CHASE: Channel-Aligned Structure Exploitation for Geometry-Aware Model Engineering
Organizations: Futurewei Technologies San Jose, CA 95131, USA · Shanghai Institute for Mathematics and Interdisciplinary Sciences (SIMIS) Shanghai, 200433, China
Abstract
Geometric and Spectral Alignment (GSA) characterizes trained networks through spectral concentration, physical-channel alignment, support structure, and changes in singular bases. In this paper, we propose CHASE (Channel-Aligned Structure Exploitation) to use these structures in practical model design. CHASE covers six applications across model modification, reconfiguration, and compression. CORA, COEC, and CORAM apply GSA to parameter-efficient finetuning, structured-pruning compensation, and model merging. We further develop three new methods. CAGA uses GSA to identify multi-head attention heads that can share a KV representation and constructs the shared key and value heads through geometric alignment and low-rank subspace extraction. SAKV uses GSA to determine which adjacent layers can share a low-rank KV-cache representation and the retained rank for each layer group. CAPS uses GSA spectral structure to group output neurons and selects retained input channels separately for each group. Results from CORA, COEC, and CORAM establish the effectiveness of GSA for adaptation, pruning compensation, and model merging. Experiments on CAGA show that geometric shared-head construction substantially improves MHA-to-GQA conversion, and SAKV and CAPS improve over representative baselines for KV-cache compression and structured pruning. These results show that the structures identified by GSA can be used directly to design methods for a range of model operations.
Figures & tables
| GSA quantity | What it measures | Use in CHASE |
|---|---|---|
| Effective-rank window | Number of leading singular directions needed to retain most of the spectral energy | SAKV rank selection, CAPS output-neuron grouping |
| Active supports | Which physical channels carry the retained inter-layer structure for each spectral group | CAGA head grouping through support overlap |
| Retained spectral and right-subspace similarity | Similarity of retained singular values and input subspaces between model components | CAGA head grouping |
| Basis rotations , and spectral change | Changes in left and right singular bases and singular values relative to pretrained weight | CORA adaptation, COEC compensation, CORAM merging |
| Active-column gap, pairwise overlap margin, | Separation and stability of the extracted physical-channel supports | GSA support stability analysis |
Appendix figures & tables8 assets
Supplementary material from the paper’s appendix.
Appendix
| Shared-head construction | WikiText-2 PPL | ZS-7 |
|---|---|---|
| Direct averaging | 926 | 32.6 |
| Procrustes alignment | 738 | 35.3 |
| CAGA | 25.1 | 44.3 |
| 100M tokens | 500M tokens | |||||
|---|---|---|---|---|---|---|
| Grouping | WT2 | C4 | ZS-7 | WT2 | C4 | ZS-7 |
| Neighboring heads | 7.78 | 9.57 | 50.39 | 6.75 | 8.66 | 53.52 |
| Jin et al. | 7.55 | 9.35 | 51.03 | 6.64 | 8.55 | 53.49 |
| CAGA | 7.67 | 9.47 | 51.58 | 6.68 | 8.60 | 54.36 |
| Model | Context | Full | Compression | xKV | SAKV | Gain |
|---|---|---|---|---|---|---|
| Llama-3.1-8B | 32K | 93.63 | 93.00 | 92.58 | -0.42 | |
| 92.24 | 92.48 | +0.24 | ||||
| 78.57 | 89.83 | +11.26 | ||||
| 46.57 | 79.89 | +33.32 | ||||
| 64K | 92.10 | 91.16 | 91.22 | +0.06 | ||
| 88.50 | 89.71 | +1.21 |
| Model | Full | Compression | xKV | SAKV |
|---|---|---|---|---|
| Llama-3.1-8B | 41.46 | 40.84 | 41.26 | |
| 40.06 | 40.20 | |||
| Qwen2.5-14B | 46.66 | 46.41 | 46.39 | |
| 46.59 | 45.96 |
| Compression | Frobenius | RoPE-aware |
|---|---|---|
| 90.94 | 90.26 | |
| 59.58 | 82.99 | |
| 55.74 | 73.89 |
| Model | Target | MAC CAPS / base | CAPS | Magnitude | Wanda-sp | FLAP | RCPU |
|---|---|---|---|---|---|---|---|
| Llama-2-7B | 10% | 9.83 / 9.79 | 5.2119 / 63.23 / 44.00 | 7.7365 / 58.51 / 24.78 | 5.3761 / 63.00 / 41.71 | 5.3932 / 62.06 / 42.49 | 5.3797 / 62.26 / 40.40 |
| 20% | 19.94 / 19.59 | 5.4775 / 61.14 / 39.37 | 10.0504 / 53.94 / 26.00 | 5.7983 / 59.43 / 36.43 | 5.8373 / 61.27 / 37.61 | 5.8405 / 60.82 / 39.79 | |
| 30% | 29.91 / 30.41 | 5.9217 / 59.91 / 33.41 | 12.4877 / 48.06 / 23.75 | 6.4232 / 55.92 / 32.61 | 6.4348 / 56.05 / 31.72 | 6.4240 / 57.39 / 34.19 | |
| Llama-3-8B | 10% | 10.03 / 10.48 | 6.2232 / 66.54 / 64.55 | 9.5231 / 59.49 / 50.40 | 6.8051 / 65.55 / 57.50 | 7.1379 / 65.64 / 58.45 | 6.8218 / 65.94 / 58.67 |
| 20% | 19.94 / 20.96 | 6.7981 / 64.87 / 61.38 | 15.1003 / 54.36 / 25.20 | 7.8110 / 60.46 / 46.78 | 8.1345 / 58.84 / 46.55 | 7.8754 / 60.38 / 46.72 | |
| 30% | 30.15 / 29.04 | 7.6100 / 62.13 / 54.18 | 22.3106 / 49.26 / 26.19 | 8.4428 / 57.12 / 41.01 | 8.7243 / 58.02 / 41.69 | 8.4145 / 59.19 / 41.36 |
| Model | Target | PPL | ZS-7 | MMLU |
|---|---|---|---|---|
| Llama-2-7B | 10% | -0.16 | +0.23 | +1.51 |
| 20% | -0.32 | -0.13 | -0.42 | |
| 30% | -0.50 | +2.52 | -0.78 | |
| Llama-3-8B | 10% | -0.58 | +0.60 | +5.88 |
| 20% | -1.01 | +4.41 | +14.60 | |
| 30% | -0.80 | +2.94 | +12.49 |
| Model | Target | ||||||
|---|---|---|---|---|---|---|---|
| Llama-2-7B | 10% | 9.83 | 6.59 | 3.41 | 1.80 | 0.72 | 0.39 |
| 20% | 19.94 | 15.13 | 9.01 | 4.88 | 1.78 | 0.94 | |
| 30% | 29.91 | 24.33 | 15.98 | 8.94 | 2.97 | 1.43 | |
| Llama-3-8B | 10% | 10.03 | 6.67 | 3.67 | 1.92 | 0.64 | 0.32 |
| 20% | 19.94 | 15.03 | 9.33 | 5.06 | 1.50 | 0.62 | |
| 30% | 30.15 | 24.49 | 16.68 | 9.55 | 2.73 | 1.02 |