Ultralytics YOLO

Abstract

🌟 Summary Ultralytics 8.4.133 improves hyperparameter tuning convergence, speeds up inference preprocessing, expands detection metrics, and simplifies edge-device setup. 🚀 📊 Key Changes Smarter hyperparameter tuning — PR #25984 by @glenn-jocher Replaces coordinate-by-coordinate crossover with fitness-weighted selection of complete, high-performing configurations. Preserves useful relationships between hyperparameters instead of mixing them independently. Mutates approximately half of the parameters in normalized search-space coordinates, allowing parameters that start at zero—such as degrees or shear—to evolve more effectively. Gradually reduces mutation size when tuning stops finding better results, encouraging refinement after broad exploration. Prevents duplicate candidates after clipping, rounding, or integer conversion, including small and discrete search spaces. Ray Tune now defaults to Optuna multivariate TPE, with parallel-aware suggestions rather than independent random search. Faster predictor preprocessing — PR #25982 by @jahsef ⚡ Moves image channel reordering and tensor-contiguity operations from CPU-side NumPy processing to the inference device. Preserves output values while reducing unnecessary CPU copies. Reported benchmarks show approximately 2.2–3.1× faster preprocessing on an RTX 5080, with additional gains on CPU. Automatic channels-last CPU inference — PR #25983 by @JESUSROYETH Enables channels-last memory layout automatically for native PyTorch inference and standalone validation on supported x86 Linux and Windows CPUs with oneDNN. Keeps training defaults and unsupported platforms unchanged. Explicit channels_last=True remains available for supported CPU and CUDA paths. Saved models are converted back to a safe contiguous format and stale EMA data is cleared to improve compatibility. More accurate INT8 calibration subsets — PR #25978 by @JESUSROYETH Fixes fraction handling during classification and detection INT8 export calibration. Scalar fractions now apply directly to the selected calibration split, while list-based fractions retain train/validation/test behavior. Prevents exports from unintentionally calibrating on an entire dataset when only a subset was requested. Size-specific mAP for custom detection datasets — PR #25981 by @fcakyon 📈 Custom detection datasets can now report small-, medium-, and large-object mAP when using save_json=True. Builds temporary COCO-format annotations internally while preserving existing native metrics and prediction files. Applies consistently during training validation, final-model validation, and standalone validation. Simpler edge-device installation Raspberry Pi, Jetson, DGX Spark, DeepStream, and related guides now install the base ultralytics package instead of the larger [export] extra. Export dependencies are installed automatically when an export is requested, reducing installation size and dependency conflicts. Improved Weights & Biases artifact control — PR #25985 by @glenn-jocher W&B model artifact uploads now follow the existing training save argument. save=False skips uploading the best checkpoint while retaining metrics and plots. Default behavior remains unchanged with save=True. Package update Version bumped to 8.4.133. 🎯 Purpose & Impact Better tuning results: Hyperparameter searches are more likely to preserve successful configurations, explore meaningful alternatives, and avoid wasting trials on duplicates. 🎯 Faster inference: Device-side preprocessing can reduce latency, particularly for batched inference and CPU-bound pipelines. Broader performance optimization: Supported x86 CPU users may benefit from channels-last inference without changing their existing commands. More reliable model export: INT8 calibration now honors requested dataset fractions, improving calibration speed and reducing unexpected resource usage. Richer evaluation: Custom detection datasets can now receive object-size performance breakdowns similar to COCO evaluations. Easier edge deployment: Base installations are smaller and less prone to dependency conflicts, while export workflows remain available when needed. More control over experiment storage: W&B users can keep experiment tracking lightweight by disabling checkpoint saving with the standard save setting. What's Changed Allow skipping W&B model artifacts by @fcakyon in https://github.com/ultralytics/ultralytics/pull/25979 Remove [export] from edge-device install guides by @Y-T-G in https://github.com/ultralytics/ultralytics/pull/25977 Accelerate predictor preprocessing on inference devices by @jahsef in https://github.com/ultralytics/ultralytics/pull/25982 Fix INT8 export calibration fractions by @JESUSROYETH in https://github.com/ultralytics/ultralytics/pull/25978 Use save argument for W&B model artifacts by @glenn-jocher in https://github.com/ultralytics/ultralytics/pull/25985 Compute size-specific mAP for custom detection datasets by @fcakyon in https://github.com/ultralytics/ultralytics/pull/25981 Enable channels-last by default for x86 CPU inference by @JESUSROYETH in https://github.com/ultralytics/ultralytics/pull/25983 Improve hyperparameter Tuner mutation convergence by @glenn-jocher in https://github.com/ultralytics/ultralytics/pull/25984 Full Changelog: https://github.com/ultralytics/ultralytics/compare/v8.4.132...v8.4.133