diff --git "a/janus/lib/python3.10/site-packages/torch/distributed/fsdp/fully_sharded_data_parallel.py" "b/janus/lib/python3.10/site-packages/torch/distributed/fsdp/fully_sharded_data_parallel.py" new file mode 100644--- /dev/null +++ "b/janus/lib/python3.10/site-packages/torch/distributed/fsdp/fully_sharded_data_parallel.py" @@ -0,0 +1,2185 @@ +# mypy: ignore-errors + +import contextlib +import copy +import functools +import math +import traceback +import warnings +from contextlib import contextmanager +from enum import auto, Enum +from typing import ( + Any, + Callable, + Dict, + Generator, + Iterable, + Iterator, + List, + Optional, + Tuple, + Union, +) + +import torch +import torch.distributed as dist +import torch.distributed.fsdp._traversal_utils as traversal_utils +import torch.nn as nn +from torch.distributed.algorithms._checkpoint.checkpoint_wrapper import ( + _CHECKPOINT_WRAPPED_MODULE, + ActivationWrapper, +) +from torch.distributed.algorithms._comm_hooks import LOW_PRECISION_HOOKS +from torch.distributed.fsdp._common_utils import ( + _FSDPState, + _get_param_to_fqns, + FSDP_PREFIX, + FSDP_WRAPPED_MODULE, + HandleTrainingState, + TrainingState, +) +from torch.distributed.fsdp._dynamo_utils import _annotate_modules_for_dynamo +from torch.distributed.fsdp._init_utils import ( + _check_orig_params_flattened, + _init_buffer_state, + _init_core_state, + _init_device_handle, + _init_extension, + _init_ignored_module_states, + _init_param_handle_from_module, + _init_prefetching_state, + _init_process_group_state, + _init_runtime_state, + _init_state_dict_state, + HYBRID_SHARDING_STRATEGIES, + ProcessGroupType, +) +from torch.distributed.fsdp._runtime_utils import ( + _get_fsdp_root_states, + _is_fsdp_root, + _lazy_init, + _post_forward, + _post_forward_reshard, + _pre_forward, + _pre_forward_unshard, + _root_pre_forward, + _unshard, + _wait_for_computation_stream, +) +from torch.distributed.fsdp._wrap_utils import _auto_wrap +from torch.distributed.fsdp.api import ( + BackwardPrefetch, + CPUOffload, + FullOptimStateDictConfig, + FullStateDictConfig, + LocalOptimStateDictConfig, + LocalStateDictConfig, + MixedPrecision, + OptimStateDictConfig, + ShardedOptimStateDictConfig, + ShardedStateDictConfig, + ShardingStrategy, + StateDictConfig, + StateDictSettings, + StateDictType, +) +from torch.distributed.tensor import DeviceMesh +from torch.distributed.utils import _p_assert + +from ._flat_param import FlatParameter, FlatParamHandle +from ._optim_utils import ( + _flatten_optim_state_dict, + _get_param_id_to_param_from_optim_input, + _get_param_key_to_param, + _get_param_to_param_id_from_optim_input, + _get_param_to_param_key, + _optim_state_dict, + _rekey_sharded_optim_state_dict, + _set_optim_use_dtensor, +) +from ._state_dict_utils import _register_all_state_dict_hooks +from ._unshard_param_utils import ( + _deregister_orig_params, + _register_flat_param, + _register_orig_params, + _unshard_params, + _unshard_params_for_summon, +) +from .wrap import CustomPolicy, ModuleWrapPolicy + + +__all__ = [ + "FullyShardedDataParallel", + "OptimStateKeyType", +] + + +FLAT_PARAM = "_flat_param" + + +class OptimStateKeyType(Enum): + """Represents the type of key in an optimizer state-dict.""" + + PARAM_NAME = auto() + PARAM_ID = auto() + + +class FullyShardedDataParallel(nn.Module, _FSDPState): + """A wrapper for sharding module parameters across data parallel workers. + + This is inspired by `Xu et al.`_ as well as the ZeRO Stage 3 from DeepSpeed_. + FullyShardedDataParallel is commonly shortened to FSDP. + + .. _`Xu et al.`: https://arxiv.org/abs/2004.13336 + .. _DeepSpeed: https://www.deepspeed.ai/ + + To understand FSDP internals, refer to the + :ref:`fsdp_notes`. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> import torch + >>> from torch.distributed.fsdp import FullyShardedDataParallel as FSDP + >>> torch.cuda.set_device(device_id) + >>> sharded_module = FSDP(my_module) + >>> optim = torch.optim.Adam(sharded_module.parameters(), lr=0.0001) + >>> x = sharded_module(x, y=3, z=torch.Tensor([1])) + >>> loss = x.sum() + >>> loss.backward() + >>> optim.step() + + Using FSDP involves wrapping your module and then initializing your + optimizer after. This is required since FSDP changes the parameter + variables. + + When setting up FSDP, you need to consider the destination CUDA + device. If the device has an ID (``dev_id``), you have three options: + + * Place the module on that device + * Set the device using ``torch.cuda.set_device(dev_id)`` + * Pass ``dev_id`` into the ``device_id`` constructor argument. + + This ensures that the FSDP instance's compute device is the + destination device. For option 1 and 3, the FSDP initialization + always occurs on GPU. For option 2, the FSDP initialization + happens on module's current device, which may be a CPU. + + If you're using the ``sync_module_states=True`` flag, you need to + ensure that the module is on a GPU or use the ``device_id`` + argument to specify a CUDA device that FSDP will move the module + to in the FSDP constructor. This is necessary because + ``sync_module_states=True`` requires GPU communication. + + FSDP also takes care of moving input tensors to the forward method + to the GPU compute device, so you don't need to manually move them + from CPU. + + For ``use_orig_params=True``, + ``ShardingStrategy.SHARD_GRAD_OP`` exposes the unsharded + parameters, not the sharded parameters after forward, unlike + ``ShardingStrategy.FULL_SHARD``. If you want + to inspect the gradients, you can use the ``summon_full_params`` + method with ``with_grads=True``. + + With ``limit_all_gathers=True``, you may see a gap in the FSDP + pre-forward where the CPU thread is not issuing any kernels. This is + intentional and shows the rate limiter in effect. Synchronizing the CPU + thread in that way prevents over-allocating memory for subsequent + all-gathers, and it should not actually delay GPU kernel execution. + + FSDP replaces managed modules' parameters with ``torch.Tensor`` + views during forward and backward computation for autograd-related + reasons. If your module's forward relies on saved references to + the parameters instead of reacquiring the references each + iteration, then it will not see FSDP's newly created views, + and autograd will not work correctly. + + Finally, when using ``sharding_strategy=ShardingStrategy.HYBRID_SHARD`` + with the sharding process group being intra-node and the + replication process group being inter-node, setting + ``NCCL_CROSS_NIC=1`` can help improve the all-reduce times over + the replication process group for some cluster setups. + + **Limitations** + + There are several limitations to be aware of when using FSDP: + + * FSDP currently does not support gradient accumulation outside + ``no_sync()`` when using CPU offloading. This is because FSDP + uses the newly-reduced gradient instead of accumulating with any + existing gradient, which can lead to incorrect results. + + * FSDP does not support running the forward pass of a submodule + that is contained in an FSDP instance. This is because the + submodule's parameters will be sharded, but the submodule itself + is not an FSDP instance, so its forward pass will not all-gather + the full parameters appropriately. + + * FSDP does not work with double backwards due to the way it + registers backward hooks. + + * FSDP has some constraints when freezing parameters. + For ``use_orig_params=False``, each FSDP instance must manage + parameters that are all frozen or all non-frozen. For + ``use_orig_params=True``, FSDP supports mixing frozen and + non-frozen parameters, but it's recommended to avoid doing so to + prevent higher than expected gradient memory usage. + + * As of PyTorch 1.12, FSDP offers limited support for shared + parameters. If enhanced shared parameter support is needed for + your use case, please post in + `this issue `__. + + * You should avoid modifying the parameters between forward and + backward without using the ``summon_full_params`` context, as + the modifications may not persist. + + Args: + module (nn.Module): + This is the module to be wrapped with FSDP. + process_group (Optional[Union[ProcessGroup, Tuple[ProcessGroup, ProcessGroup]]]): + This is the process group over which the model is sharded and thus + the one used for FSDP's all-gather and reduce-scatter collective + communications. If ``None``, then FSDP uses the default process + group. For hybrid sharding strategies such as + ``ShardingStrategy.HYBRID_SHARD``, users can pass in a tuple of + process groups, representing the groups over which to shard and + replicate, respectively. If ``None``, then FSDP constructs process + groups for the user to shard intra-node and replicate inter-node. + (Default: ``None``) + sharding_strategy (Optional[ShardingStrategy]): + This configures the sharding strategy, which may trade off memory + saving and communication overhead. See :class:`ShardingStrategy` + for details. (Default: ``FULL_SHARD``) + cpu_offload (Optional[CPUOffload]): + This configures CPU offloading. If this is set to ``None``, then + no CPU offloading happens. See :class:`CPUOffload` for details. + (Default: ``None``) + auto_wrap_policy (Optional[Union[Callable[[nn.Module, bool, int], bool], ModuleWrapPolicy, CustomPolicy]]): + This specifies a policy to apply FSDP to submodules of ``module``, + which is needed for communication and computation overlap and thus + affects performance. If ``None``, then FSDP only applies to + ``module``, and users should manually apply FSDP to parent modules + themselves (proceeding bottom-up). For convenience, this accepts + ``ModuleWrapPolicy`` directly, which allows users to specify the + module classes to wrap (e.g. the transformer block). Otherwise, + this should be a callable that takes in three arguments + ``module: nn.Module``, ``recurse: bool``, and + ``nonwrapped_numel: int`` and should return a ``bool`` specifying + whether the passed-in ``module`` should have FSDP applied if + ``recurse=False`` or if the traversal should continue into the + module's subtree if ``recurse=True``. Users may add additional + arguments to the callable. The ``size_based_auto_wrap_policy`` in + ``torch.distributed.fsdp.wrap.py`` gives an example callable that + applies FSDP to a module if the parameters in its subtree exceed + 100M numel. We recommend printing the model after applying FSDP + and adjusting as needed. + + Example:: + + >>> def custom_auto_wrap_policy( + >>> module: nn.Module, + >>> recurse: bool, + >>> nonwrapped_numel: int, + >>> # Additional custom arguments + >>> min_num_params: int = int(1e8), + >>> ) -> bool: + >>> return nonwrapped_numel >= min_num_params + >>> # Configure a custom `min_num_params` + >>> my_auto_wrap_policy = functools.partial(custom_auto_wrap_policy, min_num_params=int(1e5)) + + backward_prefetch (Optional[BackwardPrefetch]): + This configures explicit backward prefetching of all-gathers. If + ``None``, then FSDP does not backward prefetch, and there is no + communication and computation overlap in the backward pass. See + :class:`BackwardPrefetch` for details. (Default: ``BACKWARD_PRE``) + mixed_precision (Optional[MixedPrecision]): + This configures native mixed precision for FSDP. If this is set to + ``None``, then no mixed precision is used. Otherwise, parameter, + buffer, and gradient reduction dtypes can be set. See + :class:`MixedPrecision` for details. (Default: ``None``) + ignored_modules (Optional[Iterable[torch.nn.Module]]): Modules whose + own parameters and child modules' parameters and buffers are + ignored by this instance. None of the modules directly in + ``ignored_modules`` should be :class:`FullyShardedDataParallel` + instances, and any child modules that are already-constructed + :class:`FullyShardedDataParallel` instances will not be ignored if + they are nested under this instance. This argument may be used to + avoid sharding specific parameters at module granularity when using an + ``auto_wrap_policy`` or if parameters' sharding is not managed by + FSDP. (Default: ``None``) + param_init_fn (Optional[Callable[[nn.Module], None]]): + A ``Callable[torch.nn.Module] -> None`` that + specifies how modules that are currently on the meta device should + be initialized onto an actual device. As of v1.12, FSDP detects + modules with parameters or buffers on meta device via ``is_meta`` + and either applies ``param_init_fn`` if specified or calls + ``nn.Module.reset_parameters()`` otherwise. For both cases, the + implementation should *only* initialize the parameters/buffers of + the module, not those of its submodules. This is to avoid + re-initialization. In addition, FSDP also supports deferred + initialization via torchdistX's (https://github.com/pytorch/torchdistX) + ``deferred_init()`` API, where the deferred modules are initialized + by calling ``param_init_fn`` if specified or torchdistX's default + ``materialize_module()`` otherwise. If ``param_init_fn`` is + specified, then it is applied to all meta-device modules, meaning + that it should probably case on the module type. FSDP calls the + initialization function before parameter flattening and sharding. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> module = MyModule(device="meta") + >>> def my_init_fn(module: nn.Module): + >>> # E.g. initialize depending on the module type + >>> ... + >>> fsdp_model = FSDP(module, param_init_fn=my_init_fn, auto_wrap_policy=size_based_auto_wrap_policy) + >>> print(next(fsdp_model.parameters()).device) # current CUDA device + >>> # With torchdistX + >>> module = deferred_init.deferred_init(MyModule, device="cuda") + >>> # Will initialize via deferred_init.materialize_module(). + >>> fsdp_model = FSDP(module, auto_wrap_policy=size_based_auto_wrap_policy) + + device_id (Optional[Union[int, torch.device]]): An ``int`` or + ``torch.device`` giving the CUDA device on which FSDP + initialization takes place, including the module initialization + if needed and the parameter sharding. This should be specified to + improve initialization speed if ``module`` is on CPU. If the + default CUDA device was set (e.g. via ``torch.cuda.set_device``), + then the user may pass ``torch.cuda.current_device`` to this. + (Default: ``None``) + sync_module_states (bool): If ``True``, then each FSDP module will + broadcast module parameters and buffers from rank 0 to ensure that + they are replicated across ranks (adding communication overhead to + this constructor). This can help load ``state_dict`` checkpoints + via ``load_state_dict`` in a memory efficient way. See + :class:`FullStateDictConfig` for an example of this. (Default: + ``False``) + forward_prefetch (bool): If ``True``, then FSDP *explicitly* prefetches + the next forward-pass all-gather before the current forward + computation. This is only useful for CPU-bound workloads, in which + case issuing the next all-gather earlier may improve overlap. This + should only be used for static-graph models since the prefetching + follows the first iteration's execution order. (Default: ``False``) + limit_all_gathers (bool): If ``True``, then FSDP explicitly + synchronizes the CPU thread to ensure GPU memory usage from only + *two* consecutive FSDP instances (the current instance running + computation and the next instance whose all-gather is prefetched). + If ``False``, then FSDP allows the CPU thread to issue all-gathers + without any extra synchronization. (Default: ``True``) We often + refer to this feature as the "rate limiter". This flag should only + be set to ``False`` for specific CPU-bound workloads with low + memory pressure in which case the CPU thread can aggressively issue + all kernels without concern for the GPU memory usage. + use_orig_params (bool): Setting this to ``True`` has FSDP use + ``module`` 's original parameters. FSDP exposes those original + parameters to the user via :meth:`nn.Module.named_parameters` + instead of FSDP's internal :class:`FlatParameter` s. This means + that the optimizer step runs on the original parameters, enabling + per-original-parameter hyperparameters. FSDP preserves the original + parameter variables and manipulates their data between unsharded + and sharded forms, where they are always views into the underlying + unsharded or sharded :class:`FlatParameter`, respectively. With the + current algorithm, the sharded form is always 1D, losing the + original tensor structure. An original parameter may have all, + some, or none of its data present for a given rank. In the none + case, its data will be like a size-0 empty tensor. Users should not + author programs relying on what data is present for a given + original parameter in its sharded form. ``True`` is required to + use ``torch.compile()``. Setting this to ``False`` exposes FSDP's + internal :class:`FlatParameter` s to the user via + :meth:`nn.Module.named_parameters`. (Default: ``False``) + ignored_states (Optional[Iterable[torch.nn.Parameter]], Optional[Iterable[torch.nn.Module]]): + Ignored parameters or modules that will not be managed by this FSDP + instance, meaning that the parameters are not sharded and their + gradients are not reduced across ranks. This argument unifies with + the existing ``ignored_modules`` argument, and we may deprecate + ``ignored_modules`` soon. For backward compatibility, we keep both + ``ignored_states`` and `ignored_modules``, but FSDP only allows one + of them to be specified as not ``None``. + device_mesh (Optional[DeviceMesh]): DeviceMesh can be used as an altenative to + process_group. When device_mesh is passed, FSDP will use the underlying process + groups for all-gather and reduce-scatter collective communications. Therefore, + these two args need to be mutually exclusive. For hybrid sharding strategies such as + ``ShardingStrategy.HYBRID_SHARD``, users can pass in a 2D DeviceMesh instead + of a tuple of process groups. For 2D FSDP + TP, users are required to pass in + device_mesh instead of process_group. For more DeviceMesh info, please visit: + https://pytorch.org/tutorials/recipes/distributed_device_mesh.html + """ + + def __init__( + self, + module: nn.Module, + process_group: ProcessGroupType = None, + sharding_strategy: Optional[ShardingStrategy] = None, + cpu_offload: Optional[CPUOffload] = None, + auto_wrap_policy: Optional[ + Union[Callable, ModuleWrapPolicy, CustomPolicy] + ] = None, + backward_prefetch: Optional[BackwardPrefetch] = BackwardPrefetch.BACKWARD_PRE, + mixed_precision: Optional[MixedPrecision] = None, + ignored_modules: Optional[Iterable[torch.nn.Module]] = None, + param_init_fn: Optional[Callable[[nn.Module], None]] = None, + device_id: Optional[Union[int, torch.device]] = None, + sync_module_states: bool = False, + forward_prefetch: bool = False, + limit_all_gathers: bool = True, + use_orig_params: bool = False, + ignored_states: Union[ + Optional[Iterable[torch.nn.Parameter]], Optional[Iterable[torch.nn.Module]] + ] = None, + device_mesh: Optional[DeviceMesh] = None, + ): + torch._C._log_api_usage_once("torch.distributed.fsdp") + super().__init__() + if isinstance(module, (nn.ModuleList, nn.ModuleDict)): + warnings.warn( + "FSDP will not all-gather parameters for containers that do " + f"not implement forward: {module}", + stacklevel=2, + ) + _init_ignored_module_states(self, module, ignored_modules, ignored_states) + _init_device_handle(self, module, self._ignored_params, device_id) + + # Add module annotations for Dynamo support (see function for details) + _annotate_modules_for_dynamo(module, self._ignored_modules, use_orig_params) + + # Initializes self.process_group, along with rank and world size. This will + # also set another attribute, _inter_node_pg, to control the process group + # over which sharding occurs, if sharding_strategy is {HYBRID_SHARD, _HYBRID_SHARD_ZERO2}. + # Note that this is done before auto_wrapping, so that child FSDP modules simply pick up + # the same process group state as the root FSDP module. + self._device_mesh = device_mesh + _init_process_group_state( + self, + process_group, + sharding_strategy, + auto_wrap_policy, + device_mesh, + ) + if auto_wrap_policy is not None: + root_kwargs = { + "process_group": process_group, + "sharding_strategy": sharding_strategy, + "cpu_offload": cpu_offload, + "backward_prefetch": backward_prefetch, + "mixed_precision": mixed_precision, + "param_init_fn": param_init_fn, + "device_id": device_id, + "sync_module_states": sync_module_states, + "forward_prefetch": forward_prefetch, + "limit_all_gathers": limit_all_gathers, + "use_orig_params": use_orig_params, + "ignored_states": self._ignored_params, + "device_mesh": device_mesh, + } + if sharding_strategy in HYBRID_SHARDING_STRATEGIES and device_mesh is None: + # Share root process groups with children to maintain + # the invariant that all FSDP modules will have the same + # process groups. + root_kwargs["process_group"] = (self.process_group, self._inter_node_pg) + + _auto_wrap( + module, + auto_wrap_policy, + self._ignored_modules, + self._ignored_params, + root_kwargs, + FullyShardedDataParallel, + ) + + backward_prefetch_limit = 1 + forward_prefetch_limit = 1 + _init_core_state( + self, + sharding_strategy, + mixed_precision, + cpu_offload, + limit_all_gathers, + use_orig_params, + backward_prefetch_limit, + forward_prefetch_limit, + ) + _init_runtime_state(self) + _init_prefetching_state(self, backward_prefetch, forward_prefetch) + _init_buffer_state(self, module) + # extension needs to be set before `_init_param_handle_from_module()` + _init_extension(self, device_mesh) + _init_param_handle_from_module( + self, + module, + device_id, + param_init_fn, + sync_module_states, + ) + self._fsdp_wrapped_module = module + if not use_orig_params: + _check_orig_params_flattened(self, self._ignored_params) + _register_flat_param(self, self) + + # `_state_dict_type` controls the `state_dict()` behavior, which is + # implemented using post-save and pre-load hooks + _init_state_dict_state(self) + _register_all_state_dict_hooks(self) + self._zero_scalar = None + + @property + def module(self) -> nn.Module: + """Return the wrapped module.""" + # FSDP's `.module` must refer to the innermost wrapped module when + # composing with other module wrappers in order for state dict to work + if isinstance(self._fsdp_wrapped_module, ActivationWrapper): + return getattr(self._fsdp_wrapped_module, _CHECKPOINT_WRAPPED_MODULE) + return self._fsdp_wrapped_module + + @property + def _has_params(self) -> bool: + """Returns whether this FSDP instance manages any parameters.""" + return hasattr(self, "_handle") and self._handle is not None + + @property + def _flat_param(self) -> Optional[FlatParameter]: + return self._handle.flat_param if self._handle else None + + def __getattr__(self, name: str) -> Any: + """Forward missing attributes to the wrapped module.""" + try: + return super().__getattr__(name) # defer to nn.Module's logic + except AttributeError: + return getattr(self._fsdp_wrapped_module, name) + + def __getitem__(self, key: int) -> Any: + """Forward indexing calls in case the module is an ``nn.Sequential``.""" + if hasattr(self, FSDP_WRAPPED_MODULE): + return self._fsdp_wrapped_module.__getitem__(key) # type: ignore[operator] + return super().__getitem__(key) + + def check_is_root(self) -> bool: + """Check if this instance is a root FSDP module.""" + return _is_fsdp_root(self, self) + + @staticmethod + def fsdp_modules( + module: nn.Module, + root_only: bool = False, + ) -> List["FullyShardedDataParallel"]: + """Return all nested FSDP instances. + + This possibly includes ``module`` itself and only includes FSDP root modules if ``root_only=True``. + + Args: + module (torch.nn.Module): Root module, which may or may not be an + ``FSDP`` module. + root_only (bool): Whether to return only FSDP root modules. + (Default: ``False``) + + Returns: + List[FullyShardedDataParallel]: FSDP modules that are nested in + the input ``module``. + """ + if root_only: + return _get_fsdp_root_states(module) + return traversal_utils._get_fsdp_states(module) + + def apply(self, fn: Callable[[nn.Module], None]) -> "FullyShardedDataParallel": + r"""Apply ``fn`` recursively to every submodule (as returned by ``.children()``) as well as self. + + Typical use includes initializing the parameters of a model (see also :ref:`nn-init-doc`). + + Compared to ``torch.nn.Module.apply``, this version additionally gathers + the full parameters before applying ``fn``. It should not be called from + within another ``summon_full_params`` context. + + Args: + fn (:class:`Module` -> None): function to be applied to each submodule + + Returns: + Module: self + """ + uninitialized = self._is_root is None + self._assert_state(TrainingState.IDLE) + # Use `_unshard_params_for_summon()` with `recurse=False` instead of + # `_unshard_fsdp_state_params()` directly to perform lazy + # initialization, which is needed to initialize `FlatParameter` + # parameter attributes as required by the unshard logic + with _unshard_params_for_summon( + self, + self, + writeback=True, + rank0_only=False, + offload_to_cpu=False, + with_grads=False, + ): + ret = super().apply(fn) + + # Reset lazy init called in `_unshard_params_for_summon()` since + # `apply()` may have been called on FSDP instance that is not truly a + # root, in which case it will be incorrectly marked as one. + if uninitialized and self._is_root: + for module in traversal_utils._get_fsdp_states(self): + module._reset_lazy_init() + + return ret + + def _mixed_precision_enabled_for_buffers(self) -> bool: + """Return whether the user explicitly enabled buffer mixed precision. + + NOTE: Unlike parameters and gradient reduction, buffer mixed precision + is applied at the FSDP instance level, not the ``FlatParameter`` level, + which may be different for the composable code path. + """ + return self.mixed_precision.buffer_dtype is not None + + def _low_precision_hook_enabled(self) -> bool: + """Whether a low precision hook is registered or not.""" + return self._comm_hook is not None and self._comm_hook in LOW_PRECISION_HOOKS + + def _reset_lazy_init(self) -> None: + """Reset instance so :func:`_lazy_init` will run on the next forward.""" + self._is_root: Optional[bool] = None + + @staticmethod + def set_state_dict_type( + module: nn.Module, + state_dict_type: StateDictType, + state_dict_config: Optional[StateDictConfig] = None, + optim_state_dict_config: Optional[OptimStateDictConfig] = None, + ) -> StateDictSettings: + """Set the ``state_dict_type`` of all the descendant FSDP modules of the target module. + + Also takes (optional) configuration for the model's and optimizer's state dict. + The target module does not have to be a FSDP module. If the target + module is a FSDP module, its ``state_dict_type`` will also be changed. + + .. note:: This API should be called for only the top-level (root) + module. + + .. note:: This API enables users to transparently use the conventional + ``state_dict`` API to take model checkpoints in cases where the + root FSDP module is wrapped by another ``nn.Module``. For example, + the following will ensure ``state_dict`` is called on all non-FSDP + instances, while dispatching into `sharded_state_dict` implementation + for FSDP: + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> model = DDP(FSDP(...)) + >>> FSDP.set_state_dict_type( + >>> model, + >>> StateDictType.SHARDED_STATE_DICT, + >>> state_dict_config = ShardedStateDictConfig(offload_to_cpu=True), + >>> optim_state_dict_config = OptimStateDictConfig(offload_to_cpu=True), + >>> ) + >>> param_state_dict = model.state_dict() + >>> optim_state_dict = FSDP.optim_state_dict(model, optim) + + Args: + module (torch.nn.Module): Root module. + state_dict_type (StateDictType): the desired ``state_dict_type`` to set. + state_dict_config (Optional[StateDictConfig]): the configuration for the + target ``state_dict_type``. + optim_state_dict_config (Optional[OptimStateDictConfig]): the configuration + for the optimizer state dict. + + Returns: + A StateDictSettings that include the previous state_dict type and + configuration for the module. + """ + warnings.warn( + "FSDP.state_dict_type() and FSDP.set_state_dict_type() are being " + "deprecated. Please use APIs, get_state_dict() and set_state_dict(), " + "which can support different parallelisms, FSDP1, FSDP2, DDP. " + "API doc: https://pytorch.org/docs/stable/distributed.checkpoint.html" + "#torch.distributed.checkpoint.state_dict.get_state_dict ." + "Tutorial: https://pytorch.org/tutorials/recipes/distributed_checkpoint_recipe.html .", + FutureWarning, + ) + _state_dict_type_to_config = { + StateDictType.FULL_STATE_DICT: FullStateDictConfig, + StateDictType.LOCAL_STATE_DICT: LocalStateDictConfig, + StateDictType.SHARDED_STATE_DICT: ShardedStateDictConfig, + } + _optim_state_dict_type_to_config = { + StateDictType.FULL_STATE_DICT: FullOptimStateDictConfig, + StateDictType.LOCAL_STATE_DICT: LocalOptimStateDictConfig, + StateDictType.SHARDED_STATE_DICT: ShardedOptimStateDictConfig, + } + + # Use the default config if a state_dict config is not set. + state_dict_config_type = _state_dict_type_to_config[state_dict_type] + optim_state_dict_config_type = _optim_state_dict_type_to_config[state_dict_type] + if state_dict_config is None: + state_dict_config = state_dict_config_type() + if optim_state_dict_config is None: + optim_state_dict_config = optim_state_dict_config_type() + if state_dict_config_type != type(state_dict_config): + raise RuntimeError( + f"Expected state_dict_config of type {state_dict_config_type} " + f"but got {type(state_dict_config)}" + ) + if optim_state_dict_config_type != type(optim_state_dict_config): + raise RuntimeError( + f"Expected optim_state_dict_config of type {optim_state_dict_config_type} " + f"but got {type(optim_state_dict_config)}" + ) + + # Set the state_dict type and configurations. + prev_state_dict_type = None + prev_state_dict_config = None + prev_optim_state_dict_config = None + for submodule in traversal_utils._get_fsdp_states(module): + if prev_state_dict_type is None: + prev_state_dict_type = submodule._state_dict_type + else: + assert ( + prev_state_dict_type == submodule._state_dict_type + ), "All FSDP modules should have the same state_dict_type." + if prev_state_dict_config is None: + prev_state_dict_config = submodule._state_dict_config + else: + assert isinstance( + submodule._state_dict_config, type(prev_state_dict_config) + ), "All FSDP modules must have the same type of state_dict_config." + if prev_optim_state_dict_config is None: + prev_optim_state_dict_config = submodule._optim_state_dict_config + else: + assert isinstance( + submodule._optim_state_dict_config, + type(prev_optim_state_dict_config), + ), "All FSDP modules must have the same type of optim_state_dict_config." + + submodule._state_dict_type = state_dict_type + submodule._state_dict_config = state_dict_config + submodule._optim_state_dict_config = optim_state_dict_config + + return StateDictSettings( + prev_state_dict_type, prev_state_dict_config, prev_optim_state_dict_config + ) + + @staticmethod + def get_state_dict_type(module: nn.Module) -> StateDictSettings: + """Get the state_dict_type and the corresponding configurations for the FSDP modules rooted at ``module``. + + The target module does not have to be an FSDP module. + + Returns: + A ``StateDictSettings`` containing the state_dict_type and + state_dict / optim_state_dict configs that are currently set. + + Raises: + ``AssertionError`` if the ``StateDictSettings`` for different + FSDP submodules differ. + """ + state_dict_settings: Optional[StateDictSettings] = None + for submodule in FullyShardedDataParallel.fsdp_modules(module): + if state_dict_settings is None: + state_dict_settings = StateDictSettings( + state_dict_type=submodule._state_dict_type, + state_dict_config=submodule._state_dict_config, + optim_state_dict_config=submodule._optim_state_dict_config, + ) + _set_optim_use_dtensor(submodule, state_dict_settings) + else: + submodule_settings = StateDictSettings( + submodule._state_dict_type, + submodule._state_dict_config, + submodule._optim_state_dict_config, + ) + assert state_dict_settings == submodule_settings, ( + "All FSDP modules must have the same state dict settings." + f"Got {submodule_settings} and {state_dict_settings}." + ) + _set_optim_use_dtensor(submodule, submodule_settings) + return state_dict_settings + + @staticmethod + @contextlib.contextmanager + def state_dict_type( + module: nn.Module, + state_dict_type: StateDictType, + state_dict_config: Optional[StateDictConfig] = None, + optim_state_dict_config: Optional[OptimStateDictConfig] = None, + ) -> Generator: + """Set the ``state_dict_type`` of all the descendant FSDP modules of the target module. + + This context manager has the same functions as :meth:`set_state_dict_type`. Read the document of + :meth:`set_state_dict_type` for the detail. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> model = DDP(FSDP(...)) + >>> with FSDP.state_dict_type( + >>> model, + >>> StateDictType.SHARDED_STATE_DICT, + >>> ): + >>> checkpoint = model.state_dict() + + Args: + module (torch.nn.Module): Root module. + state_dict_type (StateDictType): the desired ``state_dict_type`` to set. + state_dict_config (Optional[StateDictConfig]): the model ``state_dict`` + configuration for the target ``state_dict_type``. + optim_state_dict_config (Optional[OptimStateDictConfig]): the optimizer + ``state_dict`` configuration for the target ``state_dict_type``. + """ + prev_state_dict_settings = FullyShardedDataParallel.set_state_dict_type( + module, + state_dict_type, + state_dict_config, + optim_state_dict_config, + ) + yield + FullyShardedDataParallel.set_state_dict_type( + module, + prev_state_dict_settings.state_dict_type, + prev_state_dict_settings.state_dict_config, + prev_state_dict_settings.optim_state_dict_config, + ) + + def forward(self, *args: Any, **kwargs: Any) -> Any: + """Run the forward pass for the wrapped module, inserting FSDP-specific pre- and post-forward sharding logic.""" + handle = self._handle + with torch.autograd.profiler.record_function( + "FullyShardedDataParallel.forward" + ): + args, kwargs = _root_pre_forward(self, self, args, kwargs) + unused = None + args, kwargs = _pre_forward( + self, + handle, + _pre_forward_unshard, + self._fsdp_wrapped_module, + args, + kwargs, + ) + if handle: + _p_assert( + handle.flat_param.device == self.compute_device, + "Expected `FlatParameter` to be on the compute device " + f"{self.compute_device} but got {handle.flat_param.device}", + ) + output = self._fsdp_wrapped_module(*args, **kwargs) + return _post_forward( + self, handle, _post_forward_reshard, self, unused, output + ) + + @staticmethod + @contextlib.contextmanager + def summon_full_params( + module: nn.Module, + recurse: bool = True, + writeback: bool = True, + rank0_only: bool = False, + offload_to_cpu: bool = False, + with_grads: bool = False, + ) -> Generator: + r"""Expose full params for FSDP instances with this context manager. + + Can be useful *after* forward/backward for a model to get + the params for additional processing or checking. It can take a non-FSDP + module and will summon full params for all contained FSDP modules as + well as their children, depending on the ``recurse`` argument. + + .. note:: This can be used on inner FSDPs. + .. note:: This can *not* be used within a forward or backward pass. Nor + can forward and backward be started from within this context. + .. note:: Parameters will revert to their local shards after the context + manager exits, storage behavior is the same as forward. + .. note:: The full parameters can be modified, but only the portion + corresponding to the local param shard will persist after the + context manager exits (unless ``writeback=False``, in which case + changes will be discarded). In the case where FSDP does not shard + the parameters, currently only when ``world_size == 1``, or ``NO_SHARD`` + config, the modification is persisted regardless of ``writeback``. + .. note:: This method works on modules which are not FSDP themselves but + may contain multiple independent FSDP units. In that case, the given + arguments will apply to all contained FSDP units. + + .. warning:: Note that ``rank0_only=True`` in conjunction with + ``writeback=True`` is not currently supported and will raise an + error. This is because model parameter shapes would be different + across ranks within the context, and writing to them can lead to + inconsistency across ranks when the context is exited. + + .. warning:: Note that ``offload_to_cpu`` and ``rank0_only=False`` will + result in full parameters being redundantly copied to CPU memory for + GPUs that reside on the same machine, which may incur the risk of + CPU OOM. It is recommended to use ``offload_to_cpu`` with + ``rank0_only=True``. + + Args: + recurse (bool, Optional): recursively summon all params for nested + FSDP instances (default: True). + writeback (bool, Optional): if ``False``, modifications to params are + discarded after the context manager exits; + disabling this can be slightly more efficient (default: True) + rank0_only (bool, Optional): if ``True``, full parameters are + materialized on only global rank 0. This means that within the + context, only rank 0 will have full parameters and the other + ranks will have sharded parameters. Note that setting + ``rank0_only=True`` with ``writeback=True`` is not supported, + as model parameter shapes will be different across ranks + within the context, and writing to them can lead to + inconsistency across ranks when the context is exited. + offload_to_cpu (bool, Optional): If ``True``, full parameters are + offloaded to CPU. Note that this offloading currently only + occurs if the parameter is sharded (which is only not the case + for world_size = 1 or ``NO_SHARD`` config). It is recommended + to use ``offload_to_cpu`` with ``rank0_only=True`` to avoid + redundant copies of model parameters being offloaded to the same CPU memory. + with_grads (bool, Optional): If ``True``, gradients are also + unsharded with the parameters. Currently, this is only + supported when passing ``use_orig_params=True`` to the FSDP + constructor and ``offload_to_cpu=False`` to this method. + (Default: ``False``) + """ + with _unshard_params( + module, recurse, writeback, rank0_only, offload_to_cpu, with_grads + ): + yield + + @contextlib.contextmanager + def _deregister_orig_params_ctx(self): + """Deregister the original parameters and expose the :class:`FlatParameter`. + + If a :class:`FlatParameter` is sharded, then + this refreshes the sharded views before exiting. This method should + only be called when using the original parameters. + """ + _p_assert( + self._use_orig_params, + "`_deregister_orig_params_ctx()` should only be called when " + "`_use_orig_params=True`", + ) + for fsdp_module in traversal_utils._get_fsdp_states(self): + _deregister_orig_params(fsdp_module, fsdp_module) + try: + yield + finally: + for fsdp_module in traversal_utils._get_fsdp_states(self): + _register_orig_params(fsdp_module, fsdp_module) + + def _apply(self, *args, **kwargs): + """Deregister the original parameters and expose the :class:`FlatParameter` s before calling ``_apply()``.""" + # When using the original parameters: Since (1) the `FlatParameter`s + # own the storage and (2) `_apply()` is the subroutine underlying the + # most common storage-changing ops like `to()` and `cuda()`, we + # override `_apply()` to have the storage change directly performed on + # the `FlatParameter`s instead of applying to the original parameters + # and then writing back to the `FlatParameter`s. + context = ( + self._deregister_orig_params_ctx() + if self._use_orig_params + else contextlib.nullcontext() + ) + with context: + return super()._apply(*args, **kwargs) + + def named_buffers( + self, + *args, + **kwargs, + ) -> Iterator[Tuple[str, torch.Tensor]]: + """Return an iterator over module buffers, yielding both the name of the buffer and the buffer itself. + + Intercepts buffer names and removes all occurrences of the FSDP-specific flattened buffer prefix + when inside the :meth:`summon_full_params` context manager. + """ + should_clean_name = self.training_state == TrainingState.SUMMON_FULL_PARAMS + for buffer_name, buffer in super().named_buffers(*args, **kwargs): + if should_clean_name: + # Remove any instances of the FSDP-specific prefix; there can + # be multiple in the case of nested FSDP modules + buffer_name = buffer_name.replace(FSDP_PREFIX, "") + yield (buffer_name, buffer) + + def named_parameters( + self, + *args, + **kwargs, + ) -> Iterator[Tuple[str, torch.nn.Parameter]]: + """Return an iterator over module parameters, yielding both the name of the parameter and the parameter itself. + + Intercepts parameter names and removes all occurrences of the FSDP-specific flattened parameter prefix + when inside the :meth:`summon_full_params` context manager. + """ + should_clean_name = self.training_state == TrainingState.SUMMON_FULL_PARAMS + for param_name, param in super().named_parameters(*args, **kwargs): + if should_clean_name: + # Remove any instances of the FSDP-specific prefix; there can + # be multiple in the case of nested FSDP modules + param_name = param_name.replace(FSDP_PREFIX, "") + yield (param_name, param) + + def _assert_state(self, state: Union[TrainingState, List[TrainingState]]) -> None: + """Assert we are in the given state.""" + # Since assert can be turned off and this error checking + # is really important, we use explicit error checking + # and raise a ValueError if needed. + if isinstance(state, TrainingState): + state = [state] + if self.training_state not in state: + msg = ( + f"expected to be in states {state} but current state " + f"is {self.training_state}" + ) + # In case we are failing in the context of autograd hook, asserting + # may not generate useful msg. So, let's print it to be sure. + if self.rank == 0: + print(f"Asserting FSDP instance is: {self}") + print(f"ERROR: {msg}") + traceback.print_stack() + raise ValueError(msg) + + @contextmanager + def no_sync(self) -> Generator: + """Disable gradient synchronizations across FSDP instances. + + Within this context, gradients will be accumulated in module + variables, which will later be synchronized in the first + forward-backward pass after exiting the context. This should only be + used on the root FSDP instance and will recursively apply to all + children FSDP instances. + + .. note:: This likely results in higher memory usage because FSDP will + accumulate the full model gradients (instead of gradient shards) + until the eventual sync. + + .. note:: When used with CPU offloading, the gradients will not be + offloaded to CPU when inside the context manager. Instead, they + will only be offloaded right after the eventual sync. + """ + _lazy_init(self, self) + if not self._is_root: + raise RuntimeError( + "`no_sync()` on inner FSDP instances is not supported. Please call `no_sync()` on root FSDP module." + ) + self._assert_state(TrainingState.IDLE) + old_flags = [] + for m in self.modules(): + if isinstance(m, FullyShardedDataParallel): + old_flags.append((m, m._sync_gradients)) + m._sync_gradients = False + try: + yield + finally: + for m, old_flag in old_flags: + assert not m._sync_gradients, ( + "`_sync_gradients` was incorrectly set to " + "`True` while in the `no_sync()` context manager" + ) + m._sync_gradients = old_flag + + @torch.no_grad() + def clip_grad_norm_( + self, max_norm: Union[float, int], norm_type: Union[float, int] = 2.0 + ) -> torch.Tensor: + """Clip the gradient norm of all parameters. + + The norm is computed over all parameters' gradients as viewed as a single vector, and the + gradients are modified in-place. + + Args: + max_norm (float or int): max norm of the gradients + norm_type (float or int): type of the used p-norm. Can be ``'inf'`` + for infinity norm. + + Returns: + Total norm of the parameters (viewed as a single vector). + + If every FSDP instance uses ``NO_SHARD``, meaning that no + gradients are sharded across ranks, then you may directly use + :func:`torch.nn.utils.clip_grad_norm_`. + + If at least some FSDP instance uses a sharded strategy (i.e. + one other than ``NO_SHARD``), then you should use this method + instead of :func:`torch.nn.utils.clip_grad_norm_` since this method + handles the fact that gradients are sharded across ranks. + + The total norm returned will have the "largest" dtype across + all parameters/gradients as defined by PyTorch's type promotion + semantics. For example, if *all* parameters/gradients use a low + precision dtype, then the returned norm's dtype will be that low + precision dtype, but if there exists at least one parameter/ + gradient using FP32, then the returned norm's dtype will be FP32. + + .. warning:: This needs to be called on all ranks since it uses + collective communications. + """ + _lazy_init(self, self) + if not self._is_root: + raise RuntimeError( + "`clip_grad_norm_()` should only be called on the root FSDP instance" + ) + if self._zero_scalar is None: + self._zero_scalar = torch.tensor(0.0, device=self.compute_device) + self._assert_state(TrainingState.IDLE) + # If every FSDP instance uses `NO_SHARD`, then we can directly use + # the normal `nn.utils` one targeting local gradients + all_no_shard = all( + not handle.uses_sharded_strategy for handle in self._all_handles + ) + if all_no_shard: + return torch.nn.utils.clip_grad_norm_( + self.parameters(), max_norm, norm_type + ) + # Otherwise, there exists some FSDP instance using a sharded strategy, + # where sharded and non-sharded parameters must be handled separately + max_norm = float(max_norm) + norm_type = float(norm_type) + sharded_params_set = set() + nonsharded_params_set = set() # `NO_SHARD` or not FSDP-managed + # Make sure to compute the local norm using lists for deterministic + # iteration order and hence deterministic total norm computation + sharded_params = [] + nonsharded_params = [] + grads: List[torch.Tensor] = [] + for handle in self._all_handles: + if handle.uses_sharded_strategy: + target_set = sharded_params_set + target_list = sharded_params + else: + target_set = nonsharded_params_set + target_list = nonsharded_params + if handle._use_orig_params: + for param in handle.flat_param._params: + if param not in target_set: + target_set.add(param) + target_list.append(param) + if param.grad is not None: + grads.append(param.grad) + else: + if handle.flat_param not in target_set: + target_set.add(handle.flat_param) + target_list.append(handle.flat_param) + if handle.flat_param.grad is not None: + grads.append(handle.flat_param.grad) + for param in self.parameters(): + not_fsdp_managed = ( + param not in sharded_params_set and param not in nonsharded_params_set + ) + if not_fsdp_managed: + nonsharded_params_set.add(param) + nonsharded_params.append(param) + if param.grad is not None: + grads.append(param.grad) + # Compute local norms (forced to be in FP32) + local_sharded_norm = _get_grad_norm( + sharded_params, norm_type, self._zero_scalar, self.compute_device + ) + local_nonsharded_norm = ( + _get_grad_norm( + nonsharded_params, norm_type, self._zero_scalar, self.compute_device + ) + if nonsharded_params + else None + ) + # Reconstruct the total gradient norm depending on the norm type + if norm_type == math.inf: + total_norm = ( + torch.maximum(local_sharded_norm, local_nonsharded_norm) + if local_nonsharded_norm is not None + else local_sharded_norm + ) + dist.all_reduce( + total_norm, op=torch.distributed.ReduceOp.MAX, group=self.process_group + ) + else: + total_norm = local_sharded_norm**norm_type + dist.all_reduce(total_norm, group=self.process_group) + # All-reducing the local non-sharded norm would count it an extra + # world-size-many times + if local_nonsharded_norm is not None: + total_norm += local_nonsharded_norm**norm_type + total_norm = total_norm ** (1.0 / norm_type) + if self.cpu_offload.offload_params: + total_norm = total_norm.cpu() + + clip_coef = max_norm / (total_norm + 1e-6) + # Multiplying by the clamped coefficient is meaningless when it is + # equal to 1, but it avoids the host-device sync that would result from + # `if clip_coef < 1` + clip_coef_clamped = torch.clamp(clip_coef, max=1.0) + for grad in grads: + grad.mul_(clip_coef_clamped.to(grad.device, grad.dtype)) + # Use the "largest" dtype by type promotion semantics to use the same + # dtype as if we did not force local norm computation to be in FP32 + if len(grads) == 0: + # If this rank has no gradients, then we must default to FP32 + # unless we use additional communication, which we prefer to avoid + # since `clip_grad_norm_()` is called in the training loop + warnings.warn( + f"Called FSDP.clip_grad_norm_() on rank {self.rank} with no " + "gradients -- returning the total norm in the default dtype " + f"{total_norm.dtype}" + ) # warn since this is generally unexpected + return total_norm + total_norm_dtype = functools.reduce( + torch.promote_types, + [grad.dtype for grad in grads], + ) + return total_norm.to(total_norm_dtype) + + @staticmethod + def _warn_optim_input(optim_input, *, stacklevel: int = 1): + if optim_input is not None: + warnings.warn( + "The `optim_input` argument is deprecated and will be removed after PyTorch 1.13. " + "You may remove it from your code without changing its functionality.", + FutureWarning, + stacklevel=stacklevel + 1, + ) + + @staticmethod + def _is_using_optim_input(optim_input, optim) -> bool: + if optim_input is None and optim is None: + # Use the default behavior of `optim_input`` + return True + if optim_input is not None: + # Use the `optim_input` code path + return True + # Use the `optim` code path + return False + + @staticmethod + def _warn_legacy_optim_state_dict(curr: str, new: str, *, stacklevel: int = 1): + warnings.warn( + f"``FullyShardedDataParallel.{curr}``is being deprecated and is " + f"replaced by ``FullyShardedDataParallel.{new}``. " + f"``FullyShardedDataParallel.{curr}`` may be removed after PyTorch 2.2.", + FutureWarning, + stacklevel=stacklevel + 1, + ) + + @staticmethod + def _optim_state_dict_impl( + model: torch.nn.Module, + optim: torch.optim.Optimizer, + optim_state_dict: Dict[str, Any], + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + rank0_only: bool = True, + full_state_dict: bool = True, + group: Optional[dist.ProcessGroup] = None, + cpu_offload: bool = True, + *, + _stacklevel: int = 1, + ) -> Dict[str, Any]: + """Transform the state-dict of an optimizer corresponding to a sharded model. + + This is the internal API that is used by all the optim_state_dict implementations. + Given model, optim, the original optim_state_dict, this API removes the + FSDP internal information and internal sharding from the optim_state_dict. + """ + if full_state_dict: + FullyShardedDataParallel._warn_optim_input( + optim_input, stacklevel=_stacklevel + 1 + ) + using_optim_input = FullyShardedDataParallel._is_using_optim_input( + optim_input, + optim, + ) + else: + using_optim_input = False + assert optim_input is None and not rank0_only + + use_orig_params = FullyShardedDataParallel.fsdp_modules(model)[ + 0 + ]._use_orig_params + assert all( + use_orig_params == m._use_orig_params + for m in FullyShardedDataParallel.fsdp_modules(model) + ), "Not all FSDP modules have the same _use_orig_params value" + + return _optim_state_dict( + model=model, + optim=optim, + optim_state_dict=optim_state_dict, + optim_input=optim_input, + rank0_only=rank0_only, + shard_state=not full_state_dict, + group=group, + using_optim_input=using_optim_input, + use_orig_params=use_orig_params, + cpu_offload=cpu_offload, + ) + + @staticmethod + def _optim_state_dict_to_load_impl( + optim_state_dict: Dict[str, Any], + model: torch.nn.Module, + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + optim: Optional[torch.optim.Optimizer] = None, + full_state_dict: bool = True, + rank0_only: bool = False, + is_named_optimizer: bool = False, + group: Optional[dist.ProcessGroup] = None, + ) -> Dict[str, Any]: + """ + Convert an optimizer state-dict so that it can be loaded into the optimizer associated with the FSDP model. + + This is the internal API that is used by all the load optim_state_dict implementations. + Given model, optim, and the saved optim_state_dict, this API adds the FSDP + internal information and internal sharding to the optim_state_dict. + """ + if full_state_dict: + FullyShardedDataParallel._warn_optim_input(optim_input) + using_optim_input = FullyShardedDataParallel._is_using_optim_input( + optim_input, + optim, + ) + else: + using_optim_input = False + assert optim_input is None and not rank0_only + + use_orig_params = FullyShardedDataParallel.fsdp_modules(model)[ + 0 + ]._use_orig_params + assert all( + use_orig_params == m._use_orig_params + for m in FullyShardedDataParallel.fsdp_modules(model) + ), "Not all FSDP modules have the same _use_orig_params value" + + if rank0_only and dist.get_rank(group) > 0: + optim_state_dict = {} + sharded_osd = _flatten_optim_state_dict( + optim_state_dict, + model=model, + use_orig_params=use_orig_params, + optim=(optim if is_named_optimizer else None), + rank0_only=rank0_only, + group=group, + ) + return _rekey_sharded_optim_state_dict( + sharded_osd, + model=model, + optim=optim, + optim_input=optim_input, + using_optim_input=using_optim_input, + is_named_optimizer=is_named_optimizer, + ) + + @staticmethod + def full_optim_state_dict( + model: torch.nn.Module, + optim: torch.optim.Optimizer, + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + rank0_only: bool = True, + group: Optional[dist.ProcessGroup] = None, + ) -> Dict[str, Any]: + """Return the full optimizer state-dict. + + Consolidates the full optimizer state on rank 0 and returns it + as a :class:`dict` following the convention of + :meth:`torch.optim.Optimizer.state_dict`, i.e. with keys ``"state"`` + and ``"param_groups"``. The flattened parameters in ``FSDP`` modules + contained in ``model`` are mapped back to their unflattened parameters. + + This needs to be called on all ranks since it uses + collective communications. However, if ``rank0_only=True``, then + the state dict is only populated on rank 0, and all other ranks + return an empty :class:`dict`. + + Unlike ``torch.optim.Optimizer.state_dict()``, this method + uses full parameter names as keys instead of parameter IDs. + + Like in :meth:`torch.optim.Optimizer.state_dict`, the tensors + contained in the optimizer state dict are not cloned, so there may + be aliasing surprises. For best practices, consider saving the + returned optimizer state dict immediately, e.g. using + ``torch.save()``. + + Args: + model (torch.nn.Module): Root module (which may or may not be a + :class:`FullyShardedDataParallel` instance) whose parameters + were passed into the optimizer ``optim``. + optim (torch.optim.Optimizer): Optimizer for ``model`` 's + parameters. + optim_input (Optional[Union[List[Dict[str, Any]], Iterable[torch.nn.Parameter]]]): + Input passed into the optimizer ``optim`` representing either a + :class:`list` of parameter groups or an iterable of parameters; + if ``None``, then this method assumes the input was + ``model.parameters()``. This argument is deprecated, and there + is no need to pass it in anymore. (Default: ``None``) + rank0_only (bool): If ``True``, saves the populated :class:`dict` + only on rank 0; if ``False``, saves it on all ranks. (Default: + ``True``) + group (dist.ProcessGroup): Model's process group or ``None`` if using + the default process group. (Default: ``None``) + + Returns: + Dict[str, Any]: A :class:`dict` containing the optimizer state for + ``model`` 's original unflattened parameters and including keys + "state" and "param_groups" following the convention of + :meth:`torch.optim.Optimizer.state_dict`. If ``rank0_only=True``, + then nonzero ranks return an empty :class:`dict`. + """ + FullyShardedDataParallel._warn_legacy_optim_state_dict( + "full_optim_state_dict", + "optim_state_dict", + stacklevel=2, + ) + return FullyShardedDataParallel._optim_state_dict_impl( + model=model, + optim=optim, + optim_state_dict=optim.state_dict(), + optim_input=optim_input, + rank0_only=rank0_only, + group=group, + full_state_dict=True, + _stacklevel=2, + ) + + @staticmethod + def sharded_optim_state_dict( + model: torch.nn.Module, + optim: torch.optim.Optimizer, + group: Optional[dist.ProcessGroup] = None, + ) -> Dict[str, Any]: + """Return the optimizer state-dict in its sharded form. + + The API is similar to :meth:`full_optim_state_dict` but this API chunks + all non-zero-dimension states to :class:`ShardedTensor` to save memory. + This API should only be used when the model ``state_dict`` is derived + with the context manager ``with state_dict_type(SHARDED_STATE_DICT):``. + + For the detailed usage, refer to :meth:`full_optim_state_dict`. + + .. warning:: The returned state dict contains ``ShardedTensor`` and + cannot be directly used by the regular ``optim.load_state_dict``. + """ + FullyShardedDataParallel._warn_legacy_optim_state_dict( + "sharded_optim_state_dict", + "optim_state_dict", + stacklevel=2, + ) + return FullyShardedDataParallel._optim_state_dict_impl( + model=model, + optim=optim, + optim_state_dict=optim.state_dict(), + optim_input=None, + rank0_only=False, + full_state_dict=False, + group=group, + _stacklevel=2, + ) + + @staticmethod + def shard_full_optim_state_dict( + full_optim_state_dict: Dict[str, Any], + model: torch.nn.Module, + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + optim: Optional[torch.optim.Optimizer] = None, + ) -> Dict[str, Any]: + """Shard a full optimizer state-dict. + + Remaps the state in ``full_optim_state_dict`` to flattened parameters instead of unflattened + parameters and restricts to only this rank's part of the optimizer state. + The first argument should be the return value of :meth:`full_optim_state_dict`. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> from torch.distributed.fsdp import FullyShardedDataParallel as FSDP + >>> model, optim = ... + >>> full_osd = FSDP.full_optim_state_dict(model, optim) + >>> torch.save(full_osd, PATH) + >>> # Define new model with possibly different world size + >>> new_model, new_optim = ... + >>> full_osd = torch.load(PATH) + >>> sharded_osd = FSDP.shard_full_optim_state_dict(full_osd, new_model) + >>> new_optim.load_state_dict(sharded_osd) + + .. note:: Both :meth:`shard_full_optim_state_dict` and + :meth:`scatter_full_optim_state_dict` may be used to get the + sharded optimizer state dict to load. Assuming that the full + optimizer state dict resides in CPU memory, the former requires + each rank to have the full dict in CPU memory, where each rank + individually shards the dict without any communication, while the + latter requires only rank 0 to have the full dict in CPU memory, + where rank 0 moves each shard to GPU memory (for NCCL) and + communicates it to ranks appropriately. Hence, the former has + higher aggregate CPU memory cost, while the latter has higher + communication cost. + + Args: + full_optim_state_dict (Dict[str, Any]): Optimizer state dict + corresponding to the unflattened parameters and holding the + full non-sharded optimizer state. + model (torch.nn.Module): Root module (which may or may not be a + :class:`FullyShardedDataParallel` instance) whose parameters + correspond to the optimizer state in ``full_optim_state_dict``. + optim_input (Optional[Union[List[Dict[str, Any]], Iterable[torch.nn.Parameter]]]): + Input passed into the optimizer representing either a + :class:`list` of parameter groups or an iterable of parameters; + if ``None``, then this method assumes the input was + ``model.parameters()``. This argument is deprecated, and there + is no need to pass it in anymore. (Default: ``None``) + optim (Optional[torch.optim.Optimizer]): Optimizer that will load + the state dict returned by this method. This is the preferred + argument to use over ``optim_input``. (Default: ``None``) + + Returns: + Dict[str, Any]: The full optimizer state dict now remapped to + flattened parameters instead of unflattened parameters and + restricted to only include this rank's part of the optimizer state. + """ + FullyShardedDataParallel._warn_legacy_optim_state_dict( + "shard_full_optim_state_dict", + "optim_state_dict_to_load", + stacklevel=2, + ) + return FullyShardedDataParallel._optim_state_dict_to_load_impl( + optim_state_dict=full_optim_state_dict, + model=model, + optim_input=optim_input, + optim=optim, + full_state_dict=True, + is_named_optimizer=False, + ) + + @staticmethod + def flatten_sharded_optim_state_dict( + sharded_optim_state_dict: Dict[str, Any], + model: torch.nn.Module, + optim: torch.optim.Optimizer, + ) -> Dict[str, Any]: + """Flatten a sharded optimizer state-dict. + + The API is similar to :meth:`shard_full_optim_state_dict`. The only + difference is that the input ``sharded_optim_state_dict`` should be + returned from :meth:`sharded_optim_state_dict`. Therefore, there will + be all-gather calls on each rank to gather ``ShardedTensor`` s. + + Args: + sharded_optim_state_dict (Dict[str, Any]): Optimizer state dict + corresponding to the unflattened parameters and holding the + sharded optimizer state. + model (torch.nn.Module): + Refer to :meth:`shard_full_optim_state_dict`. + optim (torch.optim.Optimizer): Optimizer for ``model`` 's + parameters. + + Returns: + Refer to :meth:`shard_full_optim_state_dict`. + """ + FullyShardedDataParallel._warn_legacy_optim_state_dict( + "flatten_sharded_optim_state_dict", + "optim_state_dict_to_load", + stacklevel=2, + ) + return FullyShardedDataParallel._optim_state_dict_to_load_impl( + optim_state_dict=sharded_optim_state_dict, + model=model, + optim_input=None, + optim=optim, + full_state_dict=False, + is_named_optimizer=False, + ) + + @staticmethod + def scatter_full_optim_state_dict( + full_optim_state_dict: Optional[Dict[str, Any]], + model: torch.nn.Module, + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + optim: Optional[torch.optim.Optimizer] = None, + group: Optional[Any] = None, + ) -> Dict[str, Any]: + """Scatter the full optimizer state dict from rank 0 to all other ranks. + + Returns the sharded optimizer state dict on each rank. + The return value is the same as :meth:`shard_full_optim_state_dict`, and on rank + 0, the first argument should be the return value of + :meth:`full_optim_state_dict`. + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> from torch.distributed.fsdp import FullyShardedDataParallel as FSDP + >>> model, optim = ... + >>> full_osd = FSDP.full_optim_state_dict(model, optim) # only non-empty on rank 0 + >>> # Define new model with possibly different world size + >>> new_model, new_optim, new_group = ... + >>> sharded_osd = FSDP.scatter_full_optim_state_dict(full_osd, new_model, group=new_group) + >>> new_optim.load_state_dict(sharded_osd) + + .. note:: Both :meth:`shard_full_optim_state_dict` and + :meth:`scatter_full_optim_state_dict` may be used to get the + sharded optimizer state dict to load. Assuming that the full + optimizer state dict resides in CPU memory, the former requires + each rank to have the full dict in CPU memory, where each rank + individually shards the dict without any communication, while the + latter requires only rank 0 to have the full dict in CPU memory, + where rank 0 moves each shard to GPU memory (for NCCL) and + communicates it to ranks appropriately. Hence, the former has + higher aggregate CPU memory cost, while the latter has higher + communication cost. + + Args: + full_optim_state_dict (Optional[Dict[str, Any]]): Optimizer state + dict corresponding to the unflattened parameters and holding + the full non-sharded optimizer state if on rank 0; the argument + is ignored on nonzero ranks. + model (torch.nn.Module): Root module (which may or may not be a + :class:`FullyShardedDataParallel` instance) whose parameters + correspond to the optimizer state in ``full_optim_state_dict``. + optim_input (Optional[Union[List[Dict[str, Any]], Iterable[torch.nn.Parameter]]]): + Input passed into the optimizer representing either a + :class:`list` of parameter groups or an iterable of parameters; + if ``None``, then this method assumes the input was + ``model.parameters()``. This argument is deprecated, and there + is no need to pass it in anymore. (Default: ``None``) + optim (Optional[torch.optim.Optimizer]): Optimizer that will load + the state dict returned by this method. This is the preferred + argument to use over ``optim_input``. (Default: ``None``) + group (dist.ProcessGroup): Model's process group or ``None`` if + using the default process group. (Default: ``None``) + + Returns: + Dict[str, Any]: The full optimizer state dict now remapped to + flattened parameters instead of unflattened parameters and + restricted to only include this rank's part of the optimizer state. + """ + FullyShardedDataParallel._warn_legacy_optim_state_dict( + "scatter_full_optim_state_dict", + "optim_state_dict_to_load", + stacklevel=2, + ) + return FullyShardedDataParallel._optim_state_dict_to_load_impl( + optim_state_dict=full_optim_state_dict, + model=model, + optim_input=optim_input, + optim=optim, + full_state_dict=True, + rank0_only=True, + is_named_optimizer=False, + group=group, + ) + + @staticmethod + def rekey_optim_state_dict( + optim_state_dict: Dict[str, Any], + optim_state_key_type: OptimStateKeyType, + model: torch.nn.Module, + optim_input: Optional[ + Union[ + List[Dict[str, Any]], + Iterable[torch.nn.Parameter], + ] + ] = None, + optim: Optional[torch.optim.Optimizer] = None, + ) -> Dict[str, Any]: + """Re-keys the optimizer state dict ``optim_state_dict`` to use the key type ``optim_state_key_type``. + + This can be used to achieve compatibility between optimizer state dicts from models with FSDP + instances and ones without. + + To re-key an FSDP full optimizer state dict (i.e. from + :meth:`full_optim_state_dict`) to use parameter IDs and be loadable to + a non-wrapped model:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> wrapped_model, wrapped_optim = ... + >>> full_osd = FSDP.full_optim_state_dict(wrapped_model, wrapped_optim) + >>> nonwrapped_model, nonwrapped_optim = ... + >>> rekeyed_osd = FSDP.rekey_optim_state_dict(full_osd, OptimStateKeyType.PARAM_ID, nonwrapped_model) + >>> nonwrapped_optim.load_state_dict(rekeyed_osd) + + To re-key a normal optimizer state dict from a non-wrapped model to be + loadable to a wrapped model:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> nonwrapped_model, nonwrapped_optim = ... + >>> osd = nonwrapped_optim.state_dict() + >>> rekeyed_osd = FSDP.rekey_optim_state_dict(osd, OptimStateKeyType.PARAM_NAME, nonwrapped_model) + >>> wrapped_model, wrapped_optim = ... + >>> sharded_osd = FSDP.shard_full_optim_state_dict(rekeyed_osd, wrapped_model) + >>> wrapped_optim.load_state_dict(sharded_osd) + + Returns: + Dict[str, Any]: The optimizer state dict re-keyed using the + parameter keys specified by ``optim_state_key_type``. + """ + FullyShardedDataParallel._warn_optim_input(optim_input) + using_optim_input = FullyShardedDataParallel._is_using_optim_input( + optim_input, + optim, + ) + assert optim_state_key_type in ( + OptimStateKeyType.PARAM_NAME, + OptimStateKeyType.PARAM_ID, + ) + osd = optim_state_dict # alias + # Validate that the existing parameter keys are uniformly typed + uses_param_name_mask = [type(param_key) is str for param_key in osd["state"]] + uses_param_id_mask = [type(param_key) is int for param_key in osd["state"]] + if (any(uses_param_name_mask) and not all(uses_param_name_mask)) or ( + any(uses_param_id_mask) and not all(uses_param_id_mask) + ): + error_msg = f"Invalid parameter keys: {osd['state'].keys()}" + raise ValueError(error_msg) + # Return directly if the existing key type matches the target key type + if ( + optim_state_key_type == OptimStateKeyType.PARAM_NAME + and all(uses_param_name_mask) + ) or ( + optim_state_key_type == OptimStateKeyType.PARAM_ID + and all(uses_param_id_mask) + ): + return osd + # Otherwise, actually perform the re-keying + new_osd = {} + if optim_state_key_type == OptimStateKeyType.PARAM_NAME: # ID -> name + param_id_to_param = ( + _get_param_id_to_param_from_optim_input(model, optim_input) + if using_optim_input + else _get_param_key_to_param(optim) + ) + param_to_param_name = _get_param_to_fqn(model) + param_id_to_param_name: List[str] = [ + param_to_param_name[param] for param in param_id_to_param.values() + ] + new_osd["state"] = { + param_id_to_param_name[param_id]: param_state + for param_id, param_state in osd["state"].items() + } + new_osd["param_groups"] = copy.deepcopy(osd["param_groups"]) + for param_group in new_osd["param_groups"]: + param_group["params"] = sorted( + [ + param_id_to_param_name[param_id] + for param_id in param_group["params"] + ] + ) + return new_osd + elif optim_state_key_type == OptimStateKeyType.PARAM_ID: # name -> ID + param_name_to_param = _get_fqn_to_param(model) + param_to_param_id = ( + _get_param_to_param_id_from_optim_input(model, optim_input) + if using_optim_input + else _get_param_to_param_key(optim) + ) + # Because not all model parameters may be passed as the optimizer + # input, we may need to drop some parameters from this mapping + param_name_to_param_id = { + param_name: param_to_param_id[param] + for param_name, param in param_name_to_param.items() + if param in param_to_param_id + } + new_osd["state"] = { + param_name_to_param_id[param_name]: param_state + for param_name, param_state in osd["state"].items() + } + new_osd["param_groups"] = copy.deepcopy(osd["param_groups"]) + for param_group in new_osd["param_groups"]: + param_group["params"] = sorted( + [ + param_name_to_param_id[param_name] + for param_name in param_group["params"] + ] + ) + return new_osd + return new_osd # should never reach here + + @staticmethod + def optim_state_dict( + model: torch.nn.Module, + optim: torch.optim.Optimizer, + optim_state_dict: Optional[Dict[str, Any]] = None, + group: Optional[dist.ProcessGroup] = None, + ) -> Dict[str, Any]: + """ + Transform the state-dict of an optimizer corresponding to a sharded model. + + The given state-dict can be transformed to one of three types: + 1) full optimizer state_dict, 2) sharded optimizer state_dict, 3) local optimizer state_dict. + + For full optimizer state_dict, all states are unflattened and not sharded. + Rank0 only and CPU only can be specified via :meth:`state_dict_type` to + avoid OOM. + + For sharded optimizer state_dict, all states are unflattened but sharded. + CPU only can be specified via :meth:`state_dict_type` to further save + memory. + + For local state_dict, no transformation will be performed. But a state + will be converted from nn.Tensor to ShardedTensor to represent its sharding + nature (this is not supported yet). + + Example:: + + >>> # xdoctest: +SKIP("undefined variables") + >>> from torch.distributed.fsdp import FullyShardedDataParallel as FSDP + >>> from torch.distributed.fsdp import StateDictType + >>> from torch.distributed.fsdp import FullStateDictConfig + >>> from torch.distributed.fsdp import FullOptimStateDictConfig + >>> # Save a checkpoint + >>> model, optim = ... + >>> FSDP.set_state_dict_type( + >>> model, + >>> StateDictType.FULL_STATE_DICT, + >>> FullStateDictConfig(rank0_only=False), + >>> FullOptimStateDictConfig(rank0_only=False), + >>> ) + >>> state_dict = model.state_dict() + >>> optim_state_dict = FSDP.optim_state_dict(model, optim) + >>> save_a_checkpoint(state_dict, optim_state_dict) + >>> # Load a checkpoint + >>> model, optim = ... + >>> state_dict, optim_state_dict = load_a_checkpoint() + >>> FSDP.set_state_dict_type( + >>> model, + >>> StateDictType.FULL_STATE_DICT, + >>> FullStateDictConfig(rank0_only=False), + >>> FullOptimStateDictConfig(rank0_only=False), + >>> ) + >>> model.load_state_dict(state_dict) + >>> optim_state_dict = FSDP.optim_state_dict_to_load( + >>> model, optim, optim_state_dict + >>> ) + >>> optim.load_state_dict(optim_state_dict) + + Args: + model (torch.nn.Module): Root module (which may or may not be a + :class:`FullyShardedDataParallel` instance) whose parameters + were passed into the optimizer ``optim``. + optim (torch.optim.Optimizer): Optimizer for ``model`` 's + parameters. + optim_state_dict (Dict[str, Any]): the target optimizer state_dict to + transform. If the value is None, optim.state_dict() will be used. ( + Default: ``None``) + group (dist.ProcessGroup): Model's process group across which parameters + are sharded or ``None`` if using the default process group. ( + Default: ``None``) + + Returns: + Dict[str, Any]: A :class:`dict` containing the optimizer state for + ``model``. The sharding of the optimizer state is based on + ``state_dict_type``. + """ + state_dict_settings = FullyShardedDataParallel.get_state_dict_type(model) + if optim_state_dict is None: + optim_state_dict = optim.state_dict() + return FullyShardedDataParallel._optim_state_dict_impl( + model=model, + optim=optim, + optim_state_dict=optim_state_dict, + optim_input=None, + rank0_only=getattr( + state_dict_settings.optim_state_dict_config, "rank0_only", False + ), + full_state_dict=state_dict_settings.state_dict_type + == StateDictType.FULL_STATE_DICT, + group=group, + cpu_offload=getattr( + state_dict_settings.optim_state_dict_config, "offload_to_cpu", True + ), + _stacklevel=2, + ) + + @staticmethod + def optim_state_dict_to_load( + model: torch.nn.Module, + optim: torch.optim.Optimizer, + optim_state_dict: Dict[str, Any], + is_named_optimizer: bool = False, + load_directly: bool = False, + group: Optional[dist.ProcessGroup] = None, + ) -> Dict[str, Any]: + """ + Convert an optimizer state-dict so that it can be loaded into the optimizer associated with the FSDP model. + + Given a ``optim_state_dict`` that is transformed through + :meth:`optim_state_dict`, it gets converted to the flattened optimizer + state_dict that can be loaded to ``optim`` which is the optimizer for + ``model``. ``model`` must be sharded by FullyShardedDataParallel. + + >>> # xdoctest: +SKIP("undefined variables") + >>> from torch.distributed.fsdp import FullyShardedDataParallel as FSDP + >>> from torch.distributed.fsdp import StateDictType + >>> from torch.distributed.fsdp import FullStateDictConfig + >>> from torch.distributed.fsdp import FullOptimStateDictConfig + >>> # Save a checkpoint + >>> model, optim = ... + >>> FSDP.set_state_dict_type( + >>> model, + >>> StateDictType.FULL_STATE_DICT, + >>> FullStateDictConfig(rank0_only=False), + >>> FullOptimStateDictConfig(rank0_only=False), + >>> ) + >>> state_dict = model.state_dict() + >>> original_osd = optim.state_dict() + >>> optim_state_dict = FSDP.optim_state_dict( + >>> model, + >>> optim, + >>> optim_state_dict=original_osd + >>> ) + >>> save_a_checkpoint(state_dict, optim_state_dict) + >>> # Load a checkpoint + >>> model, optim = ... + >>> state_dict, optim_state_dict = load_a_checkpoint() + >>> FSDP.set_state_dict_type( + >>> model, + >>> StateDictType.FULL_STATE_DICT, + >>> FullStateDictConfig(rank0_only=False), + >>> FullOptimStateDictConfig(rank0_only=False), + >>> ) + >>> model.load_state_dict(state_dict) + >>> optim_state_dict = FSDP.optim_state_dict_to_load( + >>> model, optim, optim_state_dict + >>> ) + >>> optim.load_state_dict(optim_state_dict) + + Args: + model (torch.nn.Module): Root module (which may or may not be a + :class:`FullyShardedDataParallel` instance) whose parameters + were passed into the optimizer ``optim``. + optim (torch.optim.Optimizer): Optimizer for ``model`` 's + parameters. + optim_state_dict (Dict[str, Any]): The optimizer states to be loaded. + is_named_optimizer (bool): Is this optimizer a NamedOptimizer or + KeyedOptimizer. Only set to True if ``optim`` is TorchRec's + KeyedOptimizer or torch.distributed's NamedOptimizer. + load_directly (bool): If this is set to True, this API will also + call optim.load_state_dict(result) before returning the result. + Otherwise, users are responsible to call ``optim.load_state_dict()`` + (Default: ``False``) + group (dist.ProcessGroup): Model's process group across which parameters + are sharded or ``None`` if using the default process group. ( + Default: ``None``) + """ + state_dict_settings = FullyShardedDataParallel.get_state_dict_type(model) + result = FullyShardedDataParallel._optim_state_dict_to_load_impl( + optim_state_dict=optim_state_dict, + model=model, + optim_input=None, + optim=optim, + full_state_dict=( + state_dict_settings.state_dict_type == StateDictType.FULL_STATE_DICT + ), + rank0_only=getattr( + state_dict_settings.optim_state_dict_config, "rank0_only", False + ), + is_named_optimizer=is_named_optimizer, + group=group, + ) + if load_directly: + optim.load_state_dict(result) + return result + + def register_comm_hook(self, state: object, hook: callable): + """Register a communication hook. + + This is an enhancement that provides a flexible hook to users where they can specify how FSDP aggregates + gradients across multiple workers. + This hook can be used to implement several algorithms like + `GossipGrad `_ and gradient compression + which involve different communication strategies for + parameter syncs while training with :class:`FullyShardedDataParallel`. + + .. warning :: + FSDP communication hook should be registered before running an initial forward pass + and only once. + + Args: + state (object): Passed to the hook to maintain any state information during the training process. + Examples include error feedback in gradient compression, + peers to communicate with next in `GossipGrad `_, etc. + It is locally stored by each worker + and shared by all the gradient tensors on the worker. + hook (Callable): Callable, which has one of the following signatures: + 1) ``hook: Callable[torch.Tensor] -> None``: + This function takes in a Python tensor, which represents + the full, flattened, unsharded gradient with respect to all variables + corresponding to the model this FSDP unit is wrapping + (that are not wrapped by other FSDP sub-units). + It then performs all necessary processing and returns ``None``; + 2) ``hook: Callable[torch.Tensor, torch.Tensor] -> None``: + This function takes in two Python tensors, the first one represents + the full, flattened, unsharded gradient with respect to all variables + corresponding to the model this FSDP unit is wrapping + (that are not wrapped by other FSDP sub-units). The latter + represents a pre-sized tensor to store a chunk of a sharded gradient after + reduction. + In both cases, callable performs all necessary processing and returns ``None``. + Callables with signature 1 are expected to handle gradient communication for a `NO_SHARD` case. + Callables with signature 2 are expected to handle gradient communication for sharded cases. + + """ + if not self.check_is_root(): + raise AssertionError( + "register_comm_hook can only be called on a root instance." + ) + for fsdp_state in traversal_utils._get_fsdp_states(self): + if fsdp_state.sharding_strategy in HYBRID_SHARDING_STRATEGIES: + raise AssertionError( + f"Communication hook is not supported for hybrid strategies: {fsdp_state.sharding_strategy}" + ) + if fsdp_state._comm_hook is not None: + raise AssertionError("A communication hook is already registered") + if not callable(hook): + raise ValueError( + f"The communication hook must be callable but got {hook}" + ) + fsdp_state._comm_hook = hook + fsdp_state._comm_hook_state = state + + def _unshard(self, async_op: bool = False): + class UnshardHandle: + def __init__( + self, + flat_param_handle: Optional[FlatParamHandle], + unshard_event: torch.Event, + ): + self._flat_param_handle = flat_param_handle + self._unshard_event = unshard_event + + def wait(self): + if self._flat_param_handle is not None: + current_stream = ( + self._flat_param_handle._device_handle.current_stream() + ) + current_stream.wait_event(self._unshard_event) + self._flat_param_handle = None + + if self._handle: + with self._use_training_state( + TrainingState.FORWARD_BACKWARD, HandleTrainingState.FORWARD + ): + _unshard( + self, self._handle, self._unshard_stream, self._pre_unshard_stream + ) + self._unshard_event = self._unshard_stream.record_event() + self._handle._prefetched = True + unshard_handle = UnshardHandle(self._handle, self._unshard_stream) + if async_op: + return unshard_handle + unshard_handle.wait() + return None + + def _wait_unshard_streams_on_current_stream(self): + _wait_for_computation_stream( + self._device_handle.current_stream(), + self._unshard_stream, + self._pre_unshard_stream, + ) + + @contextlib.contextmanager + def _use_training_state( + self, training_state: TrainingState, handle_training_state: HandleTrainingState + ): + prev_training_state = self.training_state + self.training_state = training_state + if self._handle: + prev_handle_training_state = self._handle._training_state + self._handle._training_state = handle_training_state + try: + yield + finally: + self.training_state = prev_training_state + if self._handle: + self._handle._training_state = prev_handle_training_state + + +def _get_grad_norm( + params: Iterable[nn.Parameter], + norm_type: float, + zero: torch.Tensor, + device: torch.device, +) -> torch.Tensor: + """ + Return the gradient norm of parameters ``param`` s, where the gradients are viewed as a single vector. + + The returned norm is in FP32 even if parameters/gradients are in a low precision. This is because the downstream + use of this return value is a reduction across ranks. + """ + params_with_grad = [param for param in params if param.grad is not None] + if len(params_with_grad) == 0: + # Reuse a tensor for zero to avoid a GPU sync + return zero + grads = [param.grad for param in params_with_grad] + grad_dtypes = {grad.dtype for grad in grads} + if len(grad_dtypes) != 1: + raise ValueError( + f"Requires uniform dtype across all gradients but got {grad_dtypes}" + ) + # Compute the gradient norm in FP32, where we treat the gradients as a + # single vector + grad_norm = torch.linalg.vector_norm( + torch.stack( + [ + torch.linalg.vector_norm(grad.detach(), norm_type, dtype=torch.float32) + for grad in grads + ], + ), + norm_type, + dtype=torch.float32, + ) + return grad_norm.to(device=device) + + +def _get_param_to_fqn( + model: torch.nn.Module, +) -> Dict[torch.nn.Parameter, str]: + """ + Construct a mapping from parameters to their parameter names. + + The ``model`` should not contain any :class:`FullyShardedDataParallel` instances, which + means that none of the parameters should be ``FlatParameter`` s. As a + result, compared to :meth:`_get_param_to_fqns`, the mapped + values may be flattened from singleton :class:`list` s to the contained + names themselves. + + Args: + model (torch.nn.Module): Root module, which should not contain any + :class:`FullyShardedDataParallel` instances. + """ + param_to_param_names = _get_param_to_fqns(model) + for param_names in param_to_param_names.values(): + assert ( + len(param_names) > 0 + ), "`_get_param_to_fqns()` should not construct empty lists" + if len(param_names) > 1: + raise RuntimeError( + "Each parameter should only map to one parameter name but got " + f"{len(param_names)}: {param_names}" + ) + param_to_param_name = { + param: param_names[0] for param, param_names in param_to_param_names.items() + } + return param_to_param_name + + +def _get_fqn_to_param( + model: torch.nn.Module, +) -> Dict[str, torch.nn.Parameter]: + """Construct the inverse mapping of :meth:`_get_param_to_fqn`.""" + param_to_param_name = _get_param_to_fqn(model) + return dict(zip(param_to_param_name.values(), param_to_param_name.keys()))