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[MASK] sequence and unmasks progressively, so the
number of forward passes (NFE) is a knob rather than a function of sequence
length.| Architecture | bidirectional DiT denoiser, AdaLN-Zero time conditioning |
| Objective | MDLM / SUBS masked-diffusion loss |
| Parameters | 55,543,634 |
| Width / depth / heads | 384 / 6 / 6 |
| Context length | 1024 |
| Vocabulary | 50,258 (GPT-2 + [MASK]) |
| Training steps | 30,000 |
| Tokens seen | 3,932,160,000 |
| License | Apache-2.0 |
aether-eval; see
the evaluation protocol.| metric | value |
|---|---|
| NELBO (nats/token) | 7.136 |
| Bits per dim | 10.3 |
| Perplexity (upper bound) | 1257 |
| MAUVE | 0.999 |
| distinct-2 | 0.971 |
| Sampler / steps | ancestral / 128 |
Perplexity here is an upper bound, not an exact likelihood. A masked diffusion model has no exact factorization oflog p(x); what is reported is a Monte Carlo estimate of a variational bound. It is comparable to other diffusion models evaluated the same way, and not directly comparable to an autoregressive model's exact perplexity, which would flatter the AR model.
1pip install "aether-dlm[serve]"
2aether-serve serve.model_version=hf:ameyg910/aether-55m@v1.0.0
3
4curl -X POST localhost:8000/generate \
5 -H 'content-type: application/json' \
6 -d '{"n_samples":2,"length":64,"steps":64,"sampler":"ancestral"}'1import torch
2from huggingface_hub import hf_hub_download
3from aether.models.loading import build_model_from_checkpoint
4from aether.diffusion.samplers import sample
5
6path = hf_hub_download("ameyg910/aether-55m", "latest.pt", revision="v1.0.0")
7model, config = build_model_from_checkpoint(
8 torch.load(path, map_location="cpu", weights_only=False)
9)
10out = sample(model.eval(), batch=2, length=64,
11 mask_token_id=config.vocab_size - 1, steps=64)
12print(out.tokens.shape, "NFE:", out.nfe)[MASK]
sequence. Prompt-conditioned infilling is a natural extension the architecture
supports but this release does not implement.1@software{aether,
2 author = {Gupta, Amey},
3 title = {Aether: a production platform for masked diffusion language models},
4 year = {2026},
5 url = {https://github.com/ameyg910/aether}
6}