HermitCrab analysis: a per-word root-search cache cut Sena work 21.3% in the port; C# repeat-lookup share unmeasured

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
38/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Activo
Stack tecnológico
csharp
Área
performance

Línea de trabajo

Read row 28 of the #490 ledger and the issue’s C# versus PanGloss comparison first. Measure the cost of repeated (stratum, shape) root-trie lookups on Sena in C# before implementing anything. Done means reporting whether that work share is material and, based on the result, whether to port the bounded per-word cache.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Claude-drafted.

A per-word root-search cache cut Sena work by 21.3% in the Rust port, but the C# record says repeated root lookups are only 0.5 to 3.3% of parser work. Whether C# has the same gap is unmeasured. Analysis branches that reach the same (stratum, shape) repeat the identical root-trie search.

Status: merged in the port; not built in C#.

What we know (port, work steps; parses identical on every completed word):

  • Sena: 182,297,249 to 143,399,740 (-21.3%, measured before the edge index of #599 landed). Mbugwe -0.6%; Cebuano -0.1%, or -1.2% with an added enclitic; the other samples and fixtures about 0.
  • It holds the raw ordered trie result per word, keyed by exact (stratum, shape), capped at 1 MiB (peak 1.04 MB on Sena), and is discarded after each word. Lexical-entry filtering, overlay and dedup still run on every lookup. A capped or timed-out search is never cached. A result is stored only if its search cost more than a hit is charged, so no path costs more.
  • Ledger row 28 closed a similar C# cache: untraced C# makes 1.13 to 1.49 calls per distinct (stratum, shape).
  • Inferred: the port's larger gain comes from charging a lookup per trie edge, which makes repeats dearer than in C#'s unit.

Not known: the share of C# work spent on repeated lookups on Sena.

Proposed change: measure that share first, on hc.dll, in lookups and work steps. Port the cache only if the share is material, and then only after an explicit decision against the no-memoization rule (ledger row 38): it is a bounded memo.

Related:

  • PanGloss: sillsdev/PanGloss#92 (closed by PR sillsdev/PanGloss#96, merged).
  • sillsdev/machine#599 (open); #490 (closed PR, retired record).

Next: count untraced repeated (stratum, shape) lookups and their work on Sena in hc.dll.

Evidence -- numbers, method

From PanGloss PR #96 and its lane report (single-threaded --stats).

Grammar Work before Work after Peak cache
Sena 182,297,249 143,399,740 (-21.3%) 1,042,524 B
Sena, with the port's edge index (#599) and cache together 182,297,249 138,405,255 (-24.1%) 1,042,524 B
Mbugwe, 1,636 completed words 35,582,069,812 35,354,992,356 (-0.6%) 1,048,396 B (cap 1,048,576)
Cebuano base 5,395,400 5,392,090 (-0.06%) 427,336 B
Cebuano with enclitic 6,340,178 6,265,316 (-1.2%) 427,336 B

Cebuano rows compare against a build with the edge index but no cache. Seven Mbugwe words never complete on either build and are unverified. Cache bounds are conservative allocation estimates, not allocator measurements.

Surprising findings -- why this reopens a closed ledger row

Row 28 closed the cache because trace mode (which disables merging) had inflated the lookup count to 97,575 over 56 shapes. Untraced, repeat-lookup work was 0.5 to 3.3% of parser work (10.4% only on row 25's pre-fix bug); lookup was 1 to 12% of parser work. PanGloss merged a narrower version anyway: per word, exact key, capped, discarded after each word.

Lookup gap (search-cost round, open lead 14): on the slowest word of one private project, the port made 18 lookups on C#'s export against C#'s 49. Parses were identical and the cause was not investigated there. Ledger row 24 later attributed a related gap (18 lookups against 1,655 on the port's own snapshot) to a loading difference, not search. Neither figure is evidence about repeats in C#.

Sources -- pinned
Lenguaje dominante
C#
Estrellas
29
Forks
16
Merge medio
5 d 21 h
PR fusionados (30 d)
9

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