v2.0 Release

[glenn-jocher]

Signed-off-by: Glenn Jocher glenn.jocher@ultralytics.com

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

YOLOv5 major updates with enhanced model definitions and performance improvements.

📊 Key Changes

• Updated YOLOv5 pretrained checkpoints with slightly different performance metrics (AP values and model names).
• Modified Detect layer initialization to accommodate new channel count parameter (ch).
• Refined anchor order check to ensure consistency with stride order.
• Adjusted values in training hyperparameters, such as class loss gain and HSV augmentation strengths.
• Implemented a cosmetic change to README.md on model public release and development start dates.
• Modified LR scheduler function for a new learning rate cosine annealing strategy.
• Increased balancing factors in loss computation to tweak the influence of each prediction head.
• Changed batch normalization momentum and epsilon values in utils/torch_utils.py.

🎯 Purpose & Impact

• 🚀 Enhanced performance: Tweaks in model and loss configuration can lead to more accurate detection and training stability.
• 🤖 Model training: Hyperparameter adjustments and learning rate scheduler optimization for better convergence.
• 👀 Clearer documentation: README update helps users to follow the timeline of significant changes and releases.
• 🧠 Backend improvements: Code modifications and cleanup contribute to maintenance and potential performance gains.

[glenn-jocher]

This v2.0 release PR is complete, all CI CPU tests are passing. Will merge and subsequently issue v2.0 release.

IMPORTANT: v2.0 release contains breaking changes. Models trained with earlier versions will not operate correctly with v2.0. The last commit before v2.0 that operates correctly with all earlier pretrained models is:
https://github.com/ultralytics/yolov5/tree/5e970d45c44fff11d1eb29bfc21bed9553abf986

[glenn-jocher]

Commands to clone last commit prior to v2.0:

git clone https://github.com/ultralytics/yolov5  # clone repo
cd yolov5
git reset --hard 5e970d4  # last commit before v2.0