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Niels Lohmann
ea03d601af
* Compare json_view values without a vector per container and a basic_json per number
operator== of views (view/view, view/json, and editable documents) built two
vectors of members for every object it entered, sorted them with stable_sort
for every object, and converted each number to a basic_json value. It now:
- keeps the members of all open objects in one vector (reserved with
geometric growth, so that nested objects do not reallocate), and orders
them by insertion sort for up to 16 members, or not at all when the keys
ascend already;
- compares numbers of one type directly, and builds a basic_json only for
numbers of different types;
- compares short texts (keys, numbers, most strings) with two overlapping
loads (bytes_equal(), in node.hpp);
- first walks both documents in lockstep, in the order of their text, which
finds most pairs of equal values without the work of the comparison. The
walk only enters an object if the comparison would visit its members in the
same order (the object type keeps the order, the keys ascend, or all values
are scalars), so a difference is never found later than before, and it
records the containers it found different, so that the comparison does not
walk them again;
- rejects values of different types and arrays of different sizes before any
of this, and, for an object type that keeps the order, objects whose first
(up to four) members have different keys, which ends a comparison that
differs near the start without preparing the members.
Results are unchanged: numbers compare by value across types, duplicate keys
resolve as parse() resolves them, and objects compare in document order for
ordered_json and by key otherwise.
Instructions of one comparison of a document with an equal copy, macOS arm64
(develop -> now), json_document / ordered_json_document / editable:
twitter 16.1M -> 7.0M 17.7M -> 1.5M 16.6M -> 7.3M
citm 45.0M -> 3.4M 47.0M -> 3.2M 45.7M -> 4.3M
canada 111.4M -> 13.7M 111.4M -> 13.7M 113.3M -> 15.0M
jeopardy 26.2M -> 3.7M 27.3M -> 3.7M 26.6M -> 12.1M
and of a view with a basic_json value:
twitter 11.4M -> 5.9M 11.2M -> 7.3M 11.6M -> 5.9M
citm 33.9M -> 9.7M 32.6M -> 9.1M 34.6M -> 9.8M
canada 92.9M -> 32.1M 92.9M -> 32.1M 93.9M -> 32.8M
and Linux instruction counts (GCC 13 / Clang 18) of the same comparisons:
document with an equal copy json_document ordered_json_document editable
twitter -49 % / -52 % -89 % / -89 % -48 % / -50 %
citm -90 % / -89 % -91 % / -90 % -88 % / -87 %
jeopardy (4,000 questions) -85 % / -85 % -86 % / -86 % -46 % / -49 %
view with a basic_json value
twitter -41 % / -45 % -28 % / -35 % -45 % / -44 %
citm -63 % / -65 % -63 % / -66 % -65 % / -64 %
jeopardy -39 % / -43 % -14 % / -24 % -44 % / -43 %
A sweep that places one difference at about 2,100 positions of eight
documents (a token at an even spacing, the first and last tokens, the first,
middle and last member of the root removed, one appended, the document
wrapped) in five kinds of comparison (view/view of read-only and of editable
documents, view/json, json_document, editable/view) finds the same results as
before and no placement slower on the Mac (Clang); on Linux no placement is
slower than 3 % (Clang and GCC).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Check the float tokens of a json_document image without a sort and a scan of every character
load(image_check::full) checked every float token of an image by sorting
the token ranges, scanning the token character by character, and comparing
the digit layout with the node's. Now:
- the ranges are sorted only if they are not sorted already (save() writes
them in the order of the nodes, so they are);
- a token of the shape [-]digits.digits whose digit counts are the ones the
node records (nearly all of them) is accepted by checking its digits eight
at a time, without the general scan;
- the general scan skips runs of digits eight at a time.
Damaged tokens are still rejected as before: the check accepts exactly the
tokens that the general scan accepts.
Instructions of load(image_check::full) (develop -> now):
macOS arm64 canada 44.6M -> 30.9M (-31 %), jeopardy 11.3M -> 10.7M,
citm 10.4M -> 10.0M, twitter 5.06M -> 4.94M
Linux GCC 13 canada -50 %, jeopardy -43 %, twitter -31 %, citm -28 %
Linux Clang 18 canada -42 %, jeopardy -48 %, twitter -35 %, citm -32 %
image_check::bounds is unchanged (within 0.4 %).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Rename names that Flawfinder takes for the file function open()
The comparison cursors' open() is now enter(), and a test's open and
close strings are head and tail.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Fix the compiler and lint failures of the json_view comparison
- all_digits(): the lambda declares its constant itself; MSVC does not
let a lambda without captures read a constexpr local of the function
- equal(): the frame's "in document order" index is a namespace-scope
constant (document_order); the local constexpr npos in the default
member initializers of the local struct crashed GCC 9 and MinGW GCC
and was not found by MSVC
- keys_differ_early() keeps the first keys in std::arrays (cpplint:
variable-length arrays; clang-tidy: C arrays), and the basic_json
side's first_keys() is not noexcept (key() may throw)
- the numbers of one type are compared in an if chain instead of a
nested conditional operator
- the dump test avoids C arrays and temporary string concatenations
View comparison instructions are unchanged (Apple clang, twitter, citm,
canada: -0.1 % to +0.1 %).
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Keep the byte comparison helpers in compare.hpp
Address review comments: bytes_equal() and bytes_less() move from node.hpp
to compare.hpp, their only user; key_less() no longer splits the comment of
resolve_indices() from its function; and the loop counters of bytes_equal()
and all_digits() are scoped to their loops.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Dispatch on the compile-time conditions of the json_view comparison
MSVC (/W4 /WX) reported C4127 (conditional expression is constant) for
the template parameter EA and the object type's ordering in an if
condition; both are now tag-dispatched.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Remove a nested duplicate guard from the json_view image test
clang-tidy reported the inner #if !defined(JSON_NOEXCEPTION) as
redundant (the test case is in the same #if) and a find() != npos, which
gets the NOLINT the other tests use.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Mark Infer's null dereference in materialize() as a false positive
Infer (ci_infer, also red on develop since #5882) reports a null
dereference in json_sax_dom_parser::null() called from materialize(). The
member pointer the parser stores a value of an object in is set by the
key() before it, so it is not null there.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Move the json_view comparison tests into their own file
With the tests this branch adds, the object file of unit-json_view_dump.cpp
got too large for the MinGW x64 assembler ("file too big"). The test case
"json_view comparison" is now unit-json_view_compare.cpp, unchanged and
also built with C++17.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* Build the DOM parser with Visual Studio 2015 again
Since #5882, the three VS 2015 jobs of AppVeyor fail on develop:
- the detection of keys that can be indexed instantiated std::hash for
every string type, which VS 2015 rejects with a static_assert for a type
it does not hash (alt_string): std::hash is now looked at only for
objects in a vector
- the frame stack copied its frames with std::copy to a raw pointer, which
VS 2015 reports as unsafe (C4996, an error with /WX): a loop now
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
* json_view: no per-object allocations in ordered_json comparisons
For an object type that keeps the order of its members (ordered_json),
resolve_indices() allocated a vector per compared object, and
resolve_members() two. They now use one working vector owned by equal(),
whose capacity is reused, and resolve_indices() needs none when the keys
are unique. resolve_members() sorts small objects by insertion, as the
other paths do.
Instructions per comparison (callgrind, GCC 13 and clang 18, x86-64):
twitter, ordered_json view == ordered_json: 0.939 / 0.941; 20000 small
objects with a duplicate key: 0.741-0.768; all other rows (json,
citm_catalog, canada, view == view) within 0.988-1.003.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
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Signed-off-by: Niels Lohmann <mail@nlohmann.me>