Support individual setup of model and optimizer in Lite (#15185)

src/lightning_lite/CHANGELOG.md

@@ -16,7 +16,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 -
 
--
+- Added `LightningLite.setup_module()` and `LightningLite.setup_optimizers()` to support strategies that need to set up the model before an optimizer can be created ([#15185](https://github.com/Lightning-AI/lightning/pull/15185))
 
 
 ### Changed

src/lightning_lite/lite.py

@@ -31,7 +31,14 @@ from torch.utils.data import BatchSampler, DataLoader, DistributedSampler
 from lightning_lite.plugins import Precision  # avoid circular imports: # isort: split
 from lightning_lite.accelerators.accelerator import Accelerator
 from lightning_lite.connector import _Connector, _PLUGIN_INPUT, _PRECISION_INPUT
-from lightning_lite.strategies import DeepSpeedStrategy, SingleDeviceStrategy, Strategy, XLAStrategy
+from lightning_lite.strategies import (
+    DDPShardedStrategy,
+    DDPSpawnShardedStrategy,
+    DeepSpeedStrategy,
+    SingleDeviceStrategy,
+    Strategy,
+    XLAStrategy,
+)
 from lightning_lite.strategies.strategy import _Sharded, TBroadcast
 from lightning_lite.utilities import move_data_to_device
 from lightning_lite.utilities.apply_func import convert_to_tensors
@@ -139,42 +146,100 @@ class LightningLite(ABC):
 
     def setup(
         self,
-        model: nn.Module,
+        module: nn.Module,
         *optimizers: Optimizer,
         move_to_device: bool = True,
     ) -> Any:  # no specific return because the way we want our API to look does not play well with mypy
         """Set up a model and its optimizers for accelerated training.
 
         Args:
-            model: A model to set up
+            module: A :class:`torch.nn.Module` to set up
             *optimizers: The optimizer(s) to set up (no optimizers is also possible)
             move_to_device: If set ``True`` (default), moves the model to the correct device. Set this to ``False``
                 and alternatively use :meth:`to_device` manually.
 
         Returns:
-            The tuple of the wrapped model and list of optimizers, in the same order they were passed in.
+            The tuple containing wrapped module and the optimizers, in the same order they were passed in.
         """
-        self._validate_setup(model, optimizers)
-        original_model = model
+        self._validate_setup(module, optimizers)
+        original_module = module
 
-        model = self._precision.convert_module(model)
+        module = self._precision.convert_module(module)
 
         if move_to_device:
-            model = self._move_model_to_device(model=model, optimizers=list(optimizers))
+            module = self._move_model_to_device(model=module, optimizers=list(optimizers))
 
         # Let accelerator/plugin wrap and connect the models and optimizers
-        model, optimizers = self._strategy.setup_module_and_optimizers(model, list(optimizers))
-        model = _LiteModule(model, self._precision, original_module=original_model)
+        if optimizers:
+            module, optimizers = self._strategy.setup_module_and_optimizers(  # type: ignore[assignment]
+                module, list(optimizers)
+            )
+        else:
+            module = self._strategy.setup_module(module)
+
+        module = _LiteModule(module, self._precision, original_module=original_module)
 
         # Update the _DeviceDtypeModuleMixin's device parameter
-        model.to(self.device if move_to_device else next(model.parameters()).device)
+        module.to(self.device if move_to_device else next(module.parameters()).device)
 
         optimizers = [_LiteOptimizer(optimizer=optimizer, strategy=self._strategy) for optimizer in optimizers]
+
         self._models_setup += 1
+
         if optimizers:
-            # join both types in a list for API convenience
-            return [model] + optimizers
-        return model
+            # join both types in a tuple for API convenience
+            return tuple((module, *optimizers))
+        return module
+
+    def setup_module(self, module: nn.Module, move_to_device: bool = True) -> _LiteModule:
+        """Set up a model for accelerated training or inference.
+
+        This is the same as calling ``.setup(model)`` with no optimizers. It is useful for inference or for certain
+        strategies like `FSDP` that require setting up the module before the optimizer can be created and set up.
+        See also :meth:`setup_optimizers`.
+
+        Args:
+            module: A :class:`torch.nn.Module` to set up
+            move_to_device: If set ``True`` (default), moves the model to the correct device. Set this to ``False``
+                and alternatively use :meth:`to_device` manually.
+
+        Returns:
+            The wrapped model.
+        """
+        self._validate_setup_module(module)
+        original_module = module
+
+        module = self._precision.convert_module(module)
+
+        if move_to_device:
+            module = self._move_model_to_device(model=module, optimizers=[])
+
+        # Let strategy wrap and connect the module alone
+        module = self._strategy.setup_module(module)
+        module = _LiteModule(module, self._precision, original_module=original_module)
+
+        # Update the _DeviceDtypeModuleMixin's device parameter
+        module.to(self.device if move_to_device else next(module.parameters()).device)
+
+        self._models_setup += 1
+        return module
+
+    def setup_optimizers(self, *optimizers: Optimizer) -> Union[_LiteOptimizer, Tuple[_LiteOptimizer, ...]]:
+        """Set up one or more optimizers for accelerated training.
+
+        Some strategies do not allow setting up model and optimizer independently. For them, you should call
+        ``.setup(model, optimizer, ...)`` instead to jointly set them up.
+
+        Args:
+            *optimizers: One or more optmizers to set up.
+
+        Returns:
+            The wrapped optimizer(s).
+        """
+        self._validate_setup_optimizers(optimizers)
+        optimizers = [self._strategy.setup_optimizer(optimizer) for optimizer in optimizers]
+        optimizers = [_LiteOptimizer(optimizer=optimizer, strategy=self._strategy) for optimizer in optimizers]
+        return optimizers[0] if len(optimizers) == 1 else tuple(optimizers)
 
     def setup_dataloaders(
         self, *dataloaders: DataLoader, replace_sampler: bool = True, move_to_device: bool = True
@@ -529,17 +594,44 @@ class LightningLite(ABC):
         setattr(self, "run", partial(self._run_impl, self.run))
 
     @staticmethod
-    def _validate_setup(model: nn.Module, optimizers: Sequence[Optimizer]) -> None:
-        if isinstance(model, _LiteModule):
+    def _validate_setup(module: nn.Module, optimizers: Sequence[Optimizer]) -> None:
+        if isinstance(module, _LiteModule):
             raise ValueError("A model should be passed only once to the `setup` method.")
 
         if any(isinstance(opt, _LiteOptimizer) for opt in optimizers):
             raise ValueError("An optimizer should be passed only once to the `setup` method.")
 
+    def _validate_setup_module(self, module: nn.Module) -> None:
+        if isinstance(module, _LiteModule):
+            raise ValueError("A model should be passed only once to the `setup_module` method.")
+
+        if isinstance(self._strategy, (DDPShardedStrategy, DDPSpawnShardedStrategy)):
+            raise RuntimeError(
+                f"The `{type(self._strategy).__name__}` requires the model and optimizer(s) to be set up jointly"
+                " through `.setup(model, optimizer, ...)`. For inference, choose a different strategy, for example"
+                " `ddp`."
+            )
+
+    def _validate_setup_optimizers(self, optimizers: Sequence[Optimizer]) -> None:
+        if isinstance(self._strategy, (DeepSpeedStrategy, DDPShardedStrategy, DDPSpawnShardedStrategy, XLAStrategy)):
+            raise RuntimeError(
+                f"The `{type(self._strategy).__name__}` requires the model and optimizer(s) to be set up jointly"
+                " through `.setup(model, optimizer, ...)`."
+            )
+
+        if not optimizers:
+            raise ValueError("`setup_optimizers` requires at least one optimizer as input.")
+
+        if any(isinstance(opt, _LiteOptimizer) for opt in optimizers):
+            raise ValueError("An optimizer should be passed only once to the `setup_optimizers` method.")
+
     @staticmethod
     def _validate_setup_dataloaders(dataloaders: Sequence[DataLoader]) -> None:
+        if not dataloaders:
+            raise ValueError("`setup_dataloaders` requires at least one dataloader as input.")
+
         if any(isinstance(dl, _LiteDataLoader) for dl in dataloaders):
-            raise ValueError("A dataloader should be passed only once to the `setup_dataloaders` method")
+            raise ValueError("A dataloader should be passed only once to the `setup_dataloaders` method.")
 
         if any(not isinstance(dl, DataLoader) for dl in dataloaders):
             raise TypeError("Only PyTorch DataLoader are currently supported in `setup_dataloaders`.")

src/lightning_lite/strategies/deepspeed.py

@@ -35,7 +35,7 @@ from lightning_lite.utilities.distributed import log
 from lightning_lite.utilities.enums import AMPType, PrecisionType
 from lightning_lite.utilities.rank_zero import rank_zero_info
 from lightning_lite.utilities.seed import reset_seed
-from lightning_lite.utilities.types import _LRScheduler, _PATH, ReduceLROnPlateau
+from lightning_lite.utilities.types import _PATH
 
 _DEEPSPEED_AVAILABLE = RequirementCache("deepspeed")
 if TYPE_CHECKING and _DEEPSPEED_AVAILABLE:
@@ -305,11 +305,11 @@ class DeepSpeedStrategy(DDPStrategy, _Sharded):
         return self._deepspeed_engine
 
     def setup_module_and_optimizers(
-        self, model: Module, optimizers: List[Optimizer]
+        self, module: Module, optimizers: List[Optimizer]
     ) -> Tuple["deepspeed.DeepSpeedEngine", List[Optimizer]]:
-        """Setup a model and multiple optimizers together.
+        """Set up a model and multiple optimizers together.
 
-        Currently only a single optimizer is supported.
+        Currently, only a single optimizer is supported.
 
         Return:
             The model wrapped into a :class:`deepspeed.DeepSpeedEngine` and a list with a single
@@ -321,10 +321,25 @@ class DeepSpeedStrategy(DDPStrategy, _Sharded):
                 f" Got {len(optimizers)} optimizers instead."
             )
 
-        self._deepspeed_engine, optimizer = self._setup_module_and_optimizer(model, optimizers[0])
+        self._deepspeed_engine, optimizer = self._initialize_engine(module, optimizers[0])
         self._set_deepspeed_activation_checkpointing()
         return self._deepspeed_engine, [optimizer]
 
+    def setup_module(self, module: Module) -> "deepspeed.DeepSpeedEngine":
+        """Set up a module for inference (no optimizers).
+
+        For training, see :meth:`setup_module_and_optimizers`.
+        """
+        self._deepspeed_engine, _ = self._initialize_engine(module)
+        return self._deepspeed_engine
+
+    def setup_optimizer(self, optimizer: Optimizer) -> Optimizer:
+        """Optimizers can only be set up jointly with the model in this strategy.
+
+        Please use :meth:`setup_module_and_optimizers` to set up both module and optimizer together.
+        """
+        raise NotImplementedError(self._err_msg_joint_setup_required())
+
     @contextmanager
     def module_sharded_context(self) -> Generator[None, None, None]:
         # Current limitation in Lite: The config needs to be fully determined at the time of calling the
@@ -401,11 +416,10 @@ class DeepSpeedStrategy(DDPStrategy, _Sharded):
             offload_optimizer_device="nvme",
         )
 
-    def _setup_module_and_optimizer(
+    def _initialize_engine(
         self,
         model: Module,
-        optimizer: Optional[Optimizer],
-        lr_scheduler: Optional[Union[_LRScheduler, ReduceLROnPlateau]] = None,
+        optimizer: Optional[Optimizer] = None,
     ) -> Tuple["deepspeed.DeepSpeedEngine", Optimizer]:
         """Initialize one model and one optimizer with an optional learning rate scheduler.
 
@@ -420,7 +434,6 @@ class DeepSpeedStrategy(DDPStrategy, _Sharded):
             model=model,
             model_parameters=model_parameters,
             optimizer=optimizer,
-            lr_scheduler=lr_scheduler,
             dist_init_required=False,
         )
         return deepspeed_engine, deepspeed_optimizer

src/lightning_lite/strategies/fairscale.py

@@ -18,6 +18,7 @@ from typing import Any, Dict, Generator, List, Optional, Tuple
 import torch
 from lightning_utilities.core.imports import module_available
 from torch.nn import Module
+from torch.nn.parallel import DistributedDataParallel
 from torch.optim import Optimizer
 
 from lightning_lite.accelerators import Accelerator
@@ -89,6 +90,20 @@ class DDPShardedStrategy(DDPStrategy):
         model = ShardedDataParallel(module, sharded_optimizer=optimizers, **self._ddp_kwargs)
         return model, optimizers
 
+    def setup_module(self, module: Module) -> DistributedDataParallel:
+        """Setting up the module without optimizers in this strategy is not supported.
+
+        Please use :meth:`setup_module_and_optimizers` instead.
+        """
+        raise NotImplementedError(self._err_msg_joint_setup_required())
+
+    def setup_optimizer(self, optimizer: Optimizer) -> Optimizer:
+        """Optimizers can only be set up jointly with the model in this strategy.
+
+        Please use :meth:`setup_module_and_optimizers` to set up both module and optimizer(s) together.
+        """
+        raise NotImplementedError(self._err_msg_joint_setup_required())
+
     @classmethod
     def register_strategies(cls, strategy_registry: Dict) -> None:
         strategy_registry.register(
@@ -153,6 +168,20 @@ class DDPSpawnShardedStrategy(DDPSpawnStrategy):
         model = ShardedDataParallel(module, sharded_optimizer=optimizers, **self._ddp_kwargs)
         return model, optimizers
 
+    def setup_module(self, module: Module) -> DistributedDataParallel:
+        """Setting up the module without optimizers in this strategy is not supported.
+
+        Please use :meth:`setup_module_and_optimizers` instead.
+        """
+        raise NotImplementedError(self._err_msg_joint_setup_required())
+
+    def setup_optimizer(self, optimizer: Optimizer) -> Optimizer:
+        """Optimizers can only be set up jointly with the model in this strategy.
+
+        Please use :meth:`setup_module_and_optimizers` to set up both module and optimizer(s) together.
+        """
+        raise NotImplementedError(self._err_msg_joint_setup_required())
+
     @classmethod
     def register_strategies(cls, strategy_registry: Dict) -> None:
         strategy_registry.register(

src/lightning_lite/strategies/strategy.py

@@ -118,7 +118,7 @@ class Strategy(ABC):
         """Set up a model and multiple optimizers together.
 
         The returned objects are expected to be in the same order they were passed in. The default implementation will
-        call :meth:`_setup_model` and :meth:`_setup_optimizer` on the inputs.
+        call :meth:`setup_module` and :meth:`setup_optimizer` on the inputs.
         """
         module = self.setup_module(module)
         optimizers = [self.setup_optimizer(optimizer) for optimizer in optimizers]
@@ -288,6 +288,12 @@ class Strategy(ABC):
     def register_strategies(cls, strategy_registry: Dict[str, Any]) -> None:
         pass
 
+    def _err_msg_joint_setup_required(self) -> str:
+        return (
+            f"The `{type(self).__name__}` does not support setting up the module and optimizer(s) independently."
+            " Please call `setup_module_and_optimizers(model, [optimizer, ...])` to jointly set them up."
+        )
+
 
 class _BackwardSyncControl(ABC):
     """Interface for any :class:`Strategy` that wants to offer a functionality to enable or disable gradient

tests/tests_lite/strategies/test_deepspeed.py

@@ -13,8 +13,12 @@
 # limitations under the License.
 import json
 import os
+from re import escape
+from unittest import mock
+from unittest.mock import ANY, Mock
 
 import pytest
+import torch
 from tests_lite.helpers.runif import RunIf
 
 from lightning_lite.accelerators import CPUAccelerator
@@ -116,3 +120,34 @@ def test_deepspeed_config_zero_offload(deepspeed_zero_config):
     deepspeed_zero_config["zero_optimization"]["offload_optimizer"] = False
     strategy = DeepSpeedStrategy(config=deepspeed_zero_config)
     assert strategy.config["zero_optimization"]["offload_optimizer"] is False
+
+
+@RunIf(deepspeed=True)
+@mock.patch("lightning_lite.strategies.deepspeed.deepspeed.initialize")
+def test_deepspeed_setup_module(init_mock):
+    """Test that the DeepSpeed strategy can set up the model for inference (no optimizer required)."""
+    model = Mock()
+    model.parameters.return_value = []
+    strategy = DeepSpeedStrategy()
+    strategy.parallel_devices = [torch.device("cuda", 1)]
+    init_mock.return_value = [Mock()] * 4  # mock to make tuple unpacking work
+
+    strategy.setup_module(model)
+    init_mock.assert_called_with(
+        args=ANY,
+        config=strategy.config,
+        model=model,
+        model_parameters=ANY,
+        optimizer=None,
+        dist_init_required=False,
+    )
+
+
+@RunIf(deepspeed=True)
+def test_deepspeed_requires_joint_setup():
+    """Test that the DeepSpeed strategy does not support setting up model and optimizer independently."""
+    strategy = DeepSpeedStrategy()
+    with pytest.raises(
+        NotImplementedError, match=escape("does not support setting up the module and optimizer(s) independently")
+    ):
+        strategy.setup_optimizer(Mock())

tests/tests_lite/strategies/test_fairscale.py

@@ -11,6 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from re import escape
 from unittest import mock
 from unittest.mock import MagicMock, Mock
 
@@ -89,3 +90,18 @@ def test_fairscale_no_backward_sync(cls):
         pass
 
     module.no_sync.assert_called_once()
+
+
+@pytest.mark.parametrize("cls", [DDPShardedStrategy, DDPSpawnShardedStrategy])
+def test_fairscale_requires_joint_setup(cls):
+    """Test that the fairscale sharded strategy does not support setting up model and optimizer independently."""
+    strategy = cls()
+    with pytest.raises(
+        NotImplementedError, match=escape("does not support setting up the module and optimizer(s) independently")
+    ):
+        strategy.setup_module(Mock())
+
+    with pytest.raises(
+        NotImplementedError, match=escape("does not support setting up the module and optimizer(s) independently")
+    ):
+        strategy.setup_optimizer(Mock())

tests/tests_lite/test_lite.py

@@ -27,7 +27,16 @@ from torch.utils.data import DataLoader, DistributedSampler, Sampler
 
 from lightning_lite.lite import LightningLite
 from lightning_lite.plugins import Precision
-from lightning_lite.strategies import DDPStrategy, ParallelStrategy, SingleDeviceStrategy, Strategy
+from lightning_lite.strategies import (
+    DDPShardedStrategy,
+    DDPSpawnShardedStrategy,
+    DDPStrategy,
+    DeepSpeedStrategy,
+    ParallelStrategy,
+    SingleDeviceStrategy,
+    Strategy,
+    XLAStrategy,
+)
 from lightning_lite.strategies.strategy import _Sharded
 from lightning_lite.utilities import _StrategyType
 from lightning_lite.utilities.exceptions import MisconfigurationException
@@ -72,11 +81,13 @@ def test_run_input_output():
 
 
 @mock.patch("lightning_lite.strategies.ddp.DistributedDataParallel")
-def test_setup_model(ddp_mock):
+@pytest.mark.parametrize("setup_method", ["setup", "setup_module"])
+def test_setup_module(ddp_mock, setup_method):
     """Test that the setup method lets the strategy wrap the model, but keeps a reference to the original model."""
     lite = EmptyLite(accelerator="cpu", strategy="ddp", devices=2)
     model = nn.Linear(1, 2)
-    lite_model = lite.setup(model)
+    setup_method = getattr(lite, setup_method)
+    lite_model = setup_method(model)
     ddp_mock.assert_called_with(module=model, device_ids=ANY)
     assert lite_model.module == model
     assert lite_model.weight is model.weight
@@ -95,7 +106,8 @@ def test_setup_model(ddp_mock):
     ],
 )
 @pytest.mark.parametrize("move_to_device", [True, False])
-def test_setup_model_move_to_device(move_to_device, accelerator, initial_device, target_device):
+@pytest.mark.parametrize("setup_method", ["setup", "setup_module"])
+def test_setup_module_move_to_device(setup_method, move_to_device, accelerator, initial_device, target_device):
     """Test that `move_to_device` leads to parameters being moved to the correct device and that the device
     attributes on the wrapper are updated."""
     initial_device = torch.device(initial_device)
@@ -105,7 +117,8 @@ def test_setup_model_move_to_device(move_to_device, accelerator, initial_device,
     lite = EmptyLite(accelerator=accelerator, devices=1)
     model = nn.Linear(1, 2)
     model.to(initial_device)
-    lite_model = lite.setup(model, move_to_device=move_to_device)
+    setup_method = getattr(lite, setup_method)
+    lite_model = setup_method(model, move_to_device=move_to_device)
 
     # all parameters on the expected device
     assert all(param.device == expected_device for param in model.parameters())
@@ -117,7 +130,8 @@ def test_setup_model_move_to_device(move_to_device, accelerator, initial_device,
 
 @RunIf(min_cuda_gpus=1)
 @pytest.mark.parametrize("move_to_device", [True, False])
-def test_setup_model_parameters_on_different_devices(move_to_device):
+@pytest.mark.parametrize("setup_method", ["setup", "setup_module"])
+def test_setup_module_parameters_on_different_devices(setup_method, move_to_device):
     """Test that a warning is emitted when model parameters are on a different device prior to calling
     `setup()`."""
     device0 = torch.device("cpu")
@@ -129,9 +143,11 @@ def test_setup_model_parameters_on_different_devices(move_to_device):
     module1 = nn.Linear(1, 2).to(device1)
     model = nn.Sequential(module0, module1)
 
+    setup_method = getattr(lite, setup_method)
+
     if move_to_device:
         with pytest.warns(PossibleUserWarning, match="has parameters on different devices"):
-            lite_model = lite.setup(model, move_to_device=move_to_device)
+            lite_model = setup_method(model, move_to_device=move_to_device)
 
         # both have the same device now
         assert lite_model.device == device1
@@ -139,11 +155,11 @@ def test_setup_model_parameters_on_different_devices(move_to_device):
         assert module1.weight.device == module1.bias.device == device1
     else:
         with no_warning_call(expected_warning=PossibleUserWarning, match="has parameters on different devices"):
-            lite.setup(model, move_to_device=move_to_device)
+            setup_method(model, move_to_device=move_to_device)
 
 
-def test_setup_optimizers():
-    """Test that setup_optimizers can handle no optimizers, one optimizer, or multiple optimizers."""
+def test_setup_module_and_optimizers():
+    """Test that `setup()` can handle no optimizers, one optimizer, or multiple optimizers."""
     lite = EmptyLite()
     model = nn.Linear(1, 2)
     optimizer0 = torch.optim.SGD(model.parameters(), lr=0.1)
@@ -171,8 +187,28 @@ def test_setup_optimizers():
     assert lite_optimizer1.optimizer is optimizer1
 
 
+def test_setup_optimizers():
+    """Test that `setup_optimizers()` can handle one or more optimizers."""
+    lite = EmptyLite()
+    model = nn.Linear(1, 2)
+    optimizer0 = torch.optim.SGD(model.parameters(), lr=0.1)
+    optimizer1 = torch.optim.Adam(model.parameters(), lr=0.1)
+
+    # single optimizer
+    lite_optimizer = lite.setup_optimizers(optimizer0)
+    assert isinstance(lite_optimizer, _LiteOptimizer)
+    assert lite_optimizer.optimizer is optimizer0
+
+    # multiple optimizers
+    lite_optimizer0, lite_optimizer1 = lite.setup_optimizers(optimizer0, optimizer1)
+    assert isinstance(lite_optimizer0, _LiteOptimizer)
+    assert isinstance(lite_optimizer1, _LiteOptimizer)
+    assert lite_optimizer0.optimizer is optimizer0
+    assert lite_optimizer1.optimizer is optimizer1
+
+
 def test_setup_twice_fails():
-    """Test that calling setup with a model or optimizer that is already wrapped fails."""
+    """Test that calling `setup` with a model or optimizer that is already wrapped fails."""
     lite = EmptyLite()
     model = nn.Linear(1, 2)
     optimizer = torch.optim.Adam(model.parameters())
@@ -186,6 +222,49 @@ def test_setup_twice_fails():
         lite.setup(model, lite_optimizer)
 
 
+def test_setup_module_twice_fails():
+    """Test that calling `setup_module` with a model that is already wrapped fails."""
+    lite = EmptyLite()
+    model = nn.Linear(1, 2)
+
+    lite_model = lite.setup_module(model)
+    with pytest.raises(ValueError, match="A model should be passed only once to the"):
+        lite.setup_module(lite_model)
+
+
+def test_setup_optimizers_twice_fails():
+    """Test that calling `setup_module` with a model that is already wrapped fails."""
+    lite = EmptyLite()
+    model = nn.Linear(1, 2)
+    optimizer = torch.optim.Adam(model.parameters())
+
+    lite_optimizer = lite.setup_optimizers(optimizer)
+    with pytest.raises(ValueError, match="An optimizer should be passed only once to"):
+        lite.setup_optimizers(lite_optimizer)
+
+
+@pytest.mark.parametrize("strategy_cls", [DDPShardedStrategy, DDPSpawnShardedStrategy])
+def test_setup_module_not_supported(strategy_cls):
+    """Test that `setup_module` validates the strategy supports setting up model and optimizers independently."""
+    lite = EmptyLite()
+    model = nn.Linear(1, 2)
+    lite._strategy = Mock(spec=strategy_cls)
+    with pytest.raises(RuntimeError, match=escape("requires the model and optimizer(s) to be set up jointly through")):
+        lite.setup_module(model)
+
+
+@pytest.mark.parametrize("strategy_cls", [DeepSpeedStrategy, DDPShardedStrategy, DDPSpawnShardedStrategy, XLAStrategy])
+def test_setup_optimizers_not_supported(strategy_cls):
+    """Test that `setup_optimizers` validates the strategy supports setting up model and optimizers
+    independently."""
+    lite = EmptyLite()
+    model = nn.Linear(1, 2)
+    optimizer = torch.optim.Adam(model.parameters())
+    lite._strategy = Mock(spec=strategy_cls)
+    with pytest.raises(RuntimeError, match=escape("requires the model and optimizer(s) to be set up jointly through")):
+        lite.setup_optimizers(optimizer)
+
+
 def test_setup_tracks_num_models():
     """Test that setup() tracks how many times it has setup a model."""
     lite = EmptyLite()
@@ -199,10 +278,15 @@ def test_setup_tracks_num_models():
     lite.setup(model, optimizer)
     assert lite._models_setup == 2
 
+    lite.setup_module(model)
+    assert lite._models_setup == 3
 
-def test_setup_dataloaders_unsupported_type():
+
+def test_setup_dataloaders_unsupported_input():
     """Test that the setup_dataloaders method fails when provided with non-DataLoader objects."""
     lite = EmptyLite()
+    with pytest.raises(ValueError, match="`setup_dataloaders` requires at least one dataloader"):
+        lite.setup_dataloaders()
     with pytest.raises(TypeError, match="Only PyTorch DataLoader are currently supported"):
         lite.setup_dataloaders(range(2))  # type: ignore