diff --git "a/parrot/lib/python3.10/site-packages/torch/distributed/distributed_c10d.py" "b/parrot/lib/python3.10/site-packages/torch/distributed/distributed_c10d.py" new file mode 100644--- /dev/null +++ "b/parrot/lib/python3.10/site-packages/torch/distributed/distributed_c10d.py" @@ -0,0 +1,4541 @@ +# mypy: allow-untyped-defs +"""Distributed Collective Communication (c10d).""" + +import itertools +import collections.abc +import contextlib +import hashlib +import io +import logging +import os +import pickle +import sys +import time +import warnings +from collections import namedtuple +from datetime import timedelta +from typing import Any, Callable, Dict, Optional, Tuple, Union, List, TYPE_CHECKING +from typing_extensions import deprecated + +import torch +from torch._C._distributed_c10d import ( + AllgatherOptions, + AllreduceCoalescedOptions, + AllreduceOptions, + AllToAllOptions, + _DistributedBackendOptions, + BarrierOptions, + BroadcastOptions, + GatherOptions, + PrefixStore, + ProcessGroup, + ReduceOp, + ReduceOptions, + ReduceScatterOptions, + ScatterOptions, + Store, + DebugLevel, + get_debug_level, + Work, + _register_process_group, + _resolve_process_group, + _unregister_all_process_groups, + _unregister_process_group, +) +from torch._utils_internal import set_pytorch_distributed_envs_from_justknobs +from .constants import default_pg_timeout, default_pg_nccl_timeout +from .c10d_logger import _exception_logger, _time_logger +from .rendezvous import register_rendezvous_handler, rendezvous # noqa: F401 +from ..utils._typing_utils import not_none +DistStoreError = torch._C._DistStoreError + +__all__ = [ + 'Backend', 'BackendConfig', 'GroupMember', 'P2POp', 'all_gather', 'all_gather_coalesced', + 'all_gather_object', 'all_reduce', + 'all_reduce_coalesced', 'all_to_all', + 'all_to_all_single', 'barrier', 'batch_isend_irecv', 'broadcast', 'send_object_list', + 'recv_object_list', 'broadcast_object_list', 'destroy_process_group', + 'gather', 'gather_object', 'get_backend_config', 'get_backend', 'get_rank', + 'get_world_size', 'get_pg_count', 'group', 'init_process_group', 'irecv', + 'is_gloo_available', 'is_initialized', 'is_mpi_available', 'is_backend_available', + 'is_nccl_available', 'is_torchelastic_launched', 'is_ucc_available', + 'isend', 'monitored_barrier', 'new_group', 'new_subgroups', + 'new_subgroups_by_enumeration', 'recv', 'reduce', + 'reduce_scatter', 'scatter', + 'scatter_object_list', 'send', 'supports_complex', + 'AllreduceCoalescedOptions', 'AllreduceOptions', 'AllToAllOptions', + 'BarrierOptions', 'BroadcastOptions', 'GatherOptions', 'PrefixStore', + 'ProcessGroup', 'ReduceOp', 'ReduceOptions', 'ReduceScatterOptions', + 'ScatterOptions', 'Store', 'DebugLevel', 'get_debug_level', 'Work', + 'default_pg_timeout', 'get_group_rank', 'get_global_rank', 'get_process_group_ranks', + 'reduce_op', 'all_gather_into_tensor', 'reduce_scatter_tensor', 'get_node_local_rank', +] + +_MPI_AVAILABLE = True +_NCCL_AVAILABLE = True +_GLOO_AVAILABLE = True +_UCC_AVAILABLE = True + +_pickler = pickle.Pickler +_unpickler = pickle.Unpickler + +# Change __module__ of all imported types from torch._C._distributed_c10d that are public +def _export_c_types() -> None: + _public_types_to_change_module = [ + AllreduceCoalescedOptions, + AllreduceOptions, + AllToAllOptions, + BarrierOptions, + BroadcastOptions, + GatherOptions, + PrefixStore, + ProcessGroup, + ReduceOp, + ReduceOptions, + ReduceScatterOptions, + ScatterOptions, + Store, + DebugLevel, + get_debug_level, + Work + ] + for type in _public_types_to_change_module: + type.__module__ = "torch.distributed.distributed_c10d" +_export_c_types() + +try: + from torch._C._distributed_c10d import ProcessGroupMPI + ProcessGroupMPI.__module__ = "torch.distributed.distributed_c10d" + __all__ += ["ProcessGroupMPI"] +except ImportError: + _MPI_AVAILABLE = False + +try: + from torch._C._distributed_c10d import ProcessGroupNCCL + from torch._C._distributed_c10d import ProcessGroupCudaP2P + ProcessGroupNCCL.__module__ = "torch.distributed.distributed_c10d" + ProcessGroupCudaP2P.__module__ = "torch.distributed.distributed_c10d" + __all__ += ["ProcessGroupNCCL", "ProcessGroupCudaP2P"] +except ImportError: + _NCCL_AVAILABLE = False + +try: + from torch._C._distributed_c10d import ProcessGroupGloo + from torch._C._distributed_c10d import _ProcessGroupWrapper + ProcessGroupGloo.__module__ = "torch.distributed.distributed_c10d" + __all__ += ["ProcessGroupGloo"] +except ImportError: + _GLOO_AVAILABLE = False + +try: + from torch._C._distributed_c10d import ProcessGroupUCC + ProcessGroupUCC.__module__ = "torch.distributed.distributed_c10d" + __all__ += ["ProcessGroupUCC"] +except ImportError: + _UCC_AVAILABLE = False + +logger = logging.getLogger(__name__) + +PG_WRAPPER_STORE_PREFIX = "pg_wrapper" + + +# Some reduce ops are not supported by complex numbers and will result in an error. +# We currently provide complex support to the distributed API by viewing +# complex tensors as real (torch.view_as_real), meaning that calling +# these unsupported ops will return garbage values rather than error out. +# (e.g. max(2+3i, 3+2i) = 3+3i) +# We'd like calls to unsupported ops to error out accordingly, +# rather than returning garbage values. +def supports_complex(reduceOp: ReduceOp) -> bool: + """Return true if reduce ops is supported. False otherwise.""" + denyList = [ + ReduceOp.MAX, + ReduceOp.MIN, + ReduceOp.PRODUCT, + ReduceOp.BAND, + ReduceOp.BOR, + ReduceOp.BXOR, + ] + return reduceOp not in denyList + + +class Backend(str): + """ + An enum-like class for backends. + + Available backends: GLOO, NCCL, UCC, MPI, and other registered backends. + + The values of this class are lowercase strings, e.g., ``"gloo"``. They can + be accessed as attributes, e.g., ``Backend.NCCL``. + + This class can be directly called to parse the string, e.g., + ``Backend(backend_str)`` will check if ``backend_str`` is valid, and + return the parsed lowercase string if so. It also accepts uppercase strings, + e.g., ``Backend("GLOO")`` returns ``"gloo"``. + + .. note:: The entry ``Backend.UNDEFINED`` is present but only used as + initial value of some fields. Users should neither use it directly + nor assume its existence. + """ + + UNDEFINED = "undefined" + GLOO = "gloo" + NCCL = "nccl" + UCC = "ucc" + MPI = "mpi" + + _BackendPlugin = namedtuple("_BackendPlugin", ["creator_fn", "extended_api"]) + + _plugins: Dict[str, _BackendPlugin] = {} + + backend_list = [UNDEFINED, GLOO, NCCL, UCC, MPI] + + default_device_backend_map: Dict[str, str] = { + 'cpu' : GLOO, + 'cuda' : NCCL, + } + + backend_capability: Dict[str, List[str]] = { + GLOO : ["cpu", "cuda"], + NCCL : ["cuda"], + UCC : ["cpu", "cuda"], + MPI : ["cpu", "cuda"], + } + + backend_type_map: Dict[str, ProcessGroup.BackendType] = { + UNDEFINED: ProcessGroup.BackendType.UNDEFINED, + GLOO : ProcessGroup.BackendType.GLOO, + NCCL: ProcessGroup.BackendType.NCCL, + UCC: ProcessGroup.BackendType.UCC, + } + + def __new__(cls, name: str): + """Create and return a new instance of the class.""" + if not isinstance(name, str): + raise ValueError("Backend constructor parameter must be string-ish") + value = getattr(Backend, name.upper(), Backend.UNDEFINED) + + if value == Backend.UNDEFINED: + value = name.lower() + return value + + @classmethod + def register_backend(cls, name, func, extended_api=False, devices: Optional[Union[str, List[str]]] = None) -> None: + """ + Register a new backend with the given name and instantiating function. + + This class method is used by 3rd party ``ProcessGroup`` extension to + register new backends. + + Args: + name (str): Backend name of the ``ProcessGroup`` extension. It + should match the one in ``init_process_group()``. + func (function): Function handler that instantiates the backend. + The function should be implemented in the backend + extension and takes four arguments, including + ``store``, ``rank``, ``world_size``, and ``timeout``. + extended_api (bool, optional): Whether the backend supports extended argument structure. + Default: ``False``. If set to ``True``, the backend + will get an instance of ``c10d::DistributedBackendOptions``, and + a process group options object as defined by the backend implementation. + device (str or list of str, optional): device type this backend + supports, e.g. "cpu", "cuda", etc. If `None`, + assuming both "cpu" and "cuda" + + .. note:: This support of 3rd party backend is experimental and subject to change. + + """ + # Allow UCC plugin if Pytorch is not built with native support. + # TODO: remove this exception once UCC plugin is fully deprecated. + if (name != Backend.UCC or (name == Backend.UCC and is_ucc_available())): + assert not hasattr(Backend, name.upper()), ( + f"{name.upper()} c10d backend already exist" + ) + assert name.upper() not in Backend._plugins, ( + f"{name.upper()} c10d backend creator function already exist" + ) + + setattr(Backend, name.upper(), name.lower()) + Backend.backend_list.append(name.lower()) + if devices is not None: + for device in devices: + if device != 'cpu' and device != 'cuda': + Backend.default_device_backend_map[device] = name.lower() + Backend.backend_type_map[name.lower()] = ProcessGroup.BackendType.CUSTOM + + # Update device capability matrix in Backend class + if devices is None: + # This is more of a backward support for groups like `threaded`: + # assume default devices "cpu" and "cuda", but warn + warnings.warn( + f"Device capability of {name} unspecified, assuming `cpu` and " + "`cuda`. Please specify it via the `devices` argument of " + "`register_backend`." + ) + Backend.backend_capability[name.lower()] = ["cpu", "cuda"] + elif isinstance(devices, str): + # Single device string specified. Simply convert to list. + Backend.backend_capability[name.lower()] = [devices] + else: + Backend.backend_capability[name.lower()] = devices + + Backend._plugins[name.upper()] = Backend._BackendPlugin(func, extended_api) + +class BackendConfig: + """Backend configuration class.""" + + def __init__(self, backend: Backend): + """Init.""" + self.device_backend_map: Dict[str, Backend] = {} + backend = str(backend) + + if backend == Backend.UNDEFINED: + # default config when backend is not specified + # supported since PyTorch 2.0 + for device, default_backend in Backend.default_device_backend_map.items(): + if is_backend_available(default_backend): + if default_backend == Backend.NCCL and not torch.cuda.is_available(): + continue + self.device_backend_map[device] = Backend(default_backend) + elif backend.lower() in Backend.backend_list: + # Cases for when backend is a single string (without device types) + # e.g. "nccl", "gloo", "ucc", "mpi" + supported_devices = Backend.backend_capability[backend.lower()] + backend_val = Backend(backend) + self.device_backend_map = dict.fromkeys(supported_devices, backend_val) + elif ":" in backend.lower(): + # Backend specified in "device:backend" format + # make sure the backend string is in the correct format + # "{device_type1}:{backend1},{device_type2}:{backend2}" + # e.g. "cpu:gloo,cuda:nccl" + backend_str_error_message = f"""The custom backend string argument is invalid: {backend}. + Custom backend string is an experimental feature where the backend string must be in the format: + ":,:...". e.g. 'cpu:gloo,cuda:nccl'""" + + # parse the backend string and populate the device_backend_map + for device_backend_pair_str in backend.lower().split(","): + device_backend_pair = device_backend_pair_str.split(":") + if len(device_backend_pair) != 2: + raise ValueError(f"Invalid device:backend pairing: \ + {device_backend_pair_str}. {backend_str_error_message}") + device, backend = device_backend_pair + if device in self.device_backend_map: + raise ValueError(f"Duplicate device type {device} \ + in backend string: {backend}. {backend_str_error_message}") + self.device_backend_map[device] = Backend(backend) + else: + # User specified a single backend name whose device capability is + # unknown, assuming it can support the default devices of PyTorch + # (cpu and cuda) + warnings.warn( + f"Device capability of {backend} unknown, assuming `cpu` and " + "`cuda`. You can specify it in `device:backend` format in " + "`init_process_group` call." + ) + backend_val = Backend(backend) + self.device_backend_map = { + "cpu" : backend_val, + "cuda" : backend_val, + "xpu" : backend_val, + } + + logger.info( + "Using backend config: %s", self.device_backend_map + ) + + def __repr__(self): + """Return all the device:backend pairs separated by commas.""" + return ",".join(f"{device}:{backend}" for device, backend in self.device_backend_map.items()) + + def get_device_backend_map(self) -> Dict[str, Backend]: + """Return backend map of the device.""" + return self.device_backend_map + +class _reduce_op: + r""" + Deprecated enum-like class. + + For reduction operations: ``SUM``, ``PRODUCT``, ``MIN``, and ``MAX``. + + :class:`~torch.distributed.ReduceOp` is recommended to use instead. + """ + + def __init__(self): + # __members__ is a dict storing key-value pairs for enum classes + for k, v in ReduceOp.RedOpType.__members__.items(): + setattr(self, k, v) + self.__members__ = ReduceOp.RedOpType.__members__ + + @deprecated( + "`torch.distributed.reduce_op` is deprecated, " + "please use `torch.distributed.ReduceOp` instead", + category=FutureWarning, + ) + def __getattribute__(self, key): + return object.__getattribute__(self, key) + + +reduce_op = _reduce_op() + + +class P2POp: + """ + A class to build point-to-point operations for ``batch_isend_irecv``. + + This class builds the type of P2P operation, communication buffer, peer rank, + Process Group, and tag. Instances of this class will be passed to + ``batch_isend_irecv`` for point-to-point communications. + + Args: + op (Callable): A function to send data to or receive data from a peer process. + The type of ``op`` is either ``torch.distributed.isend`` or + ``torch.distributed.irecv``. + tensor (Tensor): Tensor to send or receive. + peer (int): Destination or source rank. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + tag (int, optional): Tag to match send with recv. + """ + + def __init__(self, op: Callable, tensor: torch.Tensor, peer: int, + group: Optional[ProcessGroup] = None, tag: int = 0): + """Init.""" + self.op = op + self.tensor = tensor + self.peer = peer + self.group = group + self.tag = tag + + def __new__(cls, op: Callable, tensor: torch.Tensor, peer: int, + group: Optional[ProcessGroup] = None, tag: int = 0): + """Create and return a new instance of the class.""" + _check_op(op) + _check_single_tensor(tensor, "tensor") + return object.__new__(cls) + + def __repr__(self): + my_group_rank = get_rank(self.group) + peer_group_rank = get_group_rank(self.group, self.peer) if self.group else self.peer + op_name = self.op.__name__ + group_name = self.group.group_name if self.group else "default_pg" + if "send" in op_name: + s = my_group_rank + d = peer_group_rank + elif "recv" in op_name: + s = peer_group_rank + d = my_group_rank + else: + return super().__repr__() + + return f"P2POp({op_name} pg={group_name}, s={s}, d={d}, {self.tensor.shape}, {self.tensor.dtype})" + +class _CollOp: + """ + A class to capture collective operations. + + Args: + op (Callable): A collective function, e.g. ``torch.distributed.all_reduce``. + tensor (Tensor): Tensor to operate on. + dst_tensor (Tensor, optional): Provided when source and destinaton tensors are not the same. + redop (ReduceOp, optional): reduce operation. + root (int, optional): root of broadcast or reduce. + """ + + def __init__(self, op: Callable, tensor: torch.Tensor, dst_tensor: Optional[torch.Tensor] = None, + redop: Optional[ReduceOp] = None, root: Optional[int] = None): + self.op = op + self.tensor = tensor + self.dst_tensor = dst_tensor + self.redop = redop + self.root = root + + +# DO NOT USE THESE FIELDS DIRECTLY. +# Use them through the _world object to make sure the _world override mechanism +_pg_map: Dict[ProcessGroup, Tuple[str, Store]] = {} +_pg_names: Dict[ProcessGroup, str] = {} +_pg_group_ranks: Dict[ProcessGroup, Dict[int, int]] = {} +# For a pg, it is a map from ProcessGroup to BackendConfig +_pg_backend_config: Dict[ProcessGroup, str] = {} +_group_count = 0 +_tags_to_pg: Dict[str, List[ProcessGroup]] = {} +_pg_to_tag: Dict[ProcessGroup, str] = {} +_backend: Optional[str] = None + +class _World: + """ + Container class for c10d process group state. + + This is used during registration and lookup of PG state. + + .. warning:: This is an experimental API intended to expose the inner workings + of c10d and is subject to change.. + """ + + def __init__(self): + self._default_pg = None + self._pg_coalesce_state: Dict[ProcessGroup, List[_CollOp]] = {} + self._pg_default_device: Dict[ProcessGroup, torch.device] = {} + + @property + def default_pg(self) -> Optional[ProcessGroup]: + """ + Process group that includes all ranks of the cluster. + + This default ProcessGroup is used by c10d APIs when a ProcessGroup is needed + but None is provided. + """ + return self._default_pg + + @default_pg.setter + def default_pg(self, value) -> None: + self._default_pg = value + + @property + def pg_map(self) -> Dict[ProcessGroup, Tuple[str, Store]]: + """ + Provide Mapping from ProcessGroup to backend name and store. + + For NCCL and GLOO pg, it is a map from ProcessGroup to (Backend, Store) + For MPI pg, it is a map from ProcessGroup to (Backend, None) + + TODO don't expose the map, expose fine grained ops + """ + global _pg_map + return _pg_map + + @property + def pg_names(self) -> Dict[ProcessGroup, str]: + """ + Process group's names, map from ProcessGroup to str. + + TODO don't expose the map, expose fine grained ops + """ + global _pg_names + return _pg_names + + @property + def pg_group_ranks(self) -> Dict[ProcessGroup, Dict[int, int]]: + """ + Process group's global rank to local rank mapping. + + TODO don't expose the map, expose fine grained ops + """ + global _pg_group_ranks + return _pg_group_ranks + + @property + def pg_backend_config(self) -> Dict[ProcessGroup, str]: + """ + Process group's backend config. + + TODO don't expose the map, expose fine grained ops + """ + global _pg_backend_config + return _pg_backend_config + + @property + def group_count(self) -> int: + """ + Process group count for default naming. + + TODO don't expose group_count, use something else instead + """ + global _group_count + return _group_count + + @group_count.setter + def group_count(self, value: int) -> None: + """Use to compute the name of ProcessGroups when using global synchronization.""" + global _group_count + _group_count = value + + @property + def tags_to_pg(self) -> Dict[str, List[ProcessGroup]]: + global _tags_to_pg + return _tags_to_pg + + @property + def pg_to_tag(self) -> Dict[ProcessGroup, str]: + global _pg_to_tag + return _pg_to_tag + + @property + def pg_coalesce_state(self) -> Dict[ProcessGroup, List[_CollOp]]: + return self._pg_coalesce_state + + @property + def pg_default_device(self) -> Dict[ProcessGroup, torch.device]: + return self._pg_default_device + + @property + def pg_config_info(self) -> List[Dict[str, Any]]: + """ + Return a list of dict with process groups and backends. + + Along with their unique IDs and configurations (types and ranks). + """ + config_info: List[Dict[str, Any]] = [] + default_pg_size = _get_group_size(None) + for pg in self.pg_map.keys(): + ranks = self.pg_group_ranks[pg] + config_info.append( + { + "pg_name": self.pg_names[pg], + "pg_desc": pg.group_desc, + "backend_config": self.pg_backend_config[pg], + "ranks": list(ranks.keys()) + if len(ranks) != default_pg_size + else [], # 'ranks' is an empty list when all ranks are involved in a pg + "group_size": len(ranks), + "group_count": self.group_count, + } + ) + return config_info + + +_world = _World() +"""Holds the singleton instance of ``_World`` used by c10. Experimental extension point to override it""" + +class _WorldMeta(type): + """ + Meta class of ``group`` and ``GroupMember``. + + Allows them to have the class property ``WORLD``. + """ + + # Points to the default PG once initialized. + @property + def WORLD(cls) -> Optional[ProcessGroup]: + return _world.default_pg + + @WORLD.setter + def WORLD(cls, pg: Optional[ProcessGroup]): + _world.default_pg = pg + +class group(metaclass=_WorldMeta): + """Group class. Placeholder.""" + + pass + +class GroupMember(metaclass=_WorldMeta): + """Group member class.""" + + NON_GROUP_MEMBER = -100 + + +def _get_default_timeout(backend: Backend) -> timedelta: + # see note on nccl vs other backend timeout (constants.py) + if backend == Backend.NCCL: + if not isinstance(default_pg_nccl_timeout, timedelta): + # TODO moco benchmark on CPU initializes pgnccl backend today, triggered this assert in CI before it was + # changed to be a warning. We should fix the moco model. + warnings.warn("Attempted to get default timeout for nccl backend, but NCCL support is not compiled") + return default_pg_timeout + return default_pg_nccl_timeout + else: + return default_pg_timeout + +def _check_valid_timeout(timeout: Any) -> None: + if not isinstance(timeout, timedelta): + raise TypeError( + f"Expected timeout argument to be of type datetime.timedelta, got {timeout}" + ) + +# Default process group state +_default_pg_init_method: Optional[str] = None + +STORE_BASED_BARRIER_PREFIX = "store_based_barrier_key" + +def _get_pg_default_device(group: Optional[ProcessGroup] = None) -> torch.device: + """ + Return the device to use with ``group`` for control flow usage (object collectives, barrier). + + There are selection rules: + 1. If user specifies exactly one backend in ``init_process_group`` call: + use that backend + 2. Else if user specifies multiple "device:backend" pairs in init_process_group: + If "cpu" is among those pairs, use "cpu" (because the object is in cpu memory); + Otherwise, use the first backend (sort of a random pick). + + Args: + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + + Returns: + torch.device: The device to use with ``group``. + + """ + group = group or _get_default_group() + if group in _world.pg_default_device: + # Previously searched and cached; just return + return _world.pg_default_device[group] + + if not isinstance(group, ProcessGroup): + # Provide backward compatibility to cases where `group` passed in is + # actually a Backend (like `ProcessGroupGloo`) rather than a + # `ProcessGroup` in PT 2.0 sense + warnings.warn( + f"You are using a Backend {type(group)} as a ProcessGroup. " + "This usage is deprecated since PyTorch 2.0. Please use a public API " + "of PyTorch Distributed instead.", + FutureWarning, + stacklevel=3, + ) + # Most users create Gloo with private API for object collectives + _world.pg_default_device[group] = torch.device("cpu") + return _world.pg_default_device[group] + + """ + ``group._device_types`` is a property pybind that returns the devices + ("cpu", "cuda", etc) supported by ``group``. Can be multiple if the + ``group`` supports multiple devices. + """ + devices = group._device_types + + if len(devices) == 1: + # User fixed exactly one backend in `init_process_group` + _world.pg_default_device[group] = devices[0] + elif len(devices) == 0: + # No backend has been registered with this PG (maybe because no + # collective has been run?) We pick cpu as the default and hopefully + # this would lazily init Gloo or other available cpu backend. + _world.pg_default_device[group] = torch.device("cpu") + elif torch.device("cpu") in devices: + # There are multiple backends in this PG and cpu is among them. + # cpu is preferred as the object is in cpu memory. No need for device + # copy. + _world.pg_default_device[group] = torch.device("cpu") + else: + # No cpu in the backend list. Randomly pick the first backend + _world.pg_default_device[group] = devices[0] + + logger.info( + "Using device %s for object " + "collectives.", _world.pg_default_device[group] + ) + return _world.pg_default_device[group] + + +@_time_logger +def _store_based_barrier(rank, store, group_name, rendezvous_count, timeout, logging_interval=timedelta(seconds=10)) -> None: + """ + Store based barrier for synchronizing processes. + + Barrier based on store which is used for synchronizing processes after + ``init_process_group`` or ``new_group``. Intended to be used only with + those two methods and is not a generic alternative to ``barrier()``. + """ + store_key = f"{STORE_BASED_BARRIER_PREFIX}:{group_name}" + store.add(store_key, 1) + logger.debug("Added key: %s to store for rank: %s", store_key, rank) + + # Now wait for all workers to check in with the store. + world_size = rendezvous_count + worker_count = store.add(store_key, 0) + + last_worker_key = f"{store_key}:last_worker" + if worker_count == world_size: + store.set(last_worker_key, "1") + + # adjust the timeout to be at least 10secs + 1sec per thousand ranks to reduce the odds of timeout + # this value was empirically found while scale testing. + logging_interval = max(logging_interval, timedelta(seconds=10 + world_size / 1000)) + + start = time.time() + while True: + try: + # This will throw an exception after the logging_interval in which we print out + # the status of the group or time out officially, throwing runtime error + store.wait([last_worker_key], logging_interval) + break + except RuntimeError as e: + worker_count = store.add(store_key, 0) + # Print status periodically to keep track. + logger.debug( + "Waiting in store based barrier to initialize process group for " + "rank: %s, key: %s (world_size=%s, num_workers_joined=%s, timeout=%s error=%s)", + rank, store_key, world_size, worker_count, timeout, e + ) + + if timedelta(seconds=(time.time() - start)) > timeout: + raise DistStoreError( # noqa: B904 + "Timed out initializing process group in store based barrier on " + f"rank {rank}, for key: {store_key} (world_size={world_size}, " + f"num_workers_joined={worker_count}, timeout={timeout} error={e})" + ) + + logger.info( + "Rank %s: Completed store-based barrier for key:%s with %s nodes.", rank, store_key, world_size + ) + + +def _rank_not_in_group(group: Optional[ProcessGroup]) -> bool: + """Check if the current process's rank is not in a given group.""" + if group is None: + return False + return group == GroupMember.NON_GROUP_MEMBER + + +def _warn_not_in_group(op_name) -> None: + global_rank = -1 if GroupMember.WORLD is None else GroupMember.WORLD.rank() + warnings.warn( + f"Running {op_name} on global rank {global_rank} which does not " + "belong to the given group." + ) + + +def get_group_rank(group: ProcessGroup, global_rank: int) -> int: + """ + Translate a global rank into a group rank. + + ``global_rank`` must be part of ``group`` otherwise this raises RuntimeError. + + Args: + group (ProcessGroup): ProcessGroup to find the relative rank. + global_rank (int): Global rank to query. + + Returns: + Group rank of ``global_rank`` relative to ``group`` + + N.B. calling this function on the default process group returns identity + """ + if group is GroupMember.WORLD: + return global_rank + if group not in _world.pg_group_ranks: + raise ValueError(f"Group {group} is not registered, please create group with torch.distributed.new_group API") + group_ranks = _world.pg_group_ranks[group] + if global_rank not in group_ranks: + raise ValueError(f"Global rank {global_rank} is not part of group {group}") + + return group_ranks[global_rank] + +def get_global_rank(group: ProcessGroup, group_rank: int) -> int: + """ + Translate a group rank into a global rank. + + ``group_rank`` must be part of `group` otherwise this raises RuntimeError. + + Args: + group (ProcessGroup): ProcessGroup to find the global rank from. + group_rank (int): Group rank to query. + + Returns: + Global rank of ``group_rank`` relative to ``group`` + + N.B. calling this function on the default process group returns identity + """ + if group is GroupMember.WORLD: + return group_rank + if group not in _world.pg_group_ranks: + raise ValueError(f"Group {group} is not registered, please create group with torch.distributed.new_group API") + for rank, grp_rank in _world.pg_group_ranks[group].items(): + if grp_rank == group_rank: + return rank + raise ValueError(f"Group rank {group_rank} is not part of group {group}") + + +# TODO: remove this once the ecosystem moves away from it. +@deprecated( + "`torch.distributed.distributed_c10d._get_global_rank` is deprecated, " + "please use `torch.distributed.distributed_c10d.get_global_rank` instead", + category=FutureWarning, +) +def _get_global_rank(group, rank) -> int: + """Use get_global_rank as this method is deprecated.""" + return get_global_rank(group, rank) + + +def get_process_group_ranks(group: ProcessGroup) -> List[int]: + """ + Get all ranks associated with ``group``. + + Args: + group (ProcessGroup): ProcessGroup to get all ranks from. + + Returns: + List of global ranks ordered by group rank. + """ + return list(_world.pg_group_ranks[group].keys()) + +def _get_group_size(group) -> int: + """Get a given group's world size.""" + if group is GroupMember.WORLD or group is None: + default_pg = _get_default_group() + return default_pg.size() + return group.size() + + +def _get_group_size_by_name(group_name: str) -> int: + group = _resolve_process_group(group_name) + return group.size() + + +def _resolve_group_name_by_ranks_and_tag(ranks: List[int], tag: str) -> str: + # TODO(yifu): remove this function once ranks + tag is not a supported + # identifier for process group for functional collectives. + group = _find_pg_by_ranks_and_tag(tag, ranks) + if group is None: + raise ValueError("") + return group.group_name + + +def _check_single_tensor(param, param_name) -> None: + """Check that the parameter ``param_name`` is a single tensor.""" + if not isinstance(param, torch.Tensor): + raise TypeError( + f"""Invalid function argument. Expected parameter `{param_name}` of type torch.Tensor + but got {type(param)} instead.""" + ) + + +def _check_tensor_list(param, param_name) -> None: + """Check that the parameter ``param_name`` is a list of tensors.""" + if not isinstance(param, list): + raise TypeError( + f"""Invalid function argument. Expected parameter `{param_name}` of type List[torch.Tensor] + but got {type(param)} instead.""" + ) + elif not all(isinstance(p, torch.Tensor) for p in param): + raise TypeError( + f"""Invalid function argument. Expected parameter `{param_name}` of type List[torch.Tensor] + but got {type(param)} with elements of type {[type(p) for p in param]}.""" + ) + + +def _as_iterable(obj) -> collections.abc.Iterable: + return obj if isinstance(obj, list) else (obj,) + +def _ensure_all_tensors_same_dtype(*tensors) -> None: + last_dtype = None + for tensor in itertools.chain.from_iterable(map(_as_iterable, tensors)): + tensor_dtype = tensor.dtype + # Mixing complex and its element type is allowed + if tensor_dtype.is_complex: + tensor_dtype = torch.float32 if tensor_dtype == torch.complex64 else torch.complex128 + + if last_dtype is None: + last_dtype = tensor_dtype + else: + if last_dtype != tensor_dtype: + raise ValueError( + "Invalid usage of tensors with different dtypes" + f"Found {last_dtype} and {tensor.dtype}" + ) + + +def _check_op(op) -> None: + """Check that the ``op`` is either isend or irecv.""" + if op not in [isend, irecv]: + raise ValueError( + "Invalid ``op``. Expected ``op`` " + "to be of type ``torch.distributed.isend`` or " + "``torch.distributed.irecv``." + ) + + +def _check_p2p_op_list(p2p_op_list) -> None: + """ + Check that the ``p2p_op_list`` is a list of P2POp instances. + + Also, check that all ops use the same group. + """ + if not isinstance(p2p_op_list, list) or not all( + isinstance(p2p_op, P2POp) for p2p_op in p2p_op_list + ): + raise ValueError( + "Invalid ``p2p_op_list``. Each op is expected to " + "to be of type ``torch.distributed.P2POp``." + ) + + group = p2p_op_list[0].group + if not all(group == p2p_op.group for p2p_op in p2p_op_list): + raise ValueError("All ops need to use the same group.") + + +def is_mpi_available() -> bool: + """Check if the MPI backend is available.""" + return _MPI_AVAILABLE + + +def is_nccl_available() -> bool: + """Check if the NCCL backend is available.""" + return _NCCL_AVAILABLE + + +def is_gloo_available() -> bool: + """Check if the Gloo backend is available.""" + return _GLOO_AVAILABLE + + +def is_ucc_available() -> bool: + """Check if the UCC backend is available.""" + return _UCC_AVAILABLE + + +def is_backend_available(backend: str) -> bool: + """ + Check backend availability. + + Checks if the given backend is available and supports the built-in backends or + third-party backends through function ``Backend.register_backend``. + + Args: + backend (str): Backend name. + Returns: + bool: Returns true if the backend is available otherwise false. + """ + # If the backend has an ``is_backend_available`` function, return the result of that function directly + available_func = getattr(torch.distributed, f"is_{backend.lower()}_available", None) + if available_func: + return available_func() + + return backend.lower() in Backend.backend_list + + +def is_initialized() -> bool: + """Check if the default process group has been initialized.""" + return GroupMember.WORLD is not None + + +def is_torchelastic_launched() -> bool: + """ + Check whether this process was launched with ``torch.distributed.elastic`` (aka torchelastic). + + The existence of ``TORCHELASTIC_RUN_ID`` environment + variable is used as a proxy to determine whether the current process + was launched with torchelastic. This is a reasonable proxy since + ``TORCHELASTIC_RUN_ID`` maps to the rendezvous id which is always a + non-null value indicating the job id for peer discovery purposes.. + """ + return os.getenv("TORCHELASTIC_RUN_ID") is not None + + +def _is_barrier_after_init() -> int: + # Environment variable to control whether process group should perform a + # barrier after its init. Default value is 0, i.e. no barrier. If you + # experience issue with this setting, you may set + # `TORCH_DIST_INIT_BARRIER=1` to add the barrier. + return int(os.getenv("TORCH_DIST_INIT_BARRIER", "0")) + + +def _get_default_group() -> ProcessGroup: + """Get the default process group created by init_process_group.""" + if not is_initialized(): + raise ValueError( + "Default process group has not been initialized, " + "please make sure to call init_process_group." + ) + if TYPE_CHECKING: + return not_none(GroupMember.WORLD) + else: + return GroupMember.WORLD + + +def _get_default_store() -> Store: + """Get the default store created by init_process_group.""" + if not is_initialized(): + raise ValueError( + "Default process group has not been initialized, " + "please make sure to call init_process_group." + ) + default_pg = _get_default_group() + _, default_store = _world.pg_map[default_pg] + return default_store + + +def _update_default_pg(pg) -> None: + _world.default_pg = pg + rank = pg.rank() if pg is not None and pg != GroupMember.NON_GROUP_MEMBER else -1 + torch._C._distributed_c10d._set_global_rank(rank) + +def get_backend_config(group: Optional[ProcessGroup] = None) -> str: + """ + Return the backend configuration of the given process group. + + Args: + group (ProcessGroup, optional): The process group to work on. The + default is the general main process group. If another specific group + is specified, the calling process must be part of :attr:`group`. + + Returns: + The backend configuration of the given process group as a lower case string. + + """ + if group is None: + pg = _get_default_group() + else: + pg = group + if _rank_not_in_group(pg): + raise ValueError("Invalid process group specified") + backend_config = _world.pg_backend_config.get(pg) + return str(not_none(backend_config)) + +def get_backend(group: Optional[ProcessGroup] = None) -> Backend: + """ + Return the backend of the given process group. + + Args: + group (ProcessGroup, optional): The process group to work on. The + default is the general main process group. If another specific group + is specified, the calling process must be part of :attr:`group`. + + Returns: + The backend of the given process group as a lower case string. + + """ + if group is None: + pg = _get_default_group() + else: + pg = group + if _rank_not_in_group(pg): + raise ValueError("Invalid process group specified") + pg_store = _world.pg_map[pg] if pg in _world.pg_map else None + return Backend(not_none(pg_store)[0]) + +def _get_process_group_uid(pg: ProcessGroup) -> int: + backend = None + try: + backend = pg._get_backend(torch.device("cuda")) + except RuntimeError: + pass + if is_nccl_available() and isinstance(backend, ProcessGroupNCCL): + return backend.uid + return -1 + +def _get_pg_config(group: Optional[ProcessGroup] = None) -> Dict[str, Any]: + """ + Return the pg configuration of the given process group. + + """ + if group is None: + pg = _get_default_group() + else: + pg = group + return { + "pg_name": _get_process_group_name(pg), + "pg_desc": pg.group_desc, + "backend_config": get_backend_config(pg), + "pg_size": _get_group_size(pg), + "ranks": get_process_group_ranks(pg), + } + +def _get_all_pg_configs() -> List[Dict[str, Any]]: + """ + Return the pg configuration of all the process groups. + + """ + config_info: List[Dict[str, Any]] = [] + for pg in _world.pg_map.keys(): + config_info.append(_get_pg_config(pg)) + return config_info + +def get_pg_count() -> int: + """ + Return the number of process groups. + + """ + return _world.group_count + +def get_node_local_rank(fallback_rank: Optional[int] = None) -> int: + """ + Return the local rank of the current process relative to the node. + + Semantically, this is a useful concept for mapping processes to devices. + For example, on a node with 8 accelerator you could use the node local rank to decide + which accelerator device to bind the process to. + + In practice, the actual assignment of node local ranks is handled by the process launcher outside of pytorch, + and communicated via the `LOCAL_RANK` environment variable. + + Torchrun will automatically populate `LOCAL_RANK`, but other launchers may not. If `LOCAL_RANK` is unspecified, + this API will fall back to the provided kwarg 'fallback_rank' if specified, otherwise it will raise an error. The + intent is to allow writing an application that runs either in single or multi device contexts without error. + + """ + if "LOCAL_RANK" in os.environ: + return int(os.environ["LOCAL_RANK"]) + elif fallback_rank is not None: + return int(fallback_rank) + raise RuntimeError( + "LOCAL_RANK is not in the environment. Consider passing fallback_rank to allow `get_node_local_rank` to work, " + "assuming you are not running in a multi-device context and want the code to run locally instead." + ) + +def _set_pg_timeout(timeout: timedelta, group: Optional[ProcessGroup] = None) -> None: + """ + Set the timeout for the given process group when users want to use a different timeout instead of + default values. + + Args: + timeout (timedelta): Timeout for operations executed against the process group which + users want to set. Default value is 10 minutes for NCCL and 30 minutes for other backends. + This is the duration after which collectives will be aborted asynchronously and the process will crash. + This is done since CUDA execution is async and it is no longer safe to continue executing user code since + failed async NCCL operations might result in subsequent CUDA operations running on corrupted data. + When TORCH_NCCL_BLOCKING_WAIT is set, the process will block and wait for this timeout. + + group (ProcessGroup, optional): The process group to work on. The + default is the general main process group. If another specific group + is specified, the calling process must be part of :attr:`group`. + + Returns: + None + """ + if group is None: + group = _get_default_group() + if _rank_not_in_group(group): + raise ValueError("Invalid process group specified") + assert isinstance(group, ProcessGroup) + devices = group._device_types + backends = set() + if torch.device("cpu") in devices and is_gloo_available(): + backend = group._get_backend(torch.device("cpu")) + if isinstance(backend, ProcessGroupGloo): + backends.add(backend) + if torch.device("cuda") in devices: + backend = group._get_backend(torch.device("cuda")) + if is_nccl_available() and isinstance(backend, ProcessGroupNCCL): + backends.add(backend) # type: ignore[arg-type] + elif is_gloo_available() and isinstance(backend, ProcessGroupGloo): + backends.add(backend) # type: ignore[arg-type] + if len(backends) == 0: + warnings.warn("Set timeout is now only supported for either nccl or gloo.") + for backend in backends: + backend._set_default_timeout(timeout) + + +@_exception_logger +@_time_logger +def init_process_group( + backend: Optional[str] = None, + init_method: Optional[str] = None, + timeout: Optional[timedelta] = None, + world_size: int = -1, + rank: int = -1, + store: Optional[Store] = None, + group_name: str = "", + pg_options: Optional[Any] = None, + device_id: Optional[torch.device] = None, +) -> None: + """ + Initialize the default distributed process group. + + This will also initialize the distributed package. + + There are 2 main ways to initialize a process group: + 1. Specify ``store``, ``rank``, and ``world_size`` explicitly. + 2. Specify ``init_method`` (a URL string) which indicates where/how + to discover peers. Optionally specify ``rank`` and ``world_size``, + or encode all required parameters in the URL and omit them. + + If neither is specified, ``init_method`` is assumed to be "env://". + + + Args: + backend (str or Backend, optional): The backend to use. Depending on + build-time configurations, valid values include ``mpi``, ``gloo``, + ``nccl``, and ``ucc``. If the backend is not provided, then both a ``gloo`` + and ``nccl`` backend will be created, see notes below for how multiple + backends are managed. This field can be given as a lowercase string + (e.g., ``"gloo"``), which can also be accessed via + :class:`Backend` attributes (e.g., ``Backend.GLOO``). If using + multiple processes per machine with ``nccl`` backend, each process + must have exclusive access to every GPU it uses, as sharing GPUs + between processes can result in deadlocks. ``ucc`` backend is + experimental. + init_method (str, optional): URL specifying how to initialize the + process group. Default is "env://" if no + ``init_method`` or ``store`` is specified. + Mutually exclusive with ``store``. + world_size (int, optional): Number of processes participating in + the job. Required if ``store`` is specified. + rank (int, optional): Rank of the current process (it should be a + number between 0 and ``world_size``-1). + Required if ``store`` is specified. + store(Store, optional): Key/value store accessible to all workers, used + to exchange connection/address information. + Mutually exclusive with ``init_method``. + timeout (timedelta, optional): Timeout for operations executed against + the process group. Default value is 10 minutes for NCCL and 30 minutes for other backends. + This is the duration after which collectives will be aborted asynchronously and the process will crash. + This is done since CUDA execution is async and it is no longer safe to continue executing user code since + failed async NCCL operations might result in subsequent CUDA operations running on corrupted data. + When TORCH_NCCL_BLOCKING_WAIT is set, the process will block and wait for this timeout. + + group_name (str, optional, deprecated): Group name. This argument is ignored + pg_options (ProcessGroupOptions, optional): process group options + specifying what additional options need to be passed in during + the construction of specific process groups. As of now, the only + options we support is ``ProcessGroupNCCL.Options`` for the ``nccl`` + backend, ``is_high_priority_stream`` can be specified so that + the nccl backend can pick up high priority cuda streams when + there're compute kernels waiting. + device_id (torch.device, optional): a single, specific device + to "bind" this process to, allowing for backend-specific + optimizations. Currently this has two effects, only under + NCCL: the communicator is immediately formed (calling + ``ncclCommInit*`` immediately rather than the normal lazy + call) and sub-groups will use ``ncclCommSplit`` when + possible to avoid unnecessary overhead of group creation. If you + want to know NCCL initialization error early, you can also use this + field. + + .. note:: To enable ``backend == Backend.MPI``, PyTorch needs to be built from source + on a system that supports MPI. + + .. note:: Support for multiple backends is experimental. Currently when no backend is + specified, both ``gloo`` and ``nccl`` backends will be created. The ``gloo`` backend + will be used for collectives with CPU tensors and the ``nccl`` backend will be used + for collectives with CUDA tensors. A custom backend can be specified by passing in + a string with format ":,:", e.g. + "cpu:gloo,cuda:custom_backend". + + """ + + global _world + + global _backend + global _default_pg_init_method + + if GroupMember.WORLD is not None: + raise ValueError("trying to initialize the default process group twice!") + + set_pytorch_distributed_envs_from_justknobs() + + # Depending on the import order, some trace_rules functions may be evaluated + # during the import phase. In such a case, these functions may not correctly + # add the distributed related rules due to import circular dependency. + # We need to clear the lru_cache during the runtime to ensure the correctness + # of these trace_rules. + # + # Since this API must be called before all distributed code being compiled, + # clearing the cache here should be safe. + if "torch._dynamo" in sys.modules: + torch._dynamo.trace_rules.clear_lru_cache() + + assert (store is None) or ( + init_method is None + ), "Cannot specify both init_method and store." + + if store is not None: + assert world_size > 0, "world_size must be positive if using store" + assert rank >= 0, "rank must be non-negative if using store" + elif init_method is None: + init_method = "env://" + + if backend: + backend = Backend(backend) + else: + backend = Backend("undefined") + + if timeout is None: + timeout = _get_default_timeout(backend) + + _check_valid_timeout(timeout) + + """ + Group name is not visible to users unless they access + internals of c10d. This means we can ignore the value + they provide as it not exposed in a public way. + """ + group_name = _process_group_name([], use_hashed_name=False) + if backend == Backend.MPI: + if world_size != -1 or rank != -1: + warnings.warn( + f"For MPI backend, world_size ({world_size}) and rank ({rank}) " + "are ignored since they are assigned by the " + "MPI runtime." + ) + + default_pg, _ = _new_process_group_helper( + -1, -1, [], backend, None, group_name, timeout=timeout, group_desc="default_pg" + ) + _update_default_pg(default_pg) + else: + # backward compatible API + if store is None: + rendezvous_iterator = rendezvous( + not_none(init_method), rank, world_size, timeout=timeout + ) + store, rank, world_size = next(rendezvous_iterator) + store.set_timeout(timeout) + + # Use a PrefixStore to avoid accidental overrides of keys used by + # different systems (e.g. RPC) in case the store is multi-tenant. + store = PrefixStore("default_pg", store) + + default_pg, _ = _new_process_group_helper( + world_size, + rank, + [], + backend, + store, + group_name, + pg_options=pg_options, + timeout=timeout, + device_id=device_id, + group_desc="default_pg" + ) + _update_default_pg(default_pg) + + _world.pg_group_ranks[GroupMember.WORLD] = {i: i for i in range(GroupMember.WORLD.size())} # type: ignore[attr-defined, index] + _backend = _world.pg_map[not_none(GroupMember.WORLD)][0] + _default_pg_init_method = init_method + + old_hook = sys.excepthook + excepthook_prefix = f"[rank{get_rank()}]" + + def _distributed_excepthook(*args): + old_stderr = sys.stderr + sys.stderr = buf = io.StringIO() + try: + old_hook(*args) + finally: + sys.stderr = old_stderr + msg = buf.getvalue() + msg = "\n".join(f"{excepthook_prefix}: {s}" if s != "" else "" for s in msg.split("\n")) + sys.stderr.write(msg) + sys.stderr.flush() + + sys.excepthook = _distributed_excepthook + + if _is_barrier_after_init() == 1: + # barrier at the end to ensure that once we return from this method, all + # process groups including global variables (if any) are updated + # correctly on all ranks. + # Update 04/2023: for large-scale runs, this barrier (esp. store-based + # barrier) may be costly and/or unscalable. Also, in a lot of cases, + # these barriers may be unnecessary, as proven by a green CI after + # removal. An environment variable `TORCH_DIST_INIT_BARRIER` has been + # added which enables this barrier only when set to 1. + logger.debug( + "Performing barrier after ProcessGroup initialization since " + "TORCH_DIST_INIT_BARRIER = 1" + ) + if backend == Backend.MPI: + # MPI backend doesn't use store. + barrier() + else: + # Use store based barrier here since barrier() used a bunch of + # default devices and messes up NCCL internal state. + _store_based_barrier(rank, store, group_name, world_size, timeout) + +def _get_split_source(pg): + split_from = None + if pg.bound_device_id: + split_from = pg._get_backend(pg.bound_device_id) + elif pg is _world.default_pg: + try: + split_from = pg._get_backend(torch.device("cuda")) + except RuntimeError: + # no cuda device associated with this backend + pass + + if not split_from or not split_from.supports_splitting: + return None + + # If necessary, find a backend to split from by peeling process + # group wrappers from our potentially wrapped process group. + while _GLOO_AVAILABLE and isinstance(split_from, _ProcessGroupWrapper): + split_from = split_from.wrapped_pg + + return split_from + +def _shutdown_backend(pg): + """ + Try to shut down the backend of a process group. + Currently, only ProcessGroupNCCL backend is supported. + No op for other backends. + """ + backend = None + try: + backend = pg._get_backend(torch.device("cuda")) + except RuntimeError: + pass + if is_nccl_available() and isinstance(backend, (ProcessGroupNCCL, ProcessGroupCudaP2P)): + # explictly call shutdown to ensure that NCCL resources are released + backend._shutdown() + +def _new_process_group_helper( + group_size, + group_rank, + global_ranks_in_group, + backend, + store, + group_name, + pg_options=None, + timeout=None, + pg_tag=None, + device_id=None, + group_desc=None, +): + """ + Create a new distributed process group. + + This function must be called by ALL processes in the global group, even if + the calling process is not part of the newly created group. In that case, + this function returns GroupMember.NON_GROUP_MEMBER. + + This function is called with ``global_ranks_in_group == []`` for the default group. + """ + global _world + + if group_name in _world.pg_names.values(): + raise ValueError( + "The specified group name has already been " + "created, please use a different group name" + ) + + if device_id is not None and (device_id.index is None or device_id.type != 'cuda'): + raise ValueError("init_process_group device_id parameter must be a cuda device with an " + "id, e.g. cuda:0, not just cuda or cpu") + + # Note: _new_process_group_helper is only called from init_process_group, which always provides a timeout value + _check_valid_timeout(timeout) + + if pg_tag not in [None, ""]: + # creating with the same tag and rank set results in the same underlying PG + existing_group = _find_pg_by_ranks_and_tag(pg_tag, global_ranks_in_group) + if existing_group: + _, prefix_store = _world.pg_map[existing_group] + return existing_group, prefix_store + + group_desc = "undefined" if group_desc is None else group_desc + + # The list of group ranks is empty if we're creating the default group. + is_default_group = len(global_ranks_in_group) == 0 + + # nccl and potentially other backends allow creation of + # communicators based on pre-existing ones, which can save + # initialization time. Due to lazy initialization of + # communicators in some backends, we have to be careful and only + # split when we *know* the backends already are connected _on all + # ranks_. We can only know this if the group we are making is the + # entire world or if we have bound a device id to the world (which + # causes early connection initialization). + if (is_initialized() and + (len(global_ranks_in_group) == _get_default_group().size() or _get_default_group().bound_device_id)): + split_from = _get_split_source(_get_default_group()) + else: + split_from = None + + # If this is a subgroup (which means group_ranks is specified), + # we check if the current process is a member of the new group. + if not is_default_group: + global_rank = _get_default_group().rank() + if global_rank not in global_ranks_in_group: + # If we are using `ncclCommSplit` (or similar split from + # other APIs) to create the communicator, we will need to + # call `ncclCommSplit` on *all* ranks in this new group's + # parent group, even those not in the new group. This is + # a requirement of the NCCL API as otherwise we would get + # out of sync. + if split_from: + split_from.perform_nocolor_split(_get_default_group().bound_device_id) + return GroupMember.NON_GROUP_MEMBER, None + + prefix_store = PrefixStore(f"{group_name}/", store) + base_pg_options = ProcessGroup.Options(backend=str(backend)) + base_pg_options._timeout = timeout + pg: ProcessGroup = ProcessGroup(prefix_store, group_rank, group_size, base_pg_options) + if device_id: + pg.bound_device_id = device_id + backend_config = BackendConfig(backend) + backend_class: torch._C._distributed_c10d.Backend + for device, backend_str in backend_config.get_device_backend_map().items(): + # Use the group name as prefix in the default store, such that + # a single store can be reused by multiple groups. + backend_prefix_store = PrefixStore(f"{device}/", prefix_store) + + if backend_str == Backend.MPI: + if not is_mpi_available(): + raise RuntimeError( + "Distributed package doesn't have MPI built in." + " MPI is only included if you build PyTorch from" + " source on a host that has MPI installed." + ) + backend_class = ProcessGroupMPI.create(global_ranks_in_group) + backend_type = ProcessGroup.BackendType.MPI + if not backend_class: + return GroupMember.NON_GROUP_MEMBER, None + # create new process group with accurate rank and size + if pg.rank() == -1 and pg.size() == -1: + pg = ProcessGroup(backend_prefix_store, backend_class.rank(), backend_class.size(), base_pg_options) + elif backend_str == Backend.GLOO: + # TODO: remove this check after lazy initialization is supported + # if pg_options is not None: + # raise RuntimeError("GLOO options not supported") + backend_class = ProcessGroupGloo(backend_prefix_store, group_rank, group_size, timeout=timeout) + backend_type = ProcessGroup.BackendType.GLOO + elif backend_str == Backend.NCCL: + if not is_nccl_available(): + raise RuntimeError("Distributed package doesn't have NCCL built in") + if pg_options is not None: + assert isinstance( + pg_options, ProcessGroupNCCL.Options + ), "Expected pg_options argument to be of type ProcessGroupNCCL.Options" + if pg_options._timeout != timeout: + warnings.warn( + "pg_options._timeout was specified, " + "but timeout kwarg has a default value that will always override it. " + ) + else: + # default pg_options for NCCL + pg_options = ProcessGroupNCCL.Options() + pg_options.is_high_priority_stream = False + pg_options._timeout = timeout + + if split_from: + pg_options.split_from = split_from + pg_options.split_color = _process_group_color(global_ranks_in_group) + pg_options.global_ranks_in_group = global_ranks_in_group + pg_options.group_name = group_name + backend_class = ProcessGroupNCCL( + backend_prefix_store, group_rank, group_size, pg_options) + backend_type = ProcessGroup.BackendType.NCCL + elif backend_str == Backend.UCC and is_ucc_available(): + # TODO: once UCC plugin is fully deprecated, remove + # is_ucc_available() from above elif-condition and raise + # RuntimeError if is_ucc_available() returns false. + + backend_class = ProcessGroupUCC(backend_prefix_store, group_rank, group_size, timeout=timeout) + backend_type = ProcessGroup.BackendType.UCC + else: + assert backend_str.upper() in Backend._plugins, ( + f"Unknown c10d backend type {backend_str.upper()}" + ) + + backend_plugin = Backend._plugins[backend_str.upper()] + creator_fn = backend_plugin.creator_fn + extended_api = backend_plugin.extended_api + backend_type = ProcessGroup.BackendType.CUSTOM + + if not extended_api: + backend_class = creator_fn(backend_prefix_store, group_rank, group_size, timeout) + else: + dist_backend_opts = _DistributedBackendOptions() + dist_backend_opts.store = backend_prefix_store + dist_backend_opts.group_rank = group_rank + dist_backend_opts.group_size = group_size + dist_backend_opts.timeout = timeout + dist_backend_opts.group_id = group_name + dist_backend_opts.global_ranks_in_group = global_ranks_in_group + + backend_class = creator_fn(dist_backend_opts, pg_options) + + # Set sequence numbers for gloo and nccl backends. + if backend_str == Backend.GLOO: + assert isinstance(backend_class, ProcessGroupGloo) + backend_class._set_sequence_number_for_group() + elif backend_str == Backend.NCCL: + assert isinstance(backend_class, ProcessGroupNCCL) + backend_class._set_sequence_number_for_group() + + # If the type is a subclass of ProcessGroup then return this process group immediately + # TODO: This defaults to the old behavior for PythonProcessGroups which overwrites the + # ProcessGroup instance + if issubclass(type(backend_class), ProcessGroup): + pg = backend_class # type: ignore[assignment] + break + + # Process group wrapper initialization for supported PGs when TORCH_DISTRIBUTED_DEBUG is set + if backend_str in [Backend.GLOO, Backend.NCCL, Backend.UCC] or backend_str.upper() in Backend._plugins: + # In debug mode and if GLOO is available, wrap in a wrapper PG that + # enables enhanced collective checking for debuggability. + if get_debug_level() == DebugLevel.DETAIL: + if not _GLOO_AVAILABLE: + logger.info( + """TORCH_DISTRIBUTED_DEBUG was set to DETAIL, but + GLOO is not available. Build with Gloo to + create a wrapper process group in debug mode + to aid collective desynchronization debugging.""" + ) + else: + backend_class = _create_process_group_wrapper( + wrapped_pg=backend_class, + store_prefix=group_name, + store=backend_prefix_store, + rank=group_rank, + world_size=group_size, + timeout=timeout, + ) + + # register only a single backend when all get_device_backend_map values are the same + if len(set(backend_config.get_device_backend_map().values())) == 1: + for device in backend_config.get_device_backend_map().keys(): + pg._register_backend(torch.device(device), backend_type, backend_class) + + # break out of outer loop to not create any more backends + break + + pg._register_backend(torch.device(device), backend_type, backend_class) + + # set group_name and group_dsec to backend + assert group_name is not None + assert group_desc is not None + pg._set_group_name(group_name) + pg._set_group_desc(group_desc) + + if device_id and pg._get_backend(device_id).supports_splitting: + eager_backend = pg._get_backend(device_id) + eager_backend.eager_connect_single_device(device_id) + + # update global state + _world.pg_map[pg] = (backend, prefix_store) + _world.pg_names[pg] = group_name + _register_process_group(group_name, pg) + + _world.pg_backend_config[pg] = str(backend_config) + # "" is the default tag for user PGs + if pg_tag in [None, ""]: + pg_tag = f"ptd:{group_name}" + _world.tags_to_pg.setdefault("", []).append(pg) + else: + pg_tag = f"user:{pg_tag}" + + _world.tags_to_pg.setdefault(pg_tag, []).append(pg) + _world.pg_to_tag[pg] = pg_tag + return pg, prefix_store + +def destroy_process_group(group: Optional[ProcessGroup] = None): + """ + Destroy a given process group, and deinitialize the distributed package. + + Args: + group (ProcessGroup, optional): The process group to be destroyed, if + group.WORLD is given, all process + groups including the default one will + be destroyed. + """ + global _world + + if group == GroupMember.NON_GROUP_MEMBER: + return + + if group is None: + pg = GroupMember.WORLD + else: + pg = group + + assert pg is not None + if _world.pg_map.get(pg, None) is None: + raise ValueError("Invalid process group specified") + + # When users register Python onCompletion hooks, those hooks will run on a + # different thread than the main thread. Today, the ProcessGroup dtor does + # wait for that thread. However, the dtor might finish after the Python + # Interpreter exits. After that grabbing the GIL for the Python hook will crash. + # We can either revive the interpreter when running hooks or keep the main one + # alive until all works and hooks are done. The current implementation does the + # latter. Therefore, we explicitly call _wait_for_pending_works() here to wait + # for the pending hooks to finish. + if pg.name().lower() == "nccl" and pg._has_hooks(): + pg._wait_for_pending_works() + + if group is None or group == GroupMember.WORLD: + # shutdown all backends in the order of pg names. shutting down in order because + # ncclCommAbort() was a 'collective' call in some versions of NCCL. + for pg_to_shutdown in sorted(_world.pg_names, key=lambda x: _world.pg_names[x], reverse=True): + _shutdown_backend(pg_to_shutdown) + + _update_default_pg(None) + _world.pg_map.clear() + _world.pg_names.clear() + _world.pg_group_ranks.clear() + _world.pg_backend_config.clear() + _world.pg_to_tag.clear() + _world.tags_to_pg.clear() + _world.pg_coalesce_state.clear() + _world.pg_default_device.clear() + _unregister_all_process_groups() + + # when process group doesn't have an explicit name (only WORLD (default) + # process group can have an explicit name), we use global _world.group_count + # to generate the name. We need to reset the counter on destruction to + # allow consistent value to be generated when we re-create process + # groups after some trainers recover from failure + # + # We only reset this when WORLD is being destroyed because if this + # process group is in good state, we aren't dealing with failures. + _world.group_count = 0 + else: + _shutdown_backend(pg) + del _world.pg_map[pg] + del _world.pg_names[pg] + del _world.pg_group_ranks[pg] + del _world.pg_backend_config[pg] + if pg in _world.pg_default_device: + del _world.pg_default_device[pg] + if pg in _world.pg_coalesce_state.keys(): + warnings.warn( + "Some coalesced collectives haven't been launched when " + "ProcessGroup is destroyed. They will be cleaned." + ) + del _world.pg_coalesce_state[pg] + + tag = _world.pg_to_tag.get(pg) + del _world.pg_to_tag[pg] + if tag is not None: + try: + _world.tags_to_pg[tag].remove(pg) + if tag.startswith("ptd:"): + _world.tags_to_pg[""].remove(pg) + except Exception: + pass + _unregister_process_group(pg.group_name) + + +def get_rank(group: Optional[ProcessGroup] = None) -> int: + """ + Return the rank of the current process in the provided ``group``, default otherwise. + + Rank is a unique identifier assigned to each process within a distributed + process group. They are always consecutive integers ranging from 0 to + ``world_size``. + + Args: + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + + Returns: + The rank of the process group + -1, if not part of the group + + """ + if _rank_not_in_group(group): + return -1 + + default_pg = _get_default_group() + if group is None or group is GroupMember.WORLD: + return default_pg.rank() + + return get_group_rank(group, default_pg.rank()) + + +def get_world_size(group: Optional[ProcessGroup] = None) -> int: + """ + Return the number of processes in the current process group. + + Args: + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + + Returns: + The world size of the process group + -1, if not part of the group + + """ + if _rank_not_in_group(group): + return -1 + + return _get_group_size(group) + + +def isend(tensor: torch.Tensor, dst: int, group: Optional[ProcessGroup] = None, tag: int = 0) -> Optional[Work]: + """ + Send a tensor asynchronously. + + .. warning:: + Modifying ``tensor`` before the request completes causes undefined + behavior. + + .. warning:: + ``tag`` is not supported with the NCCL backend. + + Args: + tensor (Tensor): Tensor to send. + dst (int): Destination rank on global process group (regardless of ``group`` argument) + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + tag (int, optional): Tag to match send with remote recv + + Returns: + A distributed request object. + None, if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("isend") + return None + + if tensor.is_complex(): + tensor = torch.view_as_real(tensor) + + if group is None or group is GroupMember.WORLD: + pg = _get_default_group() + else: + pg = group + dst = get_group_rank(pg, dst) + + return pg.send([tensor], dst, tag) + +def irecv(tensor: torch.Tensor, src: Optional[int] = None, group: Optional[ProcessGroup] = None, tag: int = 0) -> Optional[Work]: + """ + Receives a tensor asynchronously. + + .. warning:: + ``tag`` is not supported with the NCCL backend. + + Args: + tensor (Tensor): Tensor to fill with received data. + src (int, optional): Source rank on global process group (regardless of ``group`` argument). + Will receive from any process if unspecified. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + tag (int, optional): Tag to match recv with remote send + + Returns: + A distributed request object. + None, if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("irecv") + return None + + if tensor.is_complex(): + tensor = torch.view_as_real(tensor) + + if group is None or group is GroupMember.WORLD: + pg = _get_default_group() + else: + pg = group + + if src is None: + return pg.recv_anysource([tensor], tag) + else: + if pg is GroupMember.WORLD: + return pg.recv([tensor], src, tag) + else: + group_src_rank = get_group_rank(pg, src) + return pg.recv([tensor], group_src_rank, tag) + +@_exception_logger +def send(tensor: torch.Tensor, dst: int, group: Optional[ProcessGroup] = None, tag: int = 0) -> None: + """ + Send a tensor synchronously. + + .. warning:: + ``tag`` is not supported with the NCCL backend. + + Args: + tensor (Tensor): Tensor to send. + dst (int): Destination rank on global process group (regardless of ``group`` argument). + Destination rank should not be the same as the rank of the current process. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + tag (int, optional): Tag to match send with remote recv + + """ + if get_rank() == dst: + raise ValueError( + "Invalid destination rank: destination rank should not be the same as " + "the rank of the current process." + ) + + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("send") + return None + + if tensor.is_complex(): + tensor = torch.view_as_real(tensor) + + if group is None or group is GroupMember.WORLD: + default_pg = _get_default_group() + default_pg.send([tensor], dst, tag).wait() + else: + group_dst_rank = get_group_rank(group, dst) + group.send([tensor], group_dst_rank, tag).wait() + +@_exception_logger +def recv(tensor: torch.Tensor, src: Optional[int] = None, group: Optional[ProcessGroup] = None, tag: int = 0) -> int: + """ + Receives a tensor synchronously. + + .. warning:: + ``tag`` is not supported with the NCCL backend. + + Args: + tensor (Tensor): Tensor to fill with received data. + src (int, optional): Source rank on global process group (regardless of ``group`` argument). + Will receive from any process if unspecified. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + tag (int, optional): Tag to match recv with remote send + + Returns: + Sender rank + -1, if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("recv") + return -1 + + if tensor.is_complex(): + tensor = torch.view_as_real(tensor) + + if group is None: + pg = _get_default_group() + else: + pg = group + + if src is None: + work = pg.recv_anysource([tensor], tag) + work.wait() + src_rank = work._source_rank() + if group is None or group is GroupMember.WORLD: + return src_rank + else: + return get_global_rank(pg, src_rank) + else: + if group is None or group is GroupMember.WORLD: + pg.recv([tensor], src, tag).wait() + else: + group_src_rank = get_group_rank(pg, src) + pg.recv([tensor], group_src_rank, tag).wait() + return src + + +class _IllegalWork(Work): + def __getattribute__(self, name): + if name in ["is_success", "exception", "wait", "source_rank", "_source_rank", "result", "synchronize"]: + raise ValueError(f"Illegal to call {name} on IllegalWork object") + + +class _CoalescingManager: + def __init__(self): + self.works: List[Work] = [] + + def append(self, work: Work): + if work: + self.works.append(work) + + def wait(self): + for work in self.works: + work.wait() + + +@contextlib.contextmanager +def _coalescing_manager( + group: Optional[ProcessGroup] = None, + device: Optional[torch.device] = None, + async_ops: Optional[bool] = False, +): + """ + Context manager used to coalesce collectives or P2P operations when possible. + + Args: + group (`ProcessGroup`, optional): The process group to work on. If None, + the default process group will be used. + device (`torch.device`, optional): Default is None, set to a device if + there isn't a `**_coalesced` implementation by the backend. + async_ops (`bool`, optional): whether the coalesced ops are async ops. + + Examples: + >>> # xdoctest: +SKIP("no rank") + >>> # Synchronous ops + >>> with _coalescing_manager(): + >>> for i in range(num_colls): + >>> dist.all_reduce(tensors[i]) + >>> # Asynchronous ops + >>> with _coalescing_manager(async_ops=True) as cm: + >>> for i in range(num_colls): + >>> dist.all_reduce(tensors[i]) + >>> cm.wait() + + .. warning:: + :func:`_coalescing_manager` currently do not support coalescing + all-reduces with different reduce operators, e.g. `ReduceOp.SUM` mixed + with `ReduceOp.PRODUCT`. + """ + group = group or _get_default_group() + op_list = _world.pg_coalesce_state.setdefault(group, []) + if op_list: + raise ValueError("ProcessGroup has non-empty op list at the start of coalescing") + if device: + group._start_coalescing(device) + cm = _CoalescingManager() + yield cm + op_list = _world.pg_coalesce_state.pop(group) + if op_list: + # Collectives supporting "Fast Path" coalescing are captured. + # See implementation in corresponding collective APIs. + # Currently supported: + # - coalesced `all_reduce` + # - coalesced `all_gather_into_tensor` + # - coalesced `reduce_scatter_tensor` + op0 = op_list[0].op + if op0 == all_reduce: + tensors = [] + for op in op_list: + tensors.append(op.tensor) + all_reduce_opts = AllreduceCoalescedOptions() + all_reduce_opts.reduceOp = not_none(op_list[0].redop) + work = group.allreduce_coalesced(tensors, all_reduce_opts) + elif op0 == all_gather_into_tensor: + inputs = [] + outputs = [] + for op in op_list: + inputs.append(op.tensor) + outputs.append(not_none(op.dst_tensor)) + work = group.allgather_into_tensor_coalesced(outputs, inputs) + elif op0 == reduce_scatter_tensor: + inputs = [] + outputs = [] + for op in op_list: + inputs.append(op.tensor) + outputs.append(not_none(op.dst_tensor)) + reduce_opts = ReduceScatterOptions() + reduce_opts.reduceOp = not_none(op_list[0].redop) + work = group.reduce_scatter_tensor_coalesced(outputs, inputs, reduce_opts) + else: + raise AssertionError( + f"Coalescing manager does not support fast-path coalescing of {op0}, " + f"yet {op0} is still recorded in op list. This is an internal error of c10d." + ) + + if device: + # Old style of letting each coll inside the context manager to call into C++ counterpart via python binding + work = group._end_coalescing(device) + + if async_ops: + cm.append(work) # type: ignore[possibly-undefined] + else: + work.wait() # type: ignore[possibly-undefined] + + +def batch_isend_irecv(p2p_op_list): + """ + Send or Receive a batch of tensors asynchronously and return a list of requests. + + Process each of the operations in ``p2p_op_list`` and return the corresponding + requests. NCCL, Gloo, and UCC backend are currently supported. + + Args: + p2p_op_list: A list of point-to-point operations(type of each operator is + ``torch.distributed.P2POp``). The order of the isend/irecv in the list + matters and it needs to match with corresponding isend/irecv on the + remote end. + + Returns: + A list of distributed request objects returned by calling the corresponding + op in the op_list. + + Examples: + >>> # xdoctest: +SKIP("no rank") + >>> send_tensor = torch.arange(2, dtype=torch.float32) + 2 * rank + >>> recv_tensor = torch.randn(2, dtype=torch.float32) + >>> send_op = dist.P2POp(dist.isend, send_tensor, (rank + 1)%world_size) + >>> recv_op = dist.P2POp(dist.irecv, recv_tensor, (rank - 1 + world_size)%world_size) + >>> reqs = batch_isend_irecv([send_op, recv_op]) + >>> for req in reqs: + >>> req.wait() + >>> recv_tensor + tensor([2, 3]) # Rank 0 + tensor([0, 1]) # Rank 1 + + .. note:: Note that when this API is used with the NCCL PG backend, users must set + the current GPU device with `torch.cuda.set_device`, otherwise it will + lead to unexpected hang issues. + + In addition, if this API is the first collective call in the ``group`` + passed to ``dist.P2POp``, all ranks of the ``group`` must participate in + this API call; otherwise, the behavior is undefined. If this API call is + not the first collective call in the ``group``, batched P2P operations + involving only a subset of ranks of the ``group`` are allowed. + """ + _check_p2p_op_list(p2p_op_list) + group = p2p_op_list[0].group + device = p2p_op_list[0].tensor.device + if device.type == "cuda": + # NCCL style coalescing + with _coalescing_manager(group, device, async_ops=True) as cm: + for p2p_op in p2p_op_list: + p2p_op.op(p2p_op.tensor, p2p_op.peer, p2p_op.group, p2p_op.tag) + return cm.works + else: + # Backward support for Gloo + reqs = [] + for p2p_op in p2p_op_list: + work = p2p_op.op(p2p_op.tensor, p2p_op.peer, p2p_op.group, p2p_op.tag) + if work: + reqs.append(work) + return reqs + + +@_exception_logger +def broadcast(tensor, src, group=None, async_op=False): + """ + Broadcasts the tensor to the whole group. + + ``tensor`` must have the same number of elements in all processes + participating in the collective. + + Args: + tensor (Tensor): Data to be sent if ``src`` is the rank of current + process, and tensor to be used to save received data otherwise. + src (int): Source rank on global process group (regardless of ``group`` argument). + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("broadcast") + return + + opts = BroadcastOptions() + opts.rootRank = src + opts.rootTensor = 0 + opts.asyncOp = async_op + + if group is None or group is GroupMember.WORLD: + default_pg = _get_default_group() + work = default_pg.broadcast([tensor], opts) + else: + group_src_rank = get_group_rank(group, src) + opts.rootRank = group_src_rank + work = group.broadcast([tensor], opts) + if async_op: + return work + else: + work.wait() + +@_exception_logger +def all_reduce(tensor, op=ReduceOp.SUM, group=None, async_op=False): + """ + Reduces the tensor data across all machines in a way that all get the final result. + + After the call ``tensor`` is going to be bitwise identical in all processes. + + Complex tensors are supported. + + Args: + tensor (Tensor): Input and output of the collective. The function + operates in-place. + op (optional): One of the values from + ``torch.distributed.ReduceOp`` + enum. Specifies an operation used for element-wise reductions. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + Examples: + >>> # xdoctest: +SKIP("no rank") + >>> # All tensors below are of torch.int64 type. + >>> # We have 2 process groups, 2 ranks. + >>> device = torch.device(f'cuda:{rank}') + >>> tensor = torch.arange(2, dtype=torch.int64, device=device) + 1 + 2 * rank + >>> tensor + tensor([1, 2], device='cuda:0') # Rank 0 + tensor([3, 4], device='cuda:1') # Rank 1 + >>> dist.all_reduce(tensor, op=ReduceOp.SUM) + >>> tensor + tensor([4, 6], device='cuda:0') # Rank 0 + tensor([4, 6], device='cuda:1') # Rank 1 + + >>> # All tensors below are of torch.cfloat type. + >>> # We have 2 process groups, 2 ranks. + >>> tensor = torch.tensor([1+1j, 2+2j], dtype=torch.cfloat, device=device) + 2 * rank * (1+1j) + >>> tensor + tensor([1.+1.j, 2.+2.j], device='cuda:0') # Rank 0 + tensor([3.+3.j, 4.+4.j], device='cuda:1') # Rank 1 + >>> dist.all_reduce(tensor, op=ReduceOp.SUM) + >>> tensor + tensor([4.+4.j, 6.+6.j], device='cuda:0') # Rank 0 + tensor([4.+4.j, 6.+6.j], device='cuda:1') # Rank 1 + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("all_reduce") + return + + if tensor.is_complex(): + if not supports_complex(op): + raise ValueError(f"all_reduce does not support {op} on complex tensors") + tensor = torch.view_as_real(tensor) + + opts = AllreduceOptions() + opts.reduceOp = op + if group is None: + group = _get_default_group() + + if group in _world.pg_coalesce_state.keys(): + # We are in coalescing context, do not issue single operation, just append a collective representation + coll = _CollOp(all_reduce, tensor, None, op, None) + _world.pg_coalesce_state[group].append(coll) + if async_op: + return _IllegalWork() + else: + return None + + work = group.allreduce([tensor], opts) + + if async_op: + return work + else: + work.wait() + +@_exception_logger +@deprecated( + "`torch.distributed.all_reduce_coalesced` will be deprecated. If you must " + "use it, please revisit our documentation later at " + "https://pytorch.org/docs/main/distributed.html#collective-functions", + category=FutureWarning, +) +def all_reduce_coalesced(tensors, op=ReduceOp.SUM, group=None, async_op=False): + """ + WARNING: at this time individual shape checking is not implemented across nodes. + + For example, if the rank 0 node passes [torch.rand(4), torch.rand(2)] and the + rank 1 node passes [torch.rand(2), torch.rand(2), torch.rand(2)], the allreduce + operation will proceed without complaint and return erroneous outputs. This lack + of shape checking results in significant performance improvements but users of this + function should take extra care to ensure that each node passes in tensors whose + shapes match across nodes. + + Reduces each tensor in tensors (residing on the same device) across all machines + in such a way that all get the final result. + + After the call each tensor in tensors is going to bitwise identical + in all processes. + + Complex tensors are supported. + + Args: + tensors (Union[List[Tensor], Tensor]): Input and output of the collective. + The function operates in-place. + op (Optional[ReduceOp]): One of the values from + ``torch.distributed.ReduceOp`` enum. Specifies an operation used for + element-wise reductions. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (Optional[bool]): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + """ + if isinstance(tensors, torch.Tensor): + tensors = [tensors] + _check_tensor_list(tensors, "tensor") + _ensure_all_tensors_same_dtype(tensors) + if _rank_not_in_group(group): + _warn_not_in_group("all_reduce_coalesced") + return + + if any(t.is_complex() for t in tensors) and not supports_complex(op): + raise ValueError(f"all_reduce does not support {op} on complex tensors") + + tensors = [t if not t.is_complex() else torch.view_as_real(t) for t in tensors] + + opts = AllreduceCoalescedOptions() + opts.reduceOp = op + if group is None: + default_pg = _get_default_group() + work = default_pg.allreduce_coalesced(tensors, opts) + else: + work = group.allreduce_coalesced(tensors, opts) + + if async_op: + return work.get_future() + else: + work.wait() + +@_exception_logger +def reduce(tensor, dst, op=ReduceOp.SUM, group=None, async_op=False): + """ + Reduces the tensor data across all machines. + + Only the process with rank ``dst`` is going to receive the final result. + + Args: + tensor (Tensor): Input and output of the collective. The function + operates in-place. + dst (int): Destination rank on global process group (regardless of ``group`` argument) + op (optional): One of the values from + ``torch.distributed.ReduceOp`` + enum. Specifies an operation used for element-wise reductions. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + if _rank_not_in_group(group): + _warn_not_in_group("reduce") + return + + opts = ReduceOptions() + opts.reduceOp = op + opts.rootRank = dst + + if group is None or group is GroupMember.WORLD: + default_pg = _get_default_group() + work = default_pg.reduce([tensor], opts) + else: + group_dst_rank = get_group_rank(group, dst) + opts.rootRank = group_dst_rank + work = group.reduce([tensor], opts) + + if async_op: + return work + else: + work.wait() + +def _object_to_tensor(obj, device, group): + f = io.BytesIO() + _pickler(f).dump(obj) + byte_storage = torch.ByteStorage._from_buffer(f.getvalue()) # type: ignore[attr-defined] + # Do not replace `torch.ByteTensor` or `torch.LongTensor` with torch.tensor and specifying dtype. + # Otherwise, it will casue 100X slowdown. + # See: https://github.com/pytorch/pytorch/issues/65696 + byte_tensor = torch.ByteTensor(byte_storage).to(device) + if get_debug_level() == DebugLevel.DETAIL and is_nccl_available(): + backend = get_backend(group) + if backend == Backend.NCCL: + hash = torch._C._distributed_c10d._hash_tensors([byte_tensor]) + logger.warning("_object_to_tensor size: %s hash value: %s", byte_tensor.numel(), hash) + local_size = torch.LongTensor([byte_tensor.numel()]).to(device) + return byte_tensor, local_size + + +def _tensor_to_object(tensor, tensor_size, group): + if get_debug_level() == DebugLevel.DETAIL and is_nccl_available(): + backend = get_backend(group) + if backend == Backend.NCCL: + hash = torch._C._distributed_c10d._hash_tensors([tensor]) + logger.warning("_tensor_to_object size: %s hash value: %s", tensor.numel(), hash) + tensor = tensor.cpu() + buf = tensor.numpy().tobytes()[:tensor_size] + return _unpickler(io.BytesIO(buf)).load() + + +@_exception_logger +def all_gather_object(object_list, obj, group=None): + """ + Gathers picklable objects from the whole group into a list. + + Similar to :func:`all_gather`, but Python objects can be passed in. + Note that the object must be picklable in order to be gathered. + + Args: + object_list (list[Any]): Output list. It should be correctly sized as the + size of the group for this collective and will contain the output. + obj (Any): Pickable Python object to be broadcast from current process. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + + Returns: + None. If the calling rank is part of this group, the output of the + collective will be populated into the input ``object_list``. If the + calling rank is not part of the group, the passed in ``object_list`` will + be unmodified. + + .. note:: Note that this API differs slightly from the :func:`all_gather` + collective since it does not provide an ``async_op`` handle and thus + will be a blocking call. + + .. note:: For NCCL-based processed groups, internal tensor representations + of objects must be moved to the GPU device before communication takes + place. In this case, the device used is given by + ``torch.cuda.current_device()`` and it is the user's responsiblity to + ensure that this is set so that each rank has an individual GPU, via + ``torch.cuda.set_device()``. + + .. warning:: + :func:`all_gather_object` uses ``pickle`` module implicitly, which is + known to be insecure. It is possible to construct malicious pickle data + which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`all_gather_object` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`all_gather` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> # Assumes world_size of 3. + >>> gather_objects = ["foo", 12, {1: 2}] # any picklable object + >>> output = [None for _ in gather_objects] + >>> dist.all_gather_object(output, gather_objects[dist.get_rank()]) + >>> output + ['foo', 12, {1: 2}] + """ + if _rank_not_in_group(group): + _warn_not_in_group("all_gather_object") + return + + current_device = _get_pg_default_device(group) + input_tensor, local_size = _object_to_tensor(obj, current_device, group) + + # Gather all local sizes. This is so that we can find the max size, and index + # until the correct size when deserializing the tensors. + group_size = get_world_size(group=group) + object_sizes_tensor = torch.zeros( + group_size, dtype=torch.long, device=current_device + ) + object_size_list = [ + object_sizes_tensor[i].unsqueeze(dim=0) for i in range(group_size) + ] + # Allgather tensor sizes + all_gather(object_size_list, local_size, group=group) + max_object_size = int(max(object_size_list).item()) # type: ignore[type-var] + # Resize tensor to max size across all ranks. + input_tensor.resize_(max_object_size) + coalesced_output_tensor = torch.empty( + max_object_size * group_size, dtype=torch.uint8, device=current_device + ) + # Output tensors are nonoverlapping views of coalesced_output_tensor + output_tensors = [ + coalesced_output_tensor[max_object_size * i : max_object_size * (i + 1)] + for i in range(group_size) + ] + all_gather(output_tensors, input_tensor, group=group) + # Deserialize outputs back to object. + for i, tensor in enumerate(output_tensors): + tensor = tensor.type(torch.uint8) + tensor_size = object_size_list[i] + object_list[i] = _tensor_to_object(tensor, tensor_size, group) + + +@_exception_logger +def gather_object(obj, object_gather_list=None, dst=0, group=None): + """ + Gathers picklable objects from the whole group in a single process. + + Similar to :func:`gather`, but Python objects can be passed in. Note that the + object must be picklable in order to be gathered. + + Args: + obj (Any): Input object. Must be picklable. + object_gather_list (list[Any]): Output list. On the ``dst`` rank, it + should be correctly sized as the size of the group for this + collective and will contain the output. Must be ``None`` on non-dst + ranks. (default is ``None``) + dst (int, optional): Destination rank on global process group (regardless of ``group`` argument). (default is 0) + group: (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + + Returns: + None. On the ``dst`` rank, ``object_gather_list`` will contain the + output of the collective. + + .. note:: Note that this API differs slightly from the gather collective + since it does not provide an async_op handle and thus will be a blocking + call. + + .. note:: For NCCL-based processed groups, internal tensor representations + of objects must be moved to the GPU device before communication takes + place. In this case, the device used is given by + ``torch.cuda.current_device()`` and it is the user's responsiblity to + ensure that this is set so that each rank has an individual GPU, via + ``torch.cuda.set_device()``. + + .. warning:: + :func:`gather_object` uses ``pickle`` module implicitly, which is + known to be insecure. It is possible to construct malicious pickle data + which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`gather_object` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`gather` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> # Assumes world_size of 3. + >>> gather_objects = ["foo", 12, {1: 2}] # any picklable object + >>> output = [None for _ in gather_objects] + >>> dist.gather_object( + ... gather_objects[dist.get_rank()], + ... output if dist.get_rank() == 0 else None, + ... dst=0 + ... ) + >>> # On rank 0 + >>> output + ['foo', 12, {1: 2}] + """ + if _rank_not_in_group(group): + _warn_not_in_group("gather_object") + return + + # Ensure object_gather_list is specified appropriately. + my_rank = get_rank() + _validate_output_list_for_rank(my_rank, dst, object_gather_list) + current_device = _get_pg_default_device(group) + input_tensor, local_size = _object_to_tensor(obj, current_device, group) + + # Gather all local sizes. This is so that we can find the max size, and index + # until the correct size when deserializing the tensors. + group_size = get_world_size(group=group) + object_sizes_tensor = torch.zeros( + group_size, dtype=torch.long, device=current_device + ) + object_size_list = [ + object_sizes_tensor[i].unsqueeze(dim=0) for i in range(group_size) + ] + # Allgather tensor sizes. An all-gather is needed here despite this being a + # gather, since each rank needs to broadcast a tensor of the same (maximal) + # size. + all_gather(object_size_list, local_size, group=group) + max_object_size = int(max(object_size_list).item()) # type: ignore[type-var] + # Resize tensor to max size across all ranks. + input_tensor.resize_(max_object_size) + # Avoid populating output tensors if the result won't be gathered on this rank. + if my_rank == dst: + coalesced_output_tensor = torch.empty( + max_object_size * group_size, dtype=torch.uint8, device=current_device + ) + # Output tensors are nonoverlapping views of coalesced_output_tensor + output_tensors = [ + coalesced_output_tensor[max_object_size * i : max_object_size * (i + 1)] + for i in range(group_size) + ] + # All ranks call gather with equal-sized tensors. + gather( + input_tensor, + gather_list=output_tensors if my_rank == dst else None, # type: ignore[possibly-undefined] + dst=dst, + group=group, + ) + if my_rank != dst: + return + for i, tensor in enumerate(output_tensors): + tensor = tensor.type(torch.uint8) + tensor_size = object_size_list[i] + object_gather_list[i] = _tensor_to_object(tensor, tensor_size, group) + + +@_exception_logger +def send_object_list(object_list, dst, group=None, device=None): + """ + Sends picklable objects in ``object_list`` synchronously. + + Similar to :func:`send`, but Python objects can be passed in. + Note that all objects in ``object_list`` must be picklable in order to be + sent. + + Args: + object_list (List[Any]): List of input objects to sent. + Each object must be picklable. Receiver must provide lists of equal sizes. + dst (int): Destination rank to send ``object_list`` to. + Destination rank is based on global process group (regardless of ``group`` argument) + group: (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + device (``torch.device``, optional): If not None, the objects are + serialized and converted to tensors which are moved to the + ``device`` before sending. Default is ``None``. + + Returns: + ``None``. + + .. note:: For NCCL-based process groups, internal tensor representations + of objects must be moved to the GPU device before communication takes + place. In this case, the device used is given by + ``torch.cuda.current_device()`` and it is the user's responsibility to + ensure that this is set so that each rank has an individual GPU, via + ``torch.cuda.set_device()``. + + .. warning:: + :func:`send_object_list` uses ``pickle`` module implicitly, which + is known to be insecure. It is possible to construct malicious pickle + data which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`send_object_list` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`send` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> # Assumes backend is not NCCL + >>> device = torch.device("cpu") + >>> if dist.get_rank() == 0: + >>> # Assumes world_size of 2. + >>> objects = ["foo", 12, {1: 2}] # any picklable object + >>> dist.send_object_list(objects, dst=1, device=device) + >>> else: + >>> objects = [None, None, None] + >>> dist.recv_object_list(objects, src=0, device=device) + >>> objects + ['foo', 12, {1: 2}] + """ + if get_rank() == dst: + raise ValueError( + "Invalid destination rank: destination rank should not be the same as " + "the rank of the current process." + ) + + if _rank_not_in_group(group): + _warn_not_in_group("send_object_list") + return + + # Current device selection. + # To preserve backwards compatibility, ``device`` is default to ``None`` + # in which case we run current logic of device selection, i.e. + # ``current_device`` is CUDA if backend is NCCL otherwise CPU device. In the + # case it is not ``None`` we move the size and object tensors to be + # sent to this device. + current_device = device or _get_pg_default_device(group) + # Serialize object_list elements to tensors on src rank. + tensor_list, size_list = zip(*[_object_to_tensor(obj, current_device, group) for obj in object_list]) + object_sizes_tensor = torch.cat(size_list) + + # Send object sizes + send(object_sizes_tensor, dst=dst, group=group) + + # Concatenate and send serialized object tensors + # Note: torch.cat will do an extra memory copy to the current device, if the tensor_list + # has only one element, we can skip the copy. + if len(tensor_list) == 1: # type: ignore[possibly-undefined] + object_tensor = tensor_list[0] + else: + object_tensor = torch.cat(tensor_list) + + send(object_tensor, dst=dst, group=group) + + +@_exception_logger +def recv_object_list(object_list, src=None, group=None, device=None): + """ + Receives picklable objects in ``object_list`` synchronously. + + Similar to :func:`recv`, but can receive Python objects. + + Args: + object_list (List[Any]): List of objects to receive into. + Must provide a list of sizes equal to the size of the list being sent. + src (int, optional): Source rank from which to recv ``object_list``. + Source rank is based on global process group (regardless of ``group`` argument) + Will receive from any rank if set to None. Default is ``None``. + group: (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + device (``torch.device``, optional): If not None, receives on this device. + Default is ``None``. + + Returns: + Sender rank. -1 if rank is not part of the group. If rank is part of the group, + ``object_list`` will contain the sent objects from ``src`` rank. + + .. note:: For NCCL-based process groups, internal tensor representations + of objects must be moved to the GPU device before communication takes + place. In this case, the device used is given by + ``torch.cuda.current_device()`` and it is the user's responsibility to + ensure that this is set so that each rank has an individual GPU, via + ``torch.cuda.set_device()``. + + .. warning:: + :func:`recv_object_list` uses ``pickle`` module implicitly, which + is known to be insecure. It is possible to construct malicious pickle + data which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`recv_object_list` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`recv` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> # Assumes backend is not NCCL + >>> device = torch.device("cpu") + >>> if dist.get_rank() == 0: + >>> # Assumes world_size of 2. + >>> objects = ["foo", 12, {1: 2}] # any picklable object + >>> dist.send_object_list(objects, dst=1, device=device) + >>> else: + >>> objects = [None, None, None] + >>> dist.recv_object_list(objects, src=0, device=device) + >>> objects + ['foo', 12, {1: 2}] + """ + if _rank_not_in_group(group): + _warn_not_in_group("recv_object_list") + return -1 + + # Current device selection. + # To preserve backwards compatibility, ``device`` is default to ``None`` + # in which case we run current logic of device selection, i.e. + # ``current_device`` is CUDA if backend is NCCL otherwise CPU device. In the + # case it is not ``None`` we move the size and object tensors to be + # received to this device. + current_device = device or _get_pg_default_device(group) + object_sizes_tensor = torch.empty(len(object_list), dtype=torch.long, device=current_device) + + # Receive object sizes + rank_sizes = recv(object_sizes_tensor, src=src, group=group) + + # Tensor to receive serialized objects into. + object_tensor = torch.empty( # type: ignore[call-overload] + torch.sum(object_sizes_tensor).item(), # type: ignore[arg-type] + dtype=torch.uint8, + device=current_device + ) + + rank_objects = recv(object_tensor, src=src, group=group) + assert rank_sizes == rank_objects, "Mismatch in return ranks for object sizes and objects." + # Deserialize objects using their stored sizes. + offset = 0 + for i, obj_size in enumerate(object_sizes_tensor): + obj_view = object_tensor[offset : offset + obj_size] + obj_view = obj_view.type(torch.uint8) + offset += obj_size + object_list[i] = _tensor_to_object(obj_view, obj_size, group) + return rank_objects + +@_exception_logger +def broadcast_object_list(object_list, src=0, group=None, device=None): + """ + Broadcasts picklable objects in ``object_list`` to the whole group. + + Similar to :func:`broadcast`, but Python objects can be passed in. + Note that all objects in ``object_list`` must be picklable in order to be + broadcasted. + + Args: + object_list (List[Any]): List of input objects to broadcast. + Each object must be picklable. Only objects on the ``src`` rank will + be broadcast, but each rank must provide lists of equal sizes. + src (int): Source rank from which to broadcast ``object_list``. + Source rank is based on global process group (regardless of ``group`` argument) + group: (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + device (``torch.device``, optional): If not None, the objects are + serialized and converted to tensors which are moved to the + ``device`` before broadcasting. Default is ``None``. + + Returns: + ``None``. If rank is part of the group, ``object_list`` will contain the + broadcasted objects from ``src`` rank. + + .. note:: For NCCL-based process groups, internal tensor representations + of objects must be moved to the GPU device before communication takes + place. In this case, the device used is given by + ``torch.cuda.current_device()`` and it is the user's responsibility to + ensure that this is set so that each rank has an individual GPU, via + ``torch.cuda.set_device()``. + + .. note:: Note that this API differs slightly from the :func:`broadcast` + collective since it does not provide an ``async_op`` handle and thus + will be a blocking call. + + .. warning:: + :func:`broadcast_object_list` uses ``pickle`` module implicitly, which + is known to be insecure. It is possible to construct malicious pickle + data which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`broadcast_object_list` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`broadcast` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> if dist.get_rank() == 0: + >>> # Assumes world_size of 3. + >>> objects = ["foo", 12, {1: 2}] # any picklable object + >>> else: + >>> objects = [None, None, None] + >>> # Assumes backend is not NCCL + >>> device = torch.device("cpu") + >>> dist.broadcast_object_list(objects, src=0, device=device) + >>> objects + ['foo', 12, {1: 2}] + """ + if _rank_not_in_group(group): + _warn_not_in_group("broadcast_object_list") + return + + # Current device selection. + # To preserve backwards compatibility, ``device`` is default to ``None`` + # in which case we run current logic of device selection, i.e. + # ``current_device`` is CUDA if backend is NCCL otherwise CPU device. In the + # case it is not ``None`` we move the size and object tensors to be + # broadcasted to this device. + current_device = device or _get_pg_default_device(group) + my_rank = get_rank() + # Serialize object_list elements to tensors on src rank. + if my_rank == src: + tensor_list, size_list = zip(*[_object_to_tensor(obj, current_device, group) for obj in object_list]) + object_sizes_tensor = torch.cat(size_list) + else: + object_sizes_tensor = torch.empty(len(object_list), dtype=torch.long, device=current_device) + + # Broadcast object sizes + broadcast(object_sizes_tensor, src=src, group=group) + + # Concatenate and broadcast serialized object tensors + # Note: torch.cat will do an extra memory copy to the current device, if the tensor_list + # has only one element, we can skip the copy. + if my_rank == src: + if len(tensor_list) == 1: # type: ignore[possibly-undefined] + object_tensor = tensor_list[0] + else: + object_tensor = torch.cat(tensor_list) + else: + object_tensor = torch.empty( # type: ignore[call-overload] + torch.sum(object_sizes_tensor).item(), # type: ignore[arg-type] + dtype=torch.uint8, + device=current_device + ) + + broadcast(object_tensor, src=src, group=group) + # Deserialize objects using their stored sizes. + offset = 0 + if my_rank != src: + for i, obj_size in enumerate(object_sizes_tensor): + obj_view = object_tensor[offset : offset + obj_size] + obj_view = obj_view.type(torch.uint8) + offset += obj_size + object_list[i] = _tensor_to_object(obj_view, obj_size, group) + + +@_exception_logger +def scatter_object_list( + scatter_object_output_list, scatter_object_input_list, src=0, group=None +): + """ + Scatters picklable objects in ``scatter_object_input_list`` to the whole group. + + Similar to :func:`scatter`, but Python objects can be passed in. On + each rank, the scattered object will be stored as the first element of + ``scatter_object_output_list``. Note that all objects in + ``scatter_object_input_list`` must be picklable in order to be scattered. + + Args: + scatter_object_output_list (List[Any]): Non-empty list whose first + element will store the object scattered to this rank. + scatter_object_input_list (List[Any]): List of input objects to scatter. + Each object must be picklable. Only objects on the ``src`` rank will + be scattered, and the argument can be ``None`` for non-src ranks. + src (int): Source rank from which to scatter ``scatter_object_input_list``. + Source rank is based on global process group (regardless of ``group`` argument). + group: (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. Default is ``None``. + + Returns: + ``None``. If rank is part of the group, ``scatter_object_output_list`` + will have its first element set to the scattered object for this rank. + + .. note:: Note that this API differs slightly from the scatter collective + since it does not provide an ``async_op`` handle and thus will be a + blocking call. + + .. warning:: + :func:`scatter_object_list` uses ``pickle`` module implicitly, which + is known to be insecure. It is possible to construct malicious pickle + data which will execute arbitrary code during unpickling. Only call this + function with data you trust. + + .. warning:: + Calling :func:`scatter_object_list` with GPU tensors is not well supported + and inefficient as it incurs GPU -> CPU transfer since tensors would be + pickled. Please consider using :func:`scatter` instead. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> if dist.get_rank() == 0: + >>> # Assumes world_size of 3. + >>> objects = ["foo", 12, {1: 2}] # any picklable object + >>> else: + >>> # Can be any list on non-src ranks, elements are not used. + >>> objects = [None, None, None] + >>> output_list = [None] + >>> dist.scatter_object_list(output_list, objects, src=0) + >>> # Rank i gets objects[i]. For example, on rank 2: + >>> output_list + [{1: 2}] + """ + if _rank_not_in_group(group): + _warn_not_in_group("scatter_object_list") + return + + if ( + not isinstance(scatter_object_output_list, list) + or len(scatter_object_output_list) < 1 + ): + raise ValueError( + "Expected argument scatter_object_output_list to be a list of size at least 1." + ) + + my_rank = get_rank() + pg_device = _get_pg_default_device(group) + if my_rank == src: + tensor_list, tensor_sizes = zip( + *[_object_to_tensor(obj, pg_device, group) for obj in scatter_object_input_list] + ) + tensor_list, tensor_sizes = list(tensor_list), list(tensor_sizes) + + # Src rank broadcasts the maximum tensor size. This is because all ranks are + # expected to call into scatter() with equal-sized tensors. + if my_rank == src: + max_tensor_size = max(tensor_sizes) # type: ignore[possibly-undefined] + for tensor in tensor_list: # type: ignore[possibly-undefined] + tensor.resize_(max_tensor_size) + else: + max_tensor_size = torch.tensor([0], dtype=torch.long, device=pg_device) + broadcast(max_tensor_size, src=src, group=group) + + # Scatter actual serialized objects + output_tensor = torch.empty(max_tensor_size.item(), dtype=torch.uint8, device=pg_device) + scatter( + output_tensor, + scatter_list=None if my_rank != src else tensor_list, # type: ignore[possibly-undefined] + src=src, + group=group, + ) + + # Scatter per-object sizes to trim tensors when deserializing back to object + obj_tensor_size = torch.tensor([0], dtype=torch.long, device=pg_device) + scatter( + obj_tensor_size, + scatter_list=None if my_rank != src else tensor_sizes, # type: ignore[possibly-undefined] + src=src, + group=group, + ) + + # Deserialize back to object + scatter_object_output_list[0] = _tensor_to_object(output_tensor, obj_tensor_size, group) + + +@_exception_logger +def all_gather(tensor_list, tensor, group=None, async_op=False): + """ + Gathers tensors from the whole group in a list. + + Complex tensors are supported. + + Args: + tensor_list (list[Tensor]): Output list. It should contain + correctly-sized tensors to be used for output of the collective. + tensor (Tensor): Tensor to be broadcast from current process. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + Examples: + >>> # xdoctest: +SKIP("need process group init") + >>> # All tensors below are of torch.int64 dtype. + >>> # We have 2 process groups, 2 ranks. + >>> device = torch.device(f'cuda:{rank}') + >>> tensor_list = [torch.zeros(2, dtype=torch.int64, device=device) for _ in range(2)] + >>> tensor_list + [tensor([0, 0], device='cuda:0'), tensor([0, 0], device='cuda:0')] # Rank 0 + [tensor([0, 0], device='cuda:0'), tensor([0, 0], device='cuda:1')] # Rank 1 + >>> tensor = torch.arange(2, dtype=torch.int64, device=device) + 1 + 2 * rank + >>> tensor + tensor([1, 2], device='cuda:0') # Rank 0 + tensor([3, 4], device='cuda:1') # Rank 1 + >>> dist.all_gather(tensor_list, tensor) + >>> tensor_list + [tensor([1, 2], device='cuda:0'), tensor([3, 4], device='cuda:0')] # Rank 0 + [tensor([1, 2], device='cuda:1'), tensor([3, 4], device='cuda:1')] # Rank 1 + + >>> # All tensors below are of torch.cfloat dtype. + >>> # We have 2 process groups, 2 ranks. + >>> tensor_list = [torch.zeros(2, dtype=torch.cfloat, device=device) for _ in range(2)] + >>> tensor_list + [tensor([0.+0.j, 0.+0.j], device='cuda:0'), tensor([0.+0.j, 0.+0.j], device='cuda:0')] # Rank 0 + [tensor([0.+0.j, 0.+0.j], device='cuda:1'), tensor([0.+0.j, 0.+0.j], device='cuda:1')] # Rank 1 + >>> tensor = torch.tensor([1+1j, 2+2j], dtype=torch.cfloat, device=device) + 2 * rank * (1+1j) + >>> tensor + tensor([1.+1.j, 2.+2.j], device='cuda:0') # Rank 0 + tensor([3.+3.j, 4.+4.j], device='cuda:1') # Rank 1 + >>> dist.all_gather(tensor_list, tensor) + >>> tensor_list + [tensor([1.+1.j, 2.+2.j], device='cuda:0'), tensor([3.+3.j, 4.+4.j], device='cuda:0')] # Rank 0 + [tensor([1.+1.j, 2.+2.j], device='cuda:1'), tensor([3.+3.j, 4.+4.j], device='cuda:1')] # Rank 1 + + """ + _check_tensor_list(tensor_list, "tensor_list") + _check_single_tensor(tensor, "tensor") + _ensure_all_tensors_same_dtype(tensor_list, tensor) + if _rank_not_in_group(group): + _warn_not_in_group("all_gather") + return + + tensor_list = [ + t if not t.is_complex() else torch.view_as_real(t) for t in tensor_list + ] + tensor = tensor if not tensor.is_complex() else torch.view_as_real(tensor) + + if group is None: + default_pg = _get_default_group() + work = default_pg.allgather([tensor_list], [tensor]) + else: + work = group.allgather([tensor_list], [tensor]) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +def all_gather_into_tensor(output_tensor, input_tensor, group=None, async_op=False): + """ + Gather tensors from all ranks and put them in a single output tensor. + + Args: + output_tensor (Tensor): Output tensor to accommodate tensor elements + from all ranks. It must be correctly sized to have one of the + following forms: + (i) a concatenation of all the input tensors along the primary + dimension; for definition of "concatenation", see ``torch.cat()``; + (ii) a stack of all the input tensors along the primary dimension; + for definition of "stack", see ``torch.stack()``. + Examples below may better explain the supported output forms. + input_tensor (Tensor): Tensor to be gathered from current rank. + Different from the ``all_gather`` API, the input tensors in this + API must have the same size across all ranks. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + Examples: + >>> # xdoctest: +SKIP("need process group init") + >>> # All tensors below are of torch.int64 dtype and on CUDA devices. + >>> # We have two ranks. + >>> device = torch.device(f'cuda:{rank}') + >>> tensor_in = torch.arange(2, dtype=torch.int64, device=device) + 1 + 2 * rank + >>> tensor_in + tensor([1, 2], device='cuda:0') # Rank 0 + tensor([3, 4], device='cuda:1') # Rank 1 + >>> # Output in concatenation form + >>> tensor_out = torch.zeros(world_size * 2, dtype=torch.int64, device=device) + >>> dist.all_gather_into_tensor(tensor_out, tensor_in) + >>> tensor_out + tensor([1, 2, 3, 4], device='cuda:0') # Rank 0 + tensor([1, 2, 3, 4], device='cuda:1') # Rank 1 + >>> # Output in stack form + >>> tensor_out2 = torch.zeros(world_size, 2, dtype=torch.int64, device=device) + >>> dist.all_gather_into_tensor(tensor_out2, tensor_in) + >>> tensor_out2 + tensor([[1, 2], + [3, 4]], device='cuda:0') # Rank 0 + tensor([[1, 2], + [3, 4]], device='cuda:1') # Rank 1 + + .. warning:: + The Gloo backend does not support this API. + + """ + _check_single_tensor(input_tensor, "input_tensor") + _check_single_tensor(output_tensor, "output_tensor") + if _rank_not_in_group(group): + _warn_not_in_group("all_gather_into_tensor") + return + + output_tensor = ( + output_tensor + if not output_tensor.is_complex() + else torch.view_as_real(output_tensor) + ) + input_tensor = ( + input_tensor + if not input_tensor.is_complex() + else torch.view_as_real(input_tensor) + ) + + opts = AllgatherOptions() + opts.asyncOp = async_op + + group = group or _get_default_group() + + if group in _world.pg_coalesce_state.keys(): + # We are in coalescing context, do not issue single operation, just append a collective representation + coll = _CollOp(all_gather_into_tensor, input_tensor, output_tensor) + _world.pg_coalesce_state[group].append(coll) + if async_op: + return _IllegalWork() + else: + return None + + work = group._allgather_base(output_tensor, input_tensor, opts) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +@deprecated( + "`torch.distributed._all_gather_base` is a private function and will be deprecated. " + "Please use `torch.distributed.all_gather_into_tensor` instead.", + category=FutureWarning, +) +def _all_gather_base(output_tensor, input_tensor, group=None, async_op=False): + """ + Single tensor all gather. Gathers a single tensor from all ranks, and puts them in a single output tensor. + + Args: + output_tensor (Tensor): Output tensor. It should contain + correctly-sized tensors to be used for output of the collective. + input_tensor (Tensor): Tensor to be broadcast from current process. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + .. warning:: + `_all_gather_base` is a private function. Users should use + `all_gather_into_tensor` instead. + + """ + return all_gather_into_tensor(output_tensor, input_tensor, group, async_op) + + +@_exception_logger +@deprecated( + "`torch.distributed.all_gather_coalesced` will be deprecated. If you must use it, " + "please revisit our documentation later at " + "https://pytorch.org/docs/main/distributed.html#collective-functions", + category=FutureWarning, +) +def all_gather_coalesced( + output_tensor_lists, input_tensor_list, group=None, async_op=False +): + """ + Gathers input tensors from the whole group in a list in a coalesced manner. + + Complex tensors are supported. + + Args: + output_tensor_lists (list[list[Tensor]]): Output list. It should contain + correctly-sized tensors to be used for output of the collective. + input_tensor_list (list[Tensor]): Tensors to be broadcast from + current process. At least one tensor has to be non empty. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + Example: + we have 2 process groups, 2 ranks. + rank 0 passes: + input_tensor_list = [[[1, 1], [1, 1]], [2], [3, 3]] + output_tensor_lists = + [[[[-1, -1], [-1, -1]], [-1], [-1, -1]], + [[[-1, -1], [-1, -1]], [-1], [-1, -1]]] + rank 1 passes: + input_tensor_list = [[[3, 3], [3, 3]], [5], [1, 1]] + output_tensor_lists = + [[[[-1, -1], [-1, -1]], [-1], [-1, -1]], + [[[-1, -1], [-1, -1]], [-1], [-1, -1]]] + both rank 0 and 1 get: + output_tensor_lists = + [[[1, 1], [1, 1]], [2], [3, 3]], + [[3, 3], [3, 3]], [5], [1, 1]]]. + + WARNING: at this time individual shape checking is not implemented across nodes. + For example, if the rank 0 node passes [torch.rand(4), torch.rand(2)] and the + rank 1 node passes [torch.rand(2), torch.rand(2), torch.rand(2)], the + all_gather_coalesced operation will proceed without complaint and return + erroneous outputs. This lack of shape checking results in significant + performance improvements but users of this function should take extra care + to ensure that each node passes in tensors whose shapes match across nodes. + """ + # We only check basic compatibility with C++ params here, C++ code will + # do shape and type checking. + if _rank_not_in_group(group): + _warn_not_in_group("all_gather_coalesced") + return + _check_tensor_list(input_tensor_list, "input_tensor_list") + _ensure_all_tensors_same_dtype(input_tensor_list) + if not isinstance(output_tensor_lists, list): + raise TypeError( + "Invalid function argument: output_tensor_lists should be a list" + ) + for output_tensor_list in output_tensor_lists: + _check_tensor_list(output_tensor_list, "output_tensor_lists") + _ensure_all_tensors_same_dtype(output_tensor_list) + + output_tensor_lists = [ + [t if not t.is_complex() else torch.view_as_real(t) for t in l] + for l in output_tensor_lists + ] + input_tensor_list = [ + t if not t.is_complex() else torch.view_as_real(t) for t in input_tensor_list + ] + + if group is None: + default_pg = _get_default_group() + work = default_pg.allgather_coalesced(output_tensor_lists, input_tensor_list) + else: + work = group.allgather_coalesced(output_tensor_lists, input_tensor_list) + + if async_op: + return work.get_future() + else: + work.wait() + + +def _validate_output_list_for_rank(my_rank, dst, gather_list): + if dst == my_rank: + if not gather_list: + raise ValueError( + "Argument ``gather_list`` must be specified on destination rank." + ) + elif gather_list: + raise ValueError( + "Argument ``gather_list`` must NOT be specified " + "on non-destination ranks." + ) + + +@_exception_logger +def gather(tensor, gather_list=None, dst=0, group=None, async_op=False): + """ + Gathers a list of tensors in a single process. + + Args: + tensor (Tensor): Input tensor. + gather_list (list[Tensor], optional): List of appropriately-sized + tensors to use for gathered data (default is None, must be specified + on the destination rank) + dst (int, optional): Destination rank on global process group (regardless of ``group`` argument). (default is 0) + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + """ + _check_single_tensor(tensor, "tensor") + + # Parameter ``gather_list`` may be left unspecified on non-dst ranks. + if gather_list: + _check_tensor_list(gather_list, "gather_list") + else: + gather_list = [] + _ensure_all_tensors_same_dtype(tensor, gather_list) + + if _rank_not_in_group(group): + _warn_not_in_group("gather") + return + + my_rank = get_rank() + _validate_output_list_for_rank(my_rank, dst, gather_list) + output_tensors = [gather_list] if dst == my_rank else [] + input_tensors = [tensor] + + opts = GatherOptions() + opts.rootRank = dst + + if group is None or group is GroupMember.WORLD: + default_pg = _get_default_group() + work = default_pg.gather(output_tensors, input_tensors, opts) + else: + group_dst_rank = get_group_rank(group, dst) + opts.rootRank = group_dst_rank + work = group.gather(output_tensors, input_tensors, opts) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +def scatter(tensor, scatter_list=None, src=0, group=None, async_op=False): + """ + Scatters a list of tensors to all processes in a group. + + Each process will receive exactly one tensor and store its data in the + ``tensor`` argument. + + Complex tensors are supported. + + Args: + tensor (Tensor): Output tensor. + scatter_list (list[Tensor]): List of tensors to scatter (default is + None, must be specified on the source rank) + src (int): Source rank on global process group (regardless of ``group`` argument). + Default is 0 + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + .. note:: Note that all Tensors in scatter_list must have the same size. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> tensor_size = 2 + >>> t_ones = torch.ones(tensor_size) + >>> t_fives = torch.ones(tensor_size) * 5 + >>> output_tensor = torch.zeros(tensor_size) + >>> if dist.get_rank() == 0: + >>> # Assumes world_size of 2. + >>> # Only tensors, all of which must be the same size. + >>> scatter_list = [t_ones, t_fives] + >>> else: + >>> scatter_list = None + >>> dist.scatter(output_tensor, scatter_list, src=0) + >>> # Rank i gets scatter_list[i]. For example, on rank 1: + >>> output_tensor + tensor([5., 5.]) + + """ + _check_single_tensor(tensor, "tensor") + + # Parameter ``scatter_list`` may be left unspecified on non-src ranks. + if scatter_list: + _check_tensor_list(scatter_list, "scatter_list") + else: + scatter_list = [] + _ensure_all_tensors_same_dtype(tensor, scatter_list) + + if _rank_not_in_group(group): + _warn_not_in_group("scatter") + return + scatter_list = [ + t if not t.is_complex() else torch.view_as_real(t) for t in scatter_list + ] + tensor = tensor if not tensor.is_complex() else torch.view_as_real(tensor) + + my_rank = get_rank() + if src == my_rank: + if not scatter_list: + raise ValueError( + "Argument ``scatter_list`` must be specified on source rank." + ) + input_tensors = [scatter_list] + output_tensors = [tensor] + else: + if scatter_list: + raise ValueError( + "Argument ``scatter_list`` must NOT be specified " + "on non-source ranks." + ) + input_tensors = [] + output_tensors = [tensor] + + opts = ScatterOptions() + opts.rootRank = src + opts.asyncOp = async_op + + if group is None or group is GroupMember.WORLD: + default_pg = _get_default_group() + work = default_pg.scatter(output_tensors, input_tensors, opts) + else: + group_src_rank = get_group_rank(group, src) + opts.rootRank = group_src_rank + work = group.scatter(output_tensors, input_tensors, opts) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +def reduce_scatter(output, input_list, op=ReduceOp.SUM, group=None, async_op=False): + """ + Reduces, then scatters a list of tensors to all processes in a group. + + Args: + output (Tensor): Output tensor. + input_list (list[Tensor]): List of tensors to reduce and scatter. + op (optional): One of the values from + ``torch.distributed.ReduceOp`` + enum. Specifies an operation used for element-wise reductions. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + """ + _check_single_tensor(output, "output") + _check_tensor_list(input_list, "input_list") + _ensure_all_tensors_same_dtype(output, input_list) + if _rank_not_in_group(group): + _warn_not_in_group("reduce_scatter") + return + + opts = ReduceScatterOptions() + opts.reduceOp = op + + if group is None: + default_pg = _get_default_group() + work = default_pg.reduce_scatter([output], [input_list], opts) + else: + work = group.reduce_scatter([output], [input_list], opts) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +def reduce_scatter_tensor(output, input, op=ReduceOp.SUM, group=None, async_op=False): + """ + Reduces, then scatters a tensor to all ranks in a group. + + Args: + output (Tensor): Output tensor. It should have the same size across all + ranks. + input (Tensor): Input tensor to be reduced and scattered. Its size + should be output tensor size times the world size. The input tensor + can have one of the following shapes: + (i) a concatenation of the output tensors along the primary + dimension, or + (ii) a stack of the output tensors along the primary dimension. + For definition of "concatenation", see ``torch.cat()``. + For definition of "stack", see ``torch.stack()``. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + Examples: + >>> # xdoctest: +SKIP("need process group init") + >>> # All tensors below are of torch.int64 dtype and on CUDA devices. + >>> # We have two ranks. + >>> device = torch.device(f'cuda:{rank}') + >>> tensor_out = torch.zeros(2, dtype=torch.int64, device=device) + >>> # Input in concatenation form + >>> tensor_in = torch.arange(world_size * 2, dtype=torch.int64, device=device) + >>> tensor_in + tensor([0, 1, 2, 3], device='cuda:0') # Rank 0 + tensor([0, 1, 2, 3], device='cuda:1') # Rank 1 + >>> dist.reduce_scatter_tensor(tensor_out, tensor_in) + >>> tensor_out + tensor([0, 2], device='cuda:0') # Rank 0 + tensor([4, 6], device='cuda:1') # Rank 1 + >>> # Input in stack form + >>> tensor_in = torch.reshape(tensor_in, (world_size, 2)) + >>> tensor_in + tensor([[0, 1], + [2, 3]], device='cuda:0') # Rank 0 + tensor([[0, 1], + [2, 3]], device='cuda:1') # Rank 1 + >>> dist.reduce_scatter_tensor(tensor_out, tensor_in) + >>> tensor_out + tensor([0, 2], device='cuda:0') # Rank 0 + tensor([4, 6], device='cuda:1') # Rank 1 + + .. warning:: + The Gloo backend does not support this API. + + """ + _check_single_tensor(output, "output") + _check_single_tensor(input, "input") + + if _rank_not_in_group(group): + _warn_not_in_group("reduce_scatter_tensor") + return + + opts = ReduceScatterOptions() + opts.reduceOp = op + opts.asyncOp = async_op + + group = group or _get_default_group() + + # Check if we are in coalescing context + # If we are, do not issue single operation, just append a collective representation + if group in _world.pg_coalesce_state.keys(): + coll = _CollOp(reduce_scatter_tensor, input, output, op, None) + _world.pg_coalesce_state[group].append(coll) + if async_op: + return _IllegalWork() + else: + return None + + work = group._reduce_scatter_base(output, input, opts) + + if async_op: + return work + else: + work.wait() + + +@deprecated( + "`torch.distributed._reduce_scatter_base` is a private function and will be deprecated. " + "Please use `torch.distributed.reduce_scatter_tensor` instead.", + category=FutureWarning, +) +def _reduce_scatter_base(output, input, op=ReduceOp.SUM, group=None, async_op=False): + """ + Reduces, then scatters a flattened tensor to all processes in a group. + + Args: + output (Tensor): Output tensor. + input (Tensor): Input tensor that is of size output tensor size times world size + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + .. warning:: + `_reduce_scatter_base` is a private function. Users should use + `reduce_scatter_tensor` instead. + + """ + return reduce_scatter_tensor(output, input, op, group, async_op) + + +@_exception_logger +def all_to_all_single( + output, + input, + output_split_sizes=None, + input_split_sizes=None, + group=None, + async_op=False, +): + """ + Split input tensor and then scatter the split list to all processes in a group. + + Later the received tensors are concatenated from all the processes in the group + and returned as a single output tensor. + + Complex tensors are supported. + + Args: + output (Tensor): Gathered concatenated output tensor. + input (Tensor): Input tensor to scatter. + output_split_sizes: (list[Int], optional): Output split sizes for dim 0 + if specified None or empty, dim 0 of ``output`` tensor must divide + equally by ``world_size``. + input_split_sizes: (list[Int], optional): Input split sizes for dim 0 + if specified None or empty, dim 0 of ``input`` tensor must divide + equally by ``world_size``. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + .. warning:: + `all_to_all_single` is experimental and subject to change. + + Examples: + >>> # xdoctest: +SKIP("Undefined rank") + >>> input = torch.arange(4) + rank * 4 + >>> input + tensor([0, 1, 2, 3]) # Rank 0 + tensor([4, 5, 6, 7]) # Rank 1 + tensor([8, 9, 10, 11]) # Rank 2 + tensor([12, 13, 14, 15]) # Rank 3 + >>> output = torch.empty([4], dtype=torch.int64) + >>> dist.all_to_all_single(output, input) + >>> output + tensor([0, 4, 8, 12]) # Rank 0 + tensor([1, 5, 9, 13]) # Rank 1 + tensor([2, 6, 10, 14]) # Rank 2 + tensor([3, 7, 11, 15]) # Rank 3 + + >>> # Essentially, it is similar to following operation: + >>> scatter_list = list(input.chunk(world_size)) + >>> gather_list = list(output.chunk(world_size)) + >>> for i in range(world_size): + >>> dist.scatter(gather_list[i], scatter_list if i == rank else [], src = i) + + >>> # Another example with uneven split + >>> input + tensor([0, 1, 2, 3, 4, 5]) # Rank 0 + tensor([10, 11, 12, 13, 14, 15, 16, 17, 18]) # Rank 1 + tensor([20, 21, 22, 23, 24]) # Rank 2 + tensor([30, 31, 32, 33, 34, 35, 36]) # Rank 3 + >>> input_splits + [2, 2, 1, 1] # Rank 0 + [3, 2, 2, 2] # Rank 1 + [2, 1, 1, 1] # Rank 2 + [2, 2, 2, 1] # Rank 3 + >>> output_splits + [2, 3, 2, 2] # Rank 0 + [2, 2, 1, 2] # Rank 1 + [1, 2, 1, 2] # Rank 2 + [1, 2, 1, 1] # Rank 3 + >>> output = ... + >>> dist.all_to_all_single(output, input, output_splits, input_splits) + >>> output + tensor([ 0, 1, 10, 11, 12, 20, 21, 30, 31]) # Rank 0 + tensor([ 2, 3, 13, 14, 22, 32, 33]) # Rank 1 + tensor([ 4, 15, 16, 23, 34, 35]) # Rank 2 + tensor([ 5, 17, 18, 24, 36]) # Rank 3 + + + >>> # Another example with tensors of torch.cfloat type. + >>> input = torch.tensor([1+1j, 2+2j, 3+3j, 4+4j], dtype=torch.cfloat) + 4 * rank * (1+1j) + >>> input + tensor([1+1j, 2+2j, 3+3j, 4+4j]) # Rank 0 + tensor([5+5j, 6+6j, 7+7j, 8+8j]) # Rank 1 + tensor([9+9j, 10+10j, 11+11j, 12+12j]) # Rank 2 + tensor([13+13j, 14+14j, 15+15j, 16+16j]) # Rank 3 + >>> output = torch.empty([4], dtype=torch.int64) + >>> dist.all_to_all_single(output, input) + >>> output + tensor([1+1j, 5+5j, 9+9j, 13+13j]) # Rank 0 + tensor([2+2j, 6+6j, 10+10j, 14+14j]) # Rank 1 + tensor([3+3j, 7+7j, 11+11j, 15+15j]) # Rank 2 + tensor([4+4j, 8+8j, 12+12j, 16+16j]) # Rank 3 + """ + if _rank_not_in_group(group): + _warn_not_in_group("all_to_all_single") + return + + opts = AllToAllOptions() + _check_single_tensor(output, "output") + _check_single_tensor(input, "input") + _ensure_all_tensors_same_dtype(output, input) + + if input.is_complex(): + input = torch.view_as_real(input) + if output.is_complex(): + output = torch.view_as_real(output) + + output_split_sizes = [] if output_split_sizes is None else output_split_sizes + input_split_sizes = [] if input_split_sizes is None else input_split_sizes + + if group is None: + default_pg = _get_default_group() + work = default_pg.alltoall_base( + output, input, output_split_sizes, input_split_sizes, opts + ) + else: + work = group.alltoall_base( + output, input, output_split_sizes, input_split_sizes, opts + ) + + if async_op: + return work + else: + work.wait() + + +@_exception_logger +def all_to_all(output_tensor_list, input_tensor_list, group=None, async_op=False): + """ + Scatters list of input tensors to all processes in a group and return gathered list of tensors in output list. + + Complex tensors are supported. + + Args: + output_tensor_list (list[Tensor]): List of tensors to be gathered one + per rank. + input_tensor_list (list[Tensor]): List of tensors to scatter one per rank. + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group. + + .. warning:: + `all_to_all` is experimental and subject to change. + + Examples: + >>> # xdoctest: +SKIP("Undefined rank") + >>> input = torch.arange(4) + rank * 4 + >>> input = list(input.chunk(4)) + >>> input + [tensor([0]), tensor([1]), tensor([2]), tensor([3])] # Rank 0 + [tensor([4]), tensor([5]), tensor([6]), tensor([7])] # Rank 1 + [tensor([8]), tensor([9]), tensor([10]), tensor([11])] # Rank 2 + [tensor([12]), tensor([13]), tensor([14]), tensor([15])] # Rank 3 + >>> output = list(torch.empty([4], dtype=torch.int64).chunk(4)) + >>> dist.all_to_all(output, input) + >>> output + [tensor([0]), tensor([4]), tensor([8]), tensor([12])] # Rank 0 + [tensor([1]), tensor([5]), tensor([9]), tensor([13])] # Rank 1 + [tensor([2]), tensor([6]), tensor([10]), tensor([14])] # Rank 2 + [tensor([3]), tensor([7]), tensor([11]), tensor([15])] # Rank 3 + + >>> # Essentially, it is similar to following operation: + >>> scatter_list = input + >>> gather_list = output + >>> for i in range(world_size): + >>> dist.scatter(gather_list[i], scatter_list if i == rank else [], src=i) + + >>> input + tensor([0, 1, 2, 3, 4, 5]) # Rank 0 + tensor([10, 11, 12, 13, 14, 15, 16, 17, 18]) # Rank 1 + tensor([20, 21, 22, 23, 24]) # Rank 2 + tensor([30, 31, 32, 33, 34, 35, 36]) # Rank 3 + >>> input_splits + [2, 2, 1, 1] # Rank 0 + [3, 2, 2, 2] # Rank 1 + [2, 1, 1, 1] # Rank 2 + [2, 2, 2, 1] # Rank 3 + >>> output_splits + [2, 3, 2, 2] # Rank 0 + [2, 2, 1, 2] # Rank 1 + [1, 2, 1, 2] # Rank 2 + [1, 2, 1, 1] # Rank 3 + >>> input = list(input.split(input_splits)) + >>> input + [tensor([0, 1]), tensor([2, 3]), tensor([4]), tensor([5])] # Rank 0 + [tensor([10, 11, 12]), tensor([13, 14]), tensor([15, 16]), tensor([17, 18])] # Rank 1 + [tensor([20, 21]), tensor([22]), tensor([23]), tensor([24])] # Rank 2 + [tensor([30, 31]), tensor([32, 33]), tensor([34, 35]), tensor([36])] # Rank 3 + >>> output = ... + >>> dist.all_to_all(output, input) + >>> output + [tensor([0, 1]), tensor([10, 11, 12]), tensor([20, 21]), tensor([30, 31])] # Rank 0 + [tensor([2, 3]), tensor([13, 14]), tensor([22]), tensor([32, 33])] # Rank 1 + [tensor([4]), tensor([15, 16]), tensor([23]), tensor([34, 35])] # Rank 2 + [tensor([5]), tensor([17, 18]), tensor([24]), tensor([36])] # Rank 3 + + >>> # Another example with tensors of torch.cfloat type. + >>> input = torch.tensor([1+1j, 2+2j, 3+3j, 4+4j], dtype=torch.cfloat) + 4 * rank * (1+1j) + >>> input = list(input.chunk(4)) + >>> input + [tensor([1+1j]), tensor([2+2j]), tensor([3+3j]), tensor([4+4j])] # Rank 0 + [tensor([5+5j]), tensor([6+6j]), tensor([7+7j]), tensor([8+8j])] # Rank 1 + [tensor([9+9j]), tensor([10+10j]), tensor([11+11j]), tensor([12+12j])] # Rank 2 + [tensor([13+13j]), tensor([14+14j]), tensor([15+15j]), tensor([16+16j])] # Rank 3 + >>> output = list(torch.empty([4], dtype=torch.int64).chunk(4)) + >>> dist.all_to_all(output, input) + >>> output + [tensor([1+1j]), tensor([5+5j]), tensor([9+9j]), tensor([13+13j])] # Rank 0 + [tensor([2+2j]), tensor([6+6j]), tensor([10+10j]), tensor([14+14j])] # Rank 1 + [tensor([3+3j]), tensor([7+7j]), tensor([11+11j]), tensor([15+15j])] # Rank 2 + [tensor([4+4j]), tensor([8+8j]), tensor([12+12j]), tensor([16+16j])] # Rank 3 + + """ + if _rank_not_in_group(group): + _warn_not_in_group("all_to_all") + return + + opts = AllToAllOptions() + _check_tensor_list(output_tensor_list, "output_tensor_list") + _check_tensor_list(input_tensor_list, "input_tensor_list") + _ensure_all_tensors_same_dtype(output_tensor_list, input_tensor_list) + + input_tensor_list = [ + t if not t.is_complex() else torch.view_as_real(t) for t in input_tensor_list + ] + output_tensor_list = [ + t if not t.is_complex() else torch.view_as_real(t) for t in output_tensor_list + ] + + if group is None: + default_pg = _get_default_group() + work = default_pg.alltoall(output_tensor_list, input_tensor_list, opts) + else: + work = group.alltoall(output_tensor_list, input_tensor_list, opts) + + if async_op: + return work + else: + work.wait() + +@_exception_logger +def barrier(group=GroupMember.WORLD, async_op=False, device_ids=None): + """ + Synchronize all processes. + + This collective blocks processes until the whole group enters this function, + if async_op is False, or if async work handle is called on wait(). + + Args: + group (ProcessGroup, optional): The process group to work on. If None, + the default process group will be used. + async_op (bool, optional): Whether this op should be an async op + device_ids ([int], optional): List of device/GPU ids. + + Returns: + Async work handle, if async_op is set to True. + None, if not async_op or if not part of the group + + .. note:: `ProcessGroupNCCL` now relies on stream synchronization instead of + device synchronization to block the CPU. Thus, please do not assume that + `barrier()` would perform a device synchronization. + """ + if _rank_not_in_group(group): + _warn_not_in_group("barrier") + return + + opts = BarrierOptions() + opts.device = _get_pg_default_device(group) + if device_ids is not None: + if isinstance(device_ids, list): + opts.device_ids = device_ids + else: + raise TypeError( + "Invalid function argument: device_ids type should be List[int]" + ) + + if group is None: + default_pg = _get_default_group() + work = default_pg.barrier(opts=opts) + else: + work = group.barrier(opts=opts) + + if async_op: + return work + else: + work.wait() + + +def monitored_barrier(group=GroupMember.WORLD, timeout=None, wait_all_ranks=False): + """ + Synchronize processes similar to ``torch.distributed.barrier``, but consider a configurable timeout. + + It is able to report ranks that did not pass this barrier within the provided timeout. + Specifically, for non-zero ranks, will block until a send/recv is processed from rank 0. + Rank 0 will block until all send /recv from other ranks are processed, and will report + failures for ranks that failed to respond in time. Note that if one rank does not reach the + monitored_barrier (for example due to a hang), all other ranks would fail in monitored_barrier. + + This collective will block all processes/ranks in the group, until the + whole group exits the function successfully, making it useful for debugging + and synchronizing. However, it can have a performance impact and should only + be used for debugging or scenarios that require full synchronization points + on the host-side. For debugging purposes, this barrier can be inserted + before the application's collective calls to check if any ranks are + desynchronized. + + .. note:: Note that this collective is only supported with the GLOO backend. + + Args: + group (ProcessGroup, optional): The process group to work on. If + ``None``, the default process group will be used. + timeout (datetime.timedelta, optional): Timeout for monitored_barrier. + If ``None``, the default process group timeout will be used. + wait_all_ranks (bool, optional): Whether to collect all failed ranks or + not. By default, this is ``False`` and ``monitored_barrier`` on rank 0 + will throw on the first failed rank it encounters in order to fail + fast. By setting ``wait_all_ranks=True`` ``monitored_barrier`` will + collect all failed ranks and throw an error containing information + about all failed ranks. + + Returns: + ``None``. + + Example:: + >>> # xdoctest: +SKIP("need process group init") + >>> # Note: Process group initialization omitted on each rank. + >>> import torch.distributed as dist + >>> if dist.get_rank() != 1: + >>> dist.monitored_barrier() # Raises exception indicating that + >>> # rank 1 did not call into monitored_barrier. + >>> # Example with wait_all_ranks=True + >>> if dist.get_rank() == 0: + >>> dist.monitored_barrier(wait_all_ranks=True) # Raises exception + >>> # indicating that ranks 1, 2, ... world_size - 1 did not call into + >>> # monitored_barrier. + """ + # Need to call rank not in group before using the group, otherwise + # "Invalid process group" error is raised. + if _rank_not_in_group(group): + _warn_not_in_group("monitored_barrier") + return + + if get_backend(group) != Backend.GLOO: + raise ValueError("monitored_barrier is only implemented for GLOO backend.") + + if timeout is None: + timeout = _get_default_timeout(get_backend(group)) + elif isinstance(timeout, float): + # TODO(whc) aparently some existing test case for monitored_barrier passes in a timeout in float format? + warnings.warn( + "Please specify timeout arg as a timedelta. " + f"Converting current value of {timeout} assuming it represents seconds", + ) + timeout = timedelta(seconds=timeout) + + _check_valid_timeout(timeout) + + group_to_use = _get_default_group() if group is None else group + return group_to_use.monitored_barrier(timeout, wait_all_ranks=wait_all_ranks) + + +def _create_process_group_wrapper( + wrapped_pg: torch._C._distributed_c10d.Backend, + store_prefix: str, + store: Store, + rank: int, + world_size: int, + timeout: timedelta = default_pg_timeout, +): + assert _GLOO_AVAILABLE, "ProcessGroupWrapper unsupported without GLOO backend." + + # (whc) this appears to be just for the gloo backend? if so, `default_pg_timeout` is appropriate... + + # Create a separate prefix store for the helper process group. + prefix = f"{PG_WRAPPER_STORE_PREFIX}:{store_prefix}" + store = PrefixStore(prefix, store) + helper_pg = ProcessGroupGloo(store, rank, world_size, timeout=timeout) + # Wrap the underlying pg with ProcessGroupWrapper. + wrapped_pg = _ProcessGroupWrapper(wrapped_pg, helper_pg) + return wrapped_pg + +# helper function for deterministically hashing a list of ranks +def _hash_ranks(ranks: List[int]): + return hashlib.sha1(bytes("_".join(map(str, ranks)), "utf-8")).hexdigest() + +# Takes a list of ranks and computes an integer color +def _process_group_color(ranks: List[int]) -> int: + # Convert our hash to an int, but avoid negative numbers by shifting a bit. + return int(_hash_ranks(ranks), 16) % (sys.maxsize >> 1) + +def _process_group_name(ranks, use_hashed_name): + global _world + if use_hashed_name: + pg_name = _hash_ranks(ranks) + while pg_name in _world.pg_names.values(): + pg_name = hashlib.sha1(bytes(pg_name + "_", "utf-8")).hexdigest() + else: + pg_name = str(_world.group_count) + _world.group_count += 1 + return pg_name + +def _get_backend_from_str(backend: Optional[str] = None) -> Backend: + # Default to the same backend as the global process group + # if backend is not specified. + if not backend: + backend = get_backend(_get_default_group()) + return Backend(backend) + + +@_time_logger +def new_group(ranks=None, timeout=None, backend=None, pg_options=None, use_local_synchronization=False, group_desc=None): + """ + Create a new distributed group. + + This function requires that all processes in the main group (i.e. all + processes that are part of the distributed job) enter this function, even + if they are not going to be members of the group. Additionally, groups + should be created in the same order in all processes. + + .. warning:: + Using multiple process groups with the ``NCCL`` backend concurrently + is not safe and the user should perform explicit synchronization in + their application to ensure only one process group is used at a time. + This means collectives from one process group should have completed + execution on the device (not just enqueued since CUDA execution is + async) before collectives from another process group are enqueued. + See `Using multiple NCCL communicators concurrently `_ for more details. + + Args: + ranks (list[int]): List of ranks of group members. If ``None``, will be + set to all ranks. Default is ``None``. + timeout (timedelta, optional): see `init_process_group` for details and default value. + backend (str or Backend, optional): The backend to use. Depending on + build-time configurations, valid values are ``gloo`` and ``nccl``. + By default uses the same backend as the global group. This field + should be given as a lowercase string (e.g., ``"gloo"``), which can + also be accessed via :class:`Backend` attributes (e.g., + ``Backend.GLOO``). If ``None`` is passed in, the backend + corresponding to the default process group will be used. Default is + ``None``. + pg_options (ProcessGroupOptions, optional): process group options + specifying what additional options need to be passed in during + the construction of specific process groups. i.e. for the ``nccl`` + backend, ``is_high_priority_stream`` can be specified so that + process group can pick up high priority cuda streams. + use_local_synchronization (bool, optional): perform a group-local + barrier at the end of the process group creation. This is different + in that non-member ranks don't need to call into API and don't + join the barrier. + group_desc (str, optional): a string to describe the process group. + + Returns: + A handle of distributed group that can be given to collective calls or + GroupMember.NON_GROUP_MEMBER if the rank is not part of ``ranks``. + + N.B. use_local_synchronization doesn't work with MPI. + + N.B. While use_local_synchronization=True can be significantly faster with larger + clusters and small process groups, care must be taken since it changes cluster behavior + as non-member ranks don't join the group barrier(). + + N.B. use_local_synchronization=True can lead to deadlocks when each rank creates + multiple overlaping process groups. To avoid that, make sure all ranks follow the + same global creation order. + """ + return _new_group_with_tag( + ranks, + timeout, + backend, + pg_options, + None, + use_local_synchronization=use_local_synchronization, + group_desc=group_desc, + ) + +def _new_group_with_tag( + ranks=None, + timeout=None, + backend=None, + pg_options=None, + pg_tag=None, + use_local_synchronization=False, + group_desc=None +): + """ + Variant of ``new_group`` that exposes tag creation. + + :: N.B. The mechanism is experimental and tied to the functional collectives effort, see + ``torch.distributed._functional_collectives`` for reference on how to use it. + """ + global _world + + default_pg = _get_default_group() + default_backend, default_store = _world.pg_map[default_pg] + global_rank = default_pg.rank() + global_world_size = default_pg.size() + + + # Default to the same backend as the global process group + # if the backend is not specified. + if not backend: + backend = default_backend + backend = Backend(backend) + + # this timeout defaulting/validation is used for all the new_groups/new_subgroups variants, + # which may just pass their timeout value (or None) + if timeout is None: + timeout = _get_default_timeout(backend) + _check_valid_timeout(timeout) + + if use_local_synchronization: + # MPI backend doesn't have have a way for us to perform a partial sync + if backend == Backend.MPI: + raise ValueError("MPI backend doesn't support use_local_synchronization=True") + if ranks is not None and get_rank() not in ranks: + return None + + # checks the input ranks + if ranks is not None: + ranks = sorted(ranks) + group_world_size = len(ranks) + if group_world_size > global_world_size: + raise ValueError( + "the new group's world size should be less or " + "equal to the world size set by " + "init_process_group" + ) + # check ranks' sanity + for rank in ranks: + if rank < 0 or rank >= global_world_size: + raise ValueError( + "The new group's rank should be within " + "the world_size set by init_process_group" + ) + if global_rank in ranks: + group_rank = ranks.index(global_rank) + else: + group_rank = None + else: + ranks = list(range(global_world_size)) + group_world_size = global_world_size + group_rank = global_rank + + group_name = _process_group_name(ranks, use_hashed_name=use_local_synchronization) + + pg, pg_store = _new_process_group_helper( + group_world_size, + group_rank, + ranks, + backend, + default_store, + group_name, + pg_options=pg_options, + timeout=timeout, + pg_tag=pg_tag, + group_desc=group_desc + ) + + # Create the global rank to group rank mapping + _world.pg_group_ranks[pg] = { + global_rank: group_rank for group_rank, global_rank in enumerate(ranks) + } + + if _is_barrier_after_init() == 1: + # barrier at the end to ensure that once we return from this method, all + # process groups including global variables (if any) are updated + # correctly on all ranks. + # Update 04/2023: for large-scale runs, this barrier (esp. store-based + # barrier) may be costly and/or unscalable. Also, in a lot of cases, + # these barriers may be unnecessary, as proven by a green CI after + # removal. An environment variable `TORCH_DIST_INIT_BARRIER` has been + # added which enables this barrier only when set to 1. + logger.info( + "Performing barrier after ProcessGroup initialization since " + "TORCH_DIST_INIT_BARRIER = 1" + ) + if backend == Backend.MPI: + # MPI doesn't have store. + barrier() + else: + barrier_store = pg_store if use_local_synchronization else default_store + world_size = len(ranks) if use_local_synchronization else get_world_size() + # Use store based barrier here since barrier() used a bunch of + # default devices and messes up NCCL internal state. + _store_based_barrier(global_rank, barrier_store, group_name, world_size, timeout) + + return pg + + +def new_subgroups( + group_size=None, + group=None, + timeout=None, + backend=None, + pg_options=None, + group_desc=None, +): + """ + Create subgroups of equal size. + + By default, it creates intra-machine subgroups, + where each of which contains all the ranks of a machine, based on the assumption + that each machine has the same number of devices. + + This is a convenience API that calls ``new_group`` to generate multiple subgroups. + It requires that all processes in the main group (i.e. all + processes that are part of the distributed job) enter this function, even + if they are not going to be members of the group. + + .. warning:: + If ``group_size`` is passed in, the world size must be divisible by ``group_size``. + If no ``group_size`` is passed in, it believe that you are creating a group based + on CUDA and determining the group size by number of CUDA devices, and if not all + the machines have the same number of devices, the subgroup division will be + different across nodes and can cause unexpected behaviors. Therefore, if you are + creating a subgroup that does not depend on CUDA (such as Gloo on CPU), please + pass in ``group_size`` correctly. + + .. warning:: + Using multiple process groups with the ``NCCL`` backend concurrently + is not safe and the user should perform explicit synchronization in + their application to ensure only one process group is used at a time. + This means collectives from one process group should have completed + execution on the device (not just enqueued since CUDA execution is + async) before collectives from another process group are enqueued. + See `Using multiple NCCL communicators concurrently `_ for more details. + + Args: + group_size (int, optional): The size of each subgroup. If ``None``, + the default subgroup size is equal to the number of devices on each machine, + based on the assumption that each machine has exactly the same + number of devices. Default is ``None``. + timeout (timedelta, optional): see `init_process_group` for details and default value. + backend (str or Backend, optional): The backend to use. Depending on + build-time configurations, valid values are ``gloo`` and ``nccl``. + By default uses the same backend as the global group. This field + should be given as a lowercase string (e.g., ``"gloo"``), which can + also be accessed via :class:`Backend` attributes (e.g., + ``Backend.GLOO``). If ``None`` is passed in, the backend + corresponding to the default process group will be used. Default is + ``None``. + pg_options (ProcessGroupOptions, optional): process group options + specifying what additional options need to be passed in during + the construction of specific process groups. i.e. for the ``nccl`` + backend, ``is_high_priority_stream`` can be specified so that + process group can pick up high priority cuda streams. + group_desc (str, optional): A string describing the group. Each subgroup will + inherit its group_desc + + Returns: + The subgroup containing the current rank, and all the subgroups used for cleanup. + + Examples: + >>> # Create intra-machine subgroups. + >>> # xdoctest: +SKIP("need process group init") + >>> cur_subgroup, subgroups = dist.new_subgroups() + >>> # Allreduce within the machine. + >>> rank = dist.get_rank() + >>> tensor = torch.ones(1, device=rank) * rank + >>> dist.all_reduce(tensor, group=cur_subgroup) + >>> tensor + tensor([28]) # Assume 8 CUDA devices per machine. 28 is sum(range(8)). + >>> # Cleanup. + >>> for subgroup in subgroups: + >>> dist.destroy_process_group(subgroup) + """ + if group_size is None: + if not torch.cuda.is_available(): + raise ValueError("Default group size only takes effect when CUDA is available." + "If your subgroup using a backend that does not depend on CUDA," + "please pass in 'group_size' correctly.") + group_size = torch.cuda.device_count() + if group_size <= 0: + raise ValueError(f"The arg 'group_size' ({group_size}) must be positive") + + world_size = get_world_size() + if world_size < group_size: + raise ValueError(f"The arg 'group_size' ({group_size}) must not exceed the world size ({world_size})") + if world_size % group_size != 0: + raise ValueError("The world size must be divisible by 'group_size'") + + subgroups = [] + cur_subgroup = None + + for subgroup_id in range(world_size // group_size): + start_rank = subgroup_id * group_size + end_rank = start_rank + group_size + ranks_in_subgroup = list(range(start_rank, end_rank)) + subgroup = new_group( + ranks=ranks_in_subgroup, + timeout=timeout, + backend=backend, + pg_options=pg_options, + group_desc=group_desc, + ) + subgroups.append(subgroup) + + rank = get_rank() + if rank in ranks_in_subgroup: + cur_subgroup = subgroup + logger.info( + "Rank %s is assigned to subgroup %s", + rank, ranks_in_subgroup + ) + + return cur_subgroup, subgroups + + +def new_subgroups_by_enumeration( + ranks_per_subgroup_list, + timeout=None, + backend=None, + pg_options=None, + group_desc=None, +): + """ + Create subgroups by dividing the global world. + + The division is specified by a nested list of ranks. The subgroups cannot have + overlap, and some ranks may not have to be in any subgroup. + + This is a convenience API that calls ``new_group`` to generate multiple subgroups. + It requires that all processes in the main group (i.e. all + processes that are part of the distributed job) enter this function, even + if they are not going to be members of the group. + + .. warning:: + Using multiple process groups with the ``NCCL`` backend concurrently + is not safe and the user should perform explicit synchronization in + their application to ensure only one process group is used at a time. + This means collectives from one process group should have completed + execution on the device (not just enqueued since CUDA execution is + async) before collectives from another process group are enqueued. + See `Using multiple NCCL communicators concurrently `_ for more details. + + Args: + ranks_per_subgroup_list (list[list[int]]): A nested list of ranks of + group members. + timeout (timedelta, optional): see `init_process_group` for details and default value. + backend (str or Backend, optional): The backend to use. Depending on + build-time configurations, valid values are ``gloo`` and ``nccl``. + By default uses the same backend as the global group. This field + should be given as a lowercase string (e.g., ``"gloo"``), which can + also be accessed via :class:`Backend` attributes (e.g., + ``Backend.GLOO``). If ``None`` is passed in, the backend + corresponding to the default process group will be used. Default is + ``None``. + pg_options (ProcessGroupOptions, optional): process group options + specifying what additional options need to be passed in during + the construction of specific process groups. i.e. for the ``nccl`` + backend, ``is_high_priority_stream`` can be specified so that + process group can pick up high priority cuda streams. + group_desc (str, optional): A string describing the group. Each subgroup will + inherit its group_desc. + + Returns: + The subgroup containing the current rank, and all the subgroups used for cleanup. + + Examples: + >>> # Create two subgroups, where each has 2 processes. + >>> # xdoctest: +SKIP("need process group init") + >>> cur_subgroup, subgroups = dist.new_subgroups(ranks=[[0, 2], [1, 3]]) + >>> rank = dist.get_rank() + >>> tensor = torch.ones(1, device=rank) * rank + >>> dist.all_reduce(tensor, group=cur_subgroup) + >>> tensor + tensor([2]) # Subgroup 0: ranks 0 and 2 + tensor([4]) # Subgroup 1: ranks 1 and 3 + """ + if ranks_per_subgroup_list is None or len(ranks_per_subgroup_list) == 0: + raise ValueError("The arg 'ranks_per_subgroup_list' cannot be empty") + + subgroups = [] + cur_subgroup = None + # Create a mapping from rank to subgroup to check if there is any subgroup overlap. + rank_to_ranks_dict = {} # type: ignore[var-annotated] + for ranks in ranks_per_subgroup_list: + subgroup = new_group( + ranks=ranks, + timeout=timeout, + backend=backend, + pg_options=pg_options, + group_desc=group_desc, + ) + subgroups.append(subgroup) + my_rank = get_rank() + for rank in ranks: + if rank in rank_to_ranks_dict: + raise ValueError( + f"Rank {rank} has appeared in both subgroup {rank_to_ranks_dict[rank]} and {ranks}" + ) + rank_to_ranks_dict[rank] = ranks + if my_rank == rank: + cur_subgroup = subgroup + logger.info("Rank %s is assigned to subgroup %s", rank, ranks) + + return cur_subgroup, subgroups + + +def _find_pg_by_ranks_and_tag(tag: str, ranks: List[int]) -> Optional[ProcessGroup]: + if len(tag) > 0 and not tag.startswith("ptd:") and not tag.startswith("user:"): + tag = f"user:{tag}" + + for group in _world.tags_to_pg.get(tag, []): + if group.size() != len(ranks): + continue + + group_ranks = get_process_group_ranks(group) + good = all(r in group_ranks for r in ranks) + if good: + return group + return None + +def _find_or_create_pg_by_ranks_and_tag(tag: str, ranks: List[int], stride: int) -> ProcessGroup: + assert len(ranks) % stride == 0, f"Ranks length ({len(ranks)}) must be divisible by stride ({stride})" + + my_rank = get_rank() + my_ranks = None + + if stride == len(ranks): + my_ranks = ranks.copy() + assert my_rank in my_ranks, "rankset doesn't include the current node" + else: + for i in range(0, len(ranks), stride): + rank_set = ranks[i : i + stride] + if my_rank in rank_set: + my_ranks = rank_set + assert my_ranks is not None, "rankset doesn't include the current node" + + my_ranks.sort() + + pg = _find_pg_by_ranks_and_tag(tag, my_ranks) + if pg is not None: + return pg + if tag == "": + raise ValueError("Cannot automatically create PG with empty tag") + # TODO copy settings and timeout from default PG + return _new_group_with_tag(my_ranks, pg_tag=tag) + +def _get_group_tag(pg: ProcessGroup) -> str: + """Return the tag associated with ``pg``.""" + tag = _world.pg_to_tag[pg] + if tag.startswith("user:"): + tag = tag[5:] + return tag + +def _get_process_group_name(pg: ProcessGroup) -> str: + return _world.pg_names.get(pg, "None") + +def _get_process_group_store(pg: ProcessGroup) -> Store: + return _world.pg_map[pg][1] + +# This ops are not friendly to TorchDynamo. So, we decide to disallow these ops +# in FX graph, allowing them to run them on eager, with torch.compile. +dynamo_unsupported_distributed_c10d_ops = [ + recv, + all_gather_object, + all_gather_coalesced, + all_to_all_single, + all_reduce, + gather_object, + all_to_all, + all_reduce_coalesced, + gather, + send_object_list, + recv_object_list, + broadcast_object_list, + barrier, + scatter, + scatter_object_list, + reduce, + all_gather, + reduce_scatter, + all_gather_into_tensor, + broadcast, + reduce_scatter_tensor, + send, +]