Commit Graph
1 Commits
Author SHA1 Message Date
volt 7378f65189 beam: Q59 -- pin the jump hash mapping with golden vectors from the C reference
The module's docstring claims 'results match the C reference' and no cell
graded it: _MULT ...1757->...1751 and the md5 hi^lo fold -> hi both passed
7/7 while remapping 99.0% and 99.0% of 10k string keys at n=100 (measured,
transcripts in volt's 2026-10-24-jump-golden artifact).

- jump_ref.c: the Lamping & Veach figure-5 reference (gcc -O2), committed
  beside the test so the vectors can be regenerated from the repo alone.
  Measured against the Python module on 630,910 (key, n) pairs: 0 mismatch.
- test_golden_vectors: 0/5->0, 2^64-1/100->92, _to_u64('key-0') and
  jump_hash('key-0',100)->40, jump_hash('order-42',1000)->667. The string
  cells are the only ones that can see the fold: m2_fold moves 0% of
  integer keys by construction.
- test_minimal_movement: lower bound at 0.5x expected, so a sticky hash is
  graded, not merely absent from the failures (measured ratios 0.974-1.047).
- test_uniformity_other_bucket_count: n=97 prime, +/-10%, observed -5.28/+4.57.

Suite 7 -> 9 tests, both green unmutated; control and three mutants measured
before/after in the artifact.
2026-10-24 11:46:16 +00:00