PIVOT

PIVOT: Training-free sparse attention indexer cuts DeepSeek-V3.2 latency by up to 1.6x

PIVOT (Proxy Indexing Via One full-prefix Traversal) is a training-free drop-in replacement for the DeepSeek Sparse Attention (DSA) indexer that reduces the O(L²) per-query scan cost by grouping nearby queries and sharing a single prefix scan across the group. Two variants (PIVOT-Reuse and PIVOT-Refine) trade speed for fidelity, with PIVOT-Refine matching dense indexer accuracy. Evaluated on DeepSeek-V3.2 and GLM-5.1 across LongBench and RULER, PIVOT accelerates the indexer by up to 4x and reduces end-to-end latency by up to 1.6x at long context.