HISA author reproduces Periodic Weak Spots: block indexer avoids CSA's phase sensitivity

青稞AI · wechat · 2026-10-22

The HISA author breaks down how hierarchical coarse-to-fine candidate selection speeds up the sparse-attention indexer while keeping token-level attention quality, and reproduces the Periodic Weak Spots experiments comparing DSA, CSA and HISA.

Key findings: CSA shows severe phase sensitivity (accuracy swings from 1.95% to 75.78% across training phases, a 73.83-point gap), while HISA stays as stable as DSA with higher average accuracy (50.05% vs 45.41%), pinpointing block core-attention—not block indexing—as the culprit. The piece also surveys HISA variants combining layer compression (DeepSeek-V4.1-flash's reindex), head compression (MISA) and query-block compression (PIVOT).

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