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# Source code for torch.distributed.rpc.api

    __all__ = ["shutdown", "get_worker_info", "remote", "rpc_sync",
               "rpc_async", "RRef", "AllGatherStates", "method_factory", "new_method"]

    import collections
    import contextlib
    import functools
    import inspect
    import logging
    import threading
    from typing import Dict, Generic, TypeVar, Set, Any, TYPE_CHECKING

    import torch
    from torch.futures import Future

    from torch._C._distributed_rpc import (
        PyRRef,
        RemoteProfilerManager,
        WorkerInfo,
        TensorPipeAgent,
        get_rpc_timeout,
        _cleanup_python_rpc_handler,
        _delete_all_user_and_unforked_owner_rrefs,
        _destroy_rref_context,
        _get_current_rpc_agent,
        _invoke_remote_builtin,
        _invoke_remote_python_udf,
        _invoke_remote_torchscript,
        _invoke_rpc_builtin,
        _invoke_rpc_python_udf,
        _invoke_rpc_torchscript,
        _is_current_rpc_agent_set,
        _reset_current_rpc_agent,
        _set_and_start_rpc_agent,
    )

    from .internal import (
        PythonUDF,
        RPCExecMode,
        _internal_rpc_pickler,
        _build_rpc_profiling_key,
    )

    from .constants import DEFAULT_SHUTDOWN_TIMEOUT, UNSET_RPC_TIMEOUT

    from ._utils import _group_membership_management, _update_group_membership

    logger = logging.getLogger(__name__)

    # NB: Ignoring RRef leaks during shutdown. Without this, applications have to
    # make sure there is no references to any RRef in the application code and
    # Python GC has done its job to delete those RRefs. This is could result in bad
    # debugging experiences especially when for large applications. Therefore, by
    # default, we are going to ignore RRef leaks during shutdown. This is usually
    # fine as shutdown means applications have done training and no longer care
    # about states.
    #
    # To enable RRef leak checking, set this _ignore_rref_leak to False
    _ignore_rref_leak = True
    _default_pickler = _internal_rpc_pickler

    @contextlib.contextmanager
    def _use_rpc_pickler(rpc_pickler):
        r"""
        rpc_pickler: (.internal._InternalRPCPickler) Overrides the default RPC pickler
        """
        global _default_pickler
        _default_pickler = rpc_pickler
        try:
            yield
        finally:
            _default_pickler = _internal_rpc_pickler

    def _require_initialized(func):
        @functools.wraps(func)
        def wrapper(*args, **kwargs):
            if not _is_current_rpc_agent_set():
                raise RuntimeError(
                    "RPC has not been initialized. Call "
                    "torch.distributed.rpc.init_rpc first."
                )
            return func(*args, **kwargs)

        return wrapper

    class AllGatherStates:
        def __init__(self):
            # Each `gathered_objects` is an empty dict at beginning.
            # The leader worker is elected as the first worker in a sorted worker
            # name list. Whenever there is a worker entering `_all_gather()`, it
            # runs `_gather_to_leader()` on the leader to add its own name and
            # data obj to this dict. The leader also adds itself's name to the dict
            # on calling `_all_gather()`.
            # Once `set(gathered_objects.keys()) == _ALL_WORKER_NAMES`, the leader
            # will broadcast the gathered dict to all follower workers and set their
            # `gathered_objects` field and the `proceed_signal` field.
            self.gathered_objects = {}
            # All workers wait on this signal until it receives all gathered
            # objects.
            self.proceed_signal = threading.Event()

    # States used by `def _all_gather()`.
    # `_ALL_WORKER_NAMES` is initialized on initializing RPC layer.
    _ALL_WORKER_NAMES: Set[Any] = set()
    _all_gather_dict_lock = threading.RLock()
    _all_gather_sequence_id: Dict[str, int] = {}
    _all_gather_sequence_id_to_states: collections.defaultdict = collections.defaultdict(AllGatherStates)

    def _init_rpc_states(agent):
        worker_infos = agent.get_worker_infos()
        global _ALL_WORKER_NAMES
        _ALL_WORKER_NAMES = {worker_info.name for worker_info in worker_infos}

        # NB: backend implementation might have already set the rpc_agent.
        if not _is_current_rpc_agent_set():
            _set_and_start_rpc_agent(agent)

    def _gather_to_leader(sequence_id, worker_name, obj, worker_names=None):
        with _all_gather_dict_lock:
            if not worker_names:
                worker_names = _ALL_WORKER_NAMES
                assert (
                    worker_name in worker_names
                ), f"{worker_name} is not expected by leader."
            states = _all_gather_sequence_id_to_states[sequence_id]
            assert (
                worker_name not in states.gathered_objects
            ), f"{worker_name} reported intent sequence id {sequence_id} twice. "
            states.gathered_objects[worker_name] = obj
            if worker_names == set(states.gathered_objects.keys()):
                states.proceed_signal.set()

    def _broadcast_to_followers(sequence_id, objects_map):
        with _all_gather_dict_lock:
            states = _all_gather_sequence_id_to_states[sequence_id]

        assert (
            not states.proceed_signal.is_set()
        ), f"Termination signal sequence id {sequence_id} got set twice."
        states.gathered_objects = objects_map
        states.proceed_signal.set()

    _thread_local_var = threading.local()

    @contextlib.contextmanager
    def _wait_all():
        r"""
        A context manager that collects all futures returned by ``rpc_async`` and
        waits them on the context manager's exit; relieving the user of needing
        to explicitly call wait.

        Example::
            >>> # xdoctest: +SKIP("distributed")
            >>> # On worker 0:
            >>> import torch
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> with rpc._wait_all():
            >>>    fut_1 = rpc.rpc_async(dst, torch.add, (torch.ones(2, 2), 1))
            >>>    fut_2 = rpc.rpc_async(dst, torch.add, (torch.ones(2, 2), 1))
            >>> #fut_1 and fut_2 are waited on
        """
        _thread_local_var.future_list = []
        try:
            yield
        finally:
            try:
                torch.futures.wait_all(_thread_local_var.future_list)
            finally:
                del _thread_local_var.future_list

    @_require_initialized
    def _all_gather(obj, worker_names=None, timeout: float = UNSET_RPC_TIMEOUT):
        r"""
        This is similar to torch.distributed.all_gather(), but is using RPC. It
        picks the worker with the smallest name (alphabetic order) as the leader.
        Then all followers send their data ``obj`` to the leader. After the leader
        has received all, it will broadcast the results back to all followers. This
        function blocks until all workers have received the gathered results.
        """
        if not worker_names:
            assert (
                _ALL_WORKER_NAMES is not None
            ), "`_ALL_WORKER_NAMES` is not initialized for `def _all_gather`."
            worker_names = _ALL_WORKER_NAMES
        leader_name = min(worker_names)

        self_name = _get_current_rpc_agent().get_worker_info().name

        with _all_gather_dict_lock:
            concat_names = "".join(sorted(worker_names))
            sequence_num = _all_gather_sequence_id.get(concat_names, 0)
            _all_gather_sequence_id[concat_names] = sequence_num + 1
            sequence_id = concat_names + str(sequence_num)

        is_leader = leader_name == self_name

        if timeout == UNSET_RPC_TIMEOUT:
            # Timeout is specified by agent for RPC calls
            rpc_timeout = get_rpc_timeout()
            # No timeout for signal
            signal_timeout = None
        elif timeout == DEFAULT_SHUTDOWN_TIMEOUT:
            # No timeout for RPC
            rpc_timeout = timeout
            # No timeout for signal
            signal_timeout = None
        else:
            # Signal and RPC timeout use the same timeout
            signal_timeout = rpc_timeout = timeout

        # Phase 1: Followers send it's object to the leader
        if is_leader:
            _gather_to_leader(sequence_id, self_name, obj, worker_names)
        else:
            rpc_sync(
                leader_name,
                _gather_to_leader,
                args=(sequence_id, self_name, obj, worker_names),
                timeout=rpc_timeout,
            )

        with _all_gather_dict_lock:
            states = _all_gather_sequence_id_to_states[sequence_id]

        # Timeout is either set by function parameter or None (which is indefinite)
        states.proceed_signal.wait(timeout=signal_timeout)

        # Phase 2: Leader broadcast gathered results to all followers
        # Leader's signal is the first to be unblocked, after receiving all
        # followers' data objects.
        if is_leader:
            worker_name_to_response_future_dict = {}
            for follower_name in worker_names - {leader_name}:
                fut = rpc_async(
                    follower_name,
                    _broadcast_to_followers,
                    args=(sequence_id, states.gathered_objects),
                    timeout=rpc_timeout
                )
                worker_name_to_response_future_dict[follower_name] = fut

            errors = []
            for follower_name, fut in worker_name_to_response_future_dict.items():
                try:
                    fut.wait()
                except RuntimeError as ex:
                    errors.append((follower_name, ex))

            if errors:
                raise RuntimeError(
                    f"Followers {[e[0] for e in errors]} timed out in _all_gather "
                    f"after {rpc_timeout:.2f} seconds. The first exception is {errors[0][1]}"
                )

        # Clean up for the states using the sequence_id
        with _all_gather_dict_lock:
            states = _all_gather_sequence_id_to_states.pop(sequence_id)
        return states.gathered_objects

    @_require_initialized
    def _barrier(worker_names):
        r"""
        Synchronizes local and remote RPC processes.

        This will block until all local and remote RPC processes specified under worker_names
        reach this method to wait for all outstanding work to complete.

        Args:
            worker_names (List[str]): The set of workers to synchronize.

        """
        try:
            _all_gather(None, set(worker_names))
        except RuntimeError as ex:
            logger.error(
                "Failed to complete barrier, got error %s", ex
            )

    @_require_initialized
    def _wait_all_workers(timeout=DEFAULT_SHUTDOWN_TIMEOUT):
        r"""
        Block until all local and remote RPC processes reach this method and wait
        for all outstanding work to complete. Every RPC process must call this
        method before exit to perform a graceful shutdown. This should be used to
        terminate the RPC framework, and there is no guarantee that the RPC
        framework will work after this method returns.
        """
        try:
            _all_gather(None, timeout=timeout)
        except RuntimeError as ex:
            logger.error(
                "Failed to respond to 'Shutdown Proceed' in time, got error %s", ex
            )
            raise ex

    @_require_initialized
    def shutdown(graceful=True, timeout=DEFAULT_SHUTDOWN_TIMEOUT):
        r"""
        Perform a shutdown of the RPC agent, and then destroy the RPC agent. This
        stops the local agent from accepting outstanding requests, and shuts
        down the RPC framework by terminating all RPC threads. If ``graceful=True``,
        this will block until all local and remote RPC processes reach this method
        and wait for all outstanding work to complete. Otherwise, if
        ``graceful=False``, this is a local shutdown, and it does not wait for other
        RPC processes to reach this method.

        .. warning::
            For :class:`~torch.futures.Future` objects returned by
            :meth:`~torch.distributed.rpc.rpc_async`, ``future.wait()`` should not
            be called after ``shutdown()``.

        Args:
            graceful (bool): Whether to do a graceful shutdown or not. If True,
                             this will 1) wait until there is no pending system
                             messages for ``UserRRefs`` and delete them; 2) block
                             until all local and remote RPC processes have reached
                             this method and wait for all outstanding work to
                             complete.

        Example::
            Make sure that ``MASTER_ADDR`` and ``MASTER_PORT`` are set properly
            on both workers. Refer to :meth:`~torch.distributed.init_process_group`
            API for more details. For example,

            export MASTER_ADDR=localhost
            export MASTER_PORT=5678

            Then run the following code in two different processes:

            >>> # xdoctest: +SKIP
            >>> # On worker 0:
            >>> import torch
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> # do some work
            >>> result = rpc.rpc_sync("worker1", torch.add, args=(torch.ones(1), 1))
            >>> # ready to shutdown
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> # wait for worker 0 to finish work, and then shutdown.
            >>> rpc.shutdown()
        """
        if graceful:
            try:
                agent = _get_current_rpc_agent()
                if not isinstance(agent, TensorPipeAgent) or agent.is_static_group:
                    _wait_all_workers(timeout)
                    _delete_all_user_and_unforked_owner_rrefs()
                    agent.join(shutdown=True, timeout=timeout)
                else:
                    # This is a dynamic group so we need to grab the token for the operation
                    my_worker_info = agent.get_worker_info()
                    my_name = my_worker_info.name
                    with _group_membership_management(agent.store, my_name, False):
                        all_worker_infos = agent.get_worker_infos()
                        for worker in all_worker_infos:
                            if worker.name != my_name:
                                rpc_sync(worker.name, _update_group_membership, args=(my_worker_info, [], {}, False))
                        agent.join(shutdown=True, timeout=timeout)
            finally:
                # In case of errors, continue to complete the local shutdown.
                _finalize_shutdown()
        else:
            _finalize_shutdown()

    def _finalize_shutdown():
        try:
            # This raises a `TORCH_CHECK()` exception on RRef leak detected.
            _destroy_rref_context(_ignore_rref_leak)
        finally:
            _get_current_rpc_agent().shutdown()
            # clean up python rpc handler in shutdown(), see comments in
            # PythonRpcHandler::cleanup(), call it in python API because the
            # cleanup() function has python dependency, it assumes python
            # interpreter exists.
            # No matter if RRef leak exception is raised, this clean-up code
            # must run to avoid destruction segfault in Python 3.5.
            #
            # future.wait() should not be called after shutdown().
            # pythonRpcHandler is cleaned up in shutdown(), after
            # shutdown(), python objects returned from rpc python call can not be
            # resolved.
            _cleanup_python_rpc_handler()
            _reset_current_rpc_agent()

    @_require_initialized
    def get_worker_info(worker_name=None):
        r"""
        Get :class:`~torch.distributed.rpc.WorkerInfo` of a given worker name.
        Use this :class:`~torch.distributed.rpc.WorkerInfo` to avoid passing an
        expensive string on every invocation.

        Args:
            worker_name (str): the string name of a worker. If ``None``, return the
                               the id of the current worker. (default ``None``)

        Returns:
            :class:`~torch.distributed.rpc.WorkerInfo` instance for the given
            ``worker_name`` or :class:`~torch.distributed.rpc.WorkerInfo` of the
            current worker if ``worker_name`` is ``None``.
        """
        if worker_name is not None:
            return _get_current_rpc_agent().get_worker_info(worker_name)
        else:
            return _get_current_rpc_agent().get_worker_info()

    def _to_worker_info(to):
        if isinstance(to, WorkerInfo):
            return to
        elif isinstance(to, (str, int)):
            return get_worker_info(to)
        else:
            raise ValueError(f"Cannot get WorkerInfo from name {to}")

    def _rref_typeof_on_owner(rref, blocking: bool = True):
        rref_type = type(rref.local_value())
        if blocking:
            return rref_type
        else:
            # Wrap result into a completed Future. This is so that if blocking=`False`
            # is specified, we return a future regardless of if this call is on user
            # or owner.
            future = Future[type]()
            future.set_result(rref_type)
            return future

    def _rref_typeof_on_user(rref, timeout: float = UNSET_RPC_TIMEOUT, blocking: bool = True):
        fut = rpc_async(
            rref.owner(),
            _rref_typeof_on_owner,
            args=(rref,),
            timeout=timeout
        )
        if blocking:
            return fut.wait()
        else:
            return fut

    T = TypeVar("T")
    GenericWithOneTypeVar = Generic[T]

    if TYPE_CHECKING:
        class RRef(PyRRef[T], Generic[T]):
            pass
    else:
        try:
            # Combine the implementation class and the type class.
            class RRef(PyRRef, Generic[T]):
                pass
        except TypeError:
            # TypeError: metaclass conflict: the metaclass of a derived class
            # must be a (non-strict) subclass of the metaclasses of all its bases
            # Mypy doesn't understand __class__ (mypy bug #4177)
            class RRefMeta(PyRRef.__class__, GenericWithOneTypeVar.__class__):  # type: ignore[name-defined, misc, valid-type]
                pass

            # Combine the implementation class and the type class.
            # Types for classes expecting a certain generic parameter (mypy bug #7791)
            class RRef(PyRRef, GenericWithOneTypeVar, metaclass=RRefMeta):  # type: ignore[misc, no-redef, valid-type]
                pass

    # Install docstrings from `PyRRef` to `RRef`.
    #
    # This is for the fact that pybind11 generates the parameter
    # `self` as type `rpc.PyRRef`, so a `:inherited-members:`
    # under `.. autoclass:: RRef` does not work.
    # we have to do the following process to replace `rpc.PyRRef` with `rpc.RRef`.
    #
    def method_factory(method_name, docstring):
        def method(self, *args, **kwargs):
            return getattr(super(RRef, self), method_name)(*args, **kwargs)

        if method.__doc__:
            method.__doc__ = docstring
        return method

    for method_name, method in inspect.getmembers(PyRRef):
        # Ignore magic methods, except "__str__".
        if method_name.startswith("_") and method_name != "__str__":
            continue

        # Get pybind11 generated docstring.
        # It's like,
        """
        to_here(self: torch.distributed.rpc.PyRRef, timeout: float=-1.0) -> object

            Blocking call that copies the value of the RRef from the owner
            to the local node and returns it. If the current node is the
            owner, returns a reference to the local value.
        """
        docstring = getattr(method, "__doc__", None)
        assert docstring is not None, "RRef user-facing methods should all have docstrings."

        # Do surgery on pybind11 generated docstrings.
        docstring = docstring.replace("torch.distributed.rpc.PyRRef", "torch.distributed.rpc.RRef")

        # Attach user-facing RRef method with modified docstring.
        new_method = method_factory(method_name, docstring)
        setattr(RRef, method_name, new_method)

    @_require_initialized
    def remote(to, func, args=None, kwargs=None, timeout=UNSET_RPC_TIMEOUT):
        r"""
        Make a remote call to run ``func`` on worker ``to`` and return an
        :class:`~torch.distributed.rpc.RRef` to the result value immediately.
        Worker ``to`` will be the owner of the returned
        :class:`~torch.distributed.rpc.RRef`, and the worker calling ``remote`` is
        a user. The owner manages the global reference count of its
        :class:`~torch.distributed.rpc.RRef`, and the owner
        :class:`~torch.distributed.rpc.RRef` is only destructed when globally there
        are no living references to it.

        Args:
            to (str or WorkerInfo or int): name/rank/``WorkerInfo`` of the destination worker.
            func (Callable): a callable function, such as Python callables, builtin
                             operators (e.g. :meth:`~torch.add`) and annotated
                             TorchScript functions.
            args (tuple): the argument tuple for the ``func`` invocation.
            kwargs (dict): is a dictionary of keyword arguments for the ``func``
                           invocation.

            timeout (float, optional): timeout in seconds for this remote call. If the
                                       creation of this
                                       :class:`~torch.distributed.rpc.RRef` on worker
                                       ``to`` is not successfully processed on this
                                       worker within this timeout, then the next time
                                       there is an attempt to use the RRef (such as
                                       ``to_here()``), a timeout will be raised
                                       indicating this failure. A value of 0 indicates
                                       an infinite timeout, i.e. a timeout error will
                                       never be raised. If not provided, the default
                                       value set during initialization or with
                                       ``_set_rpc_timeout`` is used.

        Returns:
            A user :class:`~torch.distributed.rpc.RRef` instance to the result
            value. Use the blocking API :meth:`torch.distributed.rpc.RRef.to_here`
            to retrieve the result value locally.

        .. warning ::
            The ``remote`` API does not copy storages of argument tensors until
            sending them over the wire, which could be done by a different thread
            depending on the RPC backend type. The caller should make sure that the
            contents of those tensors stay intact until the returned RRef is
            confirmed by the owner, which can be checked using the
            :meth:`torch.distributed.rpc.RRef.confirmed_by_owner` API.

        .. warning ::
            Errors such as timeouts for the ``remote`` API are handled on a
            best-effort basis. This means that when remote calls initiated by
            ``remote`` fail, such as with a timeout error, we take a best-effort
            approach to error handling. This means that errors are handled and set
            on the resulting RRef on an asynchronous basis. If the RRef has not been
            used by the application before this handling (such as ``to_here`` or
            fork call), then future uses of the ``RRef`` will appropriately raise
            errors. However, it is possible that the user application will use the
            ``RRef`` before the errors are handled. In this case, errors may not be
            raised as they have not yet been handled.

        Example::

            Make sure that ``MASTER_ADDR`` and ``MASTER_PORT`` are set properly
            on both workers. Refer to :meth:`~torch.distributed.init_process_group`
            API for more details. For example,

            export MASTER_ADDR=localhost
            export MASTER_PORT=5678

            Then run the following code in two different processes:

            >>> # xdoctest: +SKIP
            >>> # On worker 0:
            >>> import torch
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> rref1 = rpc.remote("worker1", torch.add, args=(torch.ones(2), 3))
            >>> rref2 = rpc.remote("worker1", torch.add, args=(torch.ones(2), 1))
            >>> x = rref1.to_here() + rref2.to_here()
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()

            Below is an example of running a TorchScript function using RPC.

            >>> # On both workers:
            >>> @torch.jit.script
            >>> def my_script_add(t1, t2):
            >>>    return torch.add(t1, t2)

            >>> # On worker 0:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> rref = rpc.remote("worker1", my_script_add, args=(torch.ones(2), 3))
            >>> rref.to_here()
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()
        """
        torch._C._log_api_usage_once("torch.distributed.rpc_remote")
        qualified_name = torch.jit._builtins._find_builtin(func)
        dst_worker_info = _to_worker_info(to)
        should_profile = _get_should_profile()

        ctx_manager = _enable_rpc_profiler(should_profile, qualified_name, func, RPCExecMode.REMOTE, dst_worker_info)

        with ctx_manager as rf:
            args = args if args else ()
            kwargs = kwargs if kwargs else {}

            is_async_exec = hasattr(func, "_wrapped_async_rpc_function")

            if is_async_exec:
                wrapped = func._wrapped_async_rpc_function
                if isinstance(wrapped, torch.jit.ScriptFunction):
                    func = wrapped

            if qualified_name is not None:
                rref = _invoke_remote_builtin(dst_worker_info, qualified_name, timeout, *args, **kwargs)
            elif isinstance(func, torch.jit.ScriptFunction):
                rref = _invoke_remote_torchscript(
                    dst_worker_info.name,
                    torch._jit_internal._qualified_name(func),
                    timeout,
                    is_async_exec,
                    *args,
                    **kwargs,
                )
            else:
                (pickled_python_udf, tensors) = _default_pickler.serialize(
                    PythonUDF(func, args, kwargs)
                )
                rref = _invoke_remote_python_udf(
                    dst_worker_info,
                    pickled_python_udf,
                    tensors,
                    timeout,
                    is_async_exec
                )
            # attach profiling information
            if should_profile:
                assert torch.autograd._profiler_enabled()
                assert rf is not None
                fut = rf._call_end_callbacks_on_future(rref._get_future())
                rref._set_profiling_future(fut)

        return rref

    def _invoke_rpc(to, func, rpc_type, args=None, kwargs=None, rpc_timeout: float = UNSET_RPC_TIMEOUT):
        if not callable(func):
            raise TypeError("function should be callable.")

        qualified_name = torch.jit._builtins._find_builtin(func)
        dst_worker_info = _to_worker_info(to)

        should_profile = _get_should_profile()

        ctx_manager = _enable_rpc_profiler(should_profile, qualified_name, func, rpc_type, dst_worker_info)

        with ctx_manager as rf:
            args = args if args else ()
            kwargs = kwargs if kwargs else {}

            is_async_exec = hasattr(func, "_wrapped_async_rpc_function")

            if is_async_exec:
                wrapped = func._wrapped_async_rpc_function
                if isinstance(wrapped, torch.jit.ScriptFunction):
                    func = wrapped

            if qualified_name is not None:
                fut = _invoke_rpc_builtin(
                    dst_worker_info,
                    qualified_name,
                    rpc_timeout,
                    *args,
                    **kwargs
                )
            elif isinstance(func, torch.jit.ScriptFunction):
                fut = _invoke_rpc_torchscript(
                    dst_worker_info.name,
                    torch._jit_internal._qualified_name(func),
                    args,
                    kwargs,
                    rpc_timeout,
                    is_async_exec
                )
            else:
                (pickled_python_udf, tensors) = _default_pickler.serialize(
                    PythonUDF(func, args, kwargs)
                )
                fut = _invoke_rpc_python_udf(
                    dst_worker_info,
                    pickled_python_udf,
                    tensors,
                    rpc_timeout,
                    is_async_exec
                )
            if should_profile:
                assert torch.autograd._profiler_enabled()
                assert rf is not None
                # Schedule profiling callbacks to run when the future completes.
                # This returns a future that is completed when the original future
                # completes and the profiling callbacks have been completed as well,
                # to guarantee that fut.wait() completes the profiling. This new
                # future will contain the same value as the original future.
                fut = rf._call_end_callbacks_on_future(fut)
        return fut

    @_require_initialized
    def rpc_sync(to, func, args=None, kwargs=None, timeout: float = UNSET_RPC_TIMEOUT):
        r"""
        Make a blocking RPC call to run function ``func`` on worker ``to``. RPC
        messages are sent and received in parallel to execution of Python code. This
        method is thread-safe.

        Args:
            to (str or WorkerInfo or int): name/rank/``WorkerInfo`` of the destination worker.
            func (Callable): a callable function, such as Python callables, builtin
                             operators (e.g. :meth:`~torch.add`) and annotated
                             TorchScript functions.
            args (tuple): the argument tuple for the ``func`` invocation.
            kwargs (dict): is a dictionary of keyword arguments for the ``func``
                           invocation.
            timeout (float, optional): timeout in seconds to use for this RPC. If
                                       the RPC does not complete in this amount of
                                       time, an exception indicating it has
                                       timed out will be raised. A value of 0
                                       indicates an infinite timeout, i.e. a timeout
                                       error will never be raised. If not provided,
                                       the default value set during initialization
                                       or with ``_set_rpc_timeout`` is used.

        Returns:
            Returns the result of running ``func`` with ``args`` and ``kwargs``.

        Example::
            Make sure that ``MASTER_ADDR`` and ``MASTER_PORT`` are set properly
            on both workers. Refer to :meth:`~torch.distributed.init_process_group`
            API for more details. For example,

            export MASTER_ADDR=localhost
            export MASTER_PORT=5678

            Then run the following code in two different processes:

            >>> # xdoctest: +SKIP
            >>> # On worker 0:
            >>> import torch
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> ret = rpc.rpc_sync("worker1", torch.add, args=(torch.ones(2), 3))
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()

            Below is an example of running a TorchScript function using RPC.

            >>> # On both workers:
            >>> @torch.jit.script
            >>> def my_script_add(t1, t2):
            >>>    return torch.add(t1, t2)

            >>> # On worker 0:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> ret = rpc.rpc_sync("worker1", my_script_add, args=(torch.ones(2), 3))
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()

        """
        torch._C._log_api_usage_once("torch.distributed.rpc_sync")
        fut = _invoke_rpc(to, func, RPCExecMode.SYNC, args, kwargs, timeout)
        return fut.wait()

    @_require_initialized
    def rpc_async(to, func, args=None, kwargs=None, timeout=UNSET_RPC_TIMEOUT):
        r"""
        Make a non-blocking RPC call to run function ``func`` on worker ``to``. RPC
        messages are sent and received in parallel to execution of Python code. This
        method is thread-safe. This method will immediately return a
        :class:`~torch.futures.Future` that can be awaited on.

        Args:
            to (str or WorkerInfo or int): name/rank/``WorkerInfo`` of the destination worker.
            func (Callable): a callable function, such as Python callables, builtin
                             operators (e.g. :meth:`~torch.add`) and annotated
                             TorchScript functions.
            args (tuple): the argument tuple for the ``func`` invocation.
            kwargs (dict): is a dictionary of keyword arguments for the ``func``
                           invocation.
            timeout (float, optional): timeout in seconds to use for this RPC. If
                                       the RPC does not complete in this amount of
                                       time, an exception indicating it has
                                       timed out will be raised. A value of 0
                                       indicates an infinite timeout, i.e. a timeout
                                       error will never be raised. If not provided,
                                       the default value set during initialization
                                       or with ``_set_rpc_timeout`` is used.

        Returns:
            Returns a :class:`~torch.futures.Future` object that can be waited
            on. When completed, the return value of ``func`` on ``args`` and
            ``kwargs`` can be retrieved from the :class:`~torch.futures.Future`
            object.

        .. warning ::
            Using GPU tensors as arguments or return values of ``func`` is not
            supported since we don't support sending GPU tensors over the wire. You
            need to explicitly copy GPU tensors to CPU before using them as
            arguments or return values of ``func``.

        .. warning ::
            The ``rpc_async`` API does not copy storages of argument tensors until
            sending them over the wire, which could be done by a different thread
            depending on the RPC backend type. The caller should make sure that the
            contents of those tensors stay intact until the returned
            :class:`~torch.futures.Future` completes.

        Example::
            Make sure that ``MASTER_ADDR`` and ``MASTER_PORT`` are set properly
            on both workers. Refer to :meth:`~torch.distributed.init_process_group`
            API for more details. For example,

            export MASTER_ADDR=localhost
            export MASTER_PORT=5678

            Then run the following code in two different processes:

            >>> # xdoctest: +SKIP
            >>> # On worker 0:
            >>> import torch
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> fut1 = rpc.rpc_async("worker1", torch.add, args=(torch.ones(2), 3))
            >>> fut2 = rpc.rpc_async("worker1", min, args=(1, 2))
            >>> result = fut1.wait() + fut2.wait()
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()

            Below is an example of running a TorchScript function using RPC.

            >>> # On both workers:
            >>> @torch.jit.script
            >>> def my_script_add(t1, t2):
            >>>    return torch.add(t1, t2)

            >>> # On worker 0:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker0", rank=0, world_size=2)
            >>> fut = rpc.rpc_async("worker1", my_script_add, args=(torch.ones(2), 3))
            >>> ret = fut.wait()
            >>> rpc.shutdown()

            >>> # On worker 1:
            >>> import torch.distributed.rpc as rpc
            >>> rpc.init_rpc("worker1", rank=1, world_size=2)
            >>> rpc.shutdown()
        """
        torch._C._log_api_usage_once("torch.distributed.rpc_async")
        fut = _invoke_rpc(to, func, RPCExecMode.ASYNC, args, kwargs, timeout)
        if hasattr(_thread_local_var, "future_list"):
            _thread_local_var.future_list.append(fut)
        return fut

    def _get_should_profile():
        # Legacy profiler should be enabled. RPC profiling is not supported with
        # Kineto profiler.
        ActiveProfilerType = torch._C._profiler.ActiveProfilerType
        return (
            torch.autograd._profiler_enabled() and
            torch._C._autograd._profiler_type() == ActiveProfilerType.LEGACY  # type: ignore[attr-defined]
        )

    def _enable_rpc_profiler(should_profile, qualified_name, func, rpc_type, dst_worker_info):
        ctx_manager = contextlib.nullcontext()

        if should_profile:
            # Create appropriate string representation based on type of func
            # (builtin, script, python)
            if qualified_name is None:
                func_name = (
                    torch._jit_internal._qualified_name(func)
                    if isinstance(func, torch.jit.ScriptFunction)
                    else func.__qualname__
                )
            else:
                func_name = qualified_name
            # Build RPC profiling key.
            rpc_profiling_key = _build_rpc_profiling_key(
                rpc_type,
                func_name,
                get_worker_info().name,
                dst_worker_info.name,
            )
            RemoteProfilerManager.set_current_profiling_key(rpc_profiling_key)
            # Mypy doesn't support re-def of a variable not in the same block (#1174)
            ctx_manager = torch.autograd.profiler.record_function(rpc_profiling_key)  # type: ignore[assignment]

        return ctx_manager

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