Record: 11L Parallel Muon + N-gram Backoff Cache — val_bpb 0.2841 (3-seed mean)

records/track_10min_16mb/2026-03-26_11L_ParallelMuon_NgramBackoff/README.md

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+# Record: 11L Parallel Muon + N-gram Backoff Cache — val_bpb 0.2841
+
+**3-seed mean val_bpb: 0.2841** (std 0.0001) | **~15.85 MB** | 8xH100 SXM
+
+## 3-Seed Results (8xH100 80GB SXM, PyTorch 2.9.1+cu128)
+
+| Seed | step_avg | steps | EMA bpb | Quantized bpb | **N-gram bpb** |
+|------|----------|-------|---------|---------------|----------------|
+| 1337 | 88.6ms | 6,774 | 1.1193 | 1.1270 | **0.2841** |
+| 42 | 88.8ms | 6,757 | 1.1194 | 1.1276 | **0.2840** |
+| 2024 | 88.7ms | 6,769 | 1.1191 | 1.1275 | **0.2840** |
+| **Mean** | **88.7ms** | **6,767** | **1.1193** | **1.1274** | **0.2841** |
+
+## Key Innovation: N-gram Backoff Cache
+
+Eval-time order 2-9 backward-looking N-gram cache with entropy-adaptive alpha blending:
+
+```
+for each 65K-token chunk:
+    Phase 1 -- SCORE: sliding window (stride=64) with N-gram interpolation
+        - For each token, blend model P(token) with N-gram P(token) using adaptive alpha
+        - Alpha determined by model entropy and N-gram order (higher orders = higher weight)
+    Phase 2 -- UPDATE: add scored tokens to N-gram frequency tables (backward-looking only)
+```
+
+N-gram cache reduces BPB by 4x (1.1274 -> 0.2841) by exploiting repeated phrases and patterns in the validation data. Score-first: cache only contains already-scored tokens.
+
+- **4M hash buckets**, order 2-9 with XOR-of-products hashing
+- **Entropy-adaptive alpha**: sigmoid(entropy_scale * (entropy - center)), scaled by per-order multipliers
+- **Per-order multipliers**: orders 2-3 suppressed (0.3x), orders 5-9 boosted (2.0x)
+- **65K-token chunks**: cache refreshes every 65K tokens for maximum coverage
+
+## Architecture (26.8M params)
+
+- 11L, 512d, 8H/4KV (GQA), MLP 3x LeakyReLU(0.5)²
+- Parallel Muon with parameter banking + batched Newton-Schulz
+- SmearGate, BigramHash(1024), Value Residual, Gated Attention
+- XSA4, Partial RoPE(16/64), U-Net skips, OrthoInit
+- EMA(0.997) + SWA, Late QAT, GPTQ-lite int6 + zstd-22
+- Flash Attention 3, torch.compile(fullgraph=True)
+
+## Timing
+
+- Training: 600s (6,770 steps at 88.7ms/step)
+- Eval (N-gram): ~420s
+- Total: ~1020s (within 600s train + 600s eval budgets)
+
+## Compliance
+
+- [x] Training under 600s
+- [x] Eval under 600s (N-gram ~420s)
+- [x] Artifact under 16,000,000 bytes
+- [x] N-gram cache is strictly backward-looking (updated AFTER scoring)
+- [x] No training data access during evaluation
+- [x] No oracle/hindsight selection
+
+## Credits
+
+- N-gram cache concept: PR #659 by @deanbrr, PR #674 by @newjordan
+- Multi-order backoff + entropy-adaptive: PR #702 by @lukacf
+- Fine-grained chunk updates: PR #843 by @quietsmile
+- Parallel Muon / Parameter Banking: PR #399 by @abaybektursun
+- LeakyReLU²: PR #493 by @parinzee
+- Base model stack: PR #414 by @signalrush

records/track_10min_16mb/2026-03-26_11L_ParallelMuon_NgramBackoff/submission.json

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+{
+  "author": "Aryan Bhosale",
+  "github_id": "aryanbhosale",
+  "name": "11L Parallel Muon + N-gram Backoff Cache (mean val_bpb=0.2841)",
+  "blurb": "11-layer 512d transformer with Parallel Muon, BigramHash(1024), Value Residual, Gated Attention, XSA4, Partial RoPE(16/64), EMA(0.997)+SWA, Late QAT, GPTQ-lite int6+zstd-22. Eval-time order 2-9 N-gram backoff cache with entropy-adaptive alpha, 65K-token chunk updates. 3-seed mean 0.2841 BPB on 8xH100 SXM.",
+  "date": "2026-03-26T12:00:00Z",
+  "val_loss": 0.4796,
+  "val_bpb": 0.2841,
+  "val_bpb_std": 0.0001,
+  "bytes_total": 15900000,
+  "bytes_code": 93397,
+  "seeds": {
+    "1337": {"val_bpb": 0.2841, "val_loss": 0.4796, "steps": 6774, "step_avg_ms": 88.6},
+    "42": {"val_bpb": 0.2840, "val_loss": 0.4796, "steps": 6757, "step_avg_ms": 88.8},
+    "2024": {"val_bpb": 0.2840, "val_loss": 0.4795, "steps": 6769, "step_avg_ms": 88.7}
+  }
+}