GCC -Werror=useless-cast on Linux x86-64 rejects
static_cast<std::size_t>(key_hash(...)): the call returns a
std::uint64_t prvalue, the same type as std::size_t there, while the cast
is needed where std::size_t is 32 bits wide. Store the hash in a variable
and cast that, which GCC does not report.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The "check" job (Check amalgamation) runs develop's amalgamate.py and read
all configurations from the develop checkout, where config_json_view.json
does not exist until this stack lands, so it failed with
FileNotFoundError. Read that configuration from the pull request's
checkout; the tool itself stays develop's.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
GCC -Werror=useless-cast on Linux x86-64 rejected
static_cast<std::uint64_t>((std::numeric_limits<std::size_t>::max)()),
as both are the same type there. Compare without the cast: std::size_t
converts to std::uint64_t implicitly on every platform.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
GCC -Werror=useless-cast (ci_test_gcc on Linux x86-64) rejected
static_cast<std::size_t>(guess + (guess / 4) + 64): the sum is a
std::uint64_t prvalue, the same type as std::size_t there, while the cast
is needed where std::size_t is 32 bits wide. Cast a named variable
instead, which GCC does not report. The build stopped at an earlier error
before, so the previous CI run did not show this one.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- ci_test_noexceptions: exception_of() and without_path() exist only
with exceptions (they catch outside a CHECK_THROWS, which aborts with
JSON_NOEXCEPTION); compile the comparisons of the conversion, value(),
and JSON pointer errors only with exceptions as well.
- ci_test_gcc: -Werror=unused-result for static_cast<void>(j.contains(p))
(GCC's warn_unused_result ignores a cast to void); store the result.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- ci_test_noexceptions: the element access tests compare the exceptions
of json_view and basic_json through exception_of(), which catches them
outside a CHECK_THROWS; with JSON_NOEXCEPTION the first one aborted the
test. Compile those comparisons only with exceptions.
- clang 3.6: value-initialize a const json_view, as in the tests of
json-view/10-view-document.
- Format three new documentation examples with the pinned astyle, which
the "check" job runs once it gets past the amalgamation step.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- ci_test_noexceptions: the helpers that compare the exceptions of
json_document::parse() and json::parse() catch them outside a
CHECK_THROWS, so with JSON_NOEXCEPTION the first parse error aborted
the test. Compile those comparisons only with exceptions, as
unit-class_parser.cpp does.
- ci_test_gcc: -Werror=unused-result for CHECK_THROWS_AS(json_document::
parse(...)); assign the result to a dummy document.
- ci_test_compilers_clang (3.6): `const json_view invalid;` needs a
user-provided default constructor there (CWG 253); value-initialize it.
- ci_test_single_header: json_view.hpp now exists as a single header and
contains the internal view headers, so unit-json_view_builder.cpp
includes it instead of the detail headers in that mode, and the test
is built again with the single header.
- Regenerate single_include/nlohmann/json_view.hpp for the builder change
merged from json-view/08-view-builder.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- msvc (Win32, /W4 /WX) reported C4127 (conditional expression is
constant) for `TrailingCommas && cur() == ']'` and the like when the
option is off. Route the template arguments through a static enabled()
function, as json.hpp's nesting_depth_exhausted() does.
- ci_test_single_header compiled unit-json_view_builder.cpp against
single_include/, which does not contain the internal
nlohmann/detail/view headers. Build that test only with the multiple
headers.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
GCC -Werror=useless-cast rejected static_cast<std::size_t>(next() % n):
on 64-bit Linux std::uint64_t and std::size_t are the same type, while
the cast is needed where std::size_t is 32 bits wide. Draw the sizes from
a 32-bit value instead, which converts to std::size_t implicitly on every
platform.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
GCC (-Werror=unused-result) rejected CHECK_THROWS_WITH_AS(json::parse(...))
because parse() is [[nodiscard]]; assign the result to a dummy json as the
other tests do. clang-tidy flagged longer.find('.') == npos with
abseil-string-find-str-contains; store the position in a variable first.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Lookups in objects are linear, as for ordered_json. Objects with 128
members or more now get a hash table after parsing (open addressing; the
first of duplicate keys is kept, as for the linear search), so that
operator[], at(), find(), contains(), count(), value(), and JSON pointers
take constant time on average in them; the idea of switching to a hash
table for large objects is Boost.JSON's. The parser notes such objects when
it closes them (out of line, so that the parse loop only has a call for
it), and the object node keeps the number of its table.
Looking up each key of an object with 10,000 members: 59.8 ms -> 0.16 ms.
Parsing (json_document::parse, best of 7, separate processes): most files
within 1%; canada +5%, mesh.pretty +3%, citm +3%.
Tests: objects with 127, 128, 129, and 10,000 members (escaped, empty,
and duplicate keys, missing keys, comparisons), nested large objects, and
documents reused with read().
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Hold the UTF-8 lookup tables in std::array, compute the length of a
sequence without nested conditionals, and use std::array in the tests.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Long runs of string bytes are scanned 16 at a time with NEON (AArch64, with
GCC and Clang) and SSE2 (x86-64): both belong to the baseline instruction
sets. A signed compare with 0x20 finds control characters and non-ASCII
bytes at once. Keys keep 16 table checks before the vector loop (their
lengths repeat from record to record, so the branches predict well);
string values have 8, as their lengths vary more.
Non-ASCII text is validated 16 bytes at a time with the "lookup4" check of
simdjson (J. Keiser and D. Lemire, "Validating UTF-8 In Less Than One
Instruction Per Byte", 2021): with NEON, and on x86-64 with SSSE3 if
JSON_VIEW_USE_SSSE3 is defined (SSSE3 is not part of x86-64, and the code
must not depend on the flags of a translation unit). JSON_VIEW_NO_SIMD
selects the portable code. The vector code sits in
detail/view/simd.hpp; the same input is accepted either way.
json_document::parse, best of 7 runs in separate processes (M1 Max):
poet.json (CJK text) -72%, random.json -25%, twitter.json -22%,
gsoc-2018.json -20%, semanticscholar -19%, github_events -11%,
apache_builds -9.5%, canada/citm -5/-6%; lottie +4%, tree-pretty +2.5%.
Tests: every two-byte sequence and three- and four-byte sequences with
continuation bytes at the edges of their ranges, at every offset around
the vector blocks of keys and values, cut short, and long runs of text
with a damaged byte, against json::accept and json::parse. CMake builds
the parser tests again with JSON_VIEW_NO_SIMD, and on x86-64 with
JSON_VIEW_USE_SSSE3 and -mssse3; the macros are documented.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
A workflow runs compare.py with pinned downloads on GitHub-hosted
Ubuntu runners and shows the results as the job summary and as an
artifact: started by hand (workflow_dispatch: x86-64 or AArch64, GCC or
Clang), or when a pull request gets the label "benchmark" (both
architectures, GCC). The label trigger gives numbers before the
workflow is on the default branch, which workflow_dispatch needs.
Shared runners are noisy, so the numbers show where json_view stands on
another architecture; published numbers still need a quiet machine.
compare.py takes the CPU name from lscpu where /proc/cpuinfo has none
(AArch64 Linux), and falls back to the architecture. Checked in Linux
containers (AArch64, Clang 15 and GCC 9, offline with the pinned
archives).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
compare.py --download now checks the SHA-256 of the yyjson 0.13.0,
simdjson 4.6.11, and Boost 1.92.0 archives. It unpacks each archive
once (Boost's directory is boost_1_92_0) and, where Python supports it,
with the 'data' filter.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
tests/benchmarks/json_view/ holds the comparison with other libraries,
which is not built by CMake or run by CI:
- bench_view.cpp: parse, traverse, select, and dump of twitter,
citm_catalog, canada, jeopardy, a single tweet, and a JSON-RPC request,
with json_view, yyjson, simdjson (DOM and On-Demand), Boost.JSON, and
json::parse; all engines must agree on every document before anything
is timed, and run interleaved in every round
- bench_corpus.cpp: parse, traverse, and dump of any list of files
- compare.py: builds both against include/ with the libraries of the
system (or pinned downloads), runs them, and writes the results with
what is needed to reproduce them (date, commit, CPU, OS, compiler,
flags, library versions) to results/<date>-<host>.md and .csv; only the
Python 3 standard library is used
- README.md: how to run it, what is measured, and which features the
engines have, so the numbers can be read correctly
Boost.JSON is optional (JSON_VIEW_BENCH_BOOST).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
The parser records where the integer digits, the fraction digits, and the
exponent of a float token are. For doubles with at most 19 digits, the
value is now read from that layout: the digits eight at a time, without
scanning the token, and rounded with Clinger's fast path where both
operands are exact, else with the Eisel-Lemire algorithm (which needs no
fallback for up to 19 digits). Both round correctly, so the values are
those of parse(); other tokens and types keep the library's conversion.
get<double>(), materialize(), dump(), and comparisons use it. Traversing
canada.json (111,000 floats, every number converted): 0.53 -> 0.86 GB/s.
Tests add tokens around the limits (19 and 20 digits, 2^53, 10^22) to the
bit-for-bit comparison with parse().
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Separate the comparison of discarded values from the other types, so
that the conditional chain has no repeated branch bodies, and mark
the deliberate comparisons of views with empty containers in the
tests.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
- API pages for operator== and operator!= of basic_json_view, linked
both ways with the basic_json pages
- the feature page and the class overview list the comparisons
- the examples show when the view helps: detecting a changed document
without building json values
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
basic_json_view gains operator== and operator!= with other views and with
basic_json values. Two views are equal if the values parse() would
produce for them are equal by basic_json's operator==: numbers compare by
value across their types, and objects by their members, with duplicate
keys resolved as parse() resolves them (the last value, at the position of
the first key). Objects are compared in member order if the object type
keeps an order (ordered_json), by key otherwise, as basic_json does.
Discarded views compare as discarded basic_json values do, which follows
JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON. Nothing is materialized except
single numbers, and the walk is iterative.
Tests compare the results for pairs of 1,200 generated documents (also
written differently: sorted keys, canonical numbers) with those of
basic_json, for json and ordered_json, plus numbers, duplicate keys,
member order, discarded values, and 100,000 levels of nesting.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann