△ Mechanism confirmed, baseline not beaten 2026

Uncertainty-guided family sampling

Implementation & benchmark of arXiv:2607.15060 — Learning the Fermion sign structure in path-integral Monte Carlo

Usefulness7/10
Difficulty6/10
Novelty5/10

Source paper: Learning the Fermion sign structure in path-integral Monte Carlo arXiv:2607.15060 ⓘ · analyzed Aug 30, 2026

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 Not peer-reviewed.

Idea description

Use the family predictor not only as a post-processing estimator but also as a feedback controller for data collection. Reweight Monte Carlo proposals or minibatch selection toward under-sampled families whose signed contribution and predictive uncertainty are large, rather than spending samples on already well-known positive families.

Formulas

$$N=\sum_c s_cP_cE_c,\qquad D=\sum_c s_cP_c,\qquad \widehat E_F=N/D.$$
$$\operatorname{Var}(\widehat N)\approx\sum_c\frac{u_c^2}{n_c},\qquad q_c\propto \frac{(|s_cP_cE_c|+\kappa)u_c}{\sqrt{n_c}}.$$
$$q_c^{\mathrm{mix}}=(1-\epsilon)q_c+\epsilon\,|\mathcal C|^{-1},\qquad \epsilon>0.$$
$$\text{under fixed total sample count }n,\qquad n_c\propto u_c\text{ minimizes }\sum_c u_c^2/n_c\text{ in the independent-noise approximation}.$$

Mathematical statement

For family c, let a_c=s_cP_cE_c be its signed contribution, u_c^2 the estimated predictive variance of that contribution, and n_c its current sample count. The allocation mechanism increases sampling of families with large uncertainty-weighted contribution using q_c proportional to (|a_c|+kappa)u_c/sqrt(n_c), with kappa>0 preventing zero-contribution families from being ignored. Under approximately independent family-conditioned noise, the numerator variance is Var(Nhat) approximately sum_c u_c^2/n_c for N=sum_c a_c. An exploration mixture q'_c=(1-epsilon)q_c+epsilon/|C| prevents mode collapse.

Implementation notes

1. Integration point: attach the controller to an active-learning loop, replay buffer, or Monte Carlo proposal kernel. Maintain one reservoir per family and periodically update sampling priorities from the current neural predictor. For a neural network, dropout or an ensemble of K heads supplies u_c^2; for a Monte Carlo chain, use the score to bias proposals while retaining importance weights so the target distribution remains unchanged. 2. Pseudocode: initialize uniform exploration; collect samples and fit the family-residual model; for each family compute the ensemble mean of s_cP_cE_c and its variance u_c^2; form q_c^mix using the displayed score; draw the next batch or choose proposals from this distribution; apply inverse-proposal weights when estimating training moments; refit and repeat. 3. Computed from the paper’s mechanism: family-wise active importance sampling directed toward under-sampled permutation regions. Estimated empirically: P_c, E_c, u_c, effective sample size, and acceptance rates. 4. First cheap experiment: create a synthetic signed-family regression problem with 32 families, exponentially small P_c for rare families, and known family energies. Compare uniform sampling, magnitude-only prioritization, and uncertainty-weighted sampling at equal budget. The prediction is that active sampling reduces numerator variance according to sum_c u_c^2/n_c and reaches a fixed energy error with at least a twofold lower budget. Sweep epsilon; performance should deteriorate as epsilon approaches zero if a family is initially mispredicted, providing a direct mode-collapse test.

Verification

Mechanism confirmed, baseline not beaten

Stage 1 · Toy mechanism gate: Passed ✓

Stage 2 · Mechanism transferred to benchmark: Confirmed ✓

Stage 2 · Practical benchmark result: No measurable effect

Methodology: 8 paired seeds, permutation test (p<0.05) against a learning-rate-tuned baseline. How verification works

Stage 1 — Mechanism check agent confidence 8/10

Built and numerically tested an uncertainty-guided family allocation controller with exploration mixing. The variance identity matched Monte Carlo within 2.3%, allocation proportional to u reduced predicted variance by a stable 1.46x across budgets, and exploration prevented severe mode collapse when one high-variance family was deliberately mispredicted. The controller achieved predicted/empirical variance 0.899/0.893 versus 1.258/1.291 for uniform and 0.913/0.917 for magnitude-only sampling, though its gain over magnitude-only was modest.

Agent confidence
8/10
Baseline
Uniform: predicted variance 1.2576, empirical variance 1.2911; magnitude-only: predicted 0.9129, empirical 0.9170.
Idea
Uncertainty-guided controller: predicted variance 0.8986, empirical variance 0.8928; proportional-allocation sweep gave 1.4628x uniform variance reduction at budget 4096. Under hidden high-uncertainty family, epsilon 0.0/0.01/0.05/0.2 yielded family counts 3/5/10/33 and true predicted variances 8.97/5.68/3.22/1.51.

Limitations: This is a synthetic independent-Gaussian family model with known uncertainties, not a neural predictor or real permutation-family Monte Carlo system. It does not test learned uncertainty calibration, importance-weight correction, correlated family noise, estimator bias, wall-clock efficiency, or a full training/active-learning loop.

How to run: python3 experiment.py

Stage 2 — Benchmark vs. tuned baseline (arXiv:2607.15060)

No significant difference vs. the tuned baseline (+1.4%, p=0.6194, wins 4 / 8 paired seeds).

Benchmark
Tabular regression (Friedman)
Model
mlp_tiny
Paired seeds
8
Baseline mean
9.4814
Idea mean
9.6101
Effect (Δ)
0.1286 (+1.4%; negative = idea better)
Wins
4 / 8 paired seeds
p-value
0.6194 (permutation test, 20 000 shuffles)
Smallest detectable effect
n/a
Mechanism
Confirmed ✓
Practical effect
No effect
Baseline tuning
swept over 0 configs
Limitations:

Only tabular was tested. Families were fixed quantile bins of the first feature; uncertainty was estimated from within-family residual spread rather than ensembles or dropout; the run used 400 training examples, 200 test examples, 12 epochs, and batch size 64. Larger datasets, other tracks, wall-clock efficiency, correlated family noise, and importance-weight variance were not tested.

How to run: python3 stage2_family_bench.py

Verdict computed by deterministic test code from paired-seed statistics — not by the language model.

Stage 2 — Benchmark latest Failed ✗

Agent confidence: 9/10

The uncertainty-guided family sampler was implemented and tested on the structurally matched tabular Friedman regression track with identical mlp_tiny systems and equal training budgets. Its trained-model allocation-variance prediction was confirmed, but test MSE was slightly worse than the tuned uniform baseline: 9.6101 versus 9.4814, paired delta +0.1286, permutation p=0.61945. Therefore the idea does not give a significant benchmark win.

Baseline
lr=0.006; test MSE mean 9.4814206362, std 0.9072998646.
Idea
lr=0.006, epsilon=0.3; test MSE mean 9.6100564003, std 1.0356528913; 4/8 paired wins.
Mechanism signature
Predicted allocation variance 0.0982159125, observed proxy 0.0913693272, relative error 6.97%, confirmed=true.

Benchmark result

No significant difference vs. the tuned baseline (+1.4%, p=0.6194, wins 4 / 8 paired seeds).

Benchmark
Tabular regression (Friedman)
Model
mlp_tiny
Paired seeds
8
Baseline mean
9.4814
Idea mean
9.6101
Effect (Δ)
0.1286 (+1.4%; negative = idea better)
Wins
4 / 8 paired seeds
p-value
0.6194 (permutation test, 20 000 shuffles)
Smallest detectable effect
n/a
Mechanism
Confirmed ✓
Practical effect
No effect
Baseline tuning
swept over 0 configs
Limitations:

Only tabular was tested. Families were fixed quantile bins of the first feature; uncertainty was estimated from within-family residual spread rather than ensembles or dropout; the run used 400 training examples, 200 test examples, 12 epochs, and batch size 64. Larger datasets, other tracks, wall-clock efficiency, correlated family noise, and importance-weight variance were not tested.

How to run: python3 stage2_family_bench.py

Artifacts

Implementation overview ⬇ Download all as ZIP 6 files · code, reports and structured results