Byrne-100M-Ultra-MC / BENCHMARKS.md
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5M 2x2 table; knock-out is not a matched train
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Byrne-100M-Ultra-MC - Benchmark Scores

All scores for the released checkpoints (base pretrained, SFT, DPO). Same byte-level tokenizer across all, so numbers are directly comparable.

Generated 2026-08-18

checkpoint stage context
base-62k pretrained (Dolma-blend, step 62k) 1024
sft-7100 SFT on UltraChat (step 7.1k) 4096
dpo-3200 DPO on the SFT model (step 3.2k) 1024

1. Downstream benchmarks (lm-eval-harness style)

Scale: capped - 200 examples/MC-task, BLiMP 150/paradigm (12 paradigms), ArithMark 500. Full-scale (uncapped) re-run in progress; this file will be updated with tighter stderr when it finishes. Binomial stderr = sqrt(p(1-p)/n).

metric base-62k sft-7100 dpo-3200 chance
WikiText-2 byte_ppl (down) 2.308 2.383 2.385 -
BLiMP acc (up) 0.811 0.780 0.779 0.50
arc_easy acc 0.410 0.395 0.400 0.25
arc_easy acc_norm 0.390 0.400 0.400 0.25
arc_challenge acc 0.205 0.265 0.255 0.25
arc_challenge acc_norm 0.270 0.260 0.260 0.25
hellaswag acc 0.370 0.375 0.370 0.25
hellaswag acc_norm 0.435 0.420 0.415 0.25
winogrande acc 0.515 0.500 0.505 0.50
piqa acc 0.565 0.590 0.590 0.50
piqa acc_norm 0.555 0.575 0.575 0.50
openbookqa acc 0.105 0.100 0.100 0.25
openbookqa acc_norm 0.290 0.285 0.295 0.25
boolq acc 0.355 0.430 0.425 0.50
ArithMark-3.0 acc_norm 0.354 0.380 0.378 0.25

Example counts (n): arc_easy=200, arc_challenge=200, hellaswag=200, winogrande=200, piqa=200, openbookqa=200, boolq=200, arithmark=500.

Read: base wins the pure-LM metrics (byte_ppl, BLiMP). SFT/DPO win the task metrics - BoolQ, ARC-Challenge, ArithMark, PIQA - the instruction-tuning trade. DPO is within noise of SFT here. Most MC tasks sit near chance at ~114M params.


2. Perplexity suite (per-token cross-entropy, lower is better)

10x1024-token streamed windows per source (WikiText-2: 40 windows).

domain base-62k sft-7100 dpo-3200
Python-Edu (code) 4.52 4.54 4.54
Cosmopedia-v2 5.51 5.38 5.35
FineMath-4+ 6.32 6.84 6.86
Dolma 7.11 7.55 7.57
Wikipedia 7.26 7.83 7.84
UltraX-web 7.95 8.58 8.60
DCLM 8.21 9.10 9.12
WikiText-2 9.08 10.11 10.13
FineWeb-Edu 10.53 11.69 11.70
mean (5-src) 6.50 6.89 6.89

mean (5-src) = Python-Edu, Cosmopedia, FineMath, UltraX, DCLM.


3. Memory Cache (base 62k + DPO 3.2k)

Paper tests from Behrouz et al. 2026 (arXiv:2602.24281) on base_62k.pt. Same 6-trial S-NIAH grid and MQAR, MC on vs mc_gate zeroed. These changed the direction: they are the recall evals, and this 114M base is at chance either way. That is not proof MC helps, and not proof it does not.

test MC on MC off
MQAR n_kv=8 (20 queries) 0/20 0/20
MQAR n_kv=16 (20 queries) 1/20 0/20
S-NIAH-1 passkey (36 trials) 0/36 0/36
S-NIAH-2 numeric (36 trials) 1/36 0/36

S-NIAH-2 MC-on hit is 1/6 at length 512 depth 0 only. n=6. Noise.

How it may be in the CE path (not a matched-train result):

metric value
gate strength DPO 3.2k (mean abs(tanh(gate)) over layers) 0.599 (range -0.75 .. +0.90)
UltraX PPL, MC on 9.87
UltraX PPL, MC off (inference knock-out) 11.86
knock-out, this checkpoint -16.7% perplexity

Gates are open; deleting the branch at inference costs ~17% PPL (was ~9% earlier in training). That is not a matched train. At 5.7M, training without the branch (std) beat training with MC alone. See section 6.


4. Fractal RoPE - schedule dependence (base 62k, natural text)

Trained fractal (Cantor-spectrum, gamma=1) vs geometric RoPE swapped in at inference on the same weights. In-distribution PPL. Dependence, not "fractal is better."

source fractal (trained) standard (swapped) delta
UltraX-web 7.95 77.86 +879%
DCLM 8.21 70.74 +762%
FineWeb-Edu 10.53 81.57 +675%
WikiText-2 9.08 71.06 +683%

5. Fractal RoPE - both models, unique text, native vs swap

eval_rope_swap.py. Unique non-repeating records, 3 windows. Twin is step 38.5k, MC off, geometric RoPE. Ultra-MC is step 62k, MC on, fractal. Two knobs, unmatched steps. Native-vs-swap within a net is the clean number. Cross-model 2048 is a hint, not an ablation.

model 256 512 1024 2048
Ultra-MC 62k native (fractal) 3.20 2.66 2.56 30.67
Ultra-MC 62k swap β†’ geometric 3.22 3.55 21.65 141.90
Twin 38.5k native (geometric) 3.06 2.55 2.50 4.48
Twin 38.5k swap β†’ fractal Ξ³=1 3.36 2.81 2.73 2.76

PPL by target position, 2048 window:

pos Ultra native Ultra swap Twin native Twin swap
0–256 3.78 3.79 3.64 3.93
256–512 2.21 3.94 2.20 2.37
512–768 2.28 127.32 2.25 2.43
768–1024 2.40 116.38 2.39 2.61
1024–1280 19.42 759.55 2.37 2.59
1280–1536 665 1132 2.68 2.57
1536–1792 1122 775 5.28 2.79
1792–2048 1171 1098 112.09 3.06

Ultra-MC: fractal load-bearing inside 1024; native also dies past 1024. Twin: geometric load-bearing inside 1024; holds to ~1536; last 256 blows on geometric and does not if you put fractal frequencies on those weights.


6. 5.7M matched 2x2 (10k steps, current FineWeb-Edu blend)

Isolation test the 114M twin is not. One seed. WikiText-2: 20 x 1024 windows, same tokenizer as the rest of this file.

run MC RoPE Wiki @1024 unique @1024 unique @2048 unique @4096 val_loss @10k
std off geometric 34.82 46.75 56.57 98.51 4.964
mc on geometric 41.23 161.49 199.41 267.31 5.055
fractal off gamma=1 40.49 145.30 217.79 303.29 4.999
both on gamma=1 32.82 26.67 76.41 158.95 4.867

Post-train RoPE switch on std (nothing else on): unique 1024 46.75 -> fractal-at-load 54.95; 2048 56.57 -> 60.58. Does not help.

MC knock-out (unique PPL): both 26.67 -> 33.93 at 1024; mc 161.49 -> 170.47. MQAR 0/16 all four.

At this size: MC alone no. Fractal alone no. Post-hoc fractal on std no. Both-together yes at 1024, then worse stretch than std. Gate strength similar on mc vs both (mean |tanh| ~0.25); mc gates have mixed sign, both layers 1-4 the same sign. Hypothesis: the branch only settled next to fractal frequencies. One seed. Not 114M.