Remove support for passing strategy strings to accelerator (#12696)

Co-authored-by: Kushashwa Ravi Shrimali <[email protected]>

Author: awaelchli

CHANGELOG.md

@@ -102,6 +102,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Removed deprecated `GPUStatsMonitor` callback ([#12554](https://github.com/PyTorchLightning/pytorch-lightning/pull/12554))
 
+
+- Removed support for passing strategy names or strategy classes to the accelerator Trainer argument ([#12696](https://github.com/PyTorchLightning/pytorch-lightning/pull/12696))
+
+
 ### Fixed
 
 - Run main progress bar updates independent of val progress bar updates in `TQDMProgressBar` ([#12563](https://github.com/PyTorchLightning/pytorch-lightning/pull/12563))

pytorch_lightning/trainer/connectors/accelerator_connector.py

@@ -111,11 +111,9 @@ def __init__(
         components such as the Accelerator and Precision plugins.
 
             A. accelerator flag could be:
-                1. strategy class (deprecated in 1.5 will be removed in 1.7)
-                2. strategy str (deprecated in 1.5 will be removed in 1.7)
-                3. accelerator class
-                4. accelerator str
-                5. accelerator auto
+                1. accelerator class
+                2. accelerator str
+                3. accelerator auto
 
             B. strategy flag could be :
                 1. strategy class
@@ -160,7 +158,6 @@ def __init__(
 
         # Raise an exception if there are conflicts between flags
         # Set each valid flag to `self._x_flag` after validation
-        # Example: If accelerator is set to a strategy type, set `self._strategy_flag = accelerator`.
         # For devices: Assign gpus, ipus, etc. to the accelerator flag and devices flag
         self._strategy_flag: Optional[Union[Strategy, str]] = None
         self._accelerator_flag: Optional[Union[Accelerator, str]] = None
@@ -231,10 +228,9 @@ def _check_config_and_set_final_flags(
     ) -> None:
         """This method checks:
 
-        1. strategy: strategy, accelerator and plugin can all be set to strategies
+        1. strategy: strategy and plugin can be set to strategies
         2. accelerator: if the value of the accelerator argument is a type of accelerator (instance or string),
-            set self._accelerator_flag accordingly. If the value is strategy related (instance or string),
-            it gets handled by 1.
+            set self._accelerator_flag accordingly.
         3. precision: The final value of the precision flag may be determined either by the precision argument or
             by a plugin instance.
         4. plugins: a plugin could occur as a value of the strategy argument (handled by 1), or the precision
@@ -258,17 +254,6 @@ def _check_config_and_set_final_flags(
                     "`Trainer(strategy='tpu_spawn')` is not a valid strategy,"
                     " you can use `Trainer(strategy='ddp_spawn', accelerator='tpu')` instead."
                 )
-            # handle duplications and conflict
-            if isinstance(accelerator, Strategy) and strategy != accelerator:
-                raise MisconfigurationException(
-                    f"Incompatible values set in `strategy` and `accelerator` arguments."
-                    f"Received both strategy={strategy} and accelerator={accelerator}"
-                )
-            if isinstance(accelerator, str) and accelerator in self._registered_strategies and strategy != accelerator:
-                raise MisconfigurationException(
-                    f"strategy {strategy} already set through `strategy` flag,"
-                    f" but have also passed {accelerator} in through the accelerator flag."
-                )
             if plugins:
                 for plugin in plugins:
                     if isinstance(plugin, Strategy):
@@ -285,14 +270,6 @@ def _check_config_and_set_final_flags(
         if accelerator is not None:
             if accelerator in self._accelerator_types or accelerator == "auto" or isinstance(accelerator, Accelerator):
                 self._accelerator_flag = accelerator
-            elif accelerator in self._registered_strategies or isinstance(accelerator, Strategy):
-                rank_zero_deprecation(
-                    f"Passing `Trainer(accelerator={accelerator!r})` has been deprecated"
-                    f" in v1.5 and will be removed in v1.7. Use `Trainer(strategy={accelerator!r})` instead."
-                )
-                self._strategy_flag = accelerator
-            elif accelerator == "ddp_cpu" and not self._strategy_flag:
-                self._strategy_flag = accelerator
 
         if precision is not None:
             if str(precision) not in self._precision_types:
@@ -431,7 +408,7 @@ def _check_device_config_and_set_final_flags(
         if self._devices_flag == "auto" and self._accelerator_flag is None:
             raise MisconfigurationException(
                 f"You passed `devices={devices}` but haven't specified"
-                " `accelerator=('auto'|'tpu'|'gpu'|'ipu'|'cpu'|'hpu)` for the devices mapping"
+                " `accelerator=('auto'|'tpu'|'gpu'|'ipu'|'cpu'|'hpu)` for the devices mapping."
             )
 
     def _map_deprecated_devices_specific_info_to_accelerator_and_device_flag(
@@ -607,22 +584,6 @@ def _check_strategy_and_fallback(self) -> None:
         # TODO this logic should apply to both str and object config
         strategy_flag = "" if isinstance(self._strategy_flag, Strategy) else self._strategy_flag
 
-        if strategy_flag == "ddp_cpu":
-            if _TPU_AVAILABLE:
-                raise MisconfigurationException(
-                    "`accelerator='ddp_cpu'` is not supported on TPU machines. "
-                    "Learn more: https://github.com/PyTorchLightning/pytorch-lightning/issues/7810"
-                )
-            if self._devices_flag == 1 and self._num_nodes_flag > 1:
-                strategy_flag = DDPStrategy.strategy_name
-            else:
-                strategy_flag = "ddp_spawn"
-            if self._accelerator_flag == "gpu":
-                rank_zero_warn(
-                    "You requested one or more GPUs, but set `accelerator='ddp_cpu'`. Training will not use GPUs."
-                )
-                self._accelerator_flag = "cpu"
-                self.accelerator = CPUAccelerator()
         if strategy_flag in ("ddp_spawn", "ddp_spawn_find_unused_parameters_false") and (
             TorchElasticEnvironment.detect() or KubeflowEnvironment.detect() or self._is_slurm_managing_tasks()
         ):
@@ -643,7 +604,7 @@ def _handle_horovod(self) -> None:
 
         if not _HOROVOD_AVAILABLE:
             raise MisconfigurationException(
-                'Requested `accelerator="horovod"`, but Horovod is not installed.'
+                'Requested `strategy="horovod"`, but Horovod is not installed.'
                 "Install with \n $HOROVOD_WITH_PYTORCH=1 pip install horovod[pytorch]"
             )
 
@@ -792,8 +753,7 @@ def _lazy_init_strategy(self) -> None:
 
         if _IS_INTERACTIVE and self.strategy.launcher and not self.strategy.launcher.is_interactive_compatible:
             raise MisconfigurationException(
-                f"`Trainer(strategy={self.strategy.strategy_name!r})` or"
-                f" `Trainer(accelerator={self.strategy.strategy_name!r})` is not compatible with an interactive"
+                f"`Trainer(strategy={self.strategy.strategy_name!r})` is not compatible with an interactive"
                 " environment. Run your code as a script, or choose one of the compatible strategies:"
                 f" Trainer(strategy=None|{'|'.join(_StrategyType.interactive_compatible_types())})."
                 " In case you are spawning processes yourself, make sure to include the Trainer"

pytorch_lightning/utilities/enums.py

@@ -115,7 +115,6 @@ class DistributedType(LightningEnum, metaclass=_OnAccessEnumMeta):
     DP = "dp"
     DDP = "ddp"
     DDP2 = "ddp2"
-    DDP_CPU = "ddp_cpu"
     DDP_SPAWN = "ddp_spawn"
     TPU_SPAWN = "tpu_spawn"
     DEEPSPEED = "deepspeed"
@@ -240,7 +239,6 @@ class _StrategyType(LightningEnum):
     DP = "dp"
     DDP = "ddp"
     DDP2 = "ddp2"
-    DDP_CPU = "ddp_cpu"
     DDP_SPAWN = "ddp_spawn"
     TPU_SPAWN = "tpu_spawn"
     DEEPSPEED = "deepspeed"