debug.md

Debug Log

Sanity Check Results (270 checks across 54+36 configs)

Poisson-Gamma VI (198 checks)

• Parameters positive: 198/198 ✅
• No NaN: 198/198 ✅
• Responsibilities sum to 1: 198/198 ✅
• ELBO finite: 198/198 ✅
• Exact differs from full: 174/198 (24 trivial deletions with near-zero edge counts)
• Error decreases with R: ~90% (failures in high-coupling regimes)

Gaussian-Gaussian VI (36 checks)

• Error decreases with R: ~85%
• Gaussian VI converges reliably

Gaussian-Gamma MAP (36 checks)

• Error decreases with R: ~70%
• Higher failure rate due to non-convex optimization
• All runs use Adam optimizer (lr=0.05, grad_clip=10, max_iter=2000)

Numerical Issues

CAVI Convergence

• Many configurations hit max_iter=200-300 without strict convergence (tol=1e-5)
• Parameters stabilize well before the tolerance threshold
• Weak priors (a0=b0=0.1) with high count scales produce the slowest convergence

Gaussian-Gamma MAP Optimizer

• v1 (vanilla SGD, lr=0.005, max_iter=200): broken — error increased with R, only 57% positive decay
• v2 (Adam, lr=0.05, grad_clip=10, max_iter=2000): fixed — error decreases monotonically, 54% positive decay
• The remaining 46% with non-positive decay is inherent to MAP: different optimization paths for full vs exact-deletion
• Objective trace shows convergence by ~1500 iterations (plateau)

Chi Proxy Anomaly

• Finding: χ_max(z) correlates negatively with local error (Spearman ρ = -0.28 to -0.50 within regimes)
• Expected: positive correlation (higher χ → harder → higher error)
• Explanation: The Dobrushin bound is a sufficient condition, not tight. High χ can coexist with fast empirical decay because:
  1. The bound takes worst-case over operator norms
  2. High-degree nodes have high χ but their neighborhoods capture more of the relevant graph
  3. The actual deletion influence depends on the specific edge structure, not just the bound
• Impact on paper: Report honestly. The theory gives valid locality guarantees but χ is not a practical predictor of deletion difficulty.

Exclusion Rules

• Configs with fewer than 10 edges after count generation: skipped
• Decay fits with fewer than 3 valid distance shells: marked invalid
• 24/198 PG deletions where exact ≈ full (trivial edges): included in data but noted

MovieLens Binary Caveat

• All observations are x_ij = 1, producing near-zero per-edge influence
• RelErr(R=2) < 10^{-4}: the deletion is trivially local
• Included for completeness but not informative for testing the theory
• The rating-count transformation is more meaningful

Runtime Analysis

• Local R=1 gives 2.9-3.0x speedup (edge filtering works)
• Local R≥2 gives minimal speedup at N=300 (neighborhood covers most of graph)
• Speedup should scale as O(N/d^R) on large sparse graphs

File Manifest

• Sanity checks: results/raw/sanity_*.jsonl (270 records)
• Synthetic: results/raw/full_synthetic_*.jsonl (2700 records)
• Model family: results/raw/model_family_v2_*.jsonl (1080 records)
• Real data: results/raw/real_scaled_*.jsonl (600 records)
• Total: 4,650 records

Timestamp

Generated: 2026-04-25