bench(nad): reproducible benchmarks for the adaptive-zoom writer perf work

[gautierbureau]

What

A benchmarks/ suite that measures — reproducibly — the three performance PRs stacked on integration/nad_create_svg_adaptive_zoom (powsybl#423). Additive only; no product code changes. Companion to #7 (metadata indexing), #8 (geometry precision) and #9 (lazyMount); the numbers in those PR descriptions come from this suite.

Benchmarks

script	measures	needs
nad-metadata-index-bench.mjs	writer metadata-lookup cost: find/filter vs Map index	node only
nad-geometry-precision-bench.mjs	emitted coordinate-text size at precision 0–3	node only
nad-lazy-mount-bench.mjs	eager vs lazy off-screen viewer construction	real headless Chromium + demo server + playwright-core

The two node benches are self-contained (the compared implementations are inlined and mirror the shipped code, which is covered byte-for-byte by unit tests). The lazy-mount bench drives the real viewer via the demo server (Vite /@fs), and can exercise either the raw-SVG-injection or the powsybl#423 client-writer construction path (CREATE_SVG_FROM_METADATA=1).

node benchmarks/nad-metadata-index-bench.mjs
node benchmarks/nad-geometry-precision-bench.mjs
npm install --no-save playwright-core && npm run start &
node benchmarks/nad-lazy-mount-bench.mjs        # N=8, raw-SVG path
N=16 node benchmarks/nad-lazy-mount-bench.mjs
CREATE_SVG_FROM_METADATA=1 node benchmarks/nad-lazy-mount-bench.mjs

Recorded results (headless Chromium, dev mode)

Absolute times are machine/run-dependent; the ratios are the portable figures.

Metadata indexing — writer access pattern, find/filter vs Map index:

diagram	old	indexed	speedup
N=1000	24.1 ms	0.49 ms	50×
N=4000	325.7 ms	2.73 ms	119×
pegase	33.2 ms	0.31 ms	~100×

Old ~quadruples per doubling of N (O(n²)); indexed grows ~linearly.

Geometry precision — coordinate-text bytes on real pegase geometry:

precision	raw	gzip	vs p2 (gzip)
2 (default)	57.1 KB	10.4 KB	—
1	49.4 KB	8.7 KB	−16.5%
0	34.0 KB	6.6 KB	−36.2%

(The whole-document figures measured by the writer's own size test — 168.5 KB gzip → 156.0 / 140.8 KB — are in #8; smaller percentages there because coordinates are only part of the SVG.)

Lazy off-screen construction — real browser, N viewers stacked in one viewport:

path	N	per-viewer	eager	lazy on load	saved	ratio
raw SVG inject	8	~41 ms	326 ms	81 ms (2 built)	~244 ms	4.0×
raw SVG inject	16	~41 ms	658 ms	82 ms (2 built)	~575 ms	8.0×
powsybl#423 client writer	8	~373 ms	2985 ms	746 ms (2 built)	~2.2 s	4.0×

Ratio ≈ N / visible, so a page showing ~1 of N approaches an N× reduction; all N build on demand while scrolling. The client-writer path costs ~9× more per viewer than raw injection — which is exactly where the metadata indexing (#7) pays off.

Notes

Draft; base is the in-progress adaptive-zoom branch. playwright-core and (for the writer's own size test referenced above) fast-xml-parser are dev-only and installed --no-save — not added to package.json here.

🤖 Generated with Claude Code

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Generated by Claude Code