[checkpointio] sharded optimizer checkpoint for DDP plugin (#4002)

colossalai/booster/booster.py

@@ -9,6 +9,7 @@ from torch.optim.lr_scheduler import _LRScheduler as LRScheduler
 from torch.utils.data import DataLoader
 
 from colossalai.checkpoint_io import GeneralCheckpointIO
+from colossalai.interface import ModelWrapper
 
 from .accelerator import Accelerator
 from .mixed_precision import MixedPrecision, mixed_precision_factory
@@ -165,11 +166,11 @@ class Booster:
         assert self.plugin.support_no_sync, f'The plugin {self.plugin.__class__.__name__} does not support no_sync.'
         return self.plugin.no_sync(model)
 
-    def load_model(self, model: nn.Module, checkpoint: str, strict: bool = True):
+    def load_model(self, model: Union[nn.Module, ModelWrapper], checkpoint: str, strict: bool = True):
         """Load model from checkpoint.
 
         Args:
-            model (nn.Module): A model boosted by Booster.
+            model (nn.Module or ModelWrapper): A model boosted by Booster.
             checkpoint (str): Path to the checkpoint. It must be a local path.
                 It should be a directory path if the checkpoint is sharded. Otherwise, it should be a file path.
             strict (bool, optional): whether to strictly enforce that the keys
@@ -179,24 +180,34 @@ class Booster:
         self.checkpoint_io.load_model(model, checkpoint, strict)
 
     def save_model(self,
-                   model: nn.Module,
+                   model: Union[nn.Module, ModelWrapper],
                    checkpoint: str,
-                   prefix: str = None,
                    shard: bool = False,
-                   size_per_shard: int = 1024):
+                   gather_dtensor: bool = True,
+                   prefix: Optional[str] = None,
+                   size_per_shard: int = 1024,
+                   use_safetensors: bool = False):
         """Save model to checkpoint.
 
         Args:
-            model (nn.Module): A model boosted by Booster.
+            model (nn.Module or ModelWrapper): A model boosted by Booster.
             checkpoint (str): Path to the checkpoint. It must be a local path.
                 It is a file path if ``shard=False``. Otherwise, it is a directory path.
-            prefix (str, optional): A prefix added to parameter and buffer
-                names to compose the keys in state_dict. Defaults to None.
             shard (bool, optional): Whether to save checkpoint a sharded way.
                 If true, the checkpoint will be a folder. Otherwise, it will be a single file. Defaults to False.
+            gather_dtensor (bool, optional): whether to gather the distributed tensor to the first device. Default: True.
+            prefix (str, optional): A prefix added to parameter and buffer
+                names to compose the keys in state_dict. Defaults to None.
             size_per_shard (int, optional): Maximum size of checkpoint shard file in MB. This is useful only when ``shard=True``. Defaults to 1024.
+            use_safetensors (bool, optional): whether to use safe tensors. Default: False. If set to True, the checkpoint will be saved.
         """
-        self.checkpoint_io.save_model(model, checkpoint=checkpoint, shard=shard, size_per_shard=size_per_shard)
+        self.checkpoint_io.save_model(model,
+                                      checkpoint=checkpoint,
+                                      shard=shard,
+                                      gather_dtensor=gather_dtensor,
+                                      prefix=prefix,
+                                      size_per_shard=size_per_shard,
+                                      use_safetensors=use_safetensors)
 
     def load_optimizer(self, optimizer: Optimizer, checkpoint: str):
         """Load optimizer from checkpoint.
@@ -205,12 +216,21 @@ class Booster:
             optimizer (Optimizer): An optimizer boosted by Booster.
             checkpoint (str): Path to the checkpoint. It must be a local path.
                 It should be a directory path if the checkpoint is sharded. Otherwise, it should be a file path.
+            prefix (str, optional): A prefix added to parameter and buffer
+                names to compose the keys in state_dict. Defaults to None.
+            size_per_shard (int, optional): Maximum size of checkpoint shard file in MB. This is useful only when ``shard=True``. Defaults to 1024.
         """
         self.checkpoint_io.load_optimizer(optimizer, checkpoint)
 
-    def save_optimizer(self, optimizer: Optimizer, checkpoint: str, shard: bool = False, size_per_shard: int = 1024):
+    def save_optimizer(self,
-        """Save optimizer to checkpoint.
+                       optimizer: Optimizer,
-        Warning: Saving sharded optimizer checkpoint is not supported yet.
+                       checkpoint: str,
+                       shard: bool = False,
+                       gather_dtensor: bool = True,
+                       prefix: Optional[str] = None,
+                       size_per_shard: int = 1024):
+        """
+        Save optimizer to checkpoint.
 
         Args:
             optimizer (Optimizer): An optimizer boosted by Booster.
@@ -218,9 +238,12 @@ class Booster:
                 It is a file path if ``shard=False``. Otherwise, it is a directory path.
             shard (bool, optional): Whether to save checkpoint a sharded way.
                 If true, the checkpoint will be a folder. Otherwise, it will be a single file. Defaults to False.
+            gather_dtensor (bool): whether to gather the distributed tensor to the first device. Default: True.
+            prefix (str, optional): A prefix added to parameter and buffer
+                names to compose the keys in state_dict. Defaults to None.
             size_per_shard (int, optional): Maximum size of checkpoint shard file in MB. This is useful only when ``shard=True``. Defaults to 1024.
         """
-        self.checkpoint_io.save_optimizer(optimizer, checkpoint, shard, size_per_shard)
+        self.checkpoint_io.save_optimizer(optimizer, checkpoint, shard, gather_dtensor, prefix, size_per_shard)
 
     def save_lr_scheduler(self, lr_scheduler: LRScheduler, checkpoint: str):
         """Save lr scheduler to checkpoint.

colossalai/booster/plugin/torch_ddp_plugin.py

@@ -52,7 +52,7 @@ class TorchDDPCheckpointIO(GeneralCheckpointIO):
     def save_sharded_model(self,
                            model: nn.Module,
                            checkpoint_path: str,
-                           gather_dtensor: bool = False,
+                           gather_dtensor: bool = True,
                            prefix: Optional[str] = None,
                            max_shard_size: int = 1024,
                            use_safetensors: bool = False):
@@ -62,8 +62,12 @@ class TorchDDPCheckpointIO(GeneralCheckpointIO):
         if self.coordinator.is_master():
             super().save_sharded_model(model, checkpoint_path, gather_dtensor, prefix, max_shard_size, use_safetensors)
 
-    def save_sharded_optimier(self, optimizer: Optimizer, checkpoint: str, gather_dtensor: bool, prefix: str,
+    def save_sharded_optimizer(self,
-                              size_per_shard: int):
+                               optimizer: Optimizer,
+                               checkpoint: str,
+                               gather_dtensor: bool = True,
+                               prefix: Optional[str] = None,
+                               size_per_shard: int = 1024):
         """
         Save optimizer to checkpoint but only on master process.
         """

colossalai/checkpoint_io/checkpoint_io_base.py

@@ -148,6 +148,9 @@ class CheckpointIO(ABC):
         Args:
             optimizer (Optimizer): optimizer to be loaded.
             checkpoint (str): checkpoint path. This value is made compatibility with the model checkpoints in the
+            prefix (str, optional): A prefix added to parameter and buffer
+                names to compose the keys in state_dict. Defaults to None.
+            size_per_shard (int, optional): Maximum size of checkpoint shard file in MB. This is useful only when ``shard=True``. Defaults to 1024.
         """
         index_file_exists, index_file_path = has_index_file(checkpoint)
 
@@ -157,7 +160,7 @@ class CheckpointIO(ABC):
 
         if index_file_exists:
             # the existence of index file means it is a sharded checkpoint
-            self.load_sharded_optimizer(optimizer, index_file_path, prefix, size_per_shard)
+            self.load_sharded_optimizer(optimizer, index_file_path, prefix)
         else:
             self.load_unsharded_optimizer(optimizer, checkpoint)
 
@@ -251,7 +254,7 @@ class CheckpointIO(ABC):
     # ========================================================
 
     @abstractmethod
-    def load_sharded_optimizer(self, optimizer: Optimizer, index_file_path: str, prefix: str, size_per_shard: int):
+    def load_sharded_optimizer(self, optimizer: Optimizer, index_file_path: str, prefix: str):
         """
         Load optimizer from sharded checkpoint.
 
@@ -259,7 +262,6 @@ class CheckpointIO(ABC):
             optimizer (Optimizer): optimizer to be loaded.
             index_file_path (str): checkpoint path. It should be path to the .index.json file or a path to a directory which contains a .index.json file.
             prefix (str): prefix for the optimizer checkpoint.
-            size_per_shard (int): size per shard in MB.
         """
         pass
 

colossalai/checkpoint_io/general_checkpoint_io.py

@@ -8,6 +8,8 @@ from typing import Iterator, Optional, OrderedDict, Tuple
 import torch.nn as nn
 from torch.optim import Optimizer
 
+from colossalai.interface import OptimizerWrapper
+
 from .checkpoint_io_base import CheckpointIO
 from .index_file import CheckpointIndexFile
 from .utils import (
@@ -50,11 +52,15 @@ class GeneralCheckpointIO(CheckpointIO):
         # save the checkpoint
         save_state_dict(state_dict, checkpoint, use_safetensors)
 
-    def load_sharded_optimizer(self, optimizer: Optimizer, index_file_path: str, prefix: str, size_per_shard: int):
+    def load_sharded_optimizer(self, optimizer: Optimizer, index_file_path: str, prefix: str):
         """
         Load sharded optimizer with the given path to index file.
         """
-        optimizer.load_state_dict
+
+        # If optimizer is wrapped, unwrap it.
+        if isinstance(optimizer, OptimizerWrapper):
+            optimizer = optimizer.optim
+
         # Read checkpoint index file.
         ckpt_index_file = CheckpointIndexFile.from_file(index_file_path)
 

colossalai/checkpoint_io/utils.py

@@ -139,6 +139,12 @@ def shard_optimizer_checkpoint(state_dict: dict, max_shard_size: int = 1024) ->
         state_size = 0
         isDTensor = False
         for state_tensor in state.values():
+
+            # When state_tensor is None (e.g., a SGD optimizer with momentum set to 0),
+            # The calculation of tensor size should be skipped to avoid error.
+            if state_tensor is None:
+                continue
+
             # If the states are stored as DTensors, mark isDTensor as true.
             if type(state_tensor) == DTensor:
                 isDTensor = True
@@ -271,7 +277,7 @@ def load_param_groups_into_optimizer(optimizer: Optimizer, param_group_path: str
     return id_map
 
 
-def load_states_into_optimizer(optimzier: Optimizer, state_dict: dict, id_map: dict):
+def load_states_into_optimizer(optimizer: Optimizer, state_dict: dict, id_map: dict):
     r"""Copies states from `state_dict` into an Optimizer object.
 
     Args:
@@ -311,10 +317,16 @@ def load_states_into_optimizer(optimzier: Optimizer, state_dict: dict, id_map: d
         else:
             new_states[k] = v
 
-    optimzier.state.update(new_states)
+    optimizer.state.update(new_states)
 
 
 def sharded_optimizer_loading_epilogue(optimizer: Optimizer):
+    r"""Do the cleaning up work after state_dict has been loaded into optimizer
+
+    Args:
+        optimizer(Optimizer): An optimizer object whose state has just been loaded.
+    """
+
     # Do the cleaning up as in src code of Pytorch.
     optimizer._hook_for_profile()    # To support multiprocessing pickle/unpickle.
     optimizer.defaults.setdefault('differentiable', False)

tests/test_checkpoint_io/test_torch_ddp_checkpoint_io.py

@@ -13,7 +13,8 @@ from colossalai.testing import check_state_dict_equal, parameterize, rerun_if_ad
 
 
 @parameterize('shard', [True, False])
-def check_torch_ddp_checkpointIO(shard: bool):
+@parameterize('size_per_shard', [16, 128])
+def check_torch_ddp_checkpointIO(shard: bool, size_per_shard: int):
     plugin = TorchDDPPlugin()
     booster = Booster(plugin=plugin)
     model = resnet18()
@@ -38,10 +39,8 @@ def check_torch_ddp_checkpointIO(shard: bool):
         model_ckpt_path = f"{tempdir}/model"
         optimizer_ckpt_path = f"{tempdir}/optimizer"
         lr_scheduler_ckpt_path = f"{tempdir}/lr_scheduler"
-        booster.save_model(model, model_ckpt_path, shard=shard)
+        booster.save_model(model, model_ckpt_path, shard=shard, size_per_shard=size_per_shard)
-        if not shard:
+        booster.save_optimizer(optimizer, optimizer_ckpt_path, shard=shard, size_per_shard=size_per_shard)
-            # TODO(ver217): optimizer checkpointing is not supported for sharded checkpoint
-            booster.save_optimizer(optimizer, optimizer_ckpt_path)
         booster.save_lr_scheduler(scheduler, lr_scheduler_ckpt_path)
         dist.barrier()
 
@@ -55,7 +54,6 @@ def check_torch_ddp_checkpointIO(shard: bool):
         booster.load_model(new_model, model_ckpt_path)
         check_state_dict_equal(model.state_dict(), new_model.state_dict(), False)
 
-        if not shard:
         booster.load_optimizer(new_optimizer, optimizer_ckpt_path)
         check_state_dict_equal(optimizer.state_dict(), new_optimizer.state_dict(), False)
         booster.load_lr_scheduler(new_scheduler, lr_scheduler_ckpt_path)