# Coarsening-Aware Global-Consensus Scheduler

- ID: 636
- Canonical URL: https://synthcore.org/idea/636/coarsening-aware-global-consensus-scheduler
- API JSON: https://synthcore.org/api/idea/636.json
- API Markdown: https://synthcore.org/api/idea/636.md
- Verification status: mechanism_failed
- Source: [arXiv:2607.09411](https://arxiv.org/abs/2607.09411)
- Category: dynamics
- Solves: stability, generalization, accuracy
- ML areas: optimizer, scheduler, training-dynamics, regularization
- Math tags: statistical-mechanics, dynamical-systems, optimization, graph-theory
- Ratings: usefulness 6/10; difficulty 5/10; novelty 7/10

## Idea description

Modify learning-rate or annealing schedules so that local improvement is not mistaken for convergence when different parameter blocks occupy incompatible global modes. Measure a local-consistency score and a global-coherence score separately; slow training whenever local consistency is high but global coherence remains low, allowing competing parameter domains to merge before cooling further.

## Mathematical statement

The source model is an Ising Hamiltonian $H=J_1\sum_{\langle i,j\rangle}s_i s_j+J_2\sum_{\langle\langle i,j\rangle\rangle}s_i s_j$, where $s_i\in\{-1,+1\}$, $J_1>0$ is the nearest-neighbor antiferromagnetic coupling, and $J_2>0$ selects stripe order. Let $P_{\mathrm{stripe}}(n,L)$ be the probability of a globally stripe-ordered final state after $n$ local-update sweeps on a system of linear size $L$. The kinetic time $n^*$ is defined by $P_{\mathrm{stripe}}(n^*,L)=p_0$ for a fixed threshold $p_0$, and the paper reports effective coarsening compatible with $n^*(L)\propto L^z$ with $z\gtrsim2$ over the simulated range. For a neural network partitioned into blocks $b=1,\ldots,B$, define local consistency $Q_t=B^{-1}\sum_b q_b(t)$, where $q_b$ is the mean cosine similarity of neighboring parameter-update vectors inside block $b$, and define global coherence $C_t=\lambda_1(G_t)/\operatorname{tr}(G_t)$, where $G_t=B^{-1}\sum_b(u_b-\bar u)(u_b-\bar u)^\top$ is the covariance of normalized block update directions $u_b$, and $\lambda_1$ is its largest eigenvalue. The adapted controller slows the schedule when $Q_t$ is high but $C_t$ is low: local consistency has been restored, but competing global update sectors remain.

## Key formulas

- $$H=J_1\sum_{\langle i,j\rangle}s_i s_j+J_2\sum_{\langle\langle i,j\rangle\rangle}s_i s_j,\qquad s_i\in\{-1,+1\},\quad J_1>0,\ J_2>0.$$
- $$P_{\mathrm{stripe}}(n^*,L)=p_0,\qquad n^*(L)\propto L^z,\quad z\gtrsim2.$$
- $$Q_t=\frac{1}{B}\sum_{b=1}^{B}q_b(t),\qquad q_b(t)=\frac{1}{|E_b|}\sum_{(i,j)\in E_b}\frac{\Delta\theta_i\cdot\Delta\theta_j}{\|\Delta\theta_i\|\,\|\Delta\theta_j\|},$$
- $$C_t=\frac{\lambda_1(G_t)}{\operatorname{tr}(G_t)},\quad G_t=\frac{1}{B}\sum_{b=1}^{B}(u_b-\bar u)(u_b-\bar u)^\top,\quad \eta_{t+1}=\eta_t\exp\{-\kappa[1-Q_t][C_0-C_t]_+\},$$

## Implementation notes

1. Integration point: partition a small MLP, CNN, or transformer into blocks such as layers, attention heads, convolutional channels, or parameter shards. Every $K$ optimizer steps, collect the recent update vector $\Delta\theta_b$ for each block and normalize it to $u_b$. Define the block adjacency graph $E_b$ using neighboring layers, adjacent channels, or attention heads in the same layer. 2. Pseudocode: initialize learning rate $\eta$ and target global coherence $C_0$. At each diagnostic interval, compute pairwise cosine similarities on adjacent update vectors to obtain $Q_t$; compute the covariance $G_t$ of block-level directions and its leading-eigenvalue ratio $C_t$ using a low-rank eigensolver; if $Q_t>q_0$ and $C_t<C_0$, set $\eta\leftarrow\eta\exp[-\kappa(1-Q_t)(C_0-C_t)]$ and optionally increase the number of steps before the next decay; otherwise apply the baseline cosine or exponential schedule. 3. Computed versus estimated: $Q_t$, $C_t$, and $G_t$ are empirical estimates, while the paper supplies the mechanism and the prediction that global ordering requires a coarsening time scaling as a power of system size, with exponent at least approximately two in its measured regime. Estimate an effective exponent $\hat z$ by repeating runs with different block counts $B$ and fitting the time to reach $C_0$ as $T_{\mathrm{coal}}(B)\propto B^{\hat z}$. 4. First cheap experiment: train a 3-layer MLP and a 6-layer small transformer on MNIST or CIFAR-10 using SGD or Adam, comparing the baseline schedule against this controller at equal update count. Log training loss, validation accuracy, $Q_t$, $C_t$, and gradient/update disagreement. The falsifiable signature is a plateau with high $Q_t$ but low $C_t$ under the baseline, followed by a measurable increase in $C_t$ after the controller slows learning. Across block counts, the predicted consensus time should follow a power law with $\hat z$ near or above $2$; if no such scaling or delayed-coherence regime appears, reject the transfer.

## Verification

- Status: mechanism_failed
- Mechanism evidence: yes
- Mechanism confirmed: no
- Verdict: Built the coarsening-aware scheduler with empirical Q/C diagnostics, gated learning-rate slowdown, formula sanity checks, and a paired fixed-seed MLP experiment. The constructed orthogonal-sector case produced high Q≈1 and low C≈0.334 and triggered the controller, verifying the gate mathematically, but the slowdown was only about 2.4e-6 in that setup. On two-moons, baseline and controller were identical because the observed high-Q/low-C regime never occurred; both reached 96.11% accuracy and validation loss 0.1061, so no promised training win was observed.

### Mechanism check

- Verdict: Built the coarsening-aware scheduler with empirical Q/C diagnostics, gated learning-rate slowdown, formula sanity checks, and a paired fixed-seed MLP experiment. The constructed orthogonal-sector case produced high Q≈1 and low C≈0.334 and triggered the controller, verifying the gate mathematically, but the slowdown was only about 2.4e-6 in that setup. On two-moons, baseline and controller were identical because the observed high-Q/low-C regime never occurred; both reached 96.11% accuracy and validation loss 0.1061, so no promised training win was observed.
- Confidence: 9/10
- Limitations: Only a small two-moons MLP was tested, not MNIST/CIFAR, CNNs, transformers, longer coarsening dynamics, multiple seeds, or block-count scaling. The empirical block-update projection and adjacency construction are lightweight approximations rather than a production optimizer integration.

## Artifacts

- [experiment.py](https://synthcore.org/code/1420/experiment.py)
- [report.md](https://synthcore.org/code/1420/report.md)
- [results.json](https://synthcore.org/code/1420/results.json)
- [Download all files as ZIP](https://synthcore.org/download/1420)

## Disclaimer

AI-generated research hypothesis, automatically tested. Not peer-reviewed.
