IndexCache Speeds Up Large Models via Cross-Layer Index Reuse
- •IndexCache reduces sparse attention computation by reusing token selections across consecutive model layers.
- •Technique achieves 1.82x prefill and 1.48x decode speedups on a 30B parameter model.
- •Method cuts redundant indexer work by 75% with negligible impact on model output quality.
Modern AI models often struggle with long conversations because the math required to track every word becomes overwhelming. While sparse attention techniques help by focusing only on the most relevant words, they still waste energy re-calculating which words are important at every single level (layer) of the model. Researchers have observed that these calculations are often identical across adjacent layers, creating a significant efficiency bottleneck.
Researchers have introduced IndexCache to solve this redundancy. The system realizes that if one level of the model identifies important words, the next level likely needs the same ones. By designating certain levels as Full layers to do the heavy lifting and letting Shared layers simply copy their results, IndexCache eliminates up to 75% of these redundant calculations. This allows the model to maintain focus without repetitive processing.
The team developed two ways to implement this: a training-free version that uses a smart search to find the best sharing pattern, and a training-aware version that teaches the model to be even more accurate while sharing. In real-world tests on a 30-billion parameter model, this approach nearly doubled the speed of the initial text processing phase (prefill) and significantly boosted the speed of generating responses (decode).
These results suggest that massive AI systems can become much leaner and faster without losing their intelligence. By confirming these gains on models as large as 744-billion parameters, the researchers demonstrate that IndexCache is ready for production-scale use, making long-context tools like AI agents more practical and affordable for everyday applications.