U
    d                      @   s   U d Z ddlmZmZmZ ddlZddlmZ ddlmZm	Z	 g Z
ee ed< i Zeeejef ef ed< ejeed	d
dZdS )z<Provides phony for arbitrary dependency in a autograd graph.    )DictListTupleN)Tensor   )default_stream
use_stream__all___phonies)devicerequires_gradreturnc                C   s^   | |f}zt | }W nD tk
rX   tt|  tjd| |d}W 5 Q R X |t |< Y nX |S )a  Gets a phony. Phony is tensor without space. It is useful to make
    arbitrary dependency in a autograd graph because it doesn't require any
    gradient accumulation.

    .. note::

        Phonies for each device are cached. If an autograd function gets a phony
        internally, the phony must be detached to be returned. Otherwise, the
        autograd engine will mutate the cached phony in-place::

            class Phonify(torch.autograd.Function):
                @staticmethod
                def forward(ctx, input):
                    phony = get_phony(input.device, requires_grad=False)
                    return phony.detach()  # detach() is necessary.

    r   )r   r   )r
   KeyErrorr   r   torchempty)r   r   keyZphony r   I/tmp/pip-unpacked-wheel-ua33x9lu/torch/distributed/pipeline/sync/phony.py	get_phony   s    r   )__doc__typingr   r   r   r   r   streamr   r   r	   str__annotations__r
   r   boolr   r   r   r   r   <module>   s   