ultralytics 8.4.137

v8.4.137 - Auto-enable channels-last CUDA training (#26007)

on Python PyPI

🌟 Summary

v8.4.137 automatically enables the faster channels-last memory layout for CUDA training on PyTorch 1.11+, improving GPU training performance while preserving clear opt-out and compatibility options. 🚀

📊 Key Changes

• Automatic channels-last training: The existing channels_last=None setting now automatically uses the NHWC memory format for CUDA training with PyTorch 1.11 and newer.
• Explicit control remains available:
  • channels_last=None: Automatically selects channels-last when supported.
  • channels_last=False: Explicitly keeps the traditional NCHW format.
  • channels_last=True: Explicitly requests channels-last, preserving previous behavior.
• Safe compatibility behavior: PyTorch 1.10 and older, CPU, and MPS training continue using NCHW by default.
• Improved resume handling: The channels_last setting is now included among the training options that can be updated when resuming a run.
• Documentation updates: Training guides and argument references now describe the automatic CUDA behavior.
• No model architecture changes: This release focuses on training performance and memory layout rather than changing model structure or outputs.

🎯 Purpose & Impact

• ⚡ Potentially faster CUDA training: Channels-last can improve convolution performance on compatible GPUs, particularly modern Tensor Core hardware.
• 🧠 Better YOLO26 training defaults: Users no longer need to manually enable the optimization when using a supported PyTorch and CUDA environment.
• 🛡️ Reduced compatibility risk: Automatic activation begins at PyTorch 1.11, the first validated version that avoids known channels-last failures in YOLO26 training.
• 🔧 Full user control: Workloads that require the traditional layout can disable the optimization with channels_last=False.
• 🌍 Broad validation: The change was tested across CUDA 11.1–13.2, PyTorch 1.8–2.12, Python 3.8–3.13, and a wide range of modern NVIDIA GPUs.
• 📦 Minimal implementation impact: The behavior is selected during trainer setup without adding new arguments, persistent state, helper utilities, or GPU-specific allowlists.

What's Changed

• Auto-enable channels-last CUDA training by @glenn-jocher in #26007

Full Changelog: v8.4.136...v8.4.137