Retrieval supervision was only being used to reward a model after the fact, and using it to steer the search instead gained 3.2 points
AspireAI community · arXiv
Multimodal embedding models augment their inputs with self-generated reasoning, but the reasoning itself is never observed and the input does not determine it, so several equally plausible traces can carry different retrieval value. PILOT treats that reasoning as a latent variable and splits it into two modes of one shared MLLM: a prior that conditions only on the input, and a posterior that also sees training-time relational evidence and therefore explores further. An importance-weighted variational objective lets the two modes co-evolve, and posterior trajectories are transferred to the prior only when they are both useful and reachable. On the 78-task MMEB-V2 benchmark PILOT beat the primary baseline across all 12 task groups at both 2B and 7B parameters, improving overall scores by 3.2 and 3.3 points, with the largest gains in visual-document retrieval at +6.1 and +6.4 points. The claim is narrower than a general quality win: relational supervision helped most as a signal for shaping reasoning exploration, not as a post-hoc reward.
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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.