TreemapMix: Dirichlet-Controlled Multi-Image Augmentation for Probability and Ordinal Supervision
Organizations: Peking University · Beijing University of Posts and Telecommunications
Abstract
Data augmentation improves visual recognition by exposing models to synthetic training examples that encourage generalization beyond the observed data. Mixed-sample methods extend this idea by combining multiple images. However, many common approaches either mix only pairs of images or rely on fixed small layouts, limiting control over source count, visible area proportions, and induced supervision. We propose TreemapMix, a distribution-controlled multi-image augmentation that samples source weights from a Dirichlet distribution and assigns them to area-proportional regions using a treemap partition. The resulting known region areas support two complementary objectives. TreemapMix with soft cross-entropy (SCE) treats areas as soft class-probability targets, while TreemapMix with a Plackett-Luce (PL) objective converts areas into ordinal supervision. On ImageNet-1K under matched training recipes, TreemapMix-SCE achieves substantially lower calibration error than evaluated mixed-sample baselines, while TreemapMix-PL achieves the strongest Top-1 accuracy. Transfer experiments on object detection and instance segmentation suggest that TreemapMix-pretrained features remain useful beyond classification. These results show that controlled multi-image composition can expose the same region-area information as either probability-matching or rank-matching supervision. Code is available at https://github.com/Ejafa/treemapmix.
Figures & tables
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| No Aug | ||||
| Single-Image Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| RICAP |
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| No Aug | ||||
| Single-Image Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| RICAP |
| ConvNeXtV2-Nano | DeiT-Tiny | Swin-Tiny | ||||
| Method | Acc. | ECE | Acc. | ECE | Acc. | ECE |
| Mixup+CutMix | ||||||
| RICAP | ||||||
| TreemapMix-SCE | ||||||
| TreemapMix-PL | ||||||
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| Top-1 accuracy (%) | ||||
| Mixup+CutMix | ||||
| RICAP | ||||
| TreemapMix-SCE | ||||
| TreemapMix-PL | ||||
| ECE (percentage points) | ||||
| Method | Throughput (images/s) | Throughput reduction | Total loader time (s) | |
| No Aug | 1 | |||
| Single-Image Aug | 1 | |||
| Mixup+CutMix | 2 | |||
| TreemapMix-SCE | 4 | |||
| TreemapMix-PL | 6 | |||
| RICAP | 4 |
| ViT-Wee | ViT-Little | |||
| Method | Acc. | ECE | Acc. | ECE |
| Single-Image Aug | ||||
| Mixup+CutMix | ||||
| TreemapMix-SCE | ||||
| TreemapMix-PL | ||||
| ViT-Wee | ViT-Betwixt | |||
| Method | Box AP | Mask AP | Box AP | Mask AP |
| Mixup+CutMix | 23.66 0.01 | 20.34 0.10 | 29.04 0.07 | 25.25 0.10 |
| RICAP | 23.08 0.17 | 19.82 0.07 | 27.86 0.08 | 24.21 0.06 |
| TreemapMix-SCE | 24.00 0.17 | 20.55 0.20 | 29.44 0.16 | 25.56 0.14 |
| TreemapMix-PL | 24.32 0.12 | 20.71 0.04 | 29.71 0.09 | 25.75 0.10 |
Appendix figures & tables16 assets
Supplementary material from the paper’s appendix.
Appendix
| Model | Setting | Original | New |
| ViT-Betwixt | |||
| dtype | float16 | bfloat16 | |
| aug_repeats | 3.0 | 0.0 | |
| warmup_epochs | 20 | 10 | |
| epochs | 600 | 110 | |
| lr | 1.2e-3 | 1.5e-3 | |
| Method | Mixing settings |
| No Aug | Single-image transforms off; Mixup+CutMix with , |
| Single-Image Aug | No mixing |
| Mixup | , |
| CutMix | , |
| Mixup+CutMix | , ; choose either method with probability |
| RICAP | ; close_epochs =10; center ; scale |
| Model | Opt. | Base LR | LR Decay | WD | DropPath | EMA |
| ViT-Wee | NAdamW | 1.5e-3 | cosine | 0.06 | 0.2 | yes |
| ViT-Little | NAdamW | 1.5e-3 | cosine | 0.06 | 0.2 | no |
| ViT-Medium | NAdamW | 1.5e-3 | cosine | 0.06 | 0.2 | no |
| ViT-Betwixt | NAdamW | 1.5e-3 | cosine | 0.08 | 0.2 | no |
| Model | Embed Dim | Depth | Heads | MLP Ratio | Drop Path | LR | Layer Decay |
| ViT-Wee | 256 | 14 | 4 | 5.0 | 0.1 | 6.0e-4 | 0.7 |
| ViT-Betwixt | 640 | 12 | 10 | 4.0 | 0.1 | 8.0e-4 | 0.7 |
| ViT-Wee | ViT-Betwixt | |||
| Method | Box AP50 | Mask AP50 | Box AP50 | Mask AP50 |
| Mixup+CutMix | 39.67 0.01 | 35.64 0.09 | 46.46 0.19 | 42.59 0.30 |
| RICAP | 38.68 0.24 | 34.82 0.20 | 44.91 0.04 | 41.05 0.20 |
| TreemapMix-SCE | 40.37 0.19 | 36.18 0.19 | 47.06 0.15 | 43.12 0.13 |
| TreemapMix-PL | 40.90 0.01 | 36.59 0.13 | 47.58 0.27 | 43.48 0.14 |
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| Single-Image Aug | ||||
| No Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| RICAP |
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| Single-Image Aug | ||||
| No Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| RICAP |
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| No Aug | ||||
| Single-Image Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| FMix |
| Method | ViT-Wee | ViT-Little | ViT-Medium | ViT-Betwixt |
| No Aug | ||||
| Single-Image Aug | ||||
| Mixup+CutMix | ||||
| Mixup | ||||
| CutMix | ||||
| FMix |
| Mixup+CutMix | TreemapMix-SCE | TreemapMix-PL | |||||
| Model | Optimizer | Acc. | ECE | Acc. | ECE | Acc. | ECE |
| ViT-Wee | AdamW | 75.76 | 8.99 | 77.18 | 0.43 | 77.75 | 5.41 |
| Muon | 77.92 | 9.88 | 78.80 | 2.04 | 79.05 | 5.93 | |
| NAdamW | 76.30 | 9.29 | 77.48 | 0.94 | 78.16 | 5.44 | |
| ViT-Little | AdamW | 78.77 | 8.11 | 79.50 | 1.36 | 79.93 | 5.96 |
| Muon | 80.27 | 8.61 | 80.72 | 3.05 | 80.87 | 6.57 | |
Data Augmentation
Data augmentation expands or transforms training examples to improve learning, data efficiency, and robustness to distribution shifts.
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