PIVOT Explained — From Paper to Working Code in 10 Minutes

You enabled sparse attention. Your model still chokes at 128K tokens. The indexer is why — and PIVOT fixes it without touching your weights. TL;DR Sparse attention's indexer scores all L tokens per query → still O(L²) PIVOT groups nearby queries (which select ~90% overlapping top-k tokens), runs one proxy scan per group → O(L²/g) Result: 4× indexer speedup , 1.6× end-to-end latency reduction on DeepSeek-V3.2 and GLM-5.1 Training-free: plug into existing DSA models at inference time Two modes:…