Non-record: MDLM Diffusion — val_var_bpb 1.1465 (first diffusion to beat AR baseline)#1106
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First discrete diffusion model to beat the AR baseline (1.22) in parameter-golf. MDLM with log-linear noise, adaLN, frozen visible-token logits, discrete ELBO eval. 27 hyperparameter experiments. Validated on 2xH100 (TensorPool), 31 min training. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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PR openai#1106 found eps=0.1 >> 0.001 was the single biggest improvement. With eps=0.1, 10% of tokens remain visible at t=1, giving the model anchors for denoising. Larger terminal KL but much easier task. Also revert lr=1e-3, warmdown=1000 (v8's lr=2e-3 made artifact >16MB). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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- train_mdlm_combined.py: full MDLM training script (PR openai#1053 infra + PR openai#1106 MDLM + our innovations) - sweep.sh/sweep2.sh: 12-experiment hyperparameter sweep (eps, arch, loss, seq_len) - results.tsv: updated with v10-v13 experiments, corrected descriptions Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
val_var_bpb: 1.1465 (512 eval steps) | 33M params | 2xH100 80GB HBM3 | Non-record
First discrete diffusion model to beat the AR baseline (1.22 BPB). Beats previous best diffusion (#820, 1.625; #1053, 1.360) by 0.21+ BPB.
Results
Approach
MDLM (Sahoo et al. 2024) with log-linear noise, adaLN timestep conditioning, frozen visible-token logits, antithetic sampling, discrete absorbing-mask ELBO eval. 11L 512d, 6000 steps, AdamW.
Key findings from 27 experiments
Hardware
Developed on GB10 (Project DIGITS). Validated on 2xH100 (TensorPool, 31 min). 8xH100 unavailable (#821). Extrapolated: ~8 min on 8xH100.