rules: forbid raw index vectors as persistent cache keys - #12
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Raw Vec<usize> / Vector{Int} keys pay an O(length) hash and equality walk
per lookup, clone on insert, and retain O(length) memory per entry. Require
mixed-radix flat integer encodings (width selected from the index-space
size) or stable interned IDs instead. Motivated by tensor4all-rs #626/#627,
where TTCache's persistent maps still key by Vec<usize>.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Adds a performance rule, in the common checklist plus Rust and Julia specializations, forbidding raw index vectors (
Vec<usize>,Vector{Int}) as keys of persistent or hot-path caches.Rationale: every lookup pays an O(length) hash and equality walk, every insert clones the vector, and retained keys can rival the cached payload in memory. The required alternative is a mixed-radix flat integer key with the width selected from the index-space size (u64, u128, then extended integers, as in tensor4all-simplett's
FlatIndexer), or stable interned IDs when the key space is unbounded.Motivated by tensor4all/tensor4all-rs#626 and tensor4all/tensor4all-rs#627, where
TTCache's persistent maps still key byVec<usize>.🤖 Generated with Claude Code