(distributed_backend="ddp_cpu", strategy="ddp_spawn")
+
+
+def test_exception_when_strategy_used_with_accelerator():
+    with pytest.raises(MisconfigurationException, match="but have also passed"):
+        Trainer(accelerator="ddp", strategy="ddp_spawn")
+
+
+def test_exception_when_strategy_used_with_plugins():
+    with pytest.raises(MisconfigurationException, match="only specify one training type plugin, but you have passed"):
+        Trainer(plugins="ddp_find_unused_parameters_false", strategy="ddp_spawn")
+
+
+@pytest.mark.parametrize(
+    ["strategy", "plugin"],
+    [
+        ("ddp_spawn", DDPSpawnPlugin),
+        ("ddp_spawn_find_unused_parameters_false", DDPSpawnPlugin),
+        ("ddp", DDPPlugin),
+        ("ddp_find_unused_parameters_false", DDPPlugin),
+    ],
+)
+def test_strategy_choice_cpu_str(tmpdir, strategy, plugin):
+    trainer = Trainer(strategy=strategy, accelerator="cpu", devices=2)
+    assert isinstance(trainer.training_type_plugin, plugin)
+
+
+@pytest.mark.parametrize("plugin", [DDPSpawnPlugin, DDPPlugin])
+def test_strategy_choice_cpu_plugin(tmpdir, plugin):
+    trainer = Trainer(strategy=plugin(), accelerator="cpu", devices=2)
+    assert isinstance(trainer.training_type_plugin, plugin)
+
+
+@RunIf(min_gpus=2)
+@pytest.mark.parametrize(
+    ["strategy", "plugin"],
+    [
+        ("ddp_spawn", DDPSpawnPlugin),
+        ("ddp_spawn_find_unused_parameters_false", DDPSpawnPlugin),
+        ("ddp", DDPPlugin),
+        ("ddp_find_unused_parameters_false", DDPPlugin),
+        ("ddp2", DDP2Plugin),
+        ("dp", DataParallelPlugin),
+        ("ddp_sharded", DDPShardedPlugin),
+        ("ddp_sharded_spawn", DDPSpawnShardedPlugin),
+        pytest.param("deepspeed", DeepSpeedPlugin, marks=RunIf(deepspeed=True)),
+    ],
+)
+def test_strategy_choice_gpu_str(tmpdir, strategy, plugin):
+    trainer = Trainer(strategy=strategy, accelerator="gpu", devices=2)
+    assert isinstance(trainer.training_type_plugin, plugin)
+
+
+@RunIf(min_gpus=2)
+@pytest.mark.parametrize("plugin", [DDPSpawnPlugin, DDPPlugin])
+def test_strategy_choice_gpu_plugin(tmpdir, plugin):
+    trainer = Trainer(strategy=plugin(), accelerator="gpu", devices=2)
+    assert isinstance(trainer.training_type_plugin, plugin)
+
+
+@RunIf(min_gpus=2)
+@pytest.mark.parametrize("plugin", [DDPSpawnPlugin, DDPPlugin])
+def test_device_type_when_training_plugin_gpu_passed(tmpdir, plugin):
+
+    trainer = Trainer(strategy=plugin(), gpus=2)
+    assert isinstance(trainer.training_type_plugin, plugin)
+    assert trainer._device_type == DeviceType.GPU
+    assert isinstance(trainer.accelerator, GPUAccelerator)
+
+
 @pytest.mark.parametrize("precision", [1, 12, "invalid"])
 def test_validate_precision_type(tmpdir, precision):
 

tests/accelerators/test_ipu.py

@@ -24,7 +24,7 @@
 from pytorch_lightning.plugins import IPUPlugin, IPUPrecisionPlugin
 from pytorch_lightning.trainer.states import RunningStage
 from pytorch_lightning.trainer.supporters import CombinedLoader
-from pytorch_lightning.utilities import _IPU_AVAILABLE
+from pytorch_lightning.utilities import _IPU_AVAILABLE, DeviceType
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from tests.helpers.boring_model import BoringModel
 from tests.helpers.datamodules import ClassifDataModule
@@ -120,7 +120,7 @@ def test_warning_if_ipus_not_used(tmpdir):
 @RunIf(ipu=True)
 def test_no_warning_plugin(tmpdir):
     with pytest.warns(None) as record:
-        Trainer(default_root_dir=tmpdir, plugins=IPUPlugin(training_opts=poptorch.Options()))
+        Trainer(default_root_dir=tmpdir, strategy=IPUPlugin(training_opts=poptorch.Options()))
     assert len(record) == 0
 
 
@@ -528,3 +528,18 @@ def test_set_devices_if_none_ipu():
 
     trainer = Trainer(accelerator="ipu", ipus=8)
     assert trainer.devices == 8
+
+
+@RunIf(ipu=True)
+def test_strategy_choice_ipu_plugin(tmpdir):
+    trainer = Trainer(strategy=IPUPlugin(), accelerator="ipu", devices=8)
+    assert isinstance(trainer.training_type_plugin, IPUPlugin)
+
+
+@RunIf(ipu=True)
+def test_device_type_when_training_plugin_ipu_passed(tmpdir):
+
+    trainer = Trainer(strategy=IPUPlugin(), ipus=8)
+    assert isinstance(trainer.training_type_plugin, IPUPlugin)
+    assert trainer._device_type == DeviceType.IPU
+    assert isinstance(trainer.accelerator, IPUAccelerator)

tests/accelerators/test_tpu_backend.py

@@ -229,6 +229,19 @@ def test_ddp_cpu_not_supported_on_tpus():
         Trainer(accelerator="ddp_cpu")
 
 
+@RunIf(tpu=True)
+@pytest.mark.parametrize("strategy", ["tpu_spawn", "tpu_spawn_debug"])
+def test_strategy_choice_tpu_str(tmpdir, strategy):
+    trainer = Trainer(strategy=strategy, accelerator="tpu", devices=8)
+    assert isinstance(trainer.training_type_plugin, TPUSpawnPlugin)
+
+
+@RunIf(tpu=True)
+def test_strategy_choice_tpu_plugin(tmpdir):
+    trainer = Trainer(strategy=TPUSpawnPlugin(), accelerator="tpu", devices=8)
+    assert isinstance(trainer.training_type_plugin, TPUSpawnPlugin)
+
+
 @RunIf(tpu=True)
 def test_auto_parameters_tying_tpus(tmpdir):
 

tests/deprecated_api/test_remove_1-6.py

@@ -330,6 +330,16 @@ def test_v1_6_0_deprecated_device_dtype_mixin_import():
         from pytorch_lightning.utilities.device_dtype_mixin import DeviceDtypeModuleMixin  # noqa: F401
 
 
+def test_v1_6_0_passing_strategy_to_accelerator_trainer_flag():
+    with pytest.deprecated_call(match="has been deprecated in v1.5 and will be removed in v1.6."):
+        Trainer(accelerator="ddp_spawn")
+
+
+def test_v1_6_0_passing_strategy_to_plugins_flag():
+    with pytest.deprecated_call(match="has been deprecated in v1.5 and will be removed in v1.6."):
+        Trainer(plugins="ddp_spawn")
+
+
 def test_v1_6_0_deprecated_accelerator_collective():
     from pytorch_lightning.plugins.precision import PrecisionPlugin
     from pytorch_lightning.plugins.training_type import SingleDevicePlugin