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Mitigating Oversmoothing Through Reverse Process of GNNs for Heterophilic Graphs
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Proposes reverse-process GNNs (ReP) that invert message-passing layers (GRAND via numerical backward integration; GCN/GAT via invertible residual layers with fixed-point inversion) to produce distinguishable representations, mitigating over-smoothing on heterophilic graphs.
Problem
GNN message passing smooths node representations with depth (over-smoothing), which hurts heterophilic node classification where adjacent nodes need different representations and long-range interactions are needed.
Approach
Apply the inverse of forward diffusion-like message-passing layers (g = f^{-1}) to obtain less-smoothed, distinguishable representations; concatenate forward and reverse representations for prediction. Invertibility of residual GCN/GAT layers is enforced via Lipschitz-constrained weight normalization and fixed-point iteration (iResNet-style).
Key results
- GCN+ReP improves over GCN on heterophilic datasets, e.g. Roman-Empire 73.69 to 86.43 and Minesweeper 89.75 to 96.05 ROC-AUC, and reaches state-of-the-art on four of seven heterophilic datasets.
- GAT+ReP improves over GAT on Chameleon (39.21 to 43.24) and Minesweeper (92.01 to 94.89).
- On homophilic datasets ReP changes results only marginally (e.g. GCN+ReP PubMed 89.37 to 89.96), with some decreases such as GCN+ReP Cora 88.00 to 87.63.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add the reverse process to GCN (ablation) | GCN · Heterophilic graph datasets | accuracy / ROC-AUC: +6.42 (Squirrel), +6.68 (Chameleon), +12.74 (Roman-Empire), +4.05 (Amazon-Ratings), +6.30 (Minesweeper), +2.44 (Tolokers | Helped |
| Add the reverse process to GRAND (ablation) | GRAND · Heterophilic graph datasets | accuracy / ROC-AUC: +4.81 (Squirrel), +4.43 (Chameleon), +2.34 (Roman-Empire), -1.04 (Amazon-Ratings), +1.01 (Minesweeper), +2.06 (Tolokers) | Mixed |
| Add the reverse process to GAT (ablation) | GAT · Heterophilic graph datasets | accuracy / ROC-AUC: +4.04 (Squirrel), +4.03 (Chameleon), +5.00 (Roman-Empire), +3.59 (Amazon-Ratings), +2.11 (Minesweeper), +0.82 (Tolokers) | Mixed |
| Add the reverse process to GCN (ablation) | GCN · Homophilic graph datasets | accuracy: -0.37 (Cora), +0.18 (CiteSeer), +0.59 (PubMed), -0.95 (Computers), +0.15 (Photo) | Mixed |
| Add the reverse process to GAT (ablation) | GAT · Homophilic graph datasets | accuracy: +0.26 (Cora), -0.30 (CiteSeer), +0.28 (PubMed), -1.12 (Computers), -0.42 (Photo) | Mixed |
| Add reverse layers to GCN+ReP (ablation) | GCN+ReP · Chameleon and Minesweeper | prediction performance | Helped |
| Use the reverse process rather than forward-only GCN | GCN+ReP · Squirrel and Chameleon | Graph Smoothness Level (GSL): below 0.6 up to 1024 reverse layers; GCN with 16 layers exceeds 0.9 after eight layers | Helped |
Surprising findings
- Reverse depth above 64 layers was consistently used by the best GCN+ReP configurations, and GSL of GCN+ReP stays below 0.6 up to 1024 reverse layers while plain 32/64-layer GCN becomes similar after eight layers.
- Inversion error from fixed-point iteration is negligible (around 1e-5) even at depth 64 with c=0.99999 and only eight iterations.
Limitations
- Invertibility requires Lipschitz constraints on the forward layer and constant hidden dimension, limiting representation power and design choices.
- Reverse process adds time and memory cost that grows with reverse depth and fixed-point iterations; deep reverse depth was memory-constrained on Minesweeper (<=256).
Experimental setup
Datasets: Chameleon Squirrel Roman-Empire Amazon-Ratings Minesweeper Tolokers Questions Cora CiteSeer PubMed Computers Photo
Benchmarks: Chameleon Squirrel Roman-Empire Amazon-Ratings Minesweeper Tolokers Questions Cora CiteSeer PubMed Computers Photo
Metrics: accuracy ROC-AUC graph smoothness level mean absolute inversion error
Baselines: GCN GAT GraphSAGE GT H2GCN GPR-GNN FSGNN GloGNN
Builds on: GRAND iResNet GCN GAT
Closest papers by meaning
- On Vanishing Gradients, Over-Smoothing, and Over-Squashing in GNNs: Bridging Recurrent and Graph Learning (NeurIPS 2025 · similarity 0.88)
- Graph Neural Networks Do Not Always Oversmooth (NeurIPS 2024 · similarity 0.87)
- A Generalized Neural Diffusion Framework on Graphs (AAAI 2024 · similarity 0.87)
- On the Impact of Feature Heterophily on Link Prediction with Graph Neural Networks (NeurIPS 2024 · similarity 0.87)
- Understanding Heterophily for Graph Neural Networks (ICML 2024 · similarity 0.87)
- Deep Graph Neural Networks via Posteriori-Sampling-based Node-Adaptative Residual Module (NeurIPS 2024 · similarity 0.87)
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