[v1] add seed for training and fix gradient checkpointing (#10211)

examples/v1/train_full/train_full_fsdp2.yaml

@@ -14,16 +14,12 @@ dist_config:
   name: fsdp2
   dcp_path: null # /mnt/f/pretrain_models/Qwen3-0.6B-dcp
 
-init_config:
-  name: init_on_meta
-
 ### data
 train_dataset: data/v1_sft_demo.yaml
 
 ### training
 output_dir: outputs/test_fsdp2
 micro_batch_size: 1
-global_batch_size: 1
 cutoff_len: 2048
 learning_rate: 1.0e-4
 bf16: false

src/llamafactory/v1/config/arg_parser.py

@@ -21,6 +21,7 @@ from omegaconf import OmegaConf
 from transformers import HfArgumentParser
 
 from ..utils.env import is_env_enabled
+from ..utils.helper import set_seed
 from .data_args import DataArguments
 from .model_args import ModelArguments
 from .sample_args import SampleArguments
@@ -56,6 +57,14 @@ def get_args(args: InputArgument = None) -> tuple[ModelArguments, DataArguments,
             print(f"Got unknown args, potentially deprecated arguments: {unknown_args}")
             raise ValueError(f"Some specified arguments are not used by the HfArgumentParser: {unknown_args}")
 
+    # Seed as early as possible after argument parsing so all downstream
+    # components (dist init, dataloader, model init in run_* entrypoints) share the same RNG state.
+    for arg in parsed_args:
+        seed = getattr(arg, "seed", None)
+        if seed is not None:
+            set_seed(seed)
+            break
+
     return tuple(parsed_args)
 
 

src/llamafactory/v1/config/training_args.py

@@ -66,7 +66,7 @@ class TrainingArguments:
         metadata={"help": "Number of workers for batching."},
     )
     enable_activation_checkpointing: bool = field(
-        default=True,
+        default=False,
         metadata={"help": "Enable activation checkpointing for training."},
     )
     dist_config: PluginConfig | None = field(
@@ -81,6 +81,10 @@ class TrainingArguments:
         default=None,
         metadata={"help": "Learning rate scheduler configuration for training."},
     )
+    seed: int = field(
+        default=42,
+        metadata={"help": "Random seed that will be set at the beginning of training."},
+    )
 
     def __post_init__(self) -> None:
         self.dist_config = get_plugin_config(self.dist_config)

src/llamafactory/v1/core/base_trainer.py

@@ -76,7 +76,7 @@ class BaseTrainer:
         if self.args.enable_activation_checkpointing:
             self.model.gradient_checkpointing_enable({"use_reentrant": False})
 
-        self._accelerate_engine = None
+        self._deepspeed_engine = None
         dist_name = self.args.dist_config.name if self.args.dist_config is not None else None
 
         if dist_name == "deepspeed":
@@ -108,6 +108,7 @@ class BaseTrainer:
             cutoff_len=self.args.cutoff_len,
             batching_workers=self.args.batching_workers,
             batching_strategy=self.args.batching_strategy,
+            seed=self.args.seed,
         )
 
     def _shard_model(self) -> None:

src/llamafactory/v1/core/utils/batching.py

@@ -26,6 +26,7 @@
 from collections.abc import Iterator
 from typing import Any
 
+import torch
 from torch.utils.data import default_collate
 from torchdata.stateful_dataloader import StatefulDataLoader
 from torchdata.stateful_dataloader.sampler import StatefulDistributedSampler
@@ -71,6 +72,7 @@ class BatchGenerator(Iterator):
         batching_strategy: BatchingStrategy = BatchingStrategy.NORMAL,
         pin_memory: bool = True,
         drop_last: bool = True,
+        seed: int = 42,
     ) -> None:
         self.dataset = dataset
         self.renderer = renderer
@@ -82,6 +84,7 @@ class BatchGenerator(Iterator):
         self.batching_strategy = batching_strategy
         self.pin_memory = pin_memory
         self.drop_last = drop_last
+        self.seed = seed
         # TODO: support length and infinity
         dp_size = DistributedInterface().get_world_size(Dim.DP)
 
@@ -128,12 +131,15 @@ class BatchGenerator(Iterator):
                 num_replicas=DistributedInterface().get_world_size(Dim.DP),
                 rank=DistributedInterface().get_rank(Dim.DP),
                 shuffle=True,
-                seed=0,
+                seed=self.seed,
                 drop_last=self.drop_last,
             )
         else:
             raise NotImplementedError("Iterable dataset is not supported yet.")
 
+        generato_seed = torch.Generator()
+        generato_seed.manual_seed(self.seed)
+
         self._data_provider = StatefulDataLoader(
             self.dataset,
             batch_size=self.micro_batch_size * self.num_micro_batch,
@@ -143,6 +149,7 @@ class BatchGenerator(Iterator):
             pin_memory=self.pin_memory,
             pin_memory_device=DistributedInterface().current_device.type,
             drop_last=self.drop_last,
+            generator=generato_seed,
         )
         if self.batching_strategy == BatchingStrategy.NORMAL:
             self._length = len(self._data_provider)

src/llamafactory/v1/plugins/trainer_plugins/distributed/fsdp2.py

@@ -166,12 +166,11 @@ class FSDP2Engine:
                     offload_policy=CPUOffloadPolicy(pin_memory=self.pin_memory) if self.offload_params else None,
                 )
 
-        use_gradient_checkpointing = True  # Could be configurable
-        if use_gradient_checkpointing:
+        # BaseTrainer is the single source of truth for gradient checkpointing.
+        # FSDP2 only applies the input-grad compatibility hook when checkpointing is already enabled.
+        if getattr(model, "is_gradient_checkpointing", False):
             if self.rank == 0:
-                logger.info("Enabling gradient checkpointing (transformers native)...")
-
-            model.gradient_checkpointing_enable(gradient_checkpointing_kwargs={"use_reentrant": False})
+                logger.info("Gradient checkpointing is enabled. Applying FSDP2 input grad preparation.")
 
             if hasattr(model, "enable_input_require_grads"):
                 model.enable_input_require_grads()

src/llamafactory/v1/utils/helper.py

@@ -15,12 +15,22 @@
 
 import torch
 from transformers import PreTrainedTokenizer
+from transformers import set_seed as hf_set_seed
 
 from ..accelerator.interface import DistributedInterface
 from .constants import IGNORE_INDEX
 from .types import BatchInput, ModelInput, Processor, Tensor
 
 
+def set_seed(seed: int) -> None:
+    """Set seed for reproducibility.
+
+    Args:
+        seed: Random seed.
+    """
+    hf_set_seed(seed)
+
+
 def is_tokenizer(processor: Processor) -> bool:
     """Check if processor is tokenizer.