Iterative sensitivity probing: how bitsandbytes2 finds each layer's compression limit

Tim_Dettmers · x · 2026-09-22

The core challenge of dynamic compression is estimating each layer's sensitivity, which shifts as other layers compress — a combinatorial problem. Iterative sensitivity probing exploits a simple intuition: the closer a model is to its instability edge, the easier it is to estimate multi-layer interactions from single-layer compression. Start uncompressed, measure sensitivities, identify sensitive layers, compress slightly while reallocating bits to sensitive layers, and iterate until the (bit, expert removal) allocation stops changing.

Related event: Dettmers Explains Iterative Sensitivity Probing and Dynamic REAP(2 posts)→

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