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Speeding up gearhash on ARM64

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  1. Faster Maps: Chasing Swiss Speed

    ParparVM’s HashMap suffered catastrophic miss latency due to linear probing on dense integer keys. By adopting CPython‑style perturbed probing (Swiss‑table style) and extending tagged immediate values to more primitives, miss latency dropped from 32 s to ~45 ms, allocation pressure fell dramatically, and overall performance stayed roughly flat despite a modest hit‑time slowdown.

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