Three reviews of "How it compares" (a maintainer audit of the harness, a
methodology review, a reader's red team) led to a full rerun on the Mac and
x86-64 with simdjson 5.1.1 and new ways in the harness:
- in-place parses with the copy made before the timer ("(copy untimed)",
never chosen as a library's best) and json_document::parse_copy();
- RapidJSON through StringStream, and with default precision in validate,
which reads no number;
- BENCH_ONLY takes several prefixes.
The post now gives the copy's real cost (11-14 us for twitter.json on the
Mac, not 30), what yyjson gains without it, the run-to-run noise, the LTO
check, the single-file losses that were missing, and qualifies the headline
claim. Every number in the section and Appendix E is recomputed; the
NUL-byte remark moved out of the body.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Measure everything again against develop with the open pull requests of
11-03 (suite, timeline, comparison on the Mac and on x86-64, compile
times, stream gap), add the suite on an Intel MacBook Pro as a check,
mark the ways that keep number text as "N" in the use-case charts, move
the loop-shape box to theme 5, and apply the style and wording fixes of
the review.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Suite, timeline endpoint, Appendix D and the scalar-run numbers now come from
develop b2674a4a2f with #5990-#5992, #5996-#6006 and #6008 merged. With #6008,
arrays of one element skip the scalar run, so nested arrays no longer pay for
it. The suite ran three rounds per version; the round of 3.12.0 and of 3.13.0
that differed from the other two was dropped, as the setup table says.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Suite, timeline endpoint, Appendix D and the scalar-run numbers now come from
develop b2674a4a2f with #5990, #5991, #5992, #5996, #5997, #5998, #5999 and
#6000 merged. The scalar runs are measured against a build without them on
develop's code, which no longer checks for a scalar before entering the loop.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The baseline is now develop 9c349b1d7c with every open non-draft pull
request merged, including #5968, #5970, #5971, #5975, #5976, #5978,
#5979, #5980, #5981 and #5982. The suite was rerun on 11-01 with every
step repeated when the load rose above 5 while it ran; the comparison
with other libraries and the held-out files were rerun on 10-31.
- suite: 3.0x geometric mean (median 2.9x); Appendix B, the overview
and the distribution regenerated
- timeline endpoint, Appendix D and the cliffs figure updated
- the held-out figure compares json_document with the fastest other
library
- new paragraphs for the pull requests listed above
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- short strings: two overlapping 16-byte loads and stores
- eight digits at a time: the three multiplications, lane by lane
- validate on the 19 held-out files, per file, Mac and x86-64
The prose the figures replace is trimmed.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The suite (Appendix B, the short-version table, the overview and distribution
figures) and the timeline endpoint now measure develop d20c4dcd89 with #5964
and #5908 merged. The geometric mean stays 2.9x (2.95); Dump/signed_ints and
Dump/unsigned_ints gain 1.5x and 2.1x from #5964; GetVectorDouble/floats drops
from 10.3x to 7.0x because the old candidate's suite binary happened to compile
that loop faster (a standalone build takes 0.97 ms with both headers).
The timeline endpoint is the 10-27 value scaled by the ratio of the new to the
old candidate, both measured on 10-30, so that it stays comparable with the
other points of the timeline.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The figures and Appendix E use the reruns with each library's fastest
modes. Skipping number conversion while reading is now allowed for
every library; copying number text is still not chosen when writing.
The text now says who set the rules, where libraries that check less
win select, how minified files change the picture, and that the
reused jeopardy.json claim holds with every library reused. A new
section covers 19 held-out files and JSONTestSuite, including where
json_document loses, and lists what was not measured. Every
comparison number was recomputed; Glaze is credited in the intro.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- deeper technical detail and code in the eight themes; pull request
numbers move to the appendix, timeline steps are labelled by theme
- comparison with other libraries by use case, as heatmaps per
platform, with validation levels and the caveats next to the results
- appendix: test files, all 182 suite rows with a histogram, timeline
steps, algorithmic fixes, per-file tables, behaviour changes, setup,
pull requests by theme
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
A post for the documentation (Home > Blog) on how 3.13.0 became faster:
eight themes with the pull requests behind them, the ideas taken from other
libraries, what did not work, how the fast paths are tested, and the
compile-time cost. Every number comes from a run on 2026-10-27 (3.12.0 against
develop plus the open non-draft PRs, Apple M1 Max) or from the linked PR.
- docs/mkdocs/docs/home/blog/how_3_13_0_got_faster.md: the post.
- docs/mkdocs/scripts/figures/perf_blog.py: draws its 12 figures (overview,
eight timeline panels, the SWAR test, the cliffs, json_view throughput) as
inline SVGs in the nj-charts style; data/perf_timeline.csv holds the
timeline.
- tests/benchmarks/history: history.cpp and history.py time one fixed program
against the header of every commit that changed it, interleaved, and write
one CSV row per commit with its PR. The timeline of the post comes from it.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann