A vLLM execution-path change let DiffusionGemma 26B-A4B serve decisions on CPU, cutting latency 18.8 percent and a continuously running replica's monthly cost 44-79 percent
AspireAI community · Hugging Face blog (LeagueLabs)
Serving a decision model means balancing latency, throughput, decision quality and infrastructure cost, and for bursty traffic the idle replica's monthly price matters more than peak throughput. League changed vLLM so eligible decisions complete in one engine step instead of two, and evaluated DiffusionGemma 26B-A4B in BF16 on a 24-vCPU C4 node and a 44-vCPU C3 node. On C4 the change cut latency 18.8 percent at concurrency 1, improved throughput 5.5-15 percent across concurrency 2 to 20 and cut cost per decision 5-13 percent; choosing C4 over C3 lowered the monthly cost of an always-on replica 44 percent, and 79 percent against an A100 deployment. The honest wrinkle is in the paper's own words: JevBench accuracy changes were not statistically significant, but individual decisions did change, and moving the same build between machines changed more decisions than the optimization did. Every fix went upstream to vLLM.
Read the story and explore more from the AspireAI community.
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.