Orthrus-Qwen3: up to 7.8×tokens/forward on Qwen3, identical output distribution (github.com)
73 points by FranckDernoncou 10 hours ago
bertili 27 minutes ago
Does this translate into a similar reduction in compute?
What's the catch?
xiphias2 3 hours ago
The most interesting part of this idea for me is how it wasn't tried / implemented before, as it makes sense.
I haven't read the paper but of course DTree tricks work here as well
FranckDernoncou 10 hours ago
Paper: https://arxiv.org/abs/2605.12825 ; Code+models: https://github.com/chiennv2000/orthrus ; Disclosure: co-author.
Idea: Inject a trainable diffusion attention module into each layer of a frozen AR Transformer. Both heads share one KV cache. Diffusion head projects K=32 tokens in parallel; AR head verifies in a second pass and accepts the longest matching prefix. Output distribution is provably identical to the base model.
Results:
- Up to 7.8x TPF, ~6x wall-clock on MATH-500.
- 16% of params trained, <1B tokens, 24h on 8xH200.
- vs. diffusion LMs (Dream, Fast-dLLM-v2, SDAR, Mercury, Gemini Diffusion): they modify base weights and lose accuracy (Fast-dLLM-v2: -11 pts on MATH-500). Orthrus freezes the backbone; accuracy matches Qwen3-8B exactly.
- vs. Speculative Decoding (EAGLE-3, DFlash): no external drafter, no separate cache, zero TTFT penalty (no drafter to init/sync). KV overhead is O(1) (~4.5 MiB flat). Acceptance length on MATH-500: 11.7 vs. 7.9 (DFlash) vs. 3.5 (EAGLE-3).
- Single-step denoising beats multi-step (6.35 vs. 3.53 TPF). KL distillation beats CE on acceptance rate.
Limitations: strictly bounded by the frozen base model (inherits its biases, hallucinations, knowledge gaps); Qwen3-only evaluation; greedy + rejection sampling only.
dot_treo 13 minutes ago
Do you plan on releasing the training code?
ilaksh 4 hours ago
Amazing. Is it possible to do this with Qwen 3.6 27B? Will it work with quants (I assume so)?
sleepyeldrazi an hour ago
From a quick and shallow view of the paper, it looks very feasible (with a little tinkering ) to be adapted to qwen3.6 27B. The process looks somewhat similar to training a LoRA, or in a way distilling your own model so that a mini model learns how to imitate it, and you glue them. I might bite the bullet and rent a gpu to do it for 3.6 27b, as this will solve a lot of my problems.
sleepyeldrazi 41 minutes ago
littlestymaar 34 minutes ago
So, it's D-Flash but at each transformer layer and share the KV cache of the original model? Very smart!