ray-project--ray
wehub-resource-sync
42 行
1.7 KiB
ReStructuredText
42 行
1.7 KiB
ReStructuredText
.. _unnecessary-ray-get:
|
|
|
|
Anti-pattern: Calling ray.get unnecessarily harms performance
|
|
=============================================================
|
|
|
|
**TLDR:** Avoid calling :func:`ray.get() <ray.get>` unnecessarily for intermediate steps. Work with object references directly, and only call ``ray.get()`` at the end to get the final result.
|
|
|
|
When ``ray.get()`` is called, objects must be transferred to the worker/node that calls ``ray.get()``. If you don't need to manipulate the object, you probably don't need to call ``ray.get()`` on it!
|
|
|
|
Typically, it’s best practice to wait as long as possible before calling ``ray.get()``, or even design your program to avoid having to call ``ray.get()`` at all.
|
|
|
|
Code example
|
|
------------
|
|
|
|
**Anti-pattern:**
|
|
|
|
.. literalinclude:: ../doc_code/anti_pattern_unnecessary_ray_get.py
|
|
:language: python
|
|
:start-after: __anti_pattern_start__
|
|
:end-before: __anti_pattern_end__
|
|
|
|
.. figure:: ../images/unnecessary-ray-get-anti.svg
|
|
|
|
**Better approach:**
|
|
|
|
.. literalinclude:: ../doc_code/anti_pattern_unnecessary_ray_get.py
|
|
:language: python
|
|
:start-after: __better_approach_start__
|
|
:end-before: __better_approach_end__
|
|
|
|
.. figure:: ../images/unnecessary-ray-get-better.svg
|
|
|
|
Notice in the anti-pattern example, we call ``ray.get()`` which forces us to transfer the large rollout to the driver, then again to the *reduce* worker.
|
|
|
|
In the fixed version, we only pass the reference to the object to the *reduce* task.
|
|
The ``reduce`` worker will implicitly call ``ray.get()`` to fetch the actual rollout data directly from the ``generate_rollout`` worker, avoiding the extra copy to the driver.
|
|
|
|
Other ``ray.get()`` related anti-patterns are:
|
|
|
|
- :doc:`ray-get-loop`
|
|
- :doc:`ray-get-submission-order`
|