Spectral Limits of Polynomial Graph Filters on the Long-Range Ising Model Benchmark
Organizations: University of Zanjan.
Abstract
The Long-Range Ising Model benchmark (LRIM) guarantees long-range dependence by construction: each label is the node's spin times the spin field convolved with a power-law coupling, so any model's distance from the target is measurable. We prove that a readout whose filter is a polynomial in the adjacency, the linear core of isotropic message passing and spectral graph networks, leaves an error floor that no degree lowers, because the target varies along a level set of the spectrum on which every such filter is constant. Computed exactly, the floor and the best filter of each degree predict two spectral networks adapted from published architectures to within a tenth of a decade. A filter escapes the floor only if it weighs separately the offsets the adjacency lumps together, and must still resolve the coupling across the whole lattice. A strided filter of about fifty coefficients does both: fitted to the training labels, its test error is 52 times below the best published network's. A dilated convolutional network beats the best published result at 256 nodes, matches it at 1,024, and gives the first in-domain results at the three larger sizes, while a Fourier neural operator with its standard modes falls further behind as the lattice grows. At its standard budget the dilated network stays two to four orders of magnitude short of a larger strided filter fitted to the labels. The analysis carries over to the benchmark's second coupling.
Figures & tables
| nodes | |||||
| 256 | 1 024 | 4 096 | 16 384 | 65 536 | |
| The operator, fitted to the training labels | |||||
| The learned quadratic readout | |||||
| The larger strided filter, fitted to the training labels | – | ||||
| The fifty-coefficient strided filter, fitted to the training labels | – | – | – | ||
| The floor for a filter polynomial in the adjacency | |||||
| reach radius | coefficients | logMSE |
|---|---|---|
| 9 | ||
| 31 | ||
| 113 | ||
| 152 |
| dilated CNN | small dilated CNN | ||||||
|---|---|---|---|---|---|---|---|
| Size | steps | batch | epochs | width | parameters | width | parameters |
| 40 000 | 48 | 240 | 136 | 2 020 145 | 52 | 296 297 | |
| 40 000 | 48 | 240 | 116 | 1 955 529 | 44 | 282 393 | |
| 25 000 | 12 | 38 | 104 | 1 962 481 | 40 | 291 441 | |
| 25 000 | 3 | 96 | 2 005 057 | 36 | 283 177 | ||
| 15 000 | 2 | 88 | 1 964 689 | 36 | 330 121 | ||
| params | ||||||
|---|---|---|---|---|---|---|
| Dilated CNN | 2.0 M | |||||
| every dilation one | 2.0 M | – | – | – | ||
| at a quarter of the learning rate | 2.0 M | – | – | – | ||
| at twice the steps | 2.0 M | – | – | – | ||
| with the target’s gate, one model | 2.0 M | – | – | – | ||
| Small dilated CNN | 0.3 M |
| Eight rounds of propagation, | |||
|---|---|---|---|
| Gated linear filter, least squares | |||
| SIGN, mean of three models | |||
| Best polynomial of degree eight (closed form) | |||
| As many rounds as the side of the lattice, | |||
| Gated linear filter, least squares | |||
| Model | training | layers width | parameters | each model, test | mean | s.d. | published | |||
|---|---|---|---|---|---|---|---|---|---|---|
| GatedGCN | 16 | standard | 20 104 | 1 995 553 | ||||||
| 16 | steps | 20 104 | 1 995 553 | |||||||
| 32 | standard | 32 84 | 2 087 905 | – | – | – | ||||
| per-direction | 16 | standard | 20 80 | 1 965 121 | – | |||||
| 32 | standard | 32 64 | 2 019 585 | – | – | – | – | |||
| per-direction, strided | 16 | standard | 20 64 | 1 929 473 | – | |||||
Appendix figures & tables9 assets
Supplementary material from the paper’s appendix.
Appendix
| Model or bound | note | |||||
| Closed forms: the operator solved exactly, and the floors | ||||||
| Least squares on the coupling, 152 coefficients | – | – | – | – | fitted to the kernel, not the labels | |
| Least squares on the labels, symmetric kernel | the square’s symmetries | |||||
| Least squares on the labels, free kernel | coefficients | |||||
| The coupling , applied to the spins | in double precision | |||||
| Larger strided filter | – | 83 to 101 coefficients, fitted to the labels | ||||
| Model | width | parameters | each model, test | mean | s.d. | validation | hours | |||
| Dilated CNN | 16 | 136 | 2 020 145 | 1.0 | ||||||
| 32 | 116 | 1 955 529 | 3.9 | |||||||
| 64 | 104 | 1 962 481 | 2.5 | |||||||
| 128 | 96 | 2 005 057 | 2.8 | |||||||
| 256 | 88 | 1 964 689 | 5.4 | |||||||
| Small dilated CNN | 16 | 52 | 296 297 | 0.3 | ||||||
| Model | learning rate | validation | against the standard rate |
|---|---|---|---|
| Dilated CNN | (standard) | – | |
| FNO | (standard) | – | |
| nodes | |||||
| 256 | 1 024 | 4 096 | 16 384 | 65 536 | |
| The operator, fitted to the training labels | |||||
| The larger strided filter, fitted to the training labels | – | ||||
| The fifty-coefficient strided filter, fitted to the training labels | |||||
| The floor for a filter polynomial in the adjacency | |||||
| A dilated CNN | |||||
| Experiment | What we expected | What would have counted against it | What happened |
|---|---|---|---|
| The learned quadratic readout, at all five sizes | or better with the larger strided basis at every size, or better with the free multiplier wherever it fits in memory | a size where either target is missed | met at every size; the free multiplier also fits at |
| The best polynomial filter in the adjacency, at four sizes | within 0.3 of at every size | a size outside that band | partly met: at degree 128 it holds at and and fails at and ; at degree 64 it holds at , 64 and 128 and fails at . The floor of Proposition 1, exact for the training spectrum, replaces the band |
| What we expected | probability | What happened |
|---|---|---|
| The dilated CNN passes the polynomial floor at every size | 75 % | not met at , where it scores against a floor of ; met at the other sizes |
| The dilated CNN lands between and at | 70 % | met: |
| The dilated CNN beats the best published in-domain result at and | 45 % | met: against (the benchmark’s transfer table, trained and tested at ) and against ; against the stronger results published since, against and against , ahead by and (the second within the spread of seeds) |
| The dilated CNN is at least below our eight-layer baseline at , 128 and 256 | 75 % | met: by , , |
| The dilated CNN stays at least above the larger strided filter from on | 95 % | met: to above |
| The small dilated CNN is worse than the dilated CNN at by to | 60 % | not met: it is better |
| What we expected | probability | What happened |
| The same network with every dilation one, at and | ||
| The same network with every dilation one is worse than the dilated CNN by at least at | 65 % | not met: against , worse |
| The same network with every dilation one is worse than the dilated CNN by at least at | 75 % | met: against , worse |
| Its shortfall against the dilated CNN is larger at than at | 70 % | met: it is worse at and worse at |
| At it lies no more than below the reference for a filter of its reach | 65 % | met: against a reference of |
| At it passes the polynomial floor | 80 % | met: against |
| What we expected | probability | What happened |
| Four graph networks under the same protocol, at and | ||
| GatedGCN at lands within of its published value | 60 % | not met: against , above |
| The per-direction GatedGCN is at least better than GatedGCN at | 65 % | not met: against , better |
| The per-direction GatedGCN is at least better than GatedGCN at | 60 % | not met: against , better |
| The strided GatedGCN lies within of the dilated CNN at and at | 50 % | not met: at , against , above; at , against , above |
| GPS with RWSE is not more than better than GatedGCN at | 60 % | not met: against , better |
| What we expected | probability | What happened |
| Two polynomial spectral networks, at , and | ||
| The gated linear filter lies within of the best polynomial of its degree at every size, for and for | 90 % | met: within everywhere |
| SIGN at does not beat the floor by more than at any size | 65 % | met: , , above the floor |
| SIGN at lies within of the best polynomial of degree at every size | 50 % | met: , , below it |
| SIGN at lies within of the best polynomial of degree eight at every size | 55 % | met: , , below it |
| The easier coupling, exponent , at every size | ||
GNN Expressivity
Graph neural network expressivity studies which graph structures and functions a model can distinguish or represent, and how its design shapes those limits.
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