r4B_arcmix_qa2x_seed1338/README.md

r4B_arcmix_qa2x_seed1338 — round 4: arm B of round 3 repeated with a different seed

Why it exists: measures run-to-run noise. Identical to r3B_arcmix_qa2x/ (same data, same checkpoint, same recipe) except the random seed (1338 instead of 1337). The difference between the two runs is therefore noise, and it sets the threshold every data comparison in this study has to beat.

Results

checkpoint	step (read from file)	ARC-Easy	BLiMP	WikiText-2 byte-ppl	eff (board formula, 62.9M)
ckpt_340k.pt	340000	47.01	75.89	2.3798	75.49
ckpt_360k.pt	360000	46.30	76.24	2.3765	75.37
ckpt_380k.pt	380000	46.38	75.87	2.3784	75.27
ckpt_400k.pt	400000	46.80	75.57	2.3722	75.32

Verdict: seed 1338 minus seed 1337 on eff: +0.26 / −0.34 / −0.32 / −0.28 at 340k / 360k / 380k / 400k. The seed alone moves eff by about ±0.3, ARC-Easy by 0.5-1.4 pp and BLiMP by 0.1-0.5. None of the data arms in rounds 3-4 differ from each other by more than this.

Common setup

• Base model: GoLLeM-v5 64M flagship (v1_muon/, 62.9M parameters, 14 layers, d_model 576, 9 heads, RoPE, SwiGLU, RMSNorm, QK-norm, value residual, Muon optimizer). Every arm of the study starts from the flagship checkpoint at step 320,000 and continues to step 400,000 (80k steps, about 2.6B tokens) with the flagship recipe unchanged (same learning-rate schedule, batch, optimizer state and seed). Only the training data differs. Exception for this arm: the data is identical to r3B_arcmix_qa2x/ and only the random seed differs (1338 vs 1337).
• Method: two arms trained in parallel from the same checkpoint, evaluated at matching steps (360k / 400k for the first round, 340k to 400k for rounds 3-4) with the same harness; the difference between arms is attributed to the data.
• Evaluation: glint_parity_eval.py in the repository root (fixed version: BLiMP on exactly 67,000 pairs), ARC-Easy test (bare prompt), BLiMP, WikiText-2 test byte-perplexity, eff by the Glint board formula. The step in the tables is read from the checkpoint file, not from its name.
• Reference: flagship v1_muon/ckpt_400k.pt scores ARC-Easy 47.94 / BLiMP 75.83 / byte-ppl 2.3718 / eff 75.81. For scale: a second run that differs only in the random seed (r4B_arcmix_qa2x_seed1338/ vs r3B_arcmix_qa2x/) moved eff by +0.26 / −0.34 / −0.32 / −0.28 at 340k-400k, so run-to-run noise is about 0.3 eff (one seed pair: an order of magnitude, not a precise estimate).
• Status: research checkpoint, not a leaderboard submission. No arm of this study beats the flagship beyond run-to-run noise.
• Format: PyTorch checkpoint dict with model, opt, step, config; train_gpt_ref.py in the repository root rebuilds the model from config.
• Data: ARC-MIX, see the root card of this repository.