Reduce number of worlds

[krammnic]

Context

What is the purpose of this PR? Is it to

• add a new feature
• fix a bug
• update tests and/or documentation
• Better engineering

Please link to any issues this PR addresses.

Changelog

What are the changes made in this PR?

• Call get_world_size_and_rank ONCE #2316

Test plan

Please make sure to do each of the following if applicable to your PR. If you're unsure about any one of these just ask and we will happily help. We also have a contributing page for some guidance on contributing.

• run pre-commit hooks and linters (make sure you've first installed via pre-commit install)
• add unit tests for any new functionality
• update docstrings for any new or updated methods or classes
• run unit tests via pytest tests
• run recipe tests via pytest tests -m integration_test
• manually run any new or modified recipes with sufficient proof of correctness
• include relevant commands and any other artifacts in this summary (pastes of loss curves, eval results, etc.)

UX

If your function changed a public API, please add a dummy example of what the user experience will look like when calling it.
Here is a docstring example
and a tutorial example

• I did not change any public API
• I have added an example to docs or docstrings

cc: @joecummings

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchtune/2391

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 1 New Failure, 2 Unrelated Failures

As of commit 3eb82c0 with merge base d5d85c5 ():

NEW FAILURE - The following job has failed:

• GPU tests / gpu_test (3.11, stable) (gh)
  tests/recipes/test_lora_finetune_distributed.py::TestLoRAFinetuneDistributedRecipe::test_save_and_load_merged_weights[llama3/8B_lora-llama3-tune-False]

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• GPU tests / gpu_test (3.10, stable) (gh) (trunk failure)
  ##[error]The operation was canceled.
• GPU tests / gpu_test (3.9, stable) (gh) (trunk failure)
  ##[error]The operation was canceled.

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[joecummings]

Missed one!

[krammnic]

Let me fix

[krammnic]

Was little bit busy, have dropped a fix

[joecummings]

Try again ;)