Configure no restart validation loop in nl.Trainer (#11029)

* Configure no restart validation loop in nl.Trainer

Signed-off-by: Hemil Desai <[email protected]>

* fix

Signed-off-by: Hemil Desai <[email protected]>

* Skip validation whenever restarting=True

Signed-off-by: Hemil Desai <[email protected]>

* PR feedback

Signed-off-by: Hemil Desai <[email protected]>

* Apply isort and black reformatting

Signed-off-by: hemildesai <[email protected]>

---------

Signed-off-by: Hemil Desai <[email protected]>
Signed-off-by: hemildesai <[email protected]>
Co-authored-by: hemildesai <[email protected]>

nemo/collections/llm/api.py

@@ -25,7 +25,14 @@
 from typing_extensions import Annotated
 
 import nemo.lightning as nl
-from nemo.lightning import AutoResume, NeMoLogger, OptimizerModule, Trainer, io
+from nemo.lightning import (
+    AutoResume,
+    NeMoLogger,
+    OptimizerModule,
+    Trainer,
+    configure_no_restart_validation_training_loop,
+    io,
+)
 from nemo.lightning.base import NEMO_MODELS_CACHE
 from nemo.lightning.pytorch.callbacks import PEFT, ModelTransform
 from nemo.utils import logging
@@ -680,6 +687,7 @@ def _setup(
     tokenizer: Optional[TokenizerType],
     model_transform: Optional[Union[PEFT, ModelTransform, Callable]],
 ) -> Any:  # Return type is Any because app_state's type is not specified
+    configure_no_restart_validation_training_loop(trainer)
     _log = log or NeMoLogger()
     if resume and isinstance(model_transform, PEFT) and _log.ckpt:
         logging.info("Disabling try_restore_best_ckpt restoration for adapters")

nemo/lightning/__init__.py

@@ -33,7 +33,7 @@
 from nemo.lightning.pytorch.plugins import data_sampler as _data_sampler
 from nemo.lightning.pytorch.strategies import FSDPStrategy, MegatronStrategy
 from nemo.lightning.pytorch.strategies.utils import RestoreConfig
-from nemo.lightning.pytorch.trainer import Trainer
+from nemo.lightning.pytorch.trainer import Trainer, configure_no_restart_validation_training_loop
 from nemo.lightning.resume import AutoResume
 
 
@@ -66,6 +66,7 @@ def _is_slurm_interactive_mode():
     "ModelCheckpoint",
     "OptimizerModule",
     "Trainer",
+    "configure_no_restart_validation_training_loop",
     "get_vocab_size",
     "teardown",
 ]

nemo/lightning/pytorch/trainer.py

@@ -12,19 +12,54 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import warnings
 from copy import deepcopy
 
 import fiddle as fdl
 import pytorch_lightning as pl
+from pytorch_lightning.loops import _TrainingEpochLoop
+from pytorch_lightning.loops.fetchers import _DataFetcher
 from typing_extensions import Self
 
 from nemo.lightning.fabric.conversion import to_fabric
 from nemo.lightning.fabric.fabric import Fabric
 from nemo.lightning.io.mixin import IOMixin, serialization, track_io
 
 
-class Trainer(pl.Trainer, IOMixin):
+class NoValOnRestartTrainingLoop(_TrainingEpochLoop):
+    """
+    Extend the PTL Epoch loop to skip validation when restarting.
+    This happens when resuming a checkpoint that has already run validation, but loading restores
+    the training state before validation has run.
+    """
+
+    def _should_check_val_fx(self, data_fetcher) -> bool:
+        if self.skip_val_on_restart:
+            return False
+        return super()._should_check_val_fx(data_fetcher)
+
+    def load_state_dict(self, state_dict: dict, prefix: str = "") -> None:
+        super().load_state_dict(state_dict, prefix)
+
+        self.skip_val_on_restart = True
+
+    def advance(self, data_fetcher: _DataFetcher) -> None:
+        super().advance(data_fetcher)
+
+        self.skip_val_on_restart = False
 
+
+def configure_no_restart_validation_training_loop(trainer: pl.Trainer) -> None:
+    if not isinstance(trainer.fit_loop.epoch_loop, _TrainingEpochLoop):
+        warnings.warn("Detected custom epoch loop. Skipping no validation on restart support.", UserWarning)
+        return
+
+    ## Pass trainer object to avoid trainer getting overwritten as None
+    loop = NoValOnRestartTrainingLoop(trainer, trainer.min_steps, trainer.max_steps)
+    trainer.fit_loop.epoch_loop = loop
+
+
+class Trainer(pl.Trainer, IOMixin):
     def add_io(self, obj):
         """Recurse to the leaves of a container and add io functionality to non-serializable leaves"""
         if isinstance(obj, (dict, list)):