pytorch/vision

Classification references does not work without distributed setup

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#6,529 opened on Sep 1, 2022

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bughelp wantedmodule: reference scripts

Description

If you don't set the respective env vars

https://github.com/pytorch/vision/blob/d5bd8b728f14c33b339fc45c90ca39be339bce3f/references/classification/utils.py#L255-L258

training will not be distributed and in turn the backend will not be initialized. However, during evaluation we check

https://github.com/pytorch/vision/blob/d5bd8b728f14c33b339fc45c90ca39be339bce3f/references/classification/train.py#L88

unguarded, which then fails with

RuntimeError: Default process group has not been initialized, please make sure to call init_process_group.

cc @datumbox

Contributor guide

Tech stack
pythonpytorch
Domain
machine learningbackend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic Pythonbasic PyTorchunderstanding of torch.distributed
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The issue is in PyTorch Vision's classification reference scripts. The bug occurs when distributed training env vars are not set, causing an unguarded `dist.*` call in `references/classification/train.py` line 88. The fix should add a check like `if dist.is available() and dist.is initialized()` before using distributed utilities. Also ensure that `utils.py` lines 255-258 properly guard the distributed initialization. See the linked lines in the issue for exact locations.